Sandbody Architecture And Gas-water Distribution Of Shaximiao Formation In Eastern Slope,Western Sichuan Depression

In view of Jurassic Shaximiao Formation in Eastern Slope,Western Sichuan Depression,predecessors have been in-depth understanding on the regional geology,the characteristics of gas reservoir,development conditions,etc.With the deepening of oil and gas exploration and development in Eastern Slope,Western Sichuan Depression,there are still more geological problems,which include that gas-water distribution does not match the existing geological knowledge,the testing production and dynamic reserves have a big difference between the single wells in the same set of sandbodies,high-yield areas are relatively limited in scale,there is a great difference in productivity between wells in the testing area,etc.For example,at the present,the same set of sandbodies which is characterized produces water at the high position near the fault of the source rock,and producing gas at the low position away from the fault of the source rock.This distribution characteristic is not in accordance with the basic understanding of the accumulation and migration of the oil and gas.Gas-water distribution in the study area needs to be further in-depth understanding.The reservoirs of Jurassic Shaximiao Formation in Eastern Slope,Western Sichuan Depression are single or overlapping channel sandstones,which have the characteristics of thin sandstone thickness,obvious changes of lithology and physical properties in the horizontal direction,longitudinal overlapping is complex,dense and low permeability.These channel sandbodies have the strong plane heterogeneity,the gas-bearing properties of different channel sandbodies are obviously different.This paper is based on the data of core,well drilling,geophysical prospecting,production dynamics,etc,taking the methods that research work on sandbody architecture and gas-water distribution in the study area is carried out by combining geology with geophysical prospecting,combining static with dynamic.This study,firstly,based on statistics and analysis for the types of and their characteristics,according to the physical properties of lithofacies,the vertical lithofacies associations type is divided into single type and combined type;accordingly,combining with the sandbody vertical overlapping characteristics and its physical properties,etc,the type of sandbody vertical structure is divided into the isotypy and the compound type;then based on division of the sandbody vertical structure,based on knowledge of genesis,to propose four types of division schemes,namely,the isotypy of progradation and retrogradation superimposition,the isotypy of lateral accretion superimposition,the compound type of hydrodynamic force changes frequently and the compound type of channel migration change,and discussing geological controlling factors and seismic response characteristics for the development of sandbody architecture,Clearing that hydrodynamic conditions,the distance from the source,the curvature of the channel and the ratio of accommodation and sediment supply are the main geological controlling factors for the development of sandbody architecture;finally,based on the sandbody architecture,channel types are divided into smooth channel and partial non-homogeneous channel from evaluation for the degree of smoothness of channels,and discussing the controlling factors of plane distribution for channel types,clearing that it is mainly controlled by hydrodynamic conditions,the curvature of the channel,the variation of lake level and ancient terrain slope,etc.Based on the research of sandbody architecture,combining with the anatomy of gas-water relation,analyzing the control effect of sandbody architecture on gas-water distribution from the vertical and horizontal direction respectively.In the vertical direction,the large single layer thickness and the development of sandbody architecture of isotypy of channel sandbodies that gas-bearing properties is better,and gas production is high;the small single layer thickness and the development of sandbody architecture of compound type of channel sandbodies that gas-bearing properties is poor,and gas production is lower.In the horizontal direction,the gas-water distribution is controlled by the degree of connectivity of channel sandbody in the study area.The research shows that the degree of filling of smooth channel is higher than partial non-homogeneous channel,and natural gas migration distance of smooth channel is farer than partial heterogeneous channel,and smooth channels often form the structural gas reservoirs,partial non-homogeneous channels often form the partial lithologic gas reservoirs.According to that tectonic evolution is different,the partial lithologic gas reservoir can be divided into the lithologic-structural gas reservoirs which is the situ structural traps and the genesis of cutting off,blocking and the lithologic gas reservoirs that structural traps disappear and the genesis of cutting off,blocking,escaping and staying.According to previous study,combined with production dynamic data,the gas-water distribution in the study area is controlled by present tectonics,fracture system characteristics,etc.In this paper,based on it,combined with the controlling effect of sandbody architecture on the gas-water distribution and the oil and gas geological conditions to construct the model of gas-water distribution in the study area,carring out the prediction and evaluation for gas-water distribution of the typical sand groups JS₁¹,JS₃^3-1,JS₃^3-2,and JS₃^3-3 in the study area.In JS₁¹ sand group,Zhongjiang area,the area which JS201H well-JS106H well is in,Huilong-Fuxing area,which are near the southern part of the research area,the fault displacementthe of the fault is large,the inclination of fault section is small,the effectiveness of fault is better,therefore the channel sandbodies in these areas contact with faults effectively,and develop the sandbody architecture of the isotypy of lateral accretion superimposition,sandbody connectivity is better,the gas-bearing properties is better,so the above areas are evaluated as natural gas enrichment areas;other areas mainly contain water in JS₁¹ sand group.The channel sandbodies are stretching to the fracture holding area in Fenggu-Gaomiaozi area,this area products water in a whole,the gas-bearing properties is poor;the channel sandbodies develop the sandbody architecture of the compound type of channel migration change,sandbody connectivity is poor,the gas-bearing properties is poor.In JS₃³-1-1 sand group,the sandbody architecture of the compound type of hydrodynamic force changes frequently develops mainly in the whole research area,in Gaomiaozi area,the channel sandbody connectivity is better,the gas-bearing properties is better,so it is evaluated as natural gas enrichment area.In JS₃³-2-2 sand group,there develops three enrichment areas.Three channels in Gaomiaozi area,sandbody connectivity is better,channel sandbodies contact with faults effectively,the gas-bearing properties is better;the channel sandbody in Zhongjiang area develops the sandbody architecture of the isotypy of lateral accretion superimposition,it is the typical partial non-homogeneous channel,the gas-bearing properties is better;the channel sandbody in Huilong-Fuxing area develops the sandbody architecture of the isotypy of lateral accretion superimposition,sandbody connectivity is better.In JS₃³-3-3 sand group,there develops three enrichment areas.the channel sandbody in Hexingchang-Gaomiaozi-Fugu area develops the sandbody architecture of the isotypy of lateral accretion superimposition,sandbody connectivity is better,the gas-bearing properties is better;the channel sandbody in Zhongjiang area develops the sandbody architecture of the isotypy of lateral accretion superimposition,it is the typical partial non-homogeneous channel,it can form the the lithologic-tructural as reservoirs which is the situ structural traps and the genesis of cutting off,blocking,the gas-bearing properties is better;the channel sandbody in Zhongjiang area which is designated as natural gas enrichment area develops the sandbody architecture of the isotypy of lateral accretion superimposition,the gas-bearing properties is better.