For volumetric closed gas reservoirs, when the gas well produces with stable production rate, it can be divided into unsteady state stage, transient stage and pseudo steady state stage according to the variation behaviours of flowing bottom hole pressure and producing time. The unsteady state stage is called the elastic one-phase stage, and the pseudo steady state stage is called the elastic two-phase stage. The latter is a dynamic method to evaluate the Original Gas in Place（OGIP） controlled by gas wells. The elastic two-phase method proposed by CHEN Yuanqian in 1991 in the pseudo steady state stage has been repeatedly listed in the National Oil and Gas Industry Standards, and has been widely valued and applied in China. Based on the diffusion equation considering the elastic expansions of natural gas, rock and irreducible water in a gas well with stable production in the finite closed gas reservoir boundary, a new elastic two-phase method for the pseudo steady state stage represented by flowing bottom hole pressure and cumulative production rate is derived, which can be used to evaluate the original gas in place（OGIP）controlled by a gas well. The new formula of elastic two-phase method is superior to the old formula which based on the relationship between flowing bottom hole pressure and production time, and the new can overcome the influence of production fluctuation on the evaluation results. The application shows that the new formula of elastic two-phase method is practical and effective.

In order to explore the beneficial development path of fault-block shale oil in Qintong Sag, a development mode for the fracturing of directional wells combined with pseudo-horizontal wells has been proposed based on the study on the geological characteristics of shale oil in the second member of Funing Formation, and two wells are successfully implemented. The results show that the east and west wings of the deep sag belt of Qitong Sag in Subei Basin are structural complex areas with fault-block shale reservoirs, which are with large thick, developed natural fracture network, high pressure coefficient, and good mobility and transformability. The geological conditions here is not suitable for the development of long horizontal wells but for the directional wells. For the multi-layer development of thick shale oil, the rectangular directional well pattern is conducive to the CO₂ huff and puff, while the diamond reverse nine-spot well pattern is reasonable for the CO₂ flooding. Therefore, with the fracturing technology system based on “large-scale liquid injection energy storage & flow limiting perforation promotion and equalization & flow adjustment and fracture-stabilizing network & three-stage support and maintenance filling & continuous construction with all electric pumps”, the fracturing of the directional wells took as the “pseudo-horizontal well” can achieve the transformation effect of the horizontal wells, and the transformation volume of the single stage is 28.6 % larger than that of horizontal wells. This new develop mode of shale oil has high initial productivity, early oil breakthrough time, low flowback rate, fast water cut decline, and long stable production time. The single stage has high elastic productivity, high recovery degree, and good economic benefits, realizing beneficial development of shale oil in advance. The beneficial development shows a good prospect for the evaluation of shale oil in complex structural areas by the directional wells.

The geological conditions of the complex fault block reservoir in the Paleogene of Jidong Oilfield, Nanpu Sag, northern Huanghua Depression, Bohai Bay Basin are complex. There are many faults, small fault blocks, the main reservoir is deeply buried, and it is shielded by the widely developed volcanic rocks. Therefore, the quality of seismic data is poor, the stratigraphic correlation and fine structural interpretation are difficult, the basin area is small, the source is close, the deposition rate is fast, and the sand body superposition relationship is complex. In order to effectively identify the distribution and connectivity of inter-well sand bodies and finely characterize the structural morphology, fine description and research on the complexity geological conditions in Jidong Oilfield have continuously carried out in recent years. Six key technologies have been gradually formed, including small layer division and fine correlation of complex fault block reservoirs, low-order fault identification, comprehensive characterization of delta reservoirs, formation and main controlling factors of dominant permeability channels in the process of water injection development, three-dimensional geological modeling of complex fault block reservoirs, and quantitative characterization and distribution of remaining oil, which are applied to five typical blocks, including two types of reservoir genesis of fan delta and braided river delta, and two types of physical properties of medium permeability and low permeability. In the development stages of medium water cut and high water cut, normal water injection development and overall fracturing water injection development are the theoretical basis for the rational development of complex fault block reservoirs in Jidong Oilfield.

Qintong Sag of Subei Basin has high abundance of oil and gas resources and great exploration potential, but the geological target has the complex characteristics of “thin, broken, small, scattered and hidden”. Since 1989, there is a series of seismic technical breakthroughs in this area. From conventional 3D to high-precision 3D for secondary acquisition, the acquisition method of “single point broadband receiving with digital geophone, medium surface element grid and high coverage times” is established, a series of processing technologies have been formed, such as sequential processing, improved SNR processing, improved resolution processing, structural-constrained mesh tomographic velocity modeling and reverse-time prestack depth migration imaging, etc., as well as the thin-bedded sandstone prediction technology with the waveform indication inversion of SP sensitive curves. Technological progress has promoted the transformation from simple structural reservoir to complex small fault block reservoir, and then to complex structure-lithology subtle reservoir exploration in Qintong Sag. The analysis shows that the high SNR, high resolution and amplitude-preserving processing effect are limited by the large difference of multi-phase data collection, narrow frequency band of original data and low sampling density of wave field. In order to solve the further problems of the complex subtle reservoir seismic exploration, wireless single-point receiving, single-point broadband excitation, small surface element, high coverage density, wide azimuth seismic acquisition, amplitude quantization quality control, broadband omni-directional processing and five-dimensional interpretation should be explored.

Tectonic and lithologic reservoirs are developed in the Dainan Formation of MJZ Oilfield, and the understanding of reservoir correlation and development characteristics has multiple solutions. In order to accurately understand the rolling expansion potential of the main layer of the structural lithologic reservoir, it is proposed to establish a regional stratigraphic development model based on the analysis of stratigraphic overlap and thickness characteristics, and through fine reservoir correlation, transform the sand body originally thought to be scattered into the main sand body with continuous scale distribution, and then clarify the rolling potential of the structural lithologic reservoir. The formation of reservoir correlation and description results based on regional stratigraphic development model has positive significance for promoting the rolling expansion of MJZ Oilfield and similar structural lithologic oil and gas reservoirs.

Volcanic rock reservoirs are affected by many factors such as lithofacies, lithology, and reservoir space types, and fluid identification is difficult, which is one of the difficulties in well logging interpretation. It is urgent to establish a convenient and quick identification method. For this reason, the SVM（Support Vector Machine） algorithm of machine learning is used to predict the fluids of unknown reservoirs for the volcanic rock reservoirs in the Nanpu Sag of the Bohai Bay Basin. The research shows that: ① Comprehensive application of core, well logging, mud logging and other data to optimize fluid sensitive characteristic parameters, single information sensitive parameters are acoustic time difference, compensation density, resistivity, multi-information fusion parameters are natural gamma relative value, total hydrocarbon Ratio, hydrocarbon gas density index, hydrocarbon gas humidity index, the above seven parameters participate in the model establishment; ②Using the SVM algorithm for volcanic fluid prediction, the reservoir fluid is divided into three types: oil layer, oil-water layer and water layer. Sensitive parameters of well logging and mud logging are selected, and a reliable sample library is trained. The correct judgment rate of the prediction library reaches 90 %. The prediction application of SVM algorithm shows that it has low calculation complexity and strong generalization ability, which can quickly identify the fluid properties of volcanic rocks and provide a reliable basis for the analysis of oil and gas accumulation rules and the production and development of geological reserves.

How to accurately evaluate the current reservoir potential directly affects the potential tapping of remaining oil by water injection in complex fault block reservoirs during the middle and late stages of development. By the comprehensive analysis of static reservoir geological characteristics and dynamic development effects, the main control factors of residual oil distribution in complex fault block reservoirs are determined, and the reservoir potential is evaluated by the analytic hierarchy process combined with unascertained measure evaluation method based on unascertained mathematical theory and attribute measurement theory. An accurate unascertained measure function is established by building an evaluation index system, and by the confidence degree identification criteria to determine the evaluation space, the evaluation result of reservoir potential is finally obtained. The research results show that the reservoir potential is comprehensively evaluated by using the analytic hierarchy process and unascertained measurement, the evaluation system consisting of seven parameters is established and the unascertained measurement function is constructed. According to the reservoir potential, the reservoirs can be divided into four categories, of which category Ⅰ and category Ⅱ have good potential. The evaluation results are similar to the numerical simulation results, and the reliability of the evaluation results is verified by the on-site implementation.

There are many oil layers in the vertical direction of complex fault block reservoirs. The development area of oil sand bodies on the plane is small, and the plane heterogeneity is strong. It is difficult to construct a regular well pattern for uniform displacement. At the same time, due to the influence of various closed boundaries of reservoirs, bypassed oil area is easy to form in the process of water flooding. In order to calculate the control degree of water drive reserves more accurately, evaluate the rationality and integrity of reservoir well pattern better, and find the way to adjust the well pattern, a more suitable new method, namely grid reserve method, is proposed for the shortcomings of traditional methods. By improving the division accuracy of the reserve control area in the well pattern on the plane, combining the geological conditions and the heterogeneity difference of the reservoir, and taking the injection-production well group as the basic unit, the geological reserves are controlled by the well pattern gridded layer by layer. The grid geological reserves are classified and counted, and those bypassed oil areas are found out, and then the control degree of the injection-production well pattern and the control degree of the water drive reserves are calculated. Finally, the potential of well pattern adjustment and encryption is obtained. This method is applied to the adaptability evaluation of the well pattern in Nanpu-101 fault block, and the uncontrolled and unused area of well pattern caused by complex boundary is found. After well pattern infilling, better potential tapping effect is show in this area. It is proved that this method has good adaptability in the evaluation of water drive reserves control degree in complex fault block reservoirs, and can be extended to other complex fault block reservoirs.

The 3D reservoir modeling technology based on seismic inversion constraints effectively combines seismic data and logging data, which not only reflects the high vertical resolution of logging data, but also considers the lateral variation characteristics of reservoirs reflected by inversion data. It is currently the mainstream method of reservoir analysis. However, in the traditional combination of seismic data and logging data, the weight of the constraints on the final lithofacies is difficult to control. And the traditional full independence or conditional independence hypotheses lead to seismic data and logging data combination algorithms are rough, they may result in inconsistencies such as probability values greater than 1 if the each conditional probabilities are valued independently one from another. An alternative combination algorithm, model τ, is proposed which is not only simple, but also can ensure consistency of results in the presence of complex data interdependencies. At the same time, the algorithm is applied to the lithofacies modeling of D oilfield in Niger, and the average error of sand body probability is reduced by 30 %, which effectively improves the prediction accuracy of the sand body.

There are many kinds of faults in ribbon-shaped composite reservoirs, which affects the change of bottom hole pressure. The location of faults and wells make it more difficult to establish and solve the model of well test analysis. Therefore, it is urgent to establish a well testing analysis model with partially permeable faults and in any location of wells in ribbon-shaped reservoir. Based on the partial permeability of the fault and considering the properties of the fluid and the composite reservoir, the physical model and the mathematical model of the ribbon-shaped composite fault and reservoir are established respectively. And then, the Laplace space solution considering partial permeability fault is obtained by Fourier transform and Laplace transform. The pressure and pressure derivative curves are drawn. The characteristics and sensitivity of the typical curves and the influence of well location on the typical curves of well testing are analyzed. And the importance of considering the partial permeable of the faults and well location is fully explained. It is of great significance to the research on well test interpretation method for ribbon-shaped composite reservoirs with partially permeable faults.

There is a lack of uniformity and standardization of the existing optimal injection allocation method. Therefore, three key parameters involved in the optimization of water injection well allocation, which are longitudinal splitting coefficient, plane splitting coefficient and injection-production ratio, are taking as the breakthrough point. And then, the research on the allocation optimization of injection wells by the scholars at home and abroad is summarized. Finally, the calculation method of injection well allocation suitable for different occasions is obtained. On this basis, a new idea of optimizing injection allocation for water injection wells is proposed with the oil production wells as the center. This new idea emphasizes that for the optimal injection allocation of the water injection wells, the optimal injection parameter calculation method should be selected according to different geological reservoir characteristics, oilfield development stages, injection accuracy and other factors, so that to make the oilfield optimized water injection effect best. After this method is applied to the field test, a good development effect is achieved with a daily oil increase of up to 10 %（daily oil increase of 20 m³） in the block. In general, the optimization of water injection direction in the future must be the integration of reservoir and oil production engineering with the water injection scheme design, intelligent optimization and synchronous adjustment are the core based on artificial intelligence. The proposed optimized injection well allocation method has guiding significance for the water injection work of different types of oilfields at different stages of development.

In order to improve the understanding of the fractional rate law of injection and production ends in each structural unit of intraformational heterogeneous reservoir, aiming at the multi section and multi rhythm characteristics of thick oil layer in Lamadian Oilfield, Daqing, a model of intraformational heterogeneous reservoir is constructed by the “separate injection and separate production” core, and the effects of permeability gradient and injection speed on the fractional rate change law of water flooding are studied by physical simulation experiment. The results show that when water flooding reaches 0.4 PV, there is an inflection point in the flow rate curve. At the injection end, before 0.4 PV the injected water mainly enters into the high permeability layer, and after 0.4 PV, the liquid absorption of the middle and low permeability layer increases. For the positive rhythm reservoir, with the increase of permeability gradient, the swept volume of medium low permeability layer decreases and the recovery factor decreases; With the increase of the average permeability, the swept volume of the low and medium permeability layer increases, and the water flooding recovery increases. For the compound rhythm reservoir, the positive and negative compound rhythm is greater than the negative compound rhythm. When the injection rate is 0.6 mL/min at the injection end of heterogeneous core, with the increase of number of pore volumes（PV）, the fractional flow rate of high permeability layer increases, while that of low permeability layer decreases. When the injection rate is 0.9 mL/min and 1.2 mL/min, with the increase of number of pore volumes（PV）, the fractional flow rate of high permeability layer increases first and then decreases, while that of low permeability layer decreases first and then increases. With the increase of injection rate, the recovery rate and its percentage in the total recovery rate of low and medium permeability layers increase gradually. The research results have a certain guiding significance for the understanding of the mechanism of the split ratio at both ends of the injection and production in the deep heterogeneous reservoir.

The shale gas wells in Dongsheng Block of Sichuan Basin are in deep reservoirs with the maximum depth of 4 300 m, with high stratum temperature up to 140 ℃ and of high mass concentration of calcium and magnesium ions up to 2.8×10^-3 kg/L. All these characteristics result in the low flowback fluid volume and poor effect of foaming agent. In order to solve these problems, the fatty alcohol polyoxyethylene lauryl ether sulfate sodium（AES）, fluorohexyl ethanol polyoxyethylene ether（FT）, modified silicone oil resin polyether（FM） and metal-chelator（EDTA-2Na） are adopted as the raw materials to prepare a high temperature foaming agent in anionic-nonionic system namely HDHP. According to the orthogonal experimental design, the effects of different ratio of AES, FT and FM on the foaming ability and foaming stability are studied, and the optimum addition are determined. The comprehensive performance of HDHP evaluated in the laboratory shows a good effect of temperature and calcium and magnesium ions resistance. In the test of three wells in Dongsheng Block, the average gas production per well has increased by 30 %. The results show that HDHP is suitable for the foam drainage technology of ultra-deep shale gas wells in Dongsheng Block, and has good popularization and application value.

Nanpu Oilfield is located in the tidal sea with limited oil well spacing, and the overall development is dominated by highly oblique directional wells. Due to the characteristics of reservoir formation, the fault blocks are developed and broken, and the transverse area is small, the longitudinal layer distribution is large, and there are many oil wells with insufficient liquid supply in the low energy area. The conventional pump running depth is difficult to meet the supply and drainage requirements of continuous production, resulting in low efficiency of a single well. At the same time, the dissatisfaction of the pump barrel aggravates the complexity and eccentric wear degree of the down-hole rod stress. Based on the comprehensive evaluation of the rod, pipe and pump of the pumping unit system, the technical countermeasures of deep pumping are put forward. And the stimulation potential of deep pumping amplified pressure difference is predicted by the reservoir pressure and production parameters. The stress calculation after multi-stage rod deepening and the extension of production cycle are studied. After the simulation of the stress change of the rod column after deep pumping by the software, the stress test and theoretical calculation of the rod column at different depths after deep pumping are compared, and the related supporting technology is optimized to ensure the stress safety of the rod column after deep pumping. After deep pumping, the oil well dynamic fluid level decreased and the productivity increased. The increase of subduction reduced the filling dissatisfaction of the pump barrel. The setting depth of the pump is deepened averagely by 800 meters and can reach a depth of 3 300 meters. The production pressure difference, the pump efficiency, and the single well oil increment increase by 6 MPa, ten percentage points and 300 tons respectively on average. At the same time, the effect analysis and experience summary are carried out for oil wells with different reservoir properties and different liquid supply capacity, and the feasibility evaluation method of deep pumping in different oil wells is formed.

For low production and low efficiency wells, interval production is usually used to tap potential. However, most practices are based on qualitative and benefit factors to determine interval production parameters, which are lack of scientific accuracy. In order to optimize and study the interval production parameters more precisely and quantitatively, combining the theoretical basis of material balance, inflow and outflow dynamics and other parameters such as well deviation and reservoir physical properties are taken into account, the mathematical model of fluid level coupling in the switch well for interval oil production is established. The coupling model calculation results are innovatively matched with the measured dynamic level recovery curve to obtain the reservoir physical parameters. On the basis of the above, the dynamic liquid level during shut in and pumping is divided into equal parts by enumeration method, the reasonable working parameters are determined by optimizing and evaluating the wellhead production, pump efficiency and formation inflow. The field application verification shows that: fitting the numerical iteration results of the coupled mathematical model with the measured liquid level recovery curve, it can more scientifically determine the interval production parameters. At the same time, it also ensures that the oil wells are in an efficient and coordinated supply and discharge relationship.

The synergistic effect of SiO₂ nanoparticles （SNP） and surfactants can provide a new idea for the preparation of foam fracturing fluid suiTable for harsh formation conditions. In order to prove it, the synergistic foam stabilization ability of SNP and five types of surfactants is evaluated, and the optimal foams system is selected based on the foams comprehensive value. The proppant carrying ability, rheology, and stability of the selected foam fracturing fluid system are evaluated, and the performance improvement of the fracturing fluid by SNP is analyzed. At the same time, the optical microscope observation and SEM experiment are used to reveal the foam stabilization mechanism of SNP. The system screening experiments show that the synergistic effect of TTAB and SNP is the most obvious. The comprehensive foam value reaches 15 288 mm·s, and the half-time of water drainage increases by 145 %. The performance evaluation experiments show that SNP can improve the elastic modulus of the interfacial liquid film, improve the proppant supporting capacity of the liquid film, reduce the settling velocity of proppant which help foam fracturing fluid bring proppants into deeper fractures. SNP can also improve the surface roughness of liquid film and thus enhance the shear resistance of foam fracturing fluid. Adding proppants to the system can weaken the stability of foam. The weakening effect of ceramsite is stronger than that of quartz sand, and the weakening effect of high mesh size is stronger than that of low mesh size. The stabilization mechanism study is revealed by the SNP aggregation at Plateau is observed in the foam microstructure which can block the drainage channels. Moreover, SNP could prevent the coarsening and drainage of foam. By the macroscopic observation, SNP-stabilized bubbles are more stable in term of more bubble number, smaller bubble size and more uniform bubble size distribution.