During the process of drilling, well completion and production, the effective stress changes, the pore structure of tight sandstone is complex, and the micro-fracture is developed. When the effective stress increases, the micro-fracture will close, and the pores volume will decrease, which make a difference in the propagation characteristics of sound waves in tight sandstone. The researches on the characteristics of acoustic wave propagation under variable effective stress are significant for the prediction of formation pressure of tight sandstone and the cognition of response characteristics of dynamic mechanical parameters of rock. Taking the typical tight sandstone of upper Paleozoic Permian in Ordos basin as the research object, velocity of P-wave and S-wave and permeability of dry rock samples with the increasingly effective stress were measured. It was proved that when the effective stress（between 0 ~ 15 MPa） was lower than the critical value, the tight sandstone was mainly characterized by the closure of micro-fractures, and there was an exponential relation between effective stress and velocity of P-wave and S-wave respectively; when the effective stress（between 15 ~ 50 MPa） was higher than the critical value, the deformation characteristics of rock gradually transited from linear elastic stage to plastic deformation stage, the interlayer dislocation occured in tight sandstone, the pores volume decreased, and the velocity of P-wave and S-wave changed with the effective stress in a liner relation. Meanwhile, the response of permeability and wave velocity on effective stress matched with each other. When it was below the critical value, it went down exponentially with the effective stress.

Gas logging of multiple wells at the top of Leikoupo formation in Puguang area is better. The laboratory analysis shows that high quality source rocks are developed in Xiaotangzi formation of the overlying strata. Therefore, as an important hydrocarbon source layer and caprock, the mudstone distribution prediction of Xiaotangzi formation is of great significance to the top weathered crust reservoir of Leikoupo formation in Puguang area. On the basis of defining the petrophysical characteristics and logging response characteristics of mudstone in Xiaotangzi formation, the fine well-seismic calibration, geological modeling and forward modeling of mudstone were carried out by using the drilling and 3D seismic data, and the seismic reflection characteristics of mudstone in Xiaotangzi formation were clarified. Finally, combined with paleogeomorphology analysis, attribute analysis and other means, the favorable facies belt of mudstone development was determined. On this basis, the thickness of mudstone was quantitatively predicted by sparse pulse inversion, a set of seismic prediction method suitable for mudstone of Xiaotangzi formation in Puguang area was established, and the distribution of Upper Triassic was predicted. Then the comparison of mudstone thickness with that of completed drilling confirmed the reliability of the prediction results.

In order to explore the effect of fractures on oil displacement in low permeability reservoirs, the oil displacement effect of fractured reservoirs in different water cut stages was studied by a series experiments on glass model micro-oil displacement, micro core dissection and natural core oil displacement, and then the utilization status of various remaining oil under the action of fractures was obtained. The results showed that the saturation of cluster residual oil decreased with the increase of water cut, while the saturation of film, blind end, droplet and column residual oil increased. The residual oil saturation of the fractured models were higher than that of the non-fractured ones, the displacement fluid was channeling in the fractures, and the swept volume was reduced. When the model permeability increased, the cluster residual oil saturation increased, but the other types of residual saturation decreased. The distribution and variation rules of residual oil in micro core dissection experiments were generally consistent with that of the photolithographic glass model, thus proving the reliability of the photolithographic glass model. Seen from the core water flooding experiment, the water flooding law curve of low permeability core was an “S” curve. Water breaks through earlier in the fractured cores than that in the non-fracture ones. And the larger the permeability ratio of fracture to matrix（k_f /k_m） was, the smaller the anhydrous recovery would be.

Water flooding is one of the most economical and effective measures for the sustainable and stable production of oil field and EOR（enhance oil recovery）. However, formation scaling is inevitable in the process of long-term water flooding, which seriously affects and restricts the effect of oil field development. Taking injection-production unit as the research object, based on thermodynamic theory and solubility product rule, and considering the influence of formation temperature, pressure, scaling ion concentration and flow rate, the numerical models of formation scaling in injection-production unit was established, including pressure field model, temperature field model, porosity and permeability distribution model and formation scaling model. Meanwhile, according to the actual production data of oil field, mathematical simulation software—MATLAB—was used to carry out the case to analyze the influence of each factor on the total scaling amount, scaling range, distribution of scaling quantity and formation scaling on apparent water absorption index and permeability in injection-production unit. The results showed that the temperature of the immediate vicinity of the injection wells was low, the dissolution equilibrium constant was small and the flow rate was high, so that scaling was difficult. When in radial outward direction, the formation temperature increased, and the flow rate decreased greatly, which made it the most easy condition for scaling. Continue outward, when the scaling ion concentration was lower than the minimum scaling concentration, scale would no longer form.

Polymer flooding is one of the important means in enhancing oil recovery. Based on the physical process of polymer flooding, the well test model of three parts composite reservoir composed of Newtonian fluid/non-Newtonian power-law fluid/Newtonian fluid was established. The Laplace transform was used to obtain the analytical solution. The analytical solution of Laplace space was inverted to the real space by using Stehfest numerical inversion algorithm, and the double logarithmic theoretical curves of well test analysis describing the seepage characteristics of polymer flooding process were obtained. According to the characteristic of the derivative curve, four typical flow stages can be identified: the pure well bore effect stage, radial flow stage of inner part, polymer part and outer part. In the radial flow stage of inner part, the double logarithmic curves of the pressure derivative is a horizontal line with the value of 0.5. The larger the radius is, the longer the horizontal line will be. In radial flow stage of polymer part, the double logarithmic curves of the pressure derivative is a line with the slope of （1-n）/（3-n）. The smaller the power law index is, the greater the slope of the derivative curve will be. In the radial flow stage of outer part, the double logarithmic curves of the pressure derivative is a horizontal line with the value of 0.5M₁₃. The model can be used to analyse the effect of polymer flooding and guide the effective interpretation of well test data in polymer flooding reservoirs.

The study on the effective control time range of polymer flooding and its influencing factors is conducive to the further development of oil recovery measures after polymer flooding. Based on the theory of characteristic curve of water flooding reservoir and the mobility controlling mechanism of polymer flooding, a judgment method was established, and the influencing factors were analyzed through the indoor flooding experiments. The results showed that there were some differences in the water flooding characteristic curves before and after polymer flooding. With the follow-up process of water flooding, its rule would gradually return to the original rule before polymer flooding. It was feasible to judge the effective mobility control range of polymer flooding by the consistency of the characteristic curve of water flooding before and after polymer flooding. The effect of increasing the viscosity of polymer solution on its mobility control time was relatively small, only 10 ^-2 order of magnitude of PV injection. Increasing the residual resistance factor（RRF） could significantly prolong the effective mobility control time of polymer flooding, and reached 10 ^-1 order of magnitude of PV injection. The residual resistance coefficient of polymer is the main factor affecting the effective mobility control time.

In order to identify the effect of ultra-fine transition metal catalyst on the in-situ combustion of heavy oil, thermal analysis and isoconversional method were used to evaluate the burning oxidation kinetics of three ultra-fine transition metal particles—NiO, α·Fe₂O₃ and Co₃O₄. And then, one-dimensional in-situ combustion experiment was carried out by the optimized catalyst. The experimental results showed that, in the presence of Co₃O₄, the activation energy of heavy oil decreased the most, up to 41.7 %. Meanwhile, Co₃O₄ had higher catalytic activity, that made it suitable for in-situ combustion experiment. Compared to conventional in-situ combustion, high temperature oxidation reaction of crude oil was enhanced under the catalytic condition of Co₃O₄. The oxygen utilization ratio increased by 6.79 %, the combustion time shortened by 11.8 %, the average temperature of the leading edge of combustion increased by 20 ℃, the maximum temperature difference of the leading edge of combustion reduced by 4 ℃, the combustion was more stable, the advance speed of the leading edge increased by 0.042 cm/min, the final oil displacement efficiency increased by 5.7 %, and the viscosity reduction rate of the produced oil increased by 7.2 %. The research results have important guiding significance for expanding the application of heavy oil recovery by in-situ combustion.

The static isothermal oxidation tube experiments were carried out for heavy crude oil in J block of Xinjiang Oilfield. The effects of temperature, pressure, quartz sand and detritus on the low temperature oxidation（LTO） characteristics of heavy crude oil were investigated by analyzing the alterations in the produced gas and SARA（saturate, aromatic, resin and asphaltene） fractions of oxidized oil. The results showed that the awerage oxygen consumption rate of the crude oil was increased by 1.42 % per day at 110 ℃ relative to that at 70 ℃. When the pressure was increased from 10 MPa to 30 MPa, the production of CO+CO₂ was increased by 2.13 %. Both quartz sand and detritus promoted oxidation reaction on the heavy oil. The oxygen consumption increased by 1.71 % and 4.08 % after the addition of quartz sand and detritus relative to the crude oil. The promotion of detritus on LTO reactions of heavy crude oil mainly derived from the catalytic effect of detritus. The oxidation behavior of the crude oil was studied by the TG-DSC, and the activation energy was calculated by Arrhenius kinetic model. The results indicated that heavy crude oil had poor reactivity in the LTO stage, and the activation energy in the LTO region was only 18.09 kJ/mol, which was much lower than that in the fuel deposition and high temperature oxidation stages（84.58 kJ/mol and 113.39 kJ/mol）.

Currently, the well control in the drilling engineering design of onshore oil and gas wells mainly includes wellhead device, pressure test and well control requirements in conventional operation, and does not involve the calculation of the overflow quantity of shut-in. In this paper, kick tolerance is considered to be added to the design above, and a calculation method of kick tolerance is given. Combined with the drilling condition of ? 311.1 mm hole of well LJ-20 in gas field A in the Sichuan-Chongqing area, examples were applied to analyze how to add kick tolerance and assist the well control of overflow in drilling site. The calculation results showed that, with the given KI value, the deeper the hole was, the smaller the kick tolerance would be; while at the same depth, the kick tolerance also decreased with the increase of the KI value. Therefore, it is necessary to add the kick tolerance to the design. Thus, whether the shut-in operation with overflow is safe or not can be effectively judged. At the same time, further considering should be given to how to obtain the dynamic kick tolerance of shut-in which is more applicable in the field, so as to assist in safe drilling in the deep formations where pressure is difficult to be predicted accurately.

The morphology and rheological properties of polymer microspheres PM1 were evaluated by optical microscope and rheometer. The effects of injection rate and concentration of microsphere system on the migration and plugging properties in porous media as well as the profile control ability of polymer microspheres to heterogeneous formation were investigated respectively by single core and parallel cores flooding experiments. The results showed that the microspheres had a high degree of sphericity with micro scale and its apparent viscosity was close to water at a relative high shear rate. The plugging ability of microspheres to pore throats increased with the decrease of seepage velocity or the increase of mass concentration. The microspheres had strong profile control ability to heterogeneous formation. If the measures that relative water absorption of low permeable core after profile control and oil displacement was greater than or equal to 35 % could be deemed to be appropriate, the upper limit of the permeability contrast, corresponding to which the microspheres could effectively improve the reservoir heterogeneity, would be about 20. For some strongly heterogeneous reservoirs existing fractures or large pores, the combined technique of profile control and flooding about alternating slugs of large-scale and micro-scale microspheres could be considered preferentially.

The production mode adopted by Dongsheng gas field is “downhole throttling and low pressure gathering and transportation”. In order to meet the production needs, some gas wells need wellhead throttling to control production. However, wellhead throttling is easy to generate hydrate on the ground. So it is necessary to increase the wellbore and surface fluid temperature before throttling. Therefore, downhole vacuum insulated tubing test was carried out in the target block of Dongsheng gas field. According to the test results, the data fitting was carried out by using the software—Pipesim—to verify the application effect of insulated tubing in gas field, and its application situation is predicted and analyzed. The test results showed that, the vacuum insulated tubing could obviously increase the fluid temperature of the wellhead, and prevent the hydrate formation in wellhead pipeline, so that to realize energy saving and consumption reduction to some extent. The fitting results of the field data also showed that the heat transfer coefficient of downhole vacuum insulated tubing was significantly lower than that of the common tubing. According to the application analysis, and considering the cost and the characteristics of low pressure gathering and transportation, it is concluded that there are certain limitations in the application of this technology in the low-pressure gas field. But it could be used as an alternative process of gas field if the wellhead throttling production must be adopted.

The shale exploration potential of Wufeng-Longmaxi formation in Dingshan area of southeastern Sichuan is huge, and it is important to clarify the characteristics of shale reservoirs and their controlling factors. Through the “X” diffraction and Maps microscopic scanning of the whole rock, the shale mineral composition and microscopic pore structure were analyzed, and the shale mineral composition, reservoir space type, porosity, permeability and its controlling factors were studied. Then the sedimentary environment and tectonic movements was used to analyze reservoir development control factors. The results showed that the shale reservoirs in the Dingshan area were characterized by high organic matter and high brittle mineral content. The pore diameter development range was between 10 nm and 100 nm. The physical parameters such as porosity and permeability of different intervals were different. The porosity and permeability of the small layer 6~9 in lower part were high, and the permeability of cracks and phylogenetic development steeply increased. Reservoir development was affected by both sedimentary and tectonic movements. The sedimentary environment was the basis for the formation of shale reservoirs. Together with the burial evolution, the development of the primary reservoir space was determined. The later tectonic movements transformed the composition and structure of the reservoir space. On one hand, the micro fractures increased the reservoir space and seepage capacity, and on the other hand, the overdeveloped cracks destroyed the effectiveness of the reservoir.

The effective prediction of high production areas of CBM is of great significance to improve the production and the development benefits of single wells. In order to the evaluate the production capacity of CBM formation quantitatively, based on the development mechanism of CBM, the data of CBM in southern Qinshui Basin was used to define the absorption efficiency index and the gas production capacity index through the theory and statistical analysis. And the reliability of gas production capacity was quantitatively evaluated from 3 aspects of gas content ability, desorption efficiency and output capacity of the reservoir. The results showed that, in the evaluation of gas content, to remove gas saturation and increase the differential pressure of formation pressure and desorption pressure—which represented the macroscopic desorption efficiency—in the desorption efficiency index can greatly improve the correlation between daily gas production and gas content, desorption efficiency index respectively. The daily gas production increased with the increasing of gas bearing index, desorption efficiency index and the production capacity index. When the gas content, the desorption efficiency index and the permeability were respectively higher than 15 m ³/t, 0.11 （MPa·d） ^-1 and 0.03×10 ^-3μm ², the daily gas production could be more than 800 m ³. When the gas content, desorption efficiency index and production capacity index were defined as the gas production capacity index of CBM, high production areas of CBM could be effectively predicted. When the gas production capacity index was great than 0.05×10 ^-3μm ²·m ³·（t·d·MPa） ^-1, the daily gas production was more than 800 m ³, while the index was greater than 1×10 ^-3μm ²·m ³·（t·d·MPa） ^-1, the daily gas production was more than 1 500 m ³.

In order to study the simulation effects of different isothermal adsorption models on isothermal adsorption experiments and better describe the adsorption rule of shale methane, isothermal adsorption experiments were carried out on seven core samples from well PY1 in southeast of Sichuan Basin. The experimental results showed that the maximum excess adsorption amount was positively correlated with the organic matter content, and the maximum correlation coefficient was 0.859 4, while it was negatively correlated with clay minerals. The experimental results were simulated by different models. The simulation results of different models were quite different. Among them, the correlation coefficient fitted by the Langmuir model was the best, while the maximum excess adsorption amount obtained by the SDR model was the largest. Followed by that was the fixed Langmuir model. Both the SDR model and the modified Langmuir model had corrected the excess adsorption amount of the experimental results, but from the correction results, the adsorption phase density obtained by the SDR model was the most reasonable. Finally, the fixed density correction Langmuir model and the SDR model were considered to describe the adsorption of methane in the shale more accurately, which could guide the calculation of the shale adsorption gas content better.

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.

Although the traditional surface process of shale gas field can effectively solve the problem of hydrate blockage, there are still many other problems such as safety production and green economy development existing in gas fields. The downhole throttlingtechnology can simplify the ground flow, lower the cost of investment, reduce the risk of gas test on the ground, and ensure on-site safety. However, due to the influence of geological conditions and the production rule of gas and liquid, it has not been applied in shale gas fields at home and abroad. By analyzing the applicable conditions of downhole throttling technology in high-pressure shale gas wells in south block of Pingqiao area, and comparing changes of gas volume and pressure before and after the application of this technology for single well, and the downhole depth, aperture and downflow time of downhole throttling were clarified. The results proved that this technology could not only effectively avoid the formation of hydrates in the high-pressure shale gas wells in south block of Pingqiao area, but also significantly reduce the pressure of the wellhead and the ground pipeline, simplify the ground flow, and have significant economic value and good application prospects.