Comprehensive Evaluation Of Sweet Spots In Interlayer Shale Oil Of The First Member Of Qingshankou Formation In Daqingzijing Area Of The Songliao Basin

Shale oil is abundant in the lacustrine facies of China,but its heterogeneity is completely strong,and there are more differences in oil content,oil occurrence characteristics,oil mobility,etc.which seriously restricts the selection and benefits of lacustrine shale oil sweet spots development.There is an urgent need to systematically conduct a comprehensive evaluation of geological and engineering parameters such as lithology,physical properties,oiliness,mobility,and brittleness of shale oil reservoirs,reveal the oil heterogeneity of lacustrine shale oil,and establish a comprehensive sweet spot evaluation standard for shale oil.,supporting the optimization and profitable development of lacustrine shale oil sweet spots.This paper takes the Qing1 Member of the Daqingzijing area in the southern Songliao Basin as the research object,analyzes the characteristics and genetic mechanisms of different types of lithofacies,constructs a lacustrine fine-grained sedimentary lithofacies architecture model,and clarifies the distribution characteristics and control of different types of shale oil reservoirs.factors,study the oil content,occurrence state and mobility of lacustrine shale oil,establish comprehensive evaluation standards for continental shale oil sweet spots,and reveal the distribution patterns and controlling factors of lacustrine shale oil sweet spots.Using the"four-end member"classification scheme of organic matter abundance,sedimentary structure,mineral components and rock types,the Qing1 Member is divided into seven types of lithofacies,including low organic matter layered siltstone facies and medium-low organic matter silt laminated shale.,medium and high organic matter mud lamina felsic shale is a favorable lithofacies type.The distribution of different types of lithofacies shows the changing pattern of"vertical stratification,north-south zoning,and east-west zoning".From the siltstone facies in the south or west of the work area,it gradually transitions to silt laminated shale(C)and long mud laminated shale in the northeast.The basal shale(B)and the mud-laminated clayey shale(A)show a three-stage transgressive process vertically,from siltstone and C lithofacies in the lower part to upward transition to B and A lithofacies.There are mainly 5 types of pores developed in the Qing1 Member shale reservoir.Intergranular pores,dissolution pores and clay intercrystalline pores are the main pore types,and organic pores are locally developed.The main peak distribution of shale pore diameter is10-100nm,with micropores and small pores being the main ones..Combined with fractal theory,30,100 and 1000nm are used as boundaries to divide shale pores into micropores,small pores,mesopores and macropores.Combining the relationship between the proportion of medium and macropores and movable porosity,different lithofacies are established.Types of reservoir classification standards.From Type I to Type III reservoirs,the proportion of medium and large pores decreases,micropores increase,and the movable porosity decreases rapidly.Based on pressure-maintained/sealed samples,the recovery model of light and heavy hydrocarbons of intercalated shale oil in the Qing1 Member Formation was established through two-dimensional nuclear magnetic resonance and step-by-step pyrolysis experiments.Shale oil occurrence is affected by pore structure(average pore diameter,effective porosity,etc.),organic matter abundance and maturity.The higher the effective porosity,the larger the average pore diameter,and the more abundant free oil;the higher the TOC,the lower the free proportion,and the proportion of free oil in medium and low TOC lithofacies is high;the higher the maturity,the higher the proportion of free oil.From the outer front to the lacustrine area,the shale oil type transitions from interlayer type to lamina type.The amount of free oil and adsorbed oil both show an increasing trend,and the free proportion increases.Based on the centrifugation experiment of sealed coring samples,the mobility rules of shale oil are revealed.Under a pressure difference of 3.2MPa,the lower limit of pore size for movable oil in shale is about 150-300nm;shale oil mobility is controlled by mineral composition and TOC.The higher the clay content,the greater the TOC,and the higher the proportion of adsorbed oil.The movable amount is closely related to the production capacity of shale oil testing.The movable oil amount,effective porosity×oil saturation are preferably used as indicators.The oil content of shale oil is divided into three categories.Type I oil layers are mainly developed in C lithofacies and B The lithofacies is divided into east-west areas on the plane,and the high-value areas are distributed in sheets or north-south strips.Based on the relationship between geological and engineering parameter indicators and oil testing productivity,movable fluid porosity,movable oil volume,maturity,pore pressure and brittleness index are optimized to establish a comprehensive sweet spot evaluation technology based on weighted combinations and classify shale-type sweet spots into,sandstone sandwich type desserts are each divided into 2 categories.The multi-parameter plane superposition method was used to determine the plane sweet spot area of the interlayered shale oil in the Qing1 Member.The sweet spot area of type I shale type is 619.69km~2,the sweet spot area of type II shale type is 1270.84 km~2,and the sweet spot area of type I sandstone interlayer type is 619.69 km~2.213.47km~2,the area of Type II sandstone interlayer sweet spot is 299.68km~2;the area of potential favorable sand and shale joint mining area is72.13km~2.