准噶尔盆地玛湖凹陷二叠系风城组页岩油储层微观孔隙形态对含油性的影响OA

The pore structure of shale reservoirs is a key factor affecting oil-bearing properties.However,pre-vious studies have mainly focused on the impacts of pore type,size,and connectivity on reservoir oil-bearing capacity,with limited research on the controlling effect of pore morphology.Pore morphology is directly related to the effectiveness of pore storage space and the occurrence state of fluids,making its influence mechanism on oil-bearing properties a crucial element for improving the theory of shale oil accumulation.In this study,field-emission scanning electron microscopy(FE-SEM),N ₂ adsorption,and high-pressure mercury injection(HPMI)experiments were conducted to quantitatively characterize the pore morphology and pore size distribu-tion of shale oil reservoirs in the Permian Fengcheng Formation.Furthermore,X-ray diffraction(XRD)and X-ray energy dispersive spectrum(EDS)analyses were used to reveal the genetic mechanisms of different pore morphologies from a mineralogical perspective.Combined with rock pyrolysis experiments and fluorescence thin section observations,the influence mechanism of pore morphology on oil-bearing properties was investi-gated from both indirect and direct perspectives.The results show that the pore structure of the Fengcheng For-mation in the Mahu Sag is complex,dominated by mesopores and macropores with good connectivity.Based on morphological characteristics,the pores are classified into three types:slit pores,elliptical-like pores,and circular-like pores.Slit pores are mostly intergranular pores of dolomite formed by compaction,which contrib-ute to the increase in macropore volume and exhibit good oil-bearing properties.Elliptical-like pores are devel-oped under the protection of a rigid quartz framework;although they compress the macropore volume to a cer-tain extent,they generally maintain favorable oil-bearing capacity.Circular-like pores,characterized by small pore sizes,are mainly intragranular dissolved pores of feldspar,making little contribution to mesopore and mac-ropore volumes and showing relatively poor oil-bearing properties.Finally,three microscopic occurrence mod-els of shale oil based on pore morphology were proposed,considering the formation mechanisms of different pore types and their influences on oil-bearing properties.This study provides a new theoretical basis and evalua-tion perspective for shale oil reservoir sweet spot prediction.