Abstract:The dolomitic barriers and baffles with different degrees of dolomitization are developed in marine clastic reservoirs，which will influence the water/oil/gas system identification and also seriously affect the further enhancement of oil recovery. The identification，formation mechanism analysis and distribution characterization of dolomitic barriers and baffles are important for the efficient development of the marine clastic reservoirs and can shed light on the mechanism of dolomitization. Typical clastic reservoir Upper Kirkuk（UK）Formation in the Middle East is taken as an example. Logging，core analysis，and dynamic production data are adopted to systematically study the classification，identification，formation mechanism，and distribution characteristics of the dolomitic barriers and baffles in the marine clastic reservoirs.The research results are as follows. ①Except for the pure sand and mudstones in the marine clastic reservoirs，the lithology of dolomitic barriers and baffles is dolomite bearing sandstones，dolomitic sandstones，sandy dolomites，and sand bearing dolomites. The dolomitic sandstones and sand bearing dolomites are the main lithology. ②The qualitative and quantitative criteria were made to identify different degrees of dolomitization. With the increase in the degree of dolomitization，the core appears to gradually brighten under normal light. The gamma，density，and resistivity values increase with the degree of dolomitization. ③The original underground magnesium-rich brine and mudstone compaction waters are the main ion sources. Pure sands with good physical properties and unconformities are main fluid migration channels.The difference in the physical properties of the reservoir leads to that in the contact time between the pore fluid and the particles（water-rock contact reaction），which ultimately results in different degrees of dolomitization. ④The distribution of dolomitic barriers and baffles is characterized in different levels. At the macro-level，the dolomitic barriers and baffles tend to occur in the middle period of sea level rising or descending semi-cycle. While at the meso-level，the dolomitic barriers and baffles are more likely to occur in the top and edge of channel and the bottom of the mouth bar with poor physical properties. When it comes to the micro-level，the dolomitic barriers and baffles tend to occur in areas where pore throats are poorly connected.

Abstract:The characteristics and thermal evolution history of source rocks in the study area are clarified based on the pyrolysis analysis data of source rocks and PetroMod basin simulation technology. The hydrocarbon generation and expulsion modes are constructed by the hydrocarbon generation potential method to analyze the hydrocarbon generation and expulsion history and intensity. As a result，the influence of thermal evolution and hydrocarbon generation and expulsion of source rocks on oil and gas migration，accumulation，and distribution is revealed in the 3 ^rd Member of Eocene Shahejie Formation（Es₃）in Qikou Sag. The results show that the source rocks in the study area are generally in mature to highly mature evolution stages. The source rocks enter the hydrocarbon generation and expulsion threshold respectively when the vitrinite reflectance is about 0.53% and 0.83%. The hydrocarbon expulsion rate is 250 mg/g and the hydrocarbon expulsion efficiency is 65%. Hydrocarbon generation began briefly at the end of the late Eocene and stopped due to tectonic uplift in the early Oligocene. Hydrocarbon expulsion began in the middle Oligocene and reached the peak of hydrocarbon generation and expulsion at the end of the middle Oligocene. The consequent hydrocarbon generation and expulsion stopped again due to the tectonic movement at the end of the late Oligocene，and the whole hydrocarbon generation and expulsion process is basically consistent with the thermal evolution stage of source rocks. The hydrocarbon expulsion center is distributed along the periphery of Qibei Subsag to Qikou main sag，and the hydrocarbon expulsion intensity is up to 90×10⁶t/km² with strong hydrocarbon expulsion characteristics. The extensive hydrocarbon generation and expulsion distribution characteristics provide rich oil and gas sources and migration power for the adjacent uplift and slope of Qikou Sag. Additionally，the hydrocarbon has the characteristics of near source reservoir formation and long-distance lateral migration reservoir formation.

Abstract:A major breakthrough in oil and gas exploration has been made in the Lower Submember of Member 4 of Shahejie Formation（Es₄^x）in the Minfeng area，Dongying Sag. However，the systematic research on the hydrocarbon generation potential，biomarker characteristics of source rock，and their environmental significance，as well as the impact of gypsum-salt rock on the maturity of the source rock is insufficient. According to the experimental results of rock organic carbon，pyrolysis，identification of kerogen macerals，and chromatography-mass spectrometry of saturated hydrocarbon，as well as the geological conditions，the Es₄^x source rocks are systematically evaluated. The research results show that：①The organic matters of source rock are mainly sapropel-type I and II1 kerogen with excellent hydrocarbon-generating parent materials. The inter-salt and inter-fan mud rocks could both generate hydrocarbon and are medium or excellent source rocks，which thus could be considered as a potential shale oil and gas development area；TOC log evaluation models of different lithology are established by multiple regression analysis，and the predicted values are consistent with the measured values. ②The upper source rocks have higher C₂₇ diasterane/C₂₇regular sterane and regular sterane/17α-hopane than the lower ones and are mainly inter-salt mud rock in a strong reduction environments with salt water. The lower source rocks are mostly inter-fan mud rocks in a reduction environments with brackish water. The above two kinds of source rocks are bounded by a vertical depth of 4 180-4 200 m and are well developed near paleogullies. ③The source rocks are mature or highly mature. The upper and lower source rocks are bounded by a vitrinite reflectance of 1.0%. The upper source rocks mainly generate oil，while the lower ones are favorable for gas generation through splitting decomposition；the geothermal gradient and vitrinite reflectance of source rock above gypsum-salt rock（mainly glutenite reservoirs）are greater than those under or without gypsum-salt rock.

Abstract:Archean granite gneiss reservoirs are complex in lithology and rich in mineral types，with a large burial depth and high reservoir temperature，and high temperature has a significant impact on rock pore structure and flow characteristics.This paper used samples of Archean granite gneiss outcrops for experiments to evaluate the temperature sensitivity of permeability and the stress sensitivity under different temperatures and explore the response characteristics of permeability to temperature and effective stress. The results reveal that for the samples of granite gneiss blocks with permeability ranging from 0.1 mD to 1 mD，the permeability under the room temperature of 20 ℃ and the effective stress of 20 MPa is 1.66-2.04 times higher than that under the reservoir temperature of 170 ℃ and the effective stress of 20 MPa，and the permeability declines exponentially with the rise in temperature. Under nitrogen flooding conditions，the stress sensitivity of granite gneiss reservoirs at 20 ℃ is moderately strong，and the stress sensitivity at 100 ℃ and 170 ℃ is moderately weak，which tends to weaken with the increase in temperature. A moderate temperature within 200 ℃ is beneficial to improve rock strength and weakens the stress sensitivity of rock.

Abstract:Given the related concepts and classification of geophysical logging stratigraphic division，this paper divided automatic stratification methods of logging curves into traditional methods and artificial intelligence methods and analyzed the application of artificial intelligence technology in logging stratigraphic division from the aspects of supervised and unsupervised learning. Then，it comprehensively compared the advantages and disadvantages of various automatic stratigraphic division methods. Finally，by exploring the development of related fields，this study considered the challenges and solutions in the future development of logging stratigraphic division from different perspectives. The specific solutions are as follows：①Semi-supervised learning can be introduced to solve the problem of scarce manual labels. ②A new understanding of logging data can be obtained from the perspective of the segmentation model. ③Methods such as logging curve reconstruction can be employed to solve the problem of data heterogeneity caused by the distortion or missing of well sections. ④The problem of data deviation caused by manual label errors can be resolved through sample weighting. ⑤Transfer learning can be used to solve the problem of data distribution differences in different regions.Artificial intelligence technology can provide vital support for solving existing problems in stratigraphic division，lithology identification，reservoir identification，as well as operation and production，and promoting the digital transformation of tasks related with logging.

Abstract:The research on the evolution of gravity flow deposits in the Scotia Basin in eastern Canada is insufficient.Therefore，according to the data of core samples，logging，seismic，and magnetic anomaly，the Lower Cretaceous gravity flow deposit units in the Sable Subbasin of the Scotia Basin are defined，and the evolution of deposits and development control factors are revealed and discussed. The results show that the Lower Cretaceous Mississauga Formation （MF）and Logan Canyon Formation（LF）in the Sable Subbasin of the Scotia Basin develop large-scale gravity flow deposits，and deposit units including mass transport deposits（MTDs），gravity flow channels，natural levees，and lobes are identified. The small-scale gravity flow deposits develop in the west of the study area at the early deposit stage of MF（147 Ma before present），and the large-scale slope bottom fans develop in the middle of the study area at the late stage of MF（130 Ma before present）. The small-scale gravity flow deposits commonly develop in the study area at the early deposit stage of LF（113 Ma before present），and the large-scale slope bottom fans develop in the southeast of the study area at the late deposit stage of LF（101 Ma before present）. The shelf-edge deltas and steep continental slopes provide the material foundation and dynamic conditions for the development of gravity flow respectively.

Abstract:Vuggs，caves and fractures are developed in the Ordovician reservoirs in Halahatang Oilfield，and these complex oil and gas reservoirs are composed of the fracture-cavity units superimposed on each other with different pressure systems and oil-water relationships. These reservoirs are characterized by the coexistence of the multiple pressure systems，oil-water relationships，and development performances. As a result，the intricate oil-water relationship increases the difficulty of development and results in a low drilling success rate. At the same time，due to their particularity，these reservoirs have massive vented and lost sections. It is difficult to identify the original oil-water interface distribution and change law by traditional direct prediction or monitoring methods，and the reliability is low. In view of this，the static volume of the reservoir is calculated by the geological modeling method based on the reservoir’s uncertainties. The dynamic oil volume and water volume are respectively calculated by the reservoir production instability analysis method. When the volumes of dynamic and static reservoirs are the same，the original oil-water interface is gradually adjusted to ensure that oil and water volumes characterized by the static model are consistent with that by dynamic evaluation，so as to determine the original oil-water interface of the well. In addition，by applying the method not only in one well or certain areas but also in the whole region，the paper can comprehensively correct the oil-water interface position with information such as geological laws，as well as production and drilling tests. The new method provides new ideas for predicting the original oil-water interface of fracture-cavity reservoirs and reserving water avoidance height，and it lays a foundation for further adjusting development measures of the oilfield.Measures such as infilling well pattern，sidetracking and gas injection can be used to tap the potential.

Abstract:Benchmarking is a powerful measure to improve the fine management level of enterprises. To fulfill the mission of ensuring national energy security and promote the domestic upstream oil and gas companies to the world-class level，SINOPEC established a systematic and applicable benchmarking system for oil and gas exploration. The effort aims to discover some common problems and weak links that constrain oil and gas exploration，exploit resource potential，enhance core competitiveness，and achieve high-quality development. Focusing on the benchmarking process of oil and gas exploration，SINOPEC established a benchmarking method of oil and gas exploration with three classes，i. e.，the enterprise class，exploration field（play）class，and investment project class. Considering the characteristics of different classes，an index system for exploration benchmarking was constructed in terms of exploration and operation management as well as theory and technology. In particular，the relative quantity benchmarking index under the unit area of mineral rights or unit residual resources was built to eliminate the influence of differences in mineral rights.Accordingly，SINOPEC carried out 24 exploration benchmarking projects. On the basis of SINOPEC-CNPC cooperation，it mainly investigated the Ordovician exploration benchmarking between Shunbei Oilfield and Fuman Oilfield and the Shaximiao Formation exploration benchmarking between Zhongjiang Gas Field and Jinqiu Gas Field. Upon the summary of previous experience，a complete management support system of exploration benchmarking was built from the aspects of organization，system，and operation.In addition，some suggestions on exploration benchmarking were put forward，including improved construction of the benchmarking index system and benchmarking management system and greater cooperation among oil and gas companies.

Abstract:Low-permeability/tight sandstone reservoirs generally have a high starting pressure gradient，which will have a certain influence on the CO2 flooding development scheme design. The commonly used methods for testing the starting pressure gradient have the limitations of inaccurate test results or long test time. In order to improve the experimental efficiency and test accuracy，an experimental method for testing the water-phase starting pressure gradient of low-permeability/tight sandstone reservoirs was proposed. By the method for observing the timing of droplet emergence in the early stage and establishing a multi-stage stable displacement in the later stage，the minimum starting pressure gradient and the pseudo starting pressure gradient were measured simultaneously in a displacement experiment. This method has the advantages of a short test period，easy observation of experimental phenomena，and high test accuracy. The method was applied to test the core samples from an actual oilfield，and the test results of the minimum starting pressure，the minimum starting pressure gradient，and the pseudo starting pressure gradient were obtained. A prediction model for the minimum starting pressure gradient of the water phase was also established for the target area.

Abstract:Enhanced oil recovery by imbibition（IEOR）is the key technology to effectively develop tight reservoirs with“three lows”characteristics. The fracturing fluid interacts with the rock and fluid in the reservoirs to produce an imbibition effect in the stages of reservoir fracturing，flowback，and subsequent development. Studying the imbibition mechanisms of steady and unsteady fracturing fluid has important guiding significance for field development. Therefore，the concepts of steady and unsteady imbibition are first put forward in this paper. On the basis of simulating high-temperature and high-pressure environments，the differences in imbibition characteristics of fracturing fluid under different conditions are quantitatively characterized by combining nuclear magnetic resonance（NMR）technology with physical simulation experiments. The results show that the scales of the steady imbibition effects of fracturing fluid are 0.01–51.52ms，and those of the unsteady imbibition effects of fracturing fluid are 0.01–27.75 ms. In the early stage of imbibition，the imbibition rates of both kinds of imbibition are the fastest，and the imbibition effects preferentially appear in small pores（0.01–1.00 ms）. As the reaction continues，they appear in mesopores（1.00–10.00 ms）and then in macropores （>10.00 ms）. The unsteady imbibition efficiency is higher than the steady imbibition efficiency，but the unsteady imbibition tends to be stable earlier. Small pores are the main contributors to the imbibition efficiency of fracturing fluid，and tend to be stable at first，followed by mesopores and macropores. Although the imbibition efficiency of double media is better than that of single media as a whole，the imbibition stability time of each pore throat is relatively lagging. The unsteady imbibition efficiency is positively correlated with reservoir permeability and reservoir quality indicator. As permeability and reservoir quality improve，the contribution of mesopores to imbibition gradually increases，and the mesopores gradually replace dominant small pores and finally occupy a leading position.

Abstract:The building of flow surrogate models is the frontier of simulation technology research for oil and gas reservoirs.However，the currently widely used pure data-driven flow surrogate models have no theoretical support and require a high data volume and data quality，which greatly limits the development of flow surrogate models. Therefore，this paper proposes a flow surrogate model based on a data-driven and physics-driven method. On the basis of the pure data-driven flow surrogate model，it takes advantage of the flow theory to simulate and predict oil and gas flow processes. Firstly，the dual-driven flow surrogate model is compared with the pure data-driven model. The results show that the proposed model can still maintain high prediction accuracy even if the training data is extremely sparse. Secondly，the robustness of the dual-driven model is explored by adding different levels of noise interference to the training data，and it is verified that the proposed model outperforms the pure data-driven flow surrogate model. Finally，the trained dual-driven flow surrogate model is applied to a new flow field through transfer learning. The model can achieve rapid convergence and save computing resources.

Abstract:The random distribution of gravel makes conglomerate reservoirs highly heterogeneous，which significantly affects the local mechanical response and makes it difficult to control and predict the propagation of fractures caused by hydraulic fracturing. The propagation mechanism of fractures caused by hydraulic fracturing when encountering gravel remains unclear，which makes the design and effective implementation of hydraulic fracturing challenging. In this paper，based on the global cohesion element，a two-dimensional（2D）fracture propagation model with flow-stress-damage multi-field coupling is established on the Abaqus platform. The conglomerate rocks are regarded as a three-phase composite material composed of gravels，matrix，and cemented surfaces on a mesoscopic scale，and the propagation mechanism of fractures caused by hydraulic fracturing when encountering gravel is studied. The results show that fractures caused by hydraulic fracturing penetrate and bypass gravel in conglomerate reservoirs. The permeability and elastic modulus of gravel have different effects on the behavior of fractures encountering gravel. The low permeability of gravel causes the pressure holding，and the fluid pressures at the crack tips increase by 13%；the effective stresses in horizontal and vertical directions decrease by 10.1% and 12.8%，respectively. The high elastic modulus of gravel results in stress shielding，and the effective stresses in the horizontal direction of the area between the tip and the gravel are reduced by 5.8%. The low permeability and high elastic modulus of gravel both cause shear stress concentration on the cemented surface，which increases the possibility of damage to the weak cemented surface and makes fractures bypass gravel.

Abstract:Reservoirs in Weizhou Formation of Weizhou11-4N Oilfield have entered the stage of high and ultra-high water cut，and the recoveries of some oil groups have approached or exceeded the measured oil displacement efficiency of existing exploratory wells. In view of the current oil displacement efficiency，reservoirs have less potential to be developed，and studies on the oil displacement efficiency of reservoirs in Weizhou Formation under high-multiple water flooding shall be carried out. According to the above problems encountered in the development，a core water flooding experiment with an injection amount of 200 PV was conducted. A flat visual water flooding model was designed to visually describe the high-multiple water flooding process and the distribution law of residual oil. In addition，nuclear magnetic resonance（NMR）technology was used to facilitate online core water flooding experiments and quantify the oil displacement efficiency in pores at large，medium，and small scales. The experimental results showed that the oil displacement efficiency of long cores reached 73.2%，which far exceeded the currently recognized oil displacement efficiency. When the permeability ratio of long cores in parallel was large，Bernoulli’s effect was proposed for the first time at the inlet end of cores with high and low permeability. During microscopic water flooding，the injected water broke through rapidly along channels with medium and high permeability，and the anhydrous recovery of the model was only 18.6%，and after a water flooding of 200 PV，the crude oil in low-permeability areas was effectively started. The results of online NMR displacement experiments showed the medium pores have contributed the most to the oil displacement efficiency，reaching 45.63%.

Abstract:Polymer flooding agents commonly used in oilfields have high consumption and poor salt resistance and tend to undergo chromatographic separation when compounded with surfactants. In view of these problems，the carboxyl nanofiber strips of the natural polymeric compound were selected as raw materials，and single-component flooding agents of hydrophobically modified nanofiber strips（CCNF-n）and amphoteric-hydrophobically modified nanofiber strips （ACCNF-n）were prepared for heavy oil. The effects of the hydrophobic modification degree and amphoteric-hydrophobic modification on the interfacial activity，emulsification ability，and oil displacement performance of carboxyl nanofiber strips were evaluated. The results showed that the increament of hydrophobic modification degree first increased and then decreased the interfacial activity of carboxyl nanofiber strips，and the interaction between the carboxyl nanofiber strips and the water was enhanced due to the introduction of cationic groups，which made the interfacial activity of amphoteric-hydrophobically modified nanofiber strips with the same hydrophobic modification degree decrease correspondingly.Under the conditions of 70 ℃ ，salinity of 50 000 mg/L，and mass fraction of 0.2%，the nanofiber strips with a greater hydrophobic modification degree indicates a higher viscosity. The viscosities of five hydrophobically modified nanofiber strips ranged from 1.54 to 3.85 mPa·s. Under the same conditions，the viscosities of the amphoteric-hydrophobically modified nanofiber strips fluctuated between 18.46 mPa·s and 27.31 mPa·s，exhibiting excellent salt resistance.The results of core displacement experiments showed that the amphoteric-hydrophobically modified nanofiber strip system could significantly enhance the oil recovery（18.91%）.

Abstract:A study on oxidation characteristics of heavy oil is the basis of mine design of improving oil recovery by in-situ combustion. However，there are relatively few studies on the effect of pressure on high-pressure in-situ combustion of heavy oil reservoirs. In order to clarify the influence of pressure on oxidation characteristics of heavy oil reservoirs by insitu combustion and effectively reduce the adverse effects of high-pressure in-situ combustion，this paper took Lukeqin heavy oil reservoirs as an example and investigated the thermal weight loss，heat release，and other oxidation characteristics of heavy oil reservoirs under different pressures based on thermogravimetric and differential scanning calorimetry experiments. The paper first calculated the kinetic parameters under different pressures and obtained the activation energy and reaction enthalpy at each oxidation stage. Secondly，the combustion effect and stability of in-situ combustion under varied pressures were evaluated through the combustion tube experiments. The experimental results show that higher pressures accelerate the oxidation reaction rates of heavy oil and intensify heat release. The oxidation paths of complex systems are changed，and the characterization parameters of reaction kinetics need to be modified under high pressures.In addition，the advancing speeds of the in-situ combustion line under high pressures are accelerated，and the temperatures of the burning fronts are more than 300 °C higher than those of atmospheric-pressure in-situ combustion；the combustion stability becomes worse，and the combustion under high-pressure in-situ combustion with oxygen reduced by 10% is stable，which effectively suppresses the combustion instability caused by fast high-pressure reaction speeds.

Abstract:Emulsification viscosity reduction flooding in common heavy oil reservoirs is a comprehensive process of surfactant flooding and emulsion flooding，which includes both the interfacial tension reduction effect of surfactants and the control and flooding effect of emulsions. Therefore，the formation mechanism and migration characteristics of emulsions in porous media were first visualized by microphysical simulation. Then，the parallel experiments of natural outcrop long cores were used to conduct water flooding + emulsification viscosity reduction flooding and direct emulsification viscosity reduction flooding experiments. The effort was to further verify the flow characteristics of emulsification viscosity reduction flooding and comparatively analyze the oil displacement effects of emulsified viscosity reducer flooding. The experimental results show that emulsions are formed in situ under the action of shearing and interfacial tension reduction. These emulsions lead to frequent detour flow diversion of displacement media through clamping，bridging，and adsorption，which play the role of expanding swept volume and enhancing oil displacement. In the migration process，the emulsions interact with the porous media to demonstrate the flow characteristics of“slow and fast in respective three aspects.”The resulting percolation causes the distribution of emulsions to change regularly along the flow path and with the increase in the displacement ratio. The results of parallel core displacement experiments under different injection modes were compared. The result indicates that the starting pressure of direct emulsification viscosity reduction flooding（0.57 MPa）is lower than that of water flooding（1.52 MPa），and the injection pressure of emulsification viscosity reduction flooding after water flooding increases from 0.37 MPa to 1.17 MPa. The displacement pressure rises to an equilibrium in a fluctuating manner during the injection of the emulsified viscosity reducer solution. At the same injection ratio，the displacement efficiency of direct emulsification viscosity reduction flooding is increased by 16.69% than that of water flooding + emulsification viscosity reduction flooding. This further verifies that emulsification viscosity reduction flooding can effectively expand the swept volume and raise oil displacement efficiency.

Abstract:The research on the production capacity of gas wells is not only the core of the performance description of gas reservoirs but also an important basis for the analysis of gas injection and production capacity and the preparation of injection and production schemes of gas storage. At present，the conventional binomial，exponential，and one-point productivity equations are established for gas reservoir development，and there is no relevant research on the adaptability of cyclic high-rate injection and production of gas storage. Therefore，this study investigated the productivity calculation methods for gas storage in oil and gas reservoirs. On the basis of the relationships between formation pressure，bottomhole flow pressure，and injection and production capacity in gas storage in oil and gas reservoirs，the productivity equation of gas wells in gas storage was established，and the physical significance of various parameters in the newly established productivity equation of gas wells was clarified to define the thresholds of laminar flow and turbulent flow. Different from the productivity equation of the conventional gas reservoirs，the newly established equation demonstrates that the ratio of the difference of squares of production pressure to the square of production decreases with the increase in production，which satisfies the power function relationship and shows a linear relationship in the double logarithmic coordinate system. The established productivity equation of gas storage in oil and gas reservoirs is an extension of the conventional productivity equation，which provides a theoretical basis for the study of gas injection and production capacity of gas storage. To verify the applicability of the equation proposed in this paper，we used the binomial productivity equation and the newly established equation to fit the measured production data of four pressure monitoring wells in X gas storage for comparison. The results show that the equation established in this paper is more in line with the productivity change laws of gas storage in oil and gas reservoirs.