Abstract:

Based on image analysis methods such as rock thin sections， scanning electron microscopy， micro fluorescence，and cathodoluminescence， combined with testing techniques such as nuclear magnetic resonance and nitrogen adsorption，two typical lithofacies of the Paleogene carbonate mineral shale and mixed shale in Dongying Sag were studied. According to the mineral composition and occurrence， shale was divided into two types of structural units： carbonate laminas and mudstone laminas. By analyzing the mineral types and related pore development characteristics of them， two typical lithofacies reservoir characteristics were revealed. In view of the relative changes in geological elements during burial， the development conditions of shale reservoir space were discussed. The research results indicate that the Paleogene shale in Dongying Sag has diverse mineral components，characterized by the widespread development of multi-component carbonate minerals， local concentration of multiple sources of felsic detrital particle，and plastic filling of rheological components such as clay minerals and organic matter. The skeletal particles limit the distribution boundaries of organic components， and the organic components contain some autogenous minerals.The pore filling materials are influenced by factors such as the high content of crude oil asphaltene and wax， as well as high surface solidification points. The organic components and inorganic minerals exhibit multiple chimeric characteristics. The shale fabric and complex evolution process jointly determine the diversity of pore types and development mechanisms. The carbonate mineral shale develops nanoscale intracrystalline pores and micrometer-scale intergranular （solution） pores， characterized by large and well-connected pores， with relatively low porosity. Mixed shale develops nano-sub micron-sized interlamellar pores of clay minerals， which are small and poorly connected， with relatively high porosity. The interlayer fracture development zone has good reservoir properties， and the reservoir space is composed of multi-scale networks rich in matrix pores. In the overall background of rich organic matter， the Paleogene rich carbonate shale has the characteristics of the oil enrichment in matrix pores and at the laminae planes.

Abstract:

Tuff reservoirs， as a type of tight oil and gas reservoir， are significantly influenced by their micro and nano-pores in terms of hydrocarbon storage. To understand the pore structure and heterogeneity characteristics of tuff reservoirs in the Permian Section 2 Feng in Hashan area，Junggar Basin，six tuff samples from Well Ha 11 in Hashan area were selected. These samples underwent total organic carbon （TOC） content measurement，whole rock mineral composition analysis，and characterization of pore structure through CO₂and N₂adsorption experiments. Using multifractal theory，the pore heterogeneity and connectivity were analyzed. The results show that the average TOCcontent of the tuff samples is 0.931%， and the mineral compo-nents are mainly feldspar， quartz，clay minerals，and dolomite. Micropores are mainly developed in the 0.33-0.38，0.50-0.68，and 0.72-0.86 nm pore size ranges，while meso-macropores are mainly developed in the 2.94-16.09 nm range. The generalized fractal dimension Dq decreases with increasing q， and the singular fractal spectrum shows a convex asymmetric parabola. The pores in tuff reservoirs have multifractal characteristics. Micropores （0-2 nm） have smaller width of the singular spectrum（Δα）values and larger Hurst index（H）values，while meso-macropores（2-100 nm）have larger Δα values and smaller Hurst index（H） values， indicating that micropores have better homogeneity and connectivity. The heterogeneity of meso-macropores is affected by the pore volume. With the increase in pore volume， pore heterogeneity increases， and connectivity decreases.TOC content and mineral composition have different effects on pore heterogeneity and connectivity. An increase in TOC content improves the connectivity of meso-macropores. An increase in plagioclase content increases the heterogeneity of mesomacropores.An increase in clay mineral content increases the heterogeneity of micropores， while an increase in dolomite and calcite content reduces the heterogeneity of meso-macropores.

Abstract:

In order to clarify the differential hydrocarbon enrichment characteristics in Guxi Buried Hill of Jiyang Depression and guide the subsequent hydrocarbon exploration， the geological characteristics of the buried hill were analyzed based on the drilling and seismic data，and the tectonic evolution of the buried hill and its control on differential hydrocarbon enrichment were studied.The results show that Guxi Buried Hill has experienced four stages of compression， two stages of extension， two stages of strikeslip，and five stages of denudation since Indochina， which are the extrusive uplift and denudation in the Late Triassic，the weak extrusion to“cut bump and fill concave” in the early-middle Jurassic， the extrusive uplift and denudation in the Late Jurassic， the leftwalking slip and stretch in the early Cretaceous， the extrusive uplift and denudation in the Late Cretaceous， and the right-walking slip and stretch and the denudation on the high buried hill in the Paleogene. In addition，according to the settlement in the Neogene， two kinds of buried hills such as high buried hills and low buried hills have been formed. The whole structure is characterized by “NW-trending fault controlling belts， NE （EW）-trending fault controlling hills， and alternating horst and graben”. The superimposi‐tion of multi-stage tectonic activities has resulted in obvious differences in source-reservoir connection， reservoir types， and hydrocarbon accumulation characteristics between the two types of buried hills. The stratigraphic reservoirs in the upper Paleozoic and Mesozoic are the most abundant in the high buried hills. All layers in the low buried hill can form reservoirs， and the tectonic reservoirs in Paleozoic strata are the most abundant. The hydrocarbon enrichment characteristics of the same type of buried hills are also different due to the different allocation of reservoir-forming factors. The stratigraphic reservoirs at the slope zone of high buried hills in Chengzhong，Chengdong，and Gudao，the weathering crust reservoirs and interior tectonic reservoirs of Lower Paleozoic，and the tectonic reservoirs of Upper Paleozoic and Mesozoic in low buried hills of Gubei and Kenli are the key targets for subsequent exploration.

Abstract:

Sand bodies in distributary channels and mouth bars of shallow water deltas are often distributed in continuous sheets， mak‐ing it difficult to accurately classify the single sand body， limiting the accurate prediction of remaining oil distribution and restricting the further enhanced oil recovery （EOR）. Based on core， well logging， and other data， the characteristics of the sedimentary architectures of single sand bodies in shallow water deltas in the 1^st Submember of the 2^nd Member of the Eocene Shahejie Formation （E s₂1）and the 2^nd Submember of 2^nd Member of the Eocene Shahejie Formation（E s₂2）in Shenger District of Shengtuo Oilfield，Dongying Sag were systematically analyzed by using dense well pattern and interwell tracer data. The results show that shallow water delta deposits are developed in Es₂21 and Es₂22 in Shenger District of Shengtuo Oilfield，Dongying Sag，including plain subfacies and front subfacies of shallow water deltas. In addition， microfacies such as distributary channels，overbanks，mouth bars，and beach bars are developed.The sand bodies of shallow water deltas were divided into four architecture units （Levels 5-8）， and the single sand bodies in this study belong to the level-8 architecture unit. Six types of lateral contact patterns between single sand bodies were identified by comprehensively using dense well pattern and interwell tracer data：channel-overbank-channel splicing type，channel-channel cutting and stacking type，beach bar-beach bar splicing type， mouth bar-mouth bar splicing type，channel on dam cutting mouth bar type，and mudstone separating type. Interwell tracer data show that the sand body has the best connectivity in the channel on dam cutting mouth bar type，followed by channel-channel cutting and stacking type，mouth bar-mouth bar splicing type，and beach bar-beach bar splicing type. The worst connectivity is from the channel-overbank-channel splicing type. Finally，the sedimentary architecture models of single sand bodies in shallow water deltas in the study area were established. The microfacies type of the shallow water delta plain is mainly a distributary channel. The contact patterns between sand bodies in a single distributary channel mainly include lateral incising and overlapping，lateral contact with sand bodies on an overbank，vertical superposition，and oblique superposition. The microfacies types of sand bodies in the shallow water delta front are distributary channels，mouth bars，and beach bars. The contact patterns between sand bodies in a single mouth bar include vertical superposition，lateral splicing，oblique superposition，and mudstone separation. Two types of lateral splicing and vertical superposition exist between sand bodies in a single beach bar.

Abstract:

Glutenite reservoirs in the north region of Lijin，Dongying Sag have complex mineral components，resulting in the low accuracy of the interpretation of physical parameters and the difficulty of defining the boundary of oil and dry layers. Based on the data of logging，mud logging，production test，and analysis testing，this paper combined crossplot chart identification with radar pattern recognition mode to effectively distinguish glutenite lithology in the area. Based on the lithology identification， oil-bearing occurrence analysis， and testing data analysis， this paper established the lower limits of physical and electrical properties of effective conglomerate and carbonate reservoirs. Combining with the production test data，this paper constructed the interpretation chart of classification and evaluation standard of the effective reservoir of glutenite in the north region of Lijin，Dongying Sag，and built the porosity and permeability parameter models of conglomerate and carbonate reservoirs，respectively，which provided a quantitative evaluation method for complex glutenite reservoirs in the north region of Lijin，Dongying Sag. The application has verified the research in the production wells of glutenite reservoirs in the north region of Lijin，Dongying Sag，and the results are promising.

Abstract:

To improve the research and evaluation effect of remaining oil in high water cut oilfields，this paper sorted out the concept and influencing factors of remaining oil，summarized the research methods and applicable conditions of remaining oil from three aspects of microscopic distribution，macroscopic distribution，and quantitative analysis of saturation of remaining oil， and discussed the distribution characteristics of remaining oil in water flooding reservoirs， heavy oil reservoirs，and chemical flooding reservoirs based on literature research. The difficulties and development trends of remaining oil research were further put forward. The results show that the influencing factors of remaining oil mainly include geological structure，sedimentary microfacies，reservoir heterogeneity，well pattern density，well pattern， perfection of injection-production system，and production performance. The remaining oil research methods include experimental analysis，numerical simulation，field testing，etc. The research purposes and applicable conditions of each method are different，and the test results reflect the distribution of remaining oil saturation at different locations and scales. The distribution of remaining oil in high water cut oilfields is highly dispersed and relatively enriched，and the microscopic distribution of remaining oil is in various forms of continuous and discontinuous phases. The development trend of remaining oil research includes but is not limited to five aspects：the construction of super-large physical models，the integration of multi-scale high-resolution imaging systems，the improvement of numerical simulation methods considering the time-varying and discontinuous nonlinear seepage of different displacement media and physical properties the comprehensive application of multidis‐ciplinary and multi-method field testing，and the wide application of big data artificial intelligence.

Abstract:

Under the dual carbon goal，the focus and difficulty of the petroleum and petrochemical industry transition lie in exploring low-cost transition development paths. This needs to conduct systematic research on the development foundation and potential of various transition technologies， coordinate the development and application timing of these technologies，and thus form a technology portfolio and comprehensive plan supporting the optimal transition path. Carbon capture，utilization，and storage（CCUS）has high technological maturity and sound coupling with the petroleum and petrochemical industry and is a key technology for petroleum and petrochemical transition. However， the high cost remains the main obstacle to large-scale development. Analyzing the economy and development mode of CCUS plays an important role in determining the future development layout of the CCUS industry，and studying the potential of CCUS for the petroleum and petrochemical industry transition. To conduct an in-depth analysis on the economy of future CCUS technology and its potential in the transition of the petroleum and petrochemical industry， this paper focuses on CCUS with enhanced oil recovery（CCUS-EOR）and proposes a new analytical approach. Firstly，by comprehensively reviewing the entire process of CCUS-EOR，the costs including carbon capture，transportation，oil displacement， and storage are analyzed in detail，with the cost reduction of each in the future evaluated. Secondly，by the prediction of future oil prices and carbon prices，the economic benefits brought by oil displacement and carbon emission reduction are analyzed， and a cost-benefit comparison is conducted. Based on the cost-benefit analysis results，this paper further carries out a comprehensive economic evaluation of CCUS-EOR projects under different modes in China，which covers different carbon capture technologies，transportation modes，and storage strategies，revealing the profitability and sustainable development potential of CCUS-EOR projects under different scenarios.The results show that the CCUS-EOR economy is deeply affected by multiple factors such as carbon price，oil price，and oil displacement efficiency. In the medium and long term，carbon price changes have a greater influence on future CCUS-EOR returns.Under the high level of both carbon price and oil price，the profitability of CCUS-EOR projects is greater and more attractive. Meanwhile，the improvement of oil displacement efficiency can significantly increase the economic benefits of the projects. Currently，there are significant differences in the economy of various projects in China，which cannot fully guarantee significant profits. However，there is great room for improving the future economy. For the future CCUS-EOR development in China， it is necessary to break through the technological bottleneck in carbon capture links and focus on developing and applying pre-combustion capture technology to reduce capture costs and improve capture efficiency. Additionally，it is necessary to optimize the industrial layout to form a source-sink matching industrial cluster and thus achieve a synergistic effect in the industrial chain. At the same time，it is important to promote the development of the carbon trading market，guide carbon emission reduction behavior via the market mechanism，and create a favorable external environment for the promotion and application of CCUS-EOR technology in the petroleum and petrochemical industry.

Abstract:

CO₂ flooding technology is an effective technical means to enhance the recovery of low permeability reservoirs. After CO₂ comes into contact with crude oil，the asphaltene in the system is deposited in a solid form， which causes a certain blockage to the reservoir，but the dissolution improves the flow capacity of the reservoir as a whole at the same time. The damage of CO₂ flooding to low permeability reservoirs under different injection methods is different. The organic scale plugging mechanism，reservoir wettability，and CO₂ -water solution corrosion evaluation experiments were carried out after continuous CO2 injection and CO₂ -water alternating injection. The variation characteristics of relative permeability curve parameters were evaluated，and the damage of different injection methods of CO₂ flooding to low permeability reservoirs was quantitatively characterized. The results show that the organic scale produced by CO₂ flooding would block the pore throat of the rock，but on the whole，the dissolution caused by the reaction of CO₂ and chlorite is stronger， which makes the recovery of the low permeability reservoirs effectively enhanced. More‐over， the organic scale blockage caused by CO₂ -water alternating injection is weaker than that caused by continuous CO₂ injection，and the dissolution effect is better. The permeability loss rate is lower. It could achieve a better oil displacement effect in pores with a radius of more than 0.2 μm and increase the pore space and flow channel of the rock so that the recovery of low permeability reservoir could be effectively improved.

Abstract:

The oil displacement technology of the water and gas dispersion system is a new enhanced oil recovery technology developed for low-permeability oilfields with low recoveries， which has obviously increased oil production in Changqing Oilfield. However，the effects among microbubbles in the dispersion system and pores are complex， and the research on its microscopic oil displacement mechanism is gradually deepening. According to the characteristics of heterogeneous low permeability core，a glass etching model with a side length of 1.5 cm was made，and the flow experiment of the CO₂-water dispersion system was carried out under the conditions of reservoir temperature and pressure. The data such as bubble adsorption capacity，oil film pushing capacity，and bubble elastic energy were obtained by observing the interaction processes among microbubbles and oil，water，and rocks，and then the oil displacement effects were quantitatively characterized and analyzed. The experimental results show that the microbubble combines with the oil interface，to form a special oil adsorption film，which is significantly different from the mechanisms of water flooding and gas flooding. The merging of adjacent bubbles in the displacement process also promotes the convergence of oil films，and the merging of microbubbles helps the flow of bubbles so that the oil film adsorbed on the surface of the bubbles moves with the bubbles. The bubble volume expands due to the decrease in pressure， and the elastic energy released can promote the migration of the oil film adsorbed on the wall when the microbubble is transported. In addition， the oil film migration process of the microbubbles in the water and gas dispersion system was simulated and analyzed with the Volume of Fluid multiphase flow model，and the main factors that displace the oil film were obtained， which are the elastic energy generated by the deformation of the microbubbles and the energy of the microbubbles themselves. The energy of the bubble acts on the leading edge of the bubble and the bubble is pushed by contact with the surface of the oil film.

Abstract:

Porous carbonate reservoirs are characterized by strong heterogeneity and diverse pore types，with significant differences in waterflooding recovery and unclear main controlling factors. Based on the pore throat size distribution curves，the microscopic pore structure of the reservoir was qualitatively classified. Through digital core technology， a method for quantitative characterization of microscopic pore structure was established to clarify the pore throat characteristics of porous carbonate rocks in a region of the Middle Eastern，and indoor physical experiments on waterflooding were conducted to clarify the differences in the oil recovery of different types of cores and their main controlling factors. The results show that ① The microscopic pore structure of the reservoir in the study area can be classified into coarse unimodal type， fine unimodal type I， fine unimodal type II， coarse bimodal type， and multimodal type. There is no significant relationship between storage performance and core homogeneity；the single-phase flow capacity of non-unimodal type is better than that of unimodal type； unimodal type becomes worse with increasing core homogeneity.②The average coordination number and pore-throat ratio of the non-unimodal type are higher than those of the unimodal type. The average coordination number and pore-throat ratio decreased with the increase of core homogeneity for the unimodal type. The upper limit of the pore-throat ratio tends to decrease with increasing throat radius for all types，and the upper limit of coordination number increases exponentially with increasing pore radius. ③Macroscopically，core homogeneity is the main controlling factor of oil displacement efficiency； microscopically，high connectivity at large pore-throat and large pore-throat ratio at small pore-throat are the fundamental reasons for non-unimodal type to have significantly lower oil displacement efficiency than unimodal type. Porethroat size is the crucial factor of oil displacement efficiency of unimodal type.

Abstract:

Shale oil reservoir is a typical unconventional oil and gas resource that plays an essential role in the international energy supply market. Due to the complex pore structure and crude oil composition of shale oil reservoirs， the flow of crude oil in organic-rich shales has a certain complexity，and its flow behavior still needs to be further studied. Based on the stochastic simulation method， the flow characteristics of fluid in mixed-wet nanopores were considered， and an apparent oil permeability （AOP） model of shale oil reservoirs was established in this paper. The results show that the AOP of shale oil reservoirs is directly related to the molecular structure of alkanes， and its influence decreases with the increase of pore radius. The organic matter can improve the flow capacity of crude oil when the boundary slip length is large，and its AOP is about ten times the absolute permeability.At the same time， the pore radius reduction and wetting reversal effect triggered by adsorbed organic matter significantly impact the flow capacity of alkane molecules，and these effects cannot be ignored. The AOP model of shale oil reservoirs considering mixed-wet nanopores established in this paper helps understand the fluid flow mechanism of shale oil reservoirs and can provide theoretical support for productivity evaluation，dynamic analysis，and production system optimization of shale oil reservoirs.

Abstract:

The majority of limestone reservoirs in China are characterized by deep burial，low porosity，and low permeability and are influenced by factors such as elevated temperatures，high closure pressures，and strong heterogeneity. Conventional hydrochloric acid fracturing techniques often fail to achieve non-uniform etching on such reservoirs， resulting in poor transformation effects and hindering the efficient development of such reservoirs. The acid fracturing technology of multi-stage alternating injection was used to facilitate non-uniform etching of fracture wall surfaces by iteratively forming viscous fingering in the prepad. However，the law governing the acid-etching fracturing of multi-stage alternating injection remains unclear，and the acid injection stage boundaries are not determined. At present， acid fracturing design typically relies on empirical approaches. To address these gaps，this study built an acid fracturing model of multi-stage alternating injection for limestone reservoirs by considering the influence of viscosity variation and alternating stages based on a two-scale continuous acidification model. Based on the acid fracturing model of multistage alternating injection，the influence of acid viscosity，acid injection rate，and acid injection stages on the acid fracture effects was analyzed by combining the acid rock reaction kinetics，acid-etched fracture experimental data，and numerical simulation results.The acid-etching law of multi-stage alternating injection in limestone reservoirs and the acid injection stage boundaries were determined， and the breakthrough volume of acid fluid was introduced to provide the basis for site optimization. The findings suggest that to enhance the non-uniform etching of fracture wall surfaces and obtain high conductivity of acid-etching fractures，an alternating injection process involving hydrochloric acid and thickened acid should be adopted for pure limestone reservoirs at a formation temperature of 90 °C. 0.4% HPAM-thickened acid should be added when the acid injection rate is 5 m³/min，with an optimal acid injection stage of no more than three. At this time，the breakthrough volume of acid fluid is the smallest，which is suitable for on-site construction.

Abstract:

Viscosity-reducer foam flooding combines the advantages of emulsification of viscosity-reducers and selective blocking of foam to further enhance oil recovery in deep low-permeability heavy oil reservoirs during the later development stages. The suitable concentration of viscosity-reducing foam agents were selected according to the viscosity-reducing effect，foaming performance and foam stability of the agents by laboratory experiments. Meanwhile，the characteristics and recovery effects of viscosity-reducer foam flooding under different displacement modes were compared by single-core displacement experiments， and the diverting capacity of viscosity-reducing foam at various permeability ratios were investigated by parallel core experiments，and thus the enhanced oil recovery （EOR）mechanisms of viscosity-reducer foam flooding ware defined. The results demonstrate that the viscosityreducing agents facilitate the emulsification and viscosity reduction of heavy oil， while the foams block large pore throat and inhibit N₂ channeling during viscosity-reducer foam flooding. Combination of the both can improve the sweep coefficient and displacement efficiency，increase displacement pressure differential，and lower the water cut. Furthermore，the viscosity-reducer foam flooding can enhance the oil recovery by an additional 13% based on the viscosity-reducer flooding. In heterogeneous conditions，viscosityreducer foam flooding decreases the high-permeability core channeling to direct the flow towards low-permeability cores，thereby exerting an emulsification and viscosity-reducing effect. Finally，this expands the swept volume and simultaneously enhances the displacement efficiency. While the viscosity-reduce foam flooding significantly enhance the oil recovery of deep low-permeability heavy oil reservoirs by optimizing the oil flow distribution，enhancing emulsification，and reducing heavy oil viscosity， thus providing an effective strategy for efficient development of deep heavy oil reservoirs.

Abstract:

Nanomaterials for enhanced oil recovery （EOR） have gained more and more attention from petroleum researchers. However，the research mainly focuses on the properties of spherical nanomaterials，and the research on two-dimensional nanosheets is insufficient. In this paper，the amphiphilic MoS₂ nanosheets （active MoS₂ nanosheets）were independently synthesized to significantly enhance the oil recovery after water flooding in reservoirs. The spreading law of active MoS₂nanosheets on a solid surface was studied，and the mechanism of active MoS₂ nanosheets on an oil film of a solid surface was elucidated. Based on the measurement of the gas-water-solid three-phase contact angle，it is determined that the equilibrium contact angles of water droplets remain unchanged at 90° after oil-wet quartz is immersed in an oil displacement system of active MoS₂nanosheets for 120 h. Eventually，the wettability of the quartz surface changes from oil-wet to neutral-wet. Both formation water and SiO₂ nanofluid（mass fraction of 0.15%） fail to make the oil film produce wedge film on the solid surface. However，the oil displacement system of active MoS₂ nanosheets（mass fraction of 0.005%）could form a prominent wedge film in the oil-water-solid three-phase contact area，then form structural disjoining pressure and eventually strip the oil film from the solid surface. Moreover，it is found that the oil film could form two contact lines（inner line and outer line）during the contraction process on the solid surface in the oil displacement system of active MoS₂ nanosheets（mass fraction of 0.005%）. The contraction velocities of the inner contact line and the outer contact line are 0.661 7 × 10^-5 and 8.581 7 × 10^-5 cm/s， respectively. From the perspective of thermodynamics，the Gibbs free energy increment of the oil-water-solid mixture system is negative in the contraction process of oil film，which proves that the contraction of the oil film in the oil displacement system of MoS₂ nanosheets is spontaneous. The research results show that the oil displacement system of MoS₂ nanosheets （mass fraction of 0.005%） has high oil displacement efficiency.

Abstract:

The optimization of injection-production modes is of great significance in alleviating intra-layer contradiction and improving longitudinal sweep efficiency for thick reservoirs. The analytical flow model of both producer and injector partially penetrating the reservoir is absent currently，which fails to support the study of the sweep characteristics of thick reservoirs. Therefore，based on the conformal mapping method，this article transformed the section formation with partially penetrating producer and injector into a formation with a circular boundary and off-center fractured well， a formation with a unit circular boundary and two-branch fractured well，and a section formation with fully penetrating injector and partially penetrating producer，sequentially. The above transformations were repeated to transform the section formation with fully penetrating injector and partially penetrating producer into that with fully penetrating injector and producer. In consequence，the original two-dimensional flow process was transformed into a one-dimensional one，achieving analytical calculations of pressure and streamline distribution in thick reservoirs under different injection-production modes. The comparison with refined numerical simulation methods shows that the proposed method has high computational accuracy for different well spacing-thickness ratios. The influence of injection-production modes on longitudinal sweep characteristics of thick reservoirs was researched using the method presented in this article. The results show that for the bottom-injection-high-production mode， the top section of the injector acts as the main injection layer，and the top 1/3 of the injector controls more than 1/2 of the formation， resulting in more than 2/3 of the producer being affected. The main impact of water injection on the formation lies in the stage before the water breakthrough. The water breakthrough of bottom-injection-high-production mode is the latest and has the highest sweep efficiency，followed by bottom-injection-medium-production mode and mediuminjection-high-production mode under the same penetrating thickness. The water breakthroughs of high-injection-high-production mode and bottom-injection-bottom-production mode are the earliest and have the lowest sweep efficiency. The larger penetrating thickness of the producer indicates a earlier water breakthrough. However，the sweep efficiency in water breakthrough increases.Therefore， the optimal penetrating thickness should be selected by comprehensively considering the factors of water breakthrough time and sweep efficiency.

Abstract:

In the late stage of development，the complex fault block reservoir faces a series of problems，such as high comprehensive water cut，lack of formation energy，complex remaining oil distribution，and poor well pattern suitability. In this paper，based on the oil-water distribution status of the waterflooding reservoir，such as water-in-oil and oil-in-water，the development mode of single-layer outer edge waterflooding was studied through theoretical model derivation and numerical simulation methods by taking Ken71 fault block reservoir in the middle of Zhanhua Sag of Jiyang Depression as an example. The results show that the reasonable water injection volume， fluid production volume， and spacing between injection and production wells during single-layer development can be obtained through the force analysis of the fluid production end and the water injection end. The key factors affecting the remaining oil saturation and the water saturation are reasonable water injection pressure difference，water injection volume，and fluid production volume of single-layer development systems. It is essential in controlling the reasonable formation pressure level and the secondary enrichment of the remaining oil. The spacing between injection and production wells increases to the periphery of the oil-water boundary，and 2.9 times the width of the oil-bearing strip is the critical value of reasonable spacing between injection and production wells. An asymmetric periodic injection and production method with short injection and long standing is adopted to establish a single-layer outer edge waterflooding development model，which is beneficial to maintain the stability of the pressure system and increase the sweep efficiency of the remaining oil of the single-layer，so as to improve the oil recovery. Field application shows that after applying the single-layer outer edge waterflooding development model，the daily production of Ken71 fault block increases to 254 t，the water cut is controlled to 93.7%，the recovery increases to 31.53%，and the oil recovery rate is increased by 4.9%，which shows an excellent yield-increasing effect. The single-layer outer edge waterflooding model solves the problems in the development of complex fault block reservoirs with high water cut， such as dispersed remaining oil distribution，low waterflooding sweep efficiency，and poor well pattern suitability and can provide guidance and reference for complex fault block reservoir development.

Abstract:

This paper aims to solve the technical problems such as poor drillability，large formation inclination，difficult well deflection control，and easy wall instability in the middle and deep Carboniferous and Permian hard formation in the Hashan area of Shengli western exploration area and realize the efficient exploration and benefit development of oil and gas reserves. Based on the current conventional drilling technology，the applicability and process optimization of segmented combined drilling technology were studied，and supporting technologies for speed acceleration and safety construction related to gas drilling were proposed for the Carboniferous and Permian hard formation of dolomitic rock and igneous rock，forming the regional construction standards. After the transformation from gas drilling to drilling fluid construction，the combined drilling technology of“ gas drilling +‘ impregnated bit + turbine/high-speed screw’” was preferred. According to the formation characteristics，efficient impregnated bit series of different sizes were developed to achieve well deflection control and improve the rate of penetration. The combined drilling technology was successfully applied in Hashan3 and Hashan2 wells and achieved good results. During gas drilling，the rate of penetration in Well Hashan3 reached 5.2 m/h，more than three times faster than the conventional drilling method. During drilling fluid construction，the technology of“ impregnated bit + turbine/high-speed screw” was adopted， and the formation inclination was 30°. The well deflection was well controlled，and the rate of penetration was close to 1 m/h，which showed a good regional application effect compared with conventional drilling technology. The field application shows that the combined drilling technology of“ gas drilling +‘impregnated bit + turbine/high-speed screw’” is an effective means to increase the speed and efficiency of middle and deep drilling in the Hashan area of Shengli west exploration area. However，the technology also has bottlenecks. Combined with the applicability research of particle impact drilling（PID）technology，it is suggested that the PID technology should be introduced and improved in the next step，so as to achieve speed and efficiency breakthrough in regional drilling.

Abstract:

The hybrid steam-solvent injection has been considered as a promising technique for enhancing heavy oil/bitumen recovery，while its main mechanisms including the heat transferred and dissolution of solvents （e.g.， CH₄，C₂H₆，C₃H₈， C₄H₁₀，CO₂，N₂，and DME）into heavy oil/bitumen to reduce its viscosity and swell it are closely related to the phase behaviour of the solvents/water/heavy oil systems. To allow the seamless integration with the existing reservoir simulators， the traditional cubic equations of state（i.e.，SRK EOS and PR EOS） have been modified and improved to accurately quantify the phase behaviour and physical properties of the aforementioned systems under equilibrium and nonequilibrium conditions. Firstly，a huge database has been built to develop the corresponding alpha functions by minimizing the deviation between the measured and calculated vapour pressures for water as well as non-hydrocarbon and hydrocarbon compounds available from the public domain. Such obtained alpha functions are further validated with enthalpy of vaporization for pure substances， and then the reduced temperature has been optimized and the eccentric factor has been redefined. Finally，a pressure-implicit strategy has been developed to optimize the binary interaction parameters（BIPs）by treating heavy oil as one pseudocomponent （PC） or multiple PCs. Also，the contributions of each solvent to the aforementioned systems have been compared and analyzed within a consistent and unified framework. In addition to new alpha functions for hydrocarbons and water， respectively，the reduced temperature is found to have its optimum value of 0.59 for the two equations of state （EOSs），while 0.60 is recommended for practical use. Such improved EOSs have been further employed to reproduce the experimentally measured multiphase boundaries （or pseudo-bubble-point pressures）， density，viscosity，（mutual）solubility，and preferential mass transfer for the aforementioned mixtures under equilibrium and nonequilibrium conditions. The swelling effect for the heavy oil can be enhanced due to the addition of C₃H₈ and/or C₄H₁₀ or their mixtures into the CO₂ stream. Due to the existence of water，isenthalpic flash leads to more accurate quantification of multiphase boundaries and physical properties for the hybrid solvent-thermal processes. Each component of a binary or ternary gas mixture is found to diffuse preferentially into heavy oil at high pressures and elevated temperatures in the absence and presence of porous media，while each of them is found to exsolve differently from gas-saturated heavy oil under nonequilibrium conditions.