Abstract:Interlayer with poor organic matter is widely developed in continental organic-rich shale，but the role of interlayer in shale oil evaluation is unclear. Aiming at this problem，the characteristics of organic-poor interlayer in organic-rich shale are discussed and their roles in shale oil exploration are clarified on base of cored wells in Jiyang Depression and numerous stratigraphic and geochemical analysis and testing. The results show that the interlayers in organic-rich shale are different from those in conventional reservoirs and can be identified by conventional logging methods with a single layer thickness defined as 0.5-3 m. There are three types of interlayers including sandstone，limestone and dolomite interlayers in Jiyang Depression. The reservoir space of these interlayers is mainly composed of intergranular/intercrystalline pore，intergranular/intercrystalline microfracture and intragranular pore. The micropores in dolomite interlayer are the most developed and the pore-throat structure is the most favorable. Pores in sandstone interlayers are moderately developed，and pores in limestone interlayer are seldom developed. Interlayer is an effective reservoir for hydrocarbon storage because of its good physical properties and oil-bearing characteristics. The permeability of shale matrix decreases rapidly with the increase of overlying pressure，while the permeability of interlayer is less sensitive to pressure. The permeability of interlayer is much higher than that of shale matrix under formation conditions. Interlayer is an effective pathway for shale oil production. The enrichment of brittle minerals in interlayer is conducive to large-scale fracturing. And interlayer shale oil should be the first choice for shale oil exploration breakthrough in Jiyang Depression.

Abstract:Deformation band is a local structure widely developed in porous sandstones and sediments. It is one of the main structural units of the fault zone and can affect fluid migration. In different diagenetic stages，the deformation bands in pure porous sandstone follow the formation sequence of disaggregation band，cataclastic band and solution band，while the formation of phyllosilicate band is mainly related to the content of phyllosilicate minerals in the rock. A complete time evolution sequence of deformation bands includes single deformation band，clusters of deformation bands，joints and faults.Different types of deformation bands can superimpose. The variation of thickness，continuity and permeability of deformation bands in three-dimensional space is the key factor affecting fluid percalotion，and it is also important to study the internal structure of the fault zone. Different types of deformation bands will result in the selective filling of hydrocarbon. At present，the research on the three-dimensional spatial distribution of outcrop deformation bands in China is rather insufficient，and the deformation bands in oil-bearing basin cannot be efficiently identified so far because of the limitation of core and logging data. Therefore，an in-depth study of the development characteristics and distribution of deformation bands will be of great advantage to guide the fault modelling and fluid migration analysis.

Abstract:The complex pore structure of unconventional reservoirs is an important factor affecting reservoir properties and hydrocarbon storage. At present，there are many methods for characterizing the pore structure of unconventional reservoirs，but the principles and application scopes for these techniques are quite different. The main characterization techniques of unconventional reservoir pore structure are reviewed from qualitative and quantitative aspects. The progress and application of current techniques are summarized，including two-dimensional scanning electron microscope（SEM）image characterization technique，three-dimensional micro-nano CT reconstruction technique，indirect quantitative characterization technique such as nitrogen adsorption experiment，and full-aperture joint characterization technique which is widely studied at present. The applicability of different characterization methods is clarified in terms of characterization principle，object and precision，and the characterization system for reservoirs with different pore scale is formed，which basically meets the requirements of unconventional reservoir evaluation. However，the current unconventional reservoir pore structure characterization techniques still need further exploration in terms of accuracy and scale，as well as joint characterization algorithm interpretation.

Abstract:In order to systematically characterize the distribution characteristics of fault-sandstone composite transport system and accurately describe its dominate migration pathways，Shale Gouge Ratio method（SGR）is used to quantitatively characterize the transport capacity of faults and determine the transport faults and lateral transport positions during the hydrocarbon accumulation. Connectivity probability method is used to quantitatively characterize the conductivity of sandstone transport layer and determine the dominant migration pathways of sandstone transport layer. Three-dimensional seismic data is used to depict the spatial distribution of fault planes，and it is used to determine the convex ridge of oil source fault by combining the buried depth of fault plane. Based on the results of paleogeomorphology restoration，the distribution of tectonic ridges is determined. By coupling the transport faults，sandstone transport layers，cross-section ridges of oil source faults and structural ridges，the characterization of dominant migration pathways in the fault-sandstone composite transport system is realized. The results show that there are mainly two types of composite transport system in the Es1 Member in Qinan Slope of Qikou Sag. One is the ridge of Nandagang Fault（oil source fault）-sandstone transport layer-transport fault-tectonic ridge. The other is sandstone transport layer-tectonic ridge-fault. The location of reservoir and hydrocarbon show of wells in different periods are in good agreement with the characterization results，which indicates that this method is effective for fine characterization of fault-sandstone composite transport system.

Abstract:Through interpreting the 3D seismic data and by combining the results with plane mapping，the deformation characteristics of structural transfer zone of LD21 Oilfield and LD16 Oilfield in the south subsag of Liaozhong Sag were discussed，and the relationship between the structural transfer zone and hydrocarbon accumulation was analyzed as well. The results show that Tan-Lu fault zone runs through the south subsag of Liaozhong Sag，in which restraining S-shaped structural transfer zone of LD21 Oilfield，restraining S-shaped structural transfer zone of the north of LD16 Oilfield and releasing S-shaped structural transfer zone of the south of LD16 Oilfield are formed in partially curved sections of central strike-slip fault，Fault LD16-3 and Fault LD16-21，respectively. Releasing intersecting structural transfer zone of the middle of LD16 Oilfield is formed in intersecting area of Fault LD16-3 and Fault LD16-21. The structural transfer zone changes the stresses transmitted by the segmental faults，so that the three-dimensional spatial strain is conserved. The fault displacementdistance method is used to investigate the deformation characteristics of the intersecting structural transfer zone of the middle of LD16 Oilfield. The control of structural transfer zone on hydrocarbon accumulation is mainly as follows：controlling the formation of structural traps，the development of high-quality reservoir，the hydrocarbon migration，and the fault blocking. Restraining structural transfer zone is a favorable field for oil and gas exploration in the south subsag of Liaozhong Sag.

Abstract:Jurassic Yan’an Formation is the main oil-bearing strata in Ordos Basin，the study of reservoir characteristics and microscopic waterflooding percolation characteristic has not been paid enough attention. Taking Yan8 Formation of Yanwu Oilfield in Ordos Basin as an example，the waterflooding front distribution features，oil-water percolation rule and residual oil state of various waterflooding types are clarified based on the reservoir characteristics analysis and real sandstone microscopic waterflooding experiments. The relationship between microscopic displacement efficiency and pressure is built，and forming mechanism and distribution rule of the residual oil are summarized. Microscopic waterflooding types in the study area can be divided into four types：uniform flooding type，network flooding type，network-finger flooding type，and finger flooding type. With the increase of unit displacement pressure，the displacement efficiency of uniform displacement model changes most obviously，followed by network flooding，network-finger flooding and finger flooding types are worst. Affected by the physical properties of rock particle surface and the pore throat structure，the different displacement types have different proportion of residual oil types after waterflooding. The residual oil types of uniform displacement type and network displacement type are mainly oil film and corner shape，the residual oil types of the finger displacement type are mainly sheet and cluster shape，and the network-finger displacement type has a similar proportion of the different residual oil types.

Abstract:The unclear evolution process of Yong1 glutenite body in Yonganzhen Oilfield，Dongying Sag adds difficulties to determine the reservoir type，which restricts the development of further exploration. The evolution process of Yong1 glutenite body and its influence on hydrocarbon accumulation are studied through 3D seismic interpretation，well logging and mud logging analysis，core observation，thin section observation，and physical property analysis. The results show that Yong1 glutenite body deposition conforms to the principle of“channel-fan correspondence”，and its provenance is provided by Chenjiazhuang uplift in the northwest，the debris transported along the NW-SE paleochannel between the uplift and Yong1 area. The isolated uplift of the Yong1 sand-conglomerate body are caused by the late intrusion of diabase. The earliest intrusion occurred in the period of the Upper Submember of the 4th Member of Shahejie Formation（the Upper Es4 Member）while diabase only intruded into the granitic gneiss basement and did not punctured the rock mass，and this process lasted until the early sedimentation of the 3rd Member of Shahejie Formation（the Es3 Member）. After the middle sedimentary period of the Es3 Member，diabase continued to intrude，Yong1 glutenite body continued to uplift，and rock was punctured gradually. This process lasted until the late sedimentary period of the Es3 Member. Magmatic activity leads to the formation of high-angle faults and fractures in the periphery of the glutenite body，which improves the reservoir space and percolation conditions，and effectively communicates the hydrocarbon source rocks in the Es3 and Es4 Member，forming a favorable accumulation area for hydrocarbon.

Abstract:The in-depth understanding of the storage and migration of coalbed methane requires qualitative analysis and quantitative characterization of the pore-fracture system in coal. In this study，the core samples of the No.3 coal seam in Mabidong Block in the southern Qinshui Basin was discussed in detail. The X-ray micro-CT scanning technology was applied，and three-dimensional digital model of the parent sample and the three-dimensional digital model of the child sample were proposed through low-resolution CT and high-resolution CT respectively. Based on that，the Avizo software was used to establish the pore-fracture system of coal sample，which realized the multi-scale quantitative characterization of the pore-fracture system. The results show that multi-scale pore structures develops in the No.3 coal seam of Mabidong Block in southern Qinshui Basin. Generally，the macropores are mainly C-type and the micropores are mainly E type. The overall pore connectivity is poor，and the fractures are isolated and distributed in sheets. According to the correlation of the mineral content between parent samples and child samples，it can be concluded that the large-scale fractures of the coal samples are mostly filled with minerals，which limits the percolation and production of the coalbed methane.

Abstract:Reservoir parameters are important for reservoir evaluation. Aiming at the difficulties of the traditional reservoir parameters prediction method to get rid of the constraint of a linear equation and the low prediction accuracy，a model combined with convolutional neural network（CNN）and gated recurrent unit（GRU）is proposed. The model not only has the local perception characteristics of CNN but also has the long-term memory function of GRU，thus having the ability to express the spatio-temporal features of data. The CNN-GRU porosity prediction model is established based on the well logging data of Well A to predict the porosity of unknown depth segment in this well area，and to further propose a variable learning rate training method. Compared with CNN or GRU models，experimental results show that CNN-GRU model can extract data features more effectively and can improve the reservoir parameters prediction accuracy，which provides a new idea to predict reservoir parameters.

Abstract:Binary composite system 1# has a non-ultralow oil-water interfacial tension（10-1 mN/m level），good emulsion stability，and strong viscosity reduction capacity by emulsification. In order to investigate the displacement efficiency of this system on conventional heavy oil，evaluations are carried out on five aspects including：interfacial tension，degree of emulsification difficulty，emulsion stability，viscosity reduction capacity by emulsification，and displacement efficiency. The results are compared with binary composite systems 2# and 3# with ultra-low interfacial tension（10-3 mN/m level）as well.The results show that the emulsion formed by 1# is more stable，indicating that there is no correlation between emulsion stability and ultra-low interfacial tension，though 1# is more difficult to emulsify heavy oil than 2# and 3#. Percolation experiment results show that 1# could significantly decrease the flowing resistance of heavy oil，while 2# and 3# have no similar effect. According to the emulsifying difference of systems 1#，2# and 3#，it is believed that the emulsion stability is the key to improve the flow of heavy oil through emulsification. The oil displacement test result show that composite system 1# could increase oil recovery by 15.6%，which is much higher than that of 2# and 3# with ultra-low interfacial tension（about 10.0%）. This indicates that emulsion stability and viscosity reduction capacity by emulsification are important to the displacement of conventional heavy oil in binary composite system.

Abstract:Multistage fractured horizontal well is the one of the key techniques that has been widely used in the development of tight oil reservoirs at present. Because the pore throat of the tight oil reservoir is at nanoscale and the reservoir has extremely low permeability，the unsteady crossflow in the rock matrix cannot be ignored. Therefore，a five-linear flow mathematical model is proposed，in which the threshold pressure gradient，the stress sensitivity and the unsteady crossflow in unstimulated area are taken into account. Laplace transformation，Pedrosa’s transformation and Perturbation transformation are applied to solve the mathematical model，and the bottomhole pressure at the Laplace Space is obtained，and the dynamic pressure curves are plotted in double logarithmic coordinates by Stehfest numerical inversion. The results show that the dynamic pressure curves can be divided into six flow stages and fit well with the field data，which verifies the model. Meanwhile，the crossflow coefficient，the elastic storativity ratio，the dimensionless permeability modulus of main fractures，the threshold pressure gradient，and the permeability of unstimulated reservoir are analyzed，so that the effects of these parameters on well testing curves are clarified.

Abstract:Complex faulted block reservoir is one of the important hydrocarbon resources in China，and it has the characteristics of complex structure，small oil-bearing area and large strata dip. It is difficult to form a perfect injection-production pattern and to produce“attic oil”at the top of the reservoir. As a method for effectively maintaining formation energy and improving displacement efficiency，secondary gas cap drive under huff and puff technique has been proposed and applied to the development of the complex faulted block reservoir. Based on the typical characteristics of the reservoir，the mechanism of the secondary gas cap drive under huff and puff is analyzed，the formation conditions and influencing factors of the secondary gas cap are determined combined with the reservoir engineering method and reservoir numerical simulation，and the forming stage of the secondary gas cap during the nitrogen huff and puff process is studied. The results show that when the gas cap index is greater than or equal to 0.5 during nitrogen huff and puff process in the complex faulted block reservoir，the secondary gas cap with a certain driving energy can be formed. The lower dissolved gas/oil ratio，the lower formation pressure and the larger cumulative gas injection and oil production are more conducive to the development and formation of the secondary gas cap.

Abstract:In order to solve the global optimization of energy consumption in the oilfield waterflooding system，the characterization approach of energy consumption in the oil reservoir system is established by using energy conservation law and characterization method of fluid energy. Physical meaning of each item for the characterization method is described. Based on the proposed model，the objective function is defined as the lowest energy consumption per ton of oil at certain stage. The characterization methods of energy consumption in the water injection system，oil reservoir system，lifting system and the oil reservoir development plan are considered as the constraint conditions. The oil production and water injection volume of single well in the water injection system are set as the decision variables. Then，global optimization model for energy con? sumption of oilfield waterflooding system is proposed. The global optimization method is applied to the plan optimization of a certain injection-production well group. Reservoir parameters may be obtained through numerical simulation. The optimal injection-production plan and formation pressure maintenance level are obtained，and the rationality of this method is verified.

Abstract:In order to ensure the performance and economic benefits of oil sands developed by steam-assisted gravity drainage（SAGD），well spacing evaluation is performed for Block A in Longlake Oilfield，Canada. Firstly，according to the distribution of geological parameters of the area，the cumulative oil production is used as the evaluation index to screen the main geological controlling factors. Secondly，numerical simulation is used to clarify the influence of single main geological controlling factor on development indicators. Finally，considering the well drilling and completion investment，crude oil price，and other economic parameters，the net present value is used as the indicator to evaluate the economic benefits of various well spacing under the complex geological factors. An optimal screening method and the process to optimize SAGD well spacing are obtained by comprehensively considering geological conditions，development effects，and economic benefits.The preferred method and process achieve a rapid optimization of reasonable well spacing at a target oil price. For Block A in Longlake Oilfield，oil layer thickness，interbed distribution，high water saturation interlayer thickness，and top water layer thickness are four main geological controlling factors. According to the geological parameters of Block A，the average thickness of the preferred oil layer is 25 m，the interbed distribution is 60%，the high water saturation interlayer thickness is 3.7 m，and the top water layer thickness is 2.2 m. When the oil price is 50 US dollars per barrel，the recommended well spacing is 102 m，which is close to the well spacing（100 m）calculated by the actual model corresponding to the maximum net present value.

Abstract:In order to clarify the distribution of residual oil in reservoirs with fining-upward，coarsening-upward，and superposition sequences in G Oilfield after polymer flooding，and to provide a reliable basis for residual oil recovery，water flooding and polymer flooding experiments were carried out in the three-dimension heterogeneous models according to reservoirs with different sequences. The experimental results show that：in the fining-upward sequence，the high-permeable layer at the bottom was flooded badly，and the swept volume in low-and medium-permeable layers was enhanced obviously after polymer flooding. Compared with water flooding，the average recovery rate in early stage increased by 3.4 times and oil recovery increased by 22.2%，the residual oil mainly distributes at the top of low-permeable reservoir near the corner production well in inverted nine-spot well pattern，and the horizontal adjustment well should be deployed at the top of reservoir to produce the residual oil；in the coarsening-upward and superposition sequences reservoirs，the modelled water flooding was more uniform in the vertical direction，and the swept volume can be further enlarged after polymer flooding. Compared with water flooding，the recovery rate in early stage increased by 2.3 times and 2.1 times，respectively，and the oil recovery enhanced by 18.5% and 18.1%，respectively. The remaining oil mainly distributes at the unswept area near the corner production well，and the directional adjustment well should be deployed to produce the residual oil. After the research result was applied to the field test of G Oilfield，the initial daily oil production of the adjustment wells was 2-3 times those of the old production wells nearby.

Abstract:The nanoparticle-stabilized CO2 foam flooding is a new technique in enhanced oil recovery（EOR），and it is still at the laboratory research stage. In this study，the research background，mechanisms，performance evaluations，and oil displacement efficiency of the nanoparticle-stabilized CO2 foam flooding are reviewed. The results show that nanoparticles would synergize with certain surfactant molecules to inhibit CO2 bubble burst，coalescence and disproportionation，to prolong liquid film discharge time，and to delay internal foam rupture speed，which could improve the stability of CO2 foam system during the oil displacement. The half-life of combined system of nanoparticle and surfactant is over 2.5 times than that of single surfactant system. The oil recovery of the combined system after changing the surface properties could be increased by 7%-10%，with a maximum up to 30%. However，the excessive amounts of nanoparticles would also lead to the increase of surface tension of CO2 foam system，and resulting in the poor foaming property，the decrease of foaming volume and the swept volume. Different kinds of nanoparticles would have different synergistic effects on surfactants. Therefore，the screening and evaluation of the combined system of nanoparticle and surfactant is the key to the nanoparticle-stabilized CO2 foam flooding.

Abstract:Maintaining a reasonable liquid production scale is one of the main measures to delay the decline of production in waterflooding reservoirs during extra-high water cut period，during which the relative permeability curve of oil and water obtained from core testing is usually used to calculate the variation of dimensionless liquid production index with water cut，so as to predict the reasonable liquid production of reservoirs in extra-high water cut period. However，the theoretical dimensionless liquid production index curve based on core testing is not suitable for the actual situation in the field due to the great difference between the water flooding process in the core and heterogeneous reservoirs. Therefore，based on parallel core water flooding experiment，the dimensionless liquid production index curve equation with permeability and permeability ratio was obtained by regression，and the dimensionless liquid production index increment chart considering the influence of reservoir physical properties and physical heterogeneity degree was established. Then，the flow field of the water flooding reservoir was divided into water flooding swept area and non-swept area，and the experimental law of core water flooding was applied to the water flooding swept area only，and the dimensionless liquid production index chart of the reservoir with different sweep coefficients was plotted. Field example analysis shows that the method requires fewer parameters and is fast in calculation，can consider the influence of reservoir heterogeneity，and can calculate the current sweep efficiency of water flooding based on the measured fluid production index in the field.

Abstract:Most tight oil reservoirs are put into production by multistage fractured horizontal well，and the distribution of the natural fractures and hydraulic fractures，and the coupling of the fractures and matrix should be considered in the productivity analysis. A model of the horizontal wellbore，and the distribution of the hydraulic fractures and natural fractures is proposed by the COMSOL and MATLAB program based on the real data of the fracture strike and density in S Oilfield. The pressure distribution，daily oil production and cumulative oil production under the different lengths and spacing of hydraulic fractures are simulated by the matrix-fracture-wellbore coupling flow model. The results show that the pressure drops can be firstly observed in the main fractures and secondary fractures with higher conductivity，and then pressure drops spread to the natural fractures and matrix slowly. Pressure drop is hard to spread to the unstimulated and disconnected reservoir regions. The low-pressure area accounted for 34.1% of the whole reservoir area when the production time is 1 000 days. Increasing fracture length and decreasing fracture spacing are helpful to the improvement of both daily and cumulative oil production. Decreasing the fracture spacing is a more effective way to increase the daily oil production so that the cumulative oil production is improved significantly.