Geological Factors Of Shale Oil And Prediction Of Sweet Spot

The exploration and development of shale gas has been achieved with commercial value in China.Such as Fuling shale gas of Sinopec Group and shale gas in ChangningWeiyuan demonstration zone of CNPC have a certain capacity and scale.However,the theoretical basis of exploration and development of continental shale oil is not fully understood,and it is still in the exploratory stage.This paper mainly carries on the research on salt shale oil geological factors of Qianjiang Formation,such as the hydrocarbon generating conditions of shale oil(organic matter abundance,organic matter type,organic matter maturity,shale thickness and depth),reservoir conditions(porosity,permeability,fracture distribution,oil-bearing),abnormal formation pressure(abnormal high pressure)and reservoir brittleness.It also provides some geophysical methods for the prediction of some geological factors(such as TOC,fractures,oil-bearing,abnormal high pressure and brittleness)and can be used for reference and guiding significance.With the increase of TOC,the S1 value is divided into three parts,the demarcation point of the TOC values is 1.0% and 0.5%,the salt shale oil resources can be divided into three classes:class ?(enriched shale oil),class ?(potential shale oil),class ?(ineffective shale oil).The type of organic matter is mainly type I,followed by type ?1,and the both types accounted for more than 95% of the total samples,but the content of type II2 is very low,and the type ? is almost nonexistent.From the perspective of maturity,The organic matter types of Eq2 source rocks are dominated by type I,the thermal evolution of overall organic matter is in the immature-low maturity stage,Ro value is mainly in the range of 0.26%-0.5%,and a small amount of wells maturity can reach 0.82%.The organic matter types of Eq3 source rocks are mainly type I and type ?1,the thermal evolution of overall organic matter is in the low maturity-medium maturity stage,Ro value is mainly in the range of 0.55%-0.88%.The organic matter types of Eq4 source rocks are mainly type I and type ?1,the thermal evolution of overall organic matter is in the medium maturity-maturity stage.Ro value is mainly in the range of 0.55%-1.3%.The mudstone reservoir in Qianjiang Formation belongs to low porosity-low permeability and medium porosity-medium permeability reservoir.The crude oil of Eq2 has the maximum density and highest viscosity,and it belongs to medium heavy oil.The crude oil of Eq3 has less density and lower viscosity,and it belongs to light medium viscosity oil.The crude oil of Eq4 s has the minimum density and higher viscosity,and it belongs to light high viscosity oil.S1 and S1/w(TOC)are used to establish the classification criteria of shale oil of Qianjiang Formation in Qianjiang Sag.The demarcation points of the S1 values are 3mg/g and 1 mg/g,S1/w(TOC)values are 300 mg/g and 100 mg/g.The oil-bearing grade can be divided into the following categories: class I(good oil-bearing content),class II(Medium oil-bearing content)and class ?(Poor oil-bearing content).Inter salt mineral composition is complex,mainly composed of detrital minerals,carbonate minerals and evaporite minerals.The author thinks that the brittleness of better salt shale oil reservoir should satisfy:(1)the content of brittle minerals such as quartz and carbonate is more than 50%,(2)Young's modulus is greater than 20 GPa,Poisson's ratio is less than 0.25,(3)the brittleness index is in the range of 40%-50%.The prediction of TOC is recommended by ?Lg R technology,because the ?Lg R value is easy to obtain according to the required logging data,and the prediction results are relatively reliable.The prediction of fracture is suggested to adopt DFN model,Under the condition of multi constraints,the unified model of the information of cracks can be used to describe the spatial distribution and geometric characteristics of the crack system.The prediction of hydrocarbon-bearing property is suggested to adopt improved Aki-Richard formula by Fatti.It is suggested that the Fillippone empirical formula is used in the prediction of abnormal high pressure,combined with the geological characteristics of the target area,using pseudo acoustic seismic inversion to determine the speed of pressure prediction coefficient K.The method of brittle mineral composition is simple and convenient,but the result is not accurate,so it is suggested to use the brittle index formula by Rickman,which adds Young's modulus and Poisson's ratio to explain the brittleness from the point of view of rock mechanical properties,which is closer to the real situation of rock brittleness.