There are broad prospects of CO₂ flooding for enhancing oil recovery and greenhouse gas storage. In this paper, we reviewed the development history and brief situation of CO₂ flooding at home and abroad, analyzed the development status of CO₂ immiscible flooding and CO₂ huff and puff, and summarized the phase state of CO₂ flooding, oil displacement mechanism evaluation and optimization design technology of CO₂ flooding reservoir engineering. The design focused on improving oil displacement efficiency and sweep efficiency, controlling viscosity index and gas breakthrough, achieving miscible or near-miscible flooding, and optimizing well pattern and injection parameters in combination with reservoir characteristics. It was pointed out that CO₂ near-miscible flooding and increasing sweep volume were the development trends of CO₂ flooding. WAG, foam flooding, fracture sealing and local gravity flooding were important means to prevent gas channeling. On the basis of summarizing the current CO₂ flooding technology and field experience at home and abroad, the top-level design of combination of CO₂ flooding and CO₂ geological storage should be done according to different types of reservoir characteristics.

The greenhouse effect caused by excessive CO₂ emissions has led to many adverse effects on human life. As an effective CO₂ disposal technology, CO₂ geological storage technology has aroused more and more attention. The solubility of CO₂ in simulated deep saline solution and its variation with burial depth（800~2 800 m）were studied. The results showed that, when the buried depth was in the range of 800~1 700 m, the solubility of CO₂ decreased with the increase of buried depth. When the buried depth was greater than 1 700 m, the solubility of CO₂ increased with the increase of saline depth. In addition, the change of CO₂ solubility with burial depth could be fitted by the equation. And based on this equation, the storage capacity of CO₂ in a certain area of storage site could be calculated.

Shale oil resources are rich around the world and have extraordinary exploitation prospects. However, drilling horizontal wells and huge amounts of hydraulic fracturing measures had sharply increased the cost. A large number of experiments and numerical simulations showed that the gas injection could significantly improve the shale oil recovery. Nevertheless, this technique had not been implemented to the practical exploitation of shale oil. Consequently, it was still controversial whether shale oil recovery could be optimized through gas injection or not. By the comparison of the gas displacement experiments of the shale cores, the numerical simulation of shale oil recovery by gas injection and the gas injection pilots in practical fields, it was found that the results from experimental conditions and numerical simulation models were different from those in field pilots. Li Chuanliang insisted that the shale reservoir was consisted of myriad micro-lithologic traps. It was concluded that only if the gas was injected after fracturing, or establishing an orthogonal horizontal well pattern to dense the well spacing, would the shale oil recovery be improved. It has essential guidance for the improvement of shale oil recovery in China or even in the world.

CO₂ flooding is effective for enhancing the oil recovery in low permeability reservoir and reducing the greenhouse gas emissions. In order to solve the technical problems of difficult miscible phase, easy gas channelling and low sweep coefficient for CO₂ flooding in low permeability reservoir in Shengli Oilfield. By the combination of physical and numerical simulation, the development mechanism of the CO₂ injection miscible flooding long in advance is clarified, and the comprehensive techniques for extra low permeability reservoir is formed. After field application, the stimulation effect is obvious, the daily production of oil per well increase by 5 times. The principle and technical idea of reducing the miscibility pressure are put forward, and the system of reducing the miscible pressure system is developed, which can make the pressure decrease by up to 22 %. The challenge and countermeasure faced by scale application of CO₂ flooding in Shengli Oilfield are analyzed, and the development directions of CO₂ flooding are proposed, such as deepening the phase state theory of oil recovery enhanced by CO₂ flooding, developing CO₂ flooding technology with expanded sweep volume at low cost, developing incomplete CO₂ miscible flooding, and description and early warning of gas channeling. All these provide technical support for oil field to realize scale application of CO₂ flooding.

Water generally exist in the gas well in west Sichuan gas field, which has a great influence on the steady production of gas wells. The timely grasp of the flow conditions of the gas wellbore can judge the fluid accumulation in gas well and guide the formulation of the drainage gas recovery measures. By using the pressure meter to judge the downhole conditions of the gas well had the disadvantages of poor timeliness and high cost, and the prediction of two phase flow theory often had deviations from the actual existence. So we used a large number of gas well production data and flow pressure test data to establish the prediction model of wellbore flow condition based on RBF neural network. The RBF network had the self adaptability and its output do not dependent on the initial weight. The coincidence rate between prediction results and actual results among 15 wells was 86.67 %, which indicated that the neural network model was reliable for predicting the wellbore flow conditions of gas well, and could be used to guide production.

Normal pressure shale gas is one of the main types of shale gas exploration and development in China. It has great resource potential and broad prospects. In recent years, Sinopec East China Oil and Gas Company has continued to carry out normal pressure shale gas exploration and practice in Nanchuan-Wulong area of the basin-margin transition zone in southeastern Chongqing. Positive progress has been made in the following aspects such as basic geological theory research, low cost engineering technology research, green mine construction of normal pressure shale gas. The enrichment and high yield geological theory of “three factors controlling gas”, and the classification and evaluation standard and the target evaluation system of shale reservoirs are established. Six low cost engineering technologies of normal pressure shale gas are proposed, that is, low density 3D seismic exploration, well completion at the “second” section, “drop ball steering+continuous sand addition”, “three steps” fracturing sand addition, electric fracturing and high efficiency drainage gas production. The development technology strategy of normal pressure shale gas is preliminarily formed. The integrated green exploration and development mode is put forward. More breakthrough and efficient development of normal pressure shale gas exploration are realized. Normal pressure shale gas shows a good prospect of exploration and development. However, the exploration and development of normal pressure shale gas in China is still in its infancy and exploration stage. There are still many challenges in aspects such as theoretical innovation, technological breakthrough and benefit development. So that five countermeasures are proposed for the development of China’s normal pressure shale gas industry: ①deepen the research on the main controlling factors of shale gas enrichment and high-yield, and strengthen the target evaluation; ②speed up the research on the supporting technology of excellent drilling and completion for the further acceleration and efficiency increasing; ③strengthen the research on high-efficiency fracturing technology to increase production, reduce cost and increase efficiency; ④strengthen the research on the production rule of normal pressure shale gas, and formulate the technical strategy of benefit development; ⑤fully implement the integrated operation mode of shale gas geological engineering, improve the management quality and create benefit. These countermeasures are counted on accelerating the development of normal pressure shale gas industry in China.

The capillary bundle model is one of the most common physical models for the porous media. The most classic physical model is the straight capillary bundle model with same diameter. But the bendability of the porous media is neglected in this physical model. Therefore, based on the tight sandstone, combined with the mercury data, and by the introduction of the correction factor-tortuosity, we put forward a new approach to establish the capillary bundle model. This approach considers the bendability of the capillary bundle model and can accurately calculate the radius of capillary, capillary porosity and permeability, capillary volume of different radius and permeability contribution of capillary bundle model with different radius. This new approach has great significance for the study of the reservoir fluid imbibition of specific pressure and quantitatively characterizing the water invasion reservoir damage.

Based on the summary of deep shale gas breakthrough wells in recent years, four geological characteristics of deep shale gas are put forward. First, the basic evaluation parameters of deep and shallow shale are similar, but gas content and porosity of deep shale are generally higher than those of medium-deep shale. Second, the horizontal stress difference of deep shale is much greater than that of medium-deep shale. Third, deep shale gas in the basin is generally overpressured, and the pressure coefficient is generally between 1.9 and 2.1, while the complex structure area at the edge of the basin is normally pressured. Fourth, the positive structure is still the main factor for high yield of deep shale gas. Based on the analysis of the decline characteristics of single well production curve in Haynesville and Barnett shale gas fields and the geological characteristics of deep shale gas in Sichuan Basin, three main problems of deep shale gas, namely theoretical understanding innovation, engineering process applicability as well as cost and benefit development. The corresponding countermeasures are also pointed out.

CO₂ flooding is a promising way to improve the crude oil recovery ratio. CO₂ could not only dissolve in crude oil, but also replace some light hydrocarbons or intermediate hydrocarbons in crude oil. So the composition has great influence on the component mass transfer and minimum miscible pressure of the CO₂ miscible flooding. Therefore, the influence of the quantitative characterization of crude oil composition on the minimum miscible pressure of the CO₂ miscible flooding has engineering significance for the reservoir screening. Taking the original formation fluid of a certain oilfield in China as the research object, we analyzed the multistage contact miscibility mechanism. Meanwhile, we used the Winprop module in CMG to carried out the phase simulation of experimental data. The results show that the minimum miscible pressure between CO₂ and crude oil is proportional to the molar composition of N₂, C₁ and C₁₁₊, and inversely proportional to that of C₂~C₁₀. While the mixing of the CO₂ and reservoir fluids needs higher reservoir pressure than minimum miscible pressure. It requires that when screening reservoirs with CO₂ flooding, we should try to consider the reservoir with high mole content of C₂ ~ C₁₀ and low mole content of C₂₄. It has great guiding significance for miscible displacement design and miscible phase prediction.

With the research and application of the geology-engineering integration technologies, North America has won the victory of shale revolution, and the United States has realized energy independence, playing a dominant role in the global energy market. Its history and experience in shale revolution are the references of great value to the exploration and production of hydrocarbon resources in China. With abundant oil and gas in the exploration areas of Sinopec and various types of favorable targets, accelerating exploration and production is of great significance to improve China's energy structure and ensure national energy security. The application of geology-engineering integration has brought benefit development for the marine shale gas in the Sichuan Basin. In terms of realizing efficient exploration and production of the ultra-deep marine carbonate, tight sandstone and shale, five key studies are suggested to be strengthened: ①fine reservoir description and adaptive fracturing technology of exploration and production for complicated reservoirs, ②ultra-deep carbonate reservoir prediction and optimal drilling technology system, ③application of big data in realizing efficient adjustment and optimize completion program for tight sandstone gas reservoirs, ④development of multi-layer and three-dimensional production technology for marine shale oil and gas, ⑤research on the key problems in the deep, normal-pressure and continental shale oil and gas. To achieve high quality exploration and efficient production of oil and gas, Sinopec will keep strengthening the basic geological research and engineering technology innovation, upgrading technical equipment and following the idea of geology-engineering integration. And then, Sinopec will establish integrated operation coordination mechanism and emphasize integrated management of whole process in order to cut costs and increase efficiency.

In view of the technical difficulties of CO₂ flooding completion string, the research process and development situation of completion string of CO₂ flooding injection-production well were systematically expounded. It was concluded that the sealing performance of the completion string of injection well and anti corrosion and gas proof performance of production well were the key technologies for the normal production of CO₂ flooding injection-production well. The pilot test of CO₂ flooding in domestic oilfield showed that the continuous optimization of packer and the gas tightness detection of tubing contributed to improve sealing of injection wells, and the technologies like CO₂ corrosion inhibitor formulation, injection strengthening, tube controlling by gas lifting, downhole oil and gas separation were helpful to improve the pumping efficiency of the production wells. Meanwhile, in view of the technical problems faced by the injection and production wells on site, the further research direction of production by CO₂ flooding injection and production technology was pointed out.

The shale gas reservoirs in Longmaxi formation in Pengshui and its adjacent areas were overpressured in geological history, but nowadays they transformed into normal pressure. Through the simulation of formation pressure evolution in the uplifting process, it is revealed that Longmaxi shale was fractured under excessive pressure in this process, resulting in shale gas loss and therefore overpressure release. By overburden pressure permeability test, it is found that when the normal stress on the mudstone fracture surface of Longmaxi formation is more than 15 MPa, that is to say, when the buried depth is more than 1 000 m, the cracks will be closed, but the degree of fracture closure is affected by overconsolidation ratio（OCR） of shale. For the mudstone or shale under the brittle zones, OCR is relatively small, the closure degree of fracture is relatively high, the overpressure may not be completely released, and a certain degree of overpressure is still maintain. But for those above the brittle zones, the lager the OCR, the worse the fracture closure degree, and it is apt to cause the overpressure released completely, finally transit to normal pressure state. There is a significant correlation between OCR and the pressure coefficient of the formation fluid, that is, the higher the OCR ratio, the more normal the pressure will tend to be.

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Nowadays, the CCUS industry is developing rapidly worldwide, of which the projects are gradually turning from single-section items to whole-industry ones. The target of capture has expanded from power plants and natural gas processing to steel, cement, kerosene, fertilizers and hydrogen production. At present, there are five major ways to drive the industry: government and public funds, national incentive policies, taxation, mandatory emission reduction policies and carbon trading. In China, the CO₂ emitting enterprises are mainly power plants, cement, steel and coal chemicals, accounting for 92 % of the total emissions. According to the concentration, the low concentration CO₂ emission sources are mainly from power plants, cement, steel and refining and chemical industries, that with high concentration are mainly from coal chemical industry, synthetic ammonia and calcium carbide, and that with medium concentration is mainly from the polyethylene industry. The first are the majority, while the latter two are relatively few. Costs of CO₂ sources are comprised of three main parts: capture cost, compression cost and transportation cost, all of which are affected by the scale of capture. Meanwhile, the cost of capture is also related to the concentration of emission source. For the type of high CO₂ concentration, the expense of compression takes the lead in accounting. And capture cost is for the low CO₂ concentration type. As the tolerance of CO₂ cost is lower than source cost for most oilfields, it is necessary to seek ways like technology, policies or markets to fill the gap and promote the sustainable development.

The Chang 6₁ reservoir was the main oil-bearing beds in the study area of Ganguyi Oilfield in Ordos Basin. The exploration and development practice showed that the reservoir characteristics had strong heterogeneity in three-dimensional space, and the vertical and horizontal distribution of the reservoirs were complex, which directly restrictsed the subsequent rolling exploration and development. In the study, based on the core observations and logging data, and combined with analytical testing, the controlling effect of the reservoir macroscopic heterogeneity on the oil layer distribution was systematically and visually analyzed. The complexity of the Chang 6₁ reservoir in the study area was caused by a variety of factors. Among them, the distribution of the sedimentary microfacies and diagenetic facies directly controlled that of the high quality reservoirs. And the interlayer heterogeneity, especially the interlayer permeability, was easy to cause the selective filling of oil, while the interlayer heterogeneity directly caused the heterogeneous distribution of oil in composite sand body. Through this study, the distribution law of ultra-low permeability and ultra-low permeability reservoirs in Ordos Basin could be better understood intuitively, which provides guidance for finding favorable zones in the future.

Deep shale gas（buried depth is larger than 3 500 m） is the potential resource for future exploration in Sichuan Basin. Although the industrial shale gas flows have been obtained at the depth of 3 500~4 000 m in Wufeng-Longmaxi Formation of Sichuan Basin, the commercial development hasn’t been put into practice due to the rapid decline and the low EUR（Estimated Ultimate Recovery）. Based on the analysis of the current status of shale gas exploration and development, the challenges in the deep shale gas development with high efficiency and large scale in Sichuan Basin have been summarized, mainly in the following aspects: the understanding of occurrence mechanism and enrichment law of deep shale gas needs to be deepened, engineering and technology of economical and effective fracturing treatment need to be established, and the organizational operations and management methods of deep shale gas development are difficult to meet the needs of the large-scale and high efficient development. Three countermeasures are proposed to realize the large-scale and highly efficient development of deep shale gas: ①deepening the understanding of deep shale gas enrichment laws, establishing the methods of area selection and evaluation, and forming the prediction and description technologies of “sweet spot” and “sweet window”; ②deepening the research on the geological conditions of deep shale gas, forming an advanced supporting technology of drilling and fracturing and an equipment system to fully release the reservoir capacity; ③promoting the geology-engineering integration, building a new system and mechanism, and greatly reducing the cost to maximize the development benefits of deep shale gas. The industrial gas flows have been obtained in several wells at the depth of more than 3 500 m of Wufeng-Longmaxi Formation in Sichuan Basin and the proven reserves have been submitted. It is the key and priority stratum of the deep shale gas development. By deepening the geological understanding, overcoming the key technical problems, and improving the management system, it can significantly accelerate the speed, reduce the cost, increase the efficiency and achieve a large-scale and highly efficient development in a relatively short period. The output is expected to be higher than that of the middle and shallow shale gas reservoir.

Based on several geological problems in the exploration and development of the normal pressure shale gas reservoir, its classification is explored. For that, the relation between the change of organic carbon content, the degree of thermal evolution and porosity in shale are analyzed. On this basis, the relation between gas content and these geological factors, and between the gas content and initial production are further studied. At the same time, compared with the typical shale gas reservoirs at home and abroad, the controlling effect of shale gas migration with different pressure gradients on the initial production of gas reservoirs is discussed. It is clearly pointed out that there are differences in the energy supply for shale gas migration between transitional normal pressure shale gas reservoir at the margin of （or in） the basin and residual normal pressure shale gas reservoir outside the basin. Although there exists loss, because of the large distribution area of shale in the basin and the sufficient migration and replenishment of shale gas, the transitional normal pressure gas reservoirs at the margin of （or in） the basin have higher initial production and better commercial benefit. While for the residual normal pressure gas reservoirs outside the basin, as they have limited shale distribution area and insufficient migration replenishment, they belong to low pressure reservoir and have low initial production. In order to realize the commercial development, it is necessary to make more breakthroughs in the technologies of increasing production and reducing cost.

In the process of the natural gas flowing from the well head to the treatment plant, some condensate water may be produced and the transport efficiency declines due to the constant changes of the temperature and the pressure. The gathering stations of the Zizhou gas field adopt the technological process of the single station with the separated water and gas at the room temperature, the moisture vapor transport, and the hydrocarbon and dehydration took off together in the treatment plant. The separation of the water and gas at the room temperature need to determine where the condensate is by analyzing the water dew point, and ensure the reasonable running temperature under the different working conditions, so as to improve the separation efficiency of the gas station. By thewater dew point tester developed independently, the water dew point test was carried out under different pressure of the natural gas from the gas gathering stations in Zizhou gas field, that is, Zhou-1 station, Zhou-4 station and Zhou-8 station, and the index prediction model of the water dew point and pressure was established, and then, the equation of the water dew point and water content was established. The calculation results of Zhou-4 station show that the condensate water of this station mainly appears in the pipelines which connect the outside to the inside of the station in summer. The daily production of the condensate water is about 8 m ³. While in winter, the condensate water appears within the gas gathering stations and the amount of which appears in the pipelines is less than that in summer, but still exists. The pressure drop and the discharge volume changed with the date show that this calculation is more reliable. The daily water production of the gathering station by the water dew point under the pressure provide the effective measures for the pigging in field and reduce the running resistance of the pipeline.

The CO₂ miscible flooding project in the Taizhou formation of Caoshe oilfield is one of the most successful CO₂ EOR projects in China. The feasibility study on the secondary miscible flooding was carried out to settle the issues of complex remaining oil distribution and severe gas channeling in the later stage after first miscible flooding. The characteristic of microscopic fractal dimension in the CO₂ miscible flooding process of real core sample was observed through metalloscope. The remaining oil types attaching to the pore surface of rock took on the forms of thin film and isolated beads. The displacement efficiency of the secondary CO₂ miscible flooding was 93.4 %, which was 9.73 % higher than that of the first CO₂ miscible flooding. The average residual oil saturation was 30.8 % in sealed coring test, indicating great potential of III formation. A feasible development plan for secondary miscible-phases flooding was proposed to develop the stratified reservoirs at the bottom position. The CO₂ injection on the higher position was adopt to suppress gas gravity overlap, and the water alternating gas was applied to slow down the gas channeling. Furthermore, the injection profile was adjusted during the whole process of gas injection. The incremental recovery ratio was estimated to be 8 % ~ 10 %.

Based on the massive analytical data of core, we comprehensively researched on the main controlling factors of the tight oil reservoir according to the property and the storage space of the tight oil formation in Chang-8 reservoir of Fu County in Ordos Basin. Fine sandstone in Chang-8 reservoir contained the movable tight oil with low density and low viscosity, and mostly concentrated in micron-sized pore throats. The accumulation of tight oil was mainly controlled by three factors that were the source rocks of Chang-7 and Chang-9 reservoirs, the main accumulation mode of "the reservoir existed in the resource, and the resource existed in the reservoir", and the high quality reservoir with composite superimposed sedimentary sand body formed in the underwater distributary channel microfacies environment. Based on the controlling factors above, and combined with the current exploration results, we predicted 6 potential blocks of Chang-8 tight oil reservoir in Fu County, and provided the basis for the further exploration.

Traditionally, laboratory testing and measurement are considered to be the most reliable characterization methods. However, in many cases, due to the unclear understanding of the sensitivity to the range of reservoir properties and local changes of heterogeneous reservoir properties, and based on the oversimplified assumptions, the feature prediction obtained by this deterministic strategy is highly uncertain. In recent years, molecular dynamics （MD） simulation has received extensive attention in the study of reservoir rock, fluid properties and their interactions, as well as at the atomic level. In MD simulation, interesting properties are extracted from the time evolution analysis of atomic position and velocity through the numerical solution of Newton's equations for all atomic motions in the system. This technology can help to carry out the computer experiments which can be used to do the experiments that may not be able to complete, with high cost or very dangerous. In this paper, we review the MD simulation technology and its application in the study of oil displacement mechanism and properties of oil displacement agent, and expounds the theoretical concept and program of MD, especially in the analysis of polymer flooding. It will provide useful guidelines to characterize reservoir rocks and fluids and their behaviors in various reservoirs, help to better optimize the operation of design and production plan, and provide a theoretical basis for the development of polymer flooding technology in oilfields.

The machine learning is not only an important tool for oil and gas big data analysis, but also a general data-driven analysis method. As an important field with a long history and a large data base, oil and gas exploration and development has a great potential for data mining. The use of big data analysis technology for oil and gas field can help decision makers to conduct investment analysis, risk assessment and production optimization, which brings significant economic benefits. The machine learning method has been tried by the researchers applying to the researches on oil and gas. Nowadays, many application scenarios have been proposed with the development of machine learning algorithms, but general solutions for specific scenario are still divided. So that, we introduces the procedure of a machine learning modeling upon the most basic principles, and summarizes the development history of the main three kinds of machine learning methods that can be applied to oil and gas big data analysis. And then based on the characteristics of oil and gas field big data, the core contents, goals and advantages of oil and gas field big data analysis and utilization are discussed, the main application scenarios of machine learning in oil and gas field are analyzed, and the existing problems and countermeasures in typical oil and gas production prediction are summarized.

The property of low porosity and ultra-low permeability of shale gas reservoirs decide that only by the horizontal well fracturing can we obtain the economic productivity, and the forecast of the production after fracture have a great influence on optimal plan of treatments and economical estimation. On the basis of summarizing the previous researches, a novel model for production forecast in the unsteady early period was established based on the corrected Warren & Root model and considered about the desorption, slippage and stress sensitivity of micro fractures. Then the analytical solution for pseudo pressure was obtained by Laplace transformation and well-test method. Lastly, the practical production data was used to verify the accuracy of this model, and the factors affecting production were analyzed. The conclusion showed that the computed value and actual value of average daily production for single well in shale gas reservoir were similar to each other, demonstrating the validity of the model. Desorption and slippage had noticeable effects on the production and it also revealed that desorption played an important role in gas output. However, stress sensitivity could also affect the production in some extent, but the extent of the influence was less than that of desorption and slippage. The conclusions were meaningful for the study of output mechanism of shale gas and early production forecast.

The improvement of experimental technologies of geological evaluation for shale gas is the key factor for the success of shale gas exploration and development in America. The progress in experimental technologies of geological evaluation of shale gas is summarized from three aspects including gas-bearing property, occurrence and fracability of shale. It mainly focuses on the ultramicroscopic organic petrology, formation porosity thermocompression simulation experiment of hydrocarbon generation and expulsion, and the characterization of pore network, which are developed for high thermal maturity marine shale of South China in recent years. The future trends of experimental technologies of geological evaluation for shale gas are discussed. It is proposed that the effectiveness and connectivity of multiscale pore structure, the characterization of organic and inorganic pore in diagenetic evolution, and dynamic evaluation for fracability are the key studying aspects in experimental technologies of geological evaluation of shale gas.

The results of surface porosity obtained by scanning electron microscopy image processing can effectively reflect the development degree of shale organic matter pore. On the premise that the statistical sample is large enough, the pore size of organic matter can be quantitatively characterized relatively accurately. Due to the limitation of absolute resolution of scanning electron microscopy, the organic pore content was underestimated in the pore size range of less than 2 nm. The results of pore size distribution obtained by adsorption method need to be corrected. Combined with TOC and effective porosity, the porosity of shale organic matter can be calculated, and the proportion of organic and inorganic pore can be obtained indirectly. The data of 4 shale gas wells in southeastern Chongqing show that organic pore is the main type in Wulong and Dongsheng area, and the proportion of organic pore in bottom layer（① to ②） is high, up to 85.89 %. Pengshui area is controlled by organic carbon, and the proportion of organic pore is not more than 20 %. The organic pore proportion in Pingqiao area ranges from 20 % to 30 %, and the bedding fissures and laminar structures are relatively developed, especially the possible fissures or grain margin fissures between clastic particles and muddy interbeds in laminar structures contribute greatly to the inorganic pore. The proportion of organic pore is mainly affected by the abundance of organic matter and the degree of pore development of organic matter. The ratio of organic pore is highly consistent with the variation of TOC content in the vertical direction.

CBM development in China focuses on the high-rank coal, which is brittle and, during drilling, fracturing and drainage, easily crushed into coal fine. During the production, coal fine flows owing to the water flashing effect. As the water production declines, the coal fine will sediment and block the flowing channels, leading to the great reduction of coal permeability. When the coal fine enter the wellbore, it may jam the pump, resulting in accidents in production such as pump stuck or buried pump, and leading to the stop of production for well repair. In order to solve this problems, the generation mechanism, migration rules and current major controlling approaches of coal fine are summarized. And then, the mechanics model, hydraulic model and migration model are investigated respectively. According to the former studies, the coal fine migration process can be summarized as four stages: denudation, detachment, suspension and sedimentation. However, the geology conditions of coal seam in China are extremely complex and the structure changes effect is dramatic on coal basins. These factors enhance the problems of production and migration. Nevertheless, the coal fine controlling approach method primarily learns from the sanding control technology in oil reservoir and is still undeveloped for the CBM reservoirs.

QK 18-1 Oilfield is located in the western Bohai sea. After 10 years of water flooding, the water injection now is difficult. In 2013, the sealed coring was conducted on the well P13. The core represented large amounts of the information after the long term of the water flooding, including the pore structure changes, the inorganic scale plugging, etc. By comparing the interstitial materials in the reservoir of the exploratory wells in the early stage and the exploitation wells in the late stage, we used many methods, such as the low field NMR, the electron microprobe, the environmental electron microscope, the cathodoluminescence and the rock cast sections, to study the inorganic scale in the reservoir and determine the formation mechanism of the scaling crystal in the reservoir. The results showed that the CaCO₃ cements in the early stage of the reservoir presented as the crystal or the porphyritic distribution were the products of the diagenetic stage. The well P13 contained a large number of rhombohedral CaCO₃ scales with the grain diameter of 5 ~ 30 μm and great euhedral degree of the scale. And the scale mainly distributed around the surface and the throat of the skeleton particles with high content of Mg and Fe formed during the water flooding. The average reservoir water damage rate was 44.5 % and the average velocity sensitive damage rate was 139.5 %. The clay minerals generated by swelling of part of the scale with water, the mobile formation particles and the suspension matter in water wrapped together to form a composite inclusion, accumulating in the pore space to damage the reservoir

The geological conditions of fault block reservoirs are complex, whose small faults are developed, and reservoir heterogeneity is serious. When the reservoir enters the development stage with ultra-high water cut, the remaining oil is highly dispersed, the streamline between injection and production wells is fixed, the benefit of water drive becomes worse, and the spread of water flooding is difficult to further expand. Streamline adjustment and development have become the main direction of cost reduction and efficiency enhancement for fault block reservoirs when the price of oil is low. Conventional dynamic analysis is not suitable for the adjustment of high water cut fault block reservoirs. In this paper, streamline simulation method is used to analyze the influence of each factor on the streamline of water flooding, and grey relational method is used to calculate the influence degree of each factor. It is found that vertically heterogeneity, areal heterogeneity and injection-production well pattern have significant influences on streamline, while injection-production well spacing and injection-production pressure difference have relatively small influences. The streamline distribution model is divided into three categories: dense area, sparse area and blank area, on this basis, the optimal adjustment technology is formed. In several fault block reservoirs in Subei Basin, the adjustments of vector allocation, adding new waterline, reducing the number of wells in the well pattern, and reorganization after subdivision have been carried out. Remarkable effect of increasing oil production and efficiency has been achieved. It has certain guiding significance for the adjustment of the same type of reservoirs.

Due to the deep buried depth（3 500~4 200 m）, high ground stress, high ground stress discrepancy（7 to 17 MPa）, low reservoir brittle（< 0.5） and the undeveloped natural fracture, the hydraulic fracture of Weirong deep shale gas face the problems of high fracturing construction pressure, narrower pressure window, low sensitive sand concentration, high fracturing difficulty. Large-scale physical model experiments show that the morphology of Weirong shale fractures are composed of main fracture and branch fracture, within low fracture complexity and forming bedding seam more easily. On the basis of geology-engineering integration, the stratigraphic segmentation and clustering are optimized in combination with geological sweet spot. Through the study of the proppant transport, the placement mode and injection timing of the three-grade particle size proppant have been optimized, which increase the sand loading. The transverse complexity of fractures is improved by the combined temporary plugging steering fracturing technology. The net pressure and complexity of fractures are improved by the temporary plugging in the fractures and the optimization of construction discharge and liquid viscosity, thereby improving the fracturing volume and control reserves. The research results have been successfully applied in Weirong Gas Field. The sand loading has been increased to 1.95 t/m, the average open flow per well is 38.5×10⁴ m³/d, and the single well EUR is 90×10⁸ m³. All those shows a significantly improvement compared with the previous stage. Post-pressure evaluation shows that the fracturing effect is positively correlated with the sand adding strength. Therefore, how to improve the sand adding strength and control the strength of the liquid used in deep shale gas is the key to economic and effective fracturing.

The fractured-vuggy carbonate reservoir is one of the main types of oil and gas reservoirs in Tarim Basin, which has great potential and broad prospect. In recent years, Sinopec Northwest Oilfield Company has continued the exploration and development for them, and has made many breakthroughs in the researches of basic geological theory of carbonate rock, seismic identification technology of fracture cavity body, and high-efficiency development engineering technology. And it has established a series of relatively perfect geological and reservoir engineering methods and technologies for carbonate reservoirs. It has realized the continuous increase of storage and production and efficient development of carbonate reservoir in Tahe oilfield, showing a good prospect of exploration and development, and also providing reference for the exploration and development of similar reservoirs at home and abroad. However, how to develop carbonate fracture-cavity reservoir sustainably also faces the problems and challenges such as theoretical innovation and technological breakthrough. It is urgent to tackle the key problems and make breakthroughs in fracture-cavity structure description, quantitative characterization of remaining oil, utilization of reserves around wells, and heavy oil recovery, so as to continuously promote high-efficiency and high-quality development of carbonate fracture-cavity reservoirs.

Recently, positive progress has been made in the exploration and development for shale gas of the Wufeng-Longmaxi formation in the area with complex structure of the southeast area of Chongqing. In order to further deepen the understanding of shale gas accumulation in this area, based on the previous research results, by using the data such as experimental analysis, geophysical exploration, drilling, fracturing and gas testing, and starting from the key factors of controlling shale gas enrichment and high yield, typical target anatomy and mechanism analyses are carried out to summarize the rules of shale gas enrichment and high yield. Meanwhile, it is found that the enrichment and high yield of shale gas are controlled by three factors: sedimentary facies, preservation conditions and in-situ stress field, concretely speaking, deep-water shelf facies controls the scale of resources; preservation conditions control the degree of shale gas enrichment; in-situ stress field influences the effect of fracturing transformation and controls the yield of single well. To optimize shale gas sweet spot targets and well location deployment in complex structural areas, firstly, the resource basis for controlling shale gas enrichment should be evaluated, that is, the development degree and indicators of high-quality shale in deep-water shelf facies. Secondly, the intensity of tectonic movements is evaluated to determine the preservation conditions and enrichment degree of shale gas. Finally, it is preferred to deploy a shale gas well with a medium-curvature zone of moderate in-situ stress to facilitate high and stable yield. The research results have important guidance and reference significance for the exploration and development of shale gas in complex structural areas.

The hydraulic fracturing is a major means of the coalbed methane（CBM） exploitation, and the effective channels of the methane seepage can be formed in the coal seams by this means. The stimulated reservoir volume（SRV） can not only help the coal seams form the seepage channels, but also increase the desorption-diffusion areas of the methane and improve the production of the single well by formed the complicated fractures. The brittleness index is one of the key parameters for evaluating the SRV implement, therefore, based on the stress-strain curves of the coal and shale, it is analyzed with the help of the strain-energy density. The higher the brittleness index of the shale is, the lower the strain-energy density will be. Based on the calculation method of the brittleness index of the shale, the calculation method of the coal brittleness index that combines with the strain-energy density and minimum energy principle is put forward, and the modified brittleness index of the coal is obtained, which can be used for the characterization of the coal brittle failure and evaluation of the fracture formation after fracturing. Finally, the analysis of the calculation results and data of 6 fracturing wells, indicates that the strong correlation between the coal brittleness index and stimulated volume, which means that the higher the brittleness index is, the larger the stimulated volume of unit fracturing fluid in the coal seams will be. This method can be applied to design the SRV of the coal seams and guide the exploitation of CBM.

In order to guarantee the fast and professional solution about types of water production and mechanism of water invasion in the Rumaila complex multilayer carbonate reservoir of Ahdeb oilfield with casing channeling, high permeability zone and situation of commingled production, a fine reservoir model which can characterize the pure aquifer zone, oil-water transition zone and pure oil zone was built. On this basis, combined with analysis of water invasion velocity in each reservoir, the various simulation curves would be calibrated by the actual typical production curves to obtain the different typical water control diagnostic plots including casing channeling with bottom aquifer coning, bottom aquifer coning with later casing channeling, single casing channeling and the section of perforation located in the oil-water transition zone with later casing channeling（including different position of casing channeling: pure aquifer zone, oil-water transition zone and pure oil zone） with dimensionless time, which would be used to distinguish and analyze the reservoir water-producing type and rules. The results showed that the water control diagnostic plots could accurately obtain the water production type and rules, decrease the downhole PLT, SWFL and other tests, and provide reliable basis for the stabilizing oil and controlling water of vertical wells.

The guanyinqiao member in Southeast of Chongqing is a suit of argillaceous limestone formation formed in the Nantes period. The sea level and the control of ancient landform are the main factors affecting the strata. The strata overlying and underlying layer are both black shale formed in deep-water sedimentary environment. On the plane, Guanyinqiao member is distributed uniformly and missing in some parts. By analyzing the characteristics of Guanyinqiao member in Nanchuan area, and combined with the static evaluation indexes and single well productivity of the shale gas wells in this area, we analyzed that whether there was the relationship between the productivity of shale gas well and the existence of the member, thus affecting the shale gas production. The conclusion has geological guidance to the selected areas of shale gas in the Southeast of Chongqing, and great guiding significance on exploration strategy of shale gas.

In shale gas reservoirs with natural fractures, the artificial fractures and natural fractures communicate with each other after fracturing. The traditional dual media model can not accurately reflect the impact of natural fractures on well production. In order to investigate the influence on shale gas well productivity caused by gas transport in nanometer-size pores, the mathematical model of multi-stage fractured horizontal well in shale gas reservoir is built, which considers the influence of the complex flow mechanism such as the viscous flow, Knudsen diffusion, surface diffusion, adsorption layerand gas desorption. Discrete fracture model（DFM） is used to simplify the fracture and finite element method is applied to solve the model. The numerical simulation results of Pingqiao shale gas reservoir indicate that the free gas in fracture system mainly contributes to shale gas production in the early stage, and the average recovery of adsorbed gas is only 10.1 %. The existence of unmodified reservoir makes the influence of bedrock permeability on cumulative production greater. The density and connectivity of fracture networks have dominant effects on gas production and its decline trend.

After the guidance of the results of gas flow conductivity test for the optimization of fracturing design of tight gas reservoirs, the prediction of post fracturing effect and the optimization evaluation of proppant were more pertinent and reasonable. The current common gas flow conductivity tests mainly focused on the influence of the closure pressure, proppant particle size and proppant type on the flow conductivity. Based on the analysis, we designed the experimental scheme about the influence of fracturing fluid type and laying mode on gas flow conductivity by using the DL—2000 fracture support conductivity tester and according to the SY/T6302—1997 "proppant filling layer short-term conductivity evaluation and recommendation method". The results showed that the fracture conductivity decreases when the closure pressure increased; the larger the proppant diameter was, the greater the conductivity would be; while the greater the closure pressure was, the greater the decreasing amplitude of the flow conductivity would be. The laying mode for the rear gas logging fracture conductivity was the best. The fracturing fluid damage made the cracks in the gas logging diversion capacity decreased by 80 %~95 %.

The oil and gas well data collection system has been widely used in the shale gas well testing. In the process of operation and management of data collection equipments, the sorting and recording of field data, reporting of field real-time and staged production reports all required to be operated by professional technicians. This work took a lot of time and was error-prone. Automatic report management was a technology combining the actual production of shale gas with the data collection system. Relay on Python, the computer programming language, we could obtain the field data and records, and on this base, compiled and sent reports. This technology can greatly improve the accuracy and efficiency of data recording, and reduce the labor intensity of technicians.

In order to study the effect of CO₂ flooding on the physical properties of crude oil, understand the mechanism of CO₂ flooding, and provide theoretical basis for the analysis of field test results of CO₂ flooding, the field test of CO₂ flooding in Huang 3 block of Jiyuan oilfield in Changqing was carried out by column chromatography and gas chromatography-mass spectrometry. The physical properties of crude oil produced before and after CO₂ flooding in Huang 3 block of Jiyuan oilfield, Changqing, were studied in detail by means of column chromatography, gas chromatography and mass spectrometry method and other methods. The changes of crude oil group content, different carbon chain alkanes content, solidification point and viscosity-temperature curve were mainly investigated. The experimental results show that after CO₂ injection, the alkane fraction of crude oil first decreases and then increases, while the non-hydrocarbon and asphaltene fraction first increases and then decreases; the light alkane（C₈—C₁₆） in the alkane fraction of crude oil first decreases and then increases, the heavy alkane（C₁₇—C₄₀） content first increases and then decreases; the pour point of crude oil first increases and then decreases, and the viscosity of crude oil at low temperature（35 ℃） increased slightly, but there was no obvious change at high temperature. The above results accord with the mechanism of CO₂ miscible flooding. The change of crude oil physical properties is the result of the interaction of CO₂ extraction mechanism. Through the above research, it provides data support for understanding the mechanism of CO₂ flooding, and provides a certain basis for further formulating plans to improve the efficiency of CO₂ flooding.

In order to solve the problems such as the breakthrough of flue gas, frontal advance of combustion drive and conventional plugging technology do not meet the requirement of fire drive in the fire drive test area of Hongshanzui oilfield in Xinjiang. We used the device for testing the foam flow in core and the visual microscopic displacement model to study the flow experiment and the microscopic mechanism of flue gas foam. The experimental investigation showed: the gas-liquid ratio was an important factor that affects the capacity of foam blocking; the foam blockage ability was the strongest when the foam system was mixed with gas and the gas-liquid with ratio 1∶1; the oil recovery factor increased by 12.6 % after the flue gas foam injection. The microscopic mechanism research showed: the main reason why foam had the ability of blockage was the new foam blocked the big pore and increased the flow resistance of the fluid. The migration of foam in porous media was a kind of separate migration of gas phase and liquid phase; the trap and flow state of the foam were constantly transformed with the change of external conditions. The study can provide reference for the control of gas channeling in the fire flooding test area of Hongshanzui oilfield in Xinjiang and is helpful to improve the theory of bubble control.

The Chang-2 reservoir of Ansai oilfield has the geological characteristics of low porosity, low permeability, fast change of physical properties and strong vertical and horizontal heterogeneity. Based on the ''four properties'' relation of reservoir, we established the minimum standards of effective thickness by using the core analysis, oil test, production dynamics and logging by the way of histogram method and cross plot method. Then we proposed the different types of interlayer logging quantitative identification chart and the elimination criterion of various interlayer on the basis of the semi-quantification and semi-qualitative analysis by many kinds of logging curves. The minimum values were as follows: the oil-bearing property was to see the grease spots; the lithological property was to see the fine-grained sandstone; the physical property were the porosity was more than or equaled to 11.5 % and the permeability was more than or equaled to 0.63×10 ^-3μm ²; the electrical property were the resistivity was more than or equaled to 13 Ω·m and the acoustic was more than or equaled to 230 μs/m. The main types of interlayer were calcareous interlayer and muddy interlayer. We could identify and eliminate the interlayer by the quantification of curves of natural gamma, acoustic and microelectrode, and the qualitative analysis of the curves of spontaneous potential, RILD, RILM, microsphere resistivity and micronormal.

The huff and puff operation by CO₂ extraction can overcome the production and development problems of tight reservoirs which are difficult to form effective displacement. Crude oil fractions were divided by PVTi module, and the pseudo-component properties of formation crude oil could be obtained by combining with the expansion experimental data of CO₂ injection. Relevant factors affecting the extraction of tight oil by CO₂ were studied by CFD simulation. The results showed that supercritical CO₂ mainly extracted the light components of crude oil in porous media, especially those below C₁₅₊. The higher injection pressure was, and the more CO₂ was injected, the stronger the solubility of crude oil would be, and it could enhance the extraction of heavy components. Meanwhile, the increase of CO₂ injection could also promote the retention of CO₂ in porous media, which was conducive to CO₂ storage. With the increase of porosity, the extraction effect of CO₂ increased first and then decreased, and was still 44 % under the condition of lower porosity. The extraction of tight oil by CO₂ has a certain application prospect.

In order to solve the problems of the uneven plane water flooding, great differences between the of vertical water absorption, and low recovery of the waterflooding during the high water cut exploitation period of the oilfield, a series of indoor evaluation experiments were conducted to improve the water absorption profile of CO₂ foam flooding. Then we established the flooding model by multiple core combination with the high and low permeability with the differential of 3, 6 and 9. We used the CO₂ foam to displace the core to study the effect of the differential permeability and oil saturation difference on the improvement of water absorption profile during CO₂ foam flooding, and the CO₂ foam displacement efficiency. The results show that the effects of CO₂ foam improving the injection profile become better when the permeability reduces. And taking into account the displacement efficiency of CO₂ under different permeability ratio, the permeability of the same layer should be controlled within 6. Meanwhile, the effects of CO₂ foam on profile improvement gets better when the oil saturation increased. In the practical application, the range of oil saturation level should be 4 ~ 6. At present, the research results have been applied in the test of CO₂ foam flooding in Block A of Jilin Oilfield.

There are some problems of drilling composite bridge plug by coiled tubing in staged fracturing of shale gas horizontal wells, such as easy to get stuck, high frequency of strong magnetic fishing and long working hours. In order to solve these problems, deep analyses were carried out on the structure and dissolution principle of soluble bridge plug. And according to the key factors affecting the fracturing and dissolution performance of soluble bridge plug, field tests of soluble bridge plugs with different temperature resistance were carried out in Nanchuan shale gas field. The test results showed that the soluble bridge plugs could bear the differential pressure of 70 MPa under the temperature of 112 ℃. The soluble bridge plugs with heat resistance of 93 ℃ could be completely dissolved, while those with heat resistance of 120 ℃ could be partly dissolved. Compared with traditional composite bridge plug, the cost of a single well was reduced by 1.087 million Yuan. The main factors that affecting the fracturing and dissolution performance of soluble bridge plug were temperature, mineralization degree of solution and dissolution time. The higher the mineralization degree and the temperature were, the faster the dissolution rate of the soluble bridge plug would be. In particular, the well temperature was of great importance to the dissolution effect of soluble bridge plug. The feasibility and economy of soluble bridge plug in staged fracturing of shale gas wells were verified either, which was proved to have application value for cost reducing and efficiency increasing in fracturing of shale gas wells.

It is well known that the supercritical CO₂ has the dual characteristic of gas and liquid. In order to study the forces of the sand in the fluidized bed formed by the supercritical CO₂ fracturing fluid and the migration of the proppant particle under the force, we analyzed the acting force between two particles, and the particle and the fluid, and that of the fluid on the particle. Based on the mathematical model, we derived the relation between the elastic restitution coefficient and the agglomeration concentration of particles. With the increasing of the elastic restitution coefficient, the distribution of the agglomeration concentration gets more evenly, the agglomeration concentration decreases, the collision of particles is more intense, the particles settle down more slowly, and the sand migration effect is better. Meanwhile, through the numerical simulation of the double Euler multiphase model based on the particle kinetic theory, we described the fluidization model in the fluidized bed formed by the supercritical CO₂ fracturing fluid in operation, and the two phase distribution of the particle of the supercritical phase and the solid phase. The simulation result is consistent with the mathematical model.

In order to further explore the migration rule of alkali/surfactant/polymer（A/S/P） system in the reservoir, guided by the reservoir engineering, surfactant chemistry and oilfield chemistry, and aimed at the fluid properties and geological characteristics, we conducted the research on change rule of viscosity, IFT tension and displacement effect of A/S/P system, and discussed the relative mechanism based on the dynamic testing result of single component concentration of compound system. The results showed that during the displacement process of A/S/P system, the polymer, surfactant and alkali presented different along-range retention characteristics, the chromatographic separation phenomenon occurred, the decrease rate of surfactant concentration was much higher than that of polymer and alkali, and both the ultra-low interfacial tension and high viscosity could only keep the length of 1/3 well distance. The contribution rate of ultra low tension was limited in the A/S/P flooding; about 60 % oil was not recovered by compound system under the condition of ultra low tension. If the A/S/P system can keep lower IFT and give consideration to proper viscosity, we can acquire the better displacement effect.

Zigong Block, which is located in the southern side of Weiyuan Slope in Sichuan Basin, is a monocline in NW-SE direction. O₃w-S₁l^1-1 is the target layer of that block, which develops black shale with rich organic matters in deep-water continental shelf, while the longitudinal heterogeneity of the reservoir is strong. Different penetration degrees in the sweet spot of horizontal shale well lead to different testing results. In order to determine the longitudinal distribution of the optimal shale target and guide the tracking and adjustment of horizontal well drilling trajectory, based on stratigraphic subdivision, fine evaluation of reservoir is carried out by the comprehensive data of drilling, logging, well testing and laboratory analysis. Meanwhile, the gas production profile data are used to evaluate the impact of the target on shale gas productivity of the horizontal wells. The research results show that: ①Under the influence of both sedimentation and tectonics, the lower part of S₁l^1-1-1 are the optimal “sweet spots” for both geology and engineering among target layers; ②The production well logging data indicate that, the lower part of S₁l^1-1-1shows highest gas production contribution of per unit length, which is the optimal target position of the research area; ③The effective fracking length of shale reservoir in the lower part of S₁l^1-1-1 for horizontal well is the key factor for gas well productivity in Zigong Block. Based on the above results, which supports the productivity evaluation of shale gas effectively, and sets the foundation for realizing large-scale and cost-efficient development of shale gas in that block, the longitudinal distribution thickness of the optimal target in Zigong Block is accurate from 2~5 m to 1~2 m.

Electric submersible reciprocating pump is a rodless oil extraction device for low-permeability reservoirs. As one of the new technologies of high efficiency and energy saving lifting, its application scale is expanding year by year. In the light of problems of oil field production: we creatively proposed an optimization method for submersible linear motors, including the motor's lifting capacity and control methods; then we developed a new double-acting load shedding pump for deep oil wells or large displacement oil wells; after that we researched and developed new aluminum alloy submersible oil cables to reduce one-time investment costs. It is applied of 90 oil wells, then we found that the average pump inspection period increased from 452 to 693 days, the longest pump inspection period exceeded 1 037 days, and the average electricity saving rate reached 45.6 %. The applications showed that the new optimized and upgraded technology had better reliability, adaptability and economy, which was beneficial to the large-scale application of electric submersible reciprocating pumps. It also provided a basis for in-depth study of variable frequency control of long line submersible oil cables and monitoring of downhole working conditions.

Because of the importance of preservation conditions and shale pore evolution to shale gas exploration and development, it is of great scientific significance and academic value to study the relation between them. The pore structure characteristics and evolution of black shale with different preservation conditions have been studied by means such as argon ion polishing, scanning electron microscope and nitrogen adsorption, and it is found that the pore structure of black shale under different preservation conditions are significantly different. This difference is caused by the difference of preservation conditions in the late uplift process, which is manifested in the following aspects. First, inorganic pores in black shale with good or bad preservation conditions are both less developed, and most of the original intergranular pores are filled with generated hydrocarbons. The inorganic pore characteristics between them are basically similar. Second, the organic pores in black shale are of great difference under different preservation conditions. The diameter of shale organic pores is larger in good preservation conditions, which are in round or bubble shape. While the organic pores are relatively smaller in diameter or totally absent in poor preservation condition, which are in flat or irregular shape with the certain characteristics of flattening and deformation. Third, the pore volume and specific surface area of the black shale under good preservation conditions are better than that under poor conditions. Fourth, the porosity evolution of black shale is affected by preservation conditions. The original pore morphology and distribution are controlled by facies and diagenesis process, and so are the organic matter（oil） distribution form. Thermal evolution of organic matter（oil cracking） influences the existence of organic pores. Whereas, in the late uplifting process, the pore structures（shape, size, pore volume） are affected by the quality of the preservation condition. Therefore, the size, morphology and porosity of the shale organic pores reflect the preservation conditions of shale gas in some extent.

As one of the important source rocks in Tarim basin, Yuertusi source rock, whose thermal evolution history is still lacking of objective knowledge which restricting the choice of exploration direction. On the basis of drilling data and analysis test, the Easy%R_o model of basin modeling technology was used to analyze the thermal evolution history and its dissimilarity of Yuertusi source rock in different tectonic units, and the favorable exploration areas were raised, that was important to the further deep carbonate reservoir exploration. The results showed that the source rocks with multiphase and differences dynamic characteristics in thermal evolution were controlled by tectonic movement and hydrothermal activity. The source rock in the ring with depression of Manjiaer and Tanggubasi entered the hydrocarbon generation threshold successively in Ordovician, but the source rock in the Kongquehe slope and eastern Guchengxu uplift entered the stagnation of hydrocarbon generation in Silurian. The Shunxi to Manxi area entered the stage of hydrocarbon generation dried up in Permian and Carboniferous and the range of depletion has gradually expanded. The thermal evolution process of the source rock in the eastern Maigaiti slope significantly was later than that of other areas; it was still in the late mature stage today. The predicted favorable zones were west Shaya uplift, west lower uplift of Shuntuoguole, east Maigaiti slope and west Tanggubasi depression slope.

The fracturing fluid leak-off in the reservoirs with developed natural fractures had a comparatively great influence on hydraulic fracture structure, proppant distribution and formation contamination. However, the current mathematical model for fracturing fluid leak-off considering natural fractures almost ignored or simplified the clustered distributed natural fractures, which limited the applications of these models. So firstly, by the multiplicative cascade method, we established a two-dimensional fractal discrete fracture networks model which reasonably showed the clustered distribution of natural fractures. Then, the established fracture networks were transformed into homogeneous anisotropic equivalent continuum media through subdividing the fractured porous domain into small elements. Ultimately, a mathematical model of fracturing fluid leak-off in fractured reservoir was established based on the permeability tensor. The results showed that the the strike of fracture rich zone determined the direction of fracturing fluid leak-off and pressure propagation. As the fracturing fluid tended to filtrate along long fractures, it was suggested to seal the natural fractures near hydraulic fractures before fracturing treatments. Moreover, fracturing fluid viscosity had certain influence on leak-off velocity.