Conditions For Shale Oil Hydrocarbon Accumulation And Optimization Of Favorable Areas In The ES_x~1 On The Southwestern Edge Of Qikou Sag

The degree of conventional oil and gas exploration in the Qikou sag is increasing day by day,and it is urgent to find a new way of resource replacement.It is of great significance to clarify the shale oil accumulation conditions in the ES¹x of the Qikou sag and to select favorable exploration areas to increase oil and gas reserves and output.This article takes the ES¹x in the southwestern margin of the Qikou Sag as an example,Using source rock geochemical research,scanning electron microscopy,whole-rock X-ray diffraction,nitrogen adsorption,mudstone reservoir particle fluorescence analysis（QGF-E）and other technical methods,combined with logging,study its accumulation conditions,evaluate its resources and select favorable areas.The following conclusions are drawn:（1）The study area is a salt water environment with arid climate,a transitional phase between land and sea,with weak land source supply,and an anaerobic environment.The dark mud shale developed in the ES¹x is thick and gradually thickens to the northeast on the plane;The content of brittle minerals is rich,mainly dolomite and calcite.After 3400m,the montmorillonite was transformed into other clay minerals in a large amount,and the proportion of the mixed layer of Imonite has been greatly reduced.（2）The main types of organic matter are typeⅠand typeⅡ₁.Kerogen is mostly composed of sapropel,with an average TOC of 2.44%,hydrocarbon generation potential and chloroform bitumen"A"are also at a high level,reflecting the high abundance of organic matter,which lays a good material foundation for the generation of shale oil.Most of the maturity is in the low-maturity stage.（3）The reservoir has developed mineral intercrystalline pores,residual intergranular pores,organic matter pores,secondary dissolution pores and other pore types.The reservoir space can be divided into slit-type pores open at both ends,wedge-shaped pores open at both ends,or relatively small pores.There are three types:narrow slit-shaped pores,wedge-shaped pores with open ends or closed ends.Generally,the pore diameter is less than 70nm,the specific surface area is less than 25m²/g,and the total pore volume is less than 30μl/g;the effective porosity of the target layer averages9.77%,and the permeability is mostly distributed in 0.1～10m D.（4）Pure mudstone samples have the highest oil saturation,followed by dolomitic mudstone and lime mudstone.The average OSI of the study interval is 141.42mg/g;The geological resources of shale oil in the study area are calculated to be about23.41×10⁸t,and the recoverable resources are about 1.52×10⁸t;Two favorable areas are selected,with total the area is about 10×10⁶m².