四川盆地PS8井区灯影组四段丘滩体储层特征及成因机制

Mound-shoal reservoirs characteristics and genesis mechanism in the fourth Member of the Dengying Formation of PS8 well area in Sichuan basin

四川盆地震旦系灯影组四段是近期的重点勘探层位,PS8井灯影组四段试气获得高产,展示出灯影组四段天然气勘探的巨大潜力。基于钻井岩心、岩屑、薄片、分析化验和测井等资料,对PS8井区灯四段丘滩体储层特征及成因机制开展研究。结果表明:①PS8井区灯影组四段从裂陷槽向台内具有逐渐增厚的趋势,储集层岩性主要为藻凝块白云岩、藻叠层白云岩、砂屑白云岩;储集空间以溶蚀孔洞及裂缝为主,柱塞样孔隙度为0.86%~6.59%,平均3.58%,渗透率为0.00085~14.75mD,平均1.71mD,全直径孔隙度为1.15%~8.42%,平均3.84%,渗透率为0.003~16.8mD,平均2.16mD,属于低孔低渗型储层;②台缘带发育的微生物丘滩沉积是PS8井区灯影组四段优质储层发育的物质基础,表生期风化壳岩溶和埋藏期热液溶蚀作用是PS8井区灯影组四段储层大量溶蚀孔洞发育的关键因素。研究成果落实了研究区灯影组四段丘滩体储层特征,并明确了储层的成因机制,为后期储层发育分布预测提供了理论支撑,同时为评价方案的部署提供了地质依据。

The fourth Member of the Sinian Dengying Formation(Deng 4 Member)in Sichuan basin is a key petroleum exploration stratum recently.High gas yield was obtained in the well PS8 during the gas test in the Deng 4 Member,indicating a promising gas exploration potential.Based on drilling cores,cuttings,thin sections,analysis tests,and logging data,the characteristics and genesis mechanism of mound-shoal reservoirs of the Deng 4 Member in the PS8 well area were conducted.Results show that,OThe Deng 4 Member in the PS8 well area has a tendency to thicken from aulacogen to platform.The lithology of the reservoir is mainly algal clot dolomite,algal stromatolite dolomite,and granular dolomite.Reservoir space is given priority to with solution pores and cracks,reservoir space is given priority to with solution pores and cracks.The porosity of plunger samples ranges from 0.86%~6.59%(average:3.58%);the permeability is 0.00085~14.75 mD(average:1.71 mD).The porosity of full diameter cores is 1.15%~8.42%(average:3.84%);the permeability is 0.003~16.8 mD(average:2.16 mD).The reservoir is mainly dissolution pores and fractures,and belongs to the low porosity and permeability reservoir.@The platform margin microbial mound sedimentation is the basis for the development of high-quality reservoirs in the Deng 4 Member in the PS8 well area.Supergene regolith karst and buried hydrothermal dissolution are the key factors controlling the development of dissolution pores of the reservoir.This study evaluated the mound-shoal reservoir characteristics defined the genesis mechanism of the Deng 4 Member.It provides a theoretical basis for the reservoir development and distribution prediction,as well as geological evidence for the designation of evaluation schemes.