川中地区蓬莱气田震旦系灯影组二段储层发育主控因素及分布规律

Main controlling factors and distribution of reservoirs of the second member of Sinian Dengying Formation in Penglai gas field,central Sichuan Basin

结合岩心、薄片及分析测试等资料,对川中蓬莱气田震旦系灯影组二段储层的主控因素及分布规律进行了详细研究。研究结果表明:(1)蓬莱气田震旦系灯二段储层主要由凝块石白云岩、泡沫绵层白云岩及砂屑白云岩组成,储集空间包括孔隙、溶洞及裂缝,以残余格架孔和中小型溶洞为主,孔隙多发育于微生物黏结白云岩及颗粒白云岩中。灯二上亚段储层孔隙度为2.0%~11.0%,平均为4.43%,渗透率为0.005~10.000 mD,平均为1.190 m D;灯二下亚段储层孔隙度为2.00%~6.98%,平均为3.64%,渗透率为0.030 9~2.600 0 mD,平均为0.950 0 mD。(2)微生物丘滩体展布及准同生期岩溶作用、表生期岩溶作用共同控制了研究区灯二段储层的分布及品质,优质储层多发育于灯二上亚段中上部和灯二下亚段顶部。(3)研究区灯二下亚段总体属海进半旋回产物,仅上部发育孔洞/缝洞型储层,中部及下部储层欠发育。灯二上亚段多为海退半旋回产物,其1小层为次级海侵背景,丘滩体厚度薄,以孔隙型储层为主;2小层在海退背景下发育连片分布的丘滩体,储层厚,以孔洞型储层为主(多为Ⅱ类储层),为区内主力产气层段;3小层总体为海退晚期浅水台坪沉积,葡萄花边构造发育,岩溶改造作用较明显,储层多为缝洞叠加岩溶型储层(Ⅲ类储层)。

Based on data of rock cores,thin sections and analysis tests,a detailed study was conducted on the main controlling factors and distribution of the second member of Sinian Dengying Formation in Penglai gas field in central Sichuan Basin.The results show that:(1)The reservoirs of the second member of Sinian Dengying Formation in Penglai gas field are mainly composed of thrombolite dolomite,foam spongy dolomite and doloarenite.The reservoir space includes pores,caves and fractures,dominated by residual framework pores and small and medium-sized caves.The pores are mostly developed in microbial bonded dolomite and grain dolomite.The porosity of the reservoir in the upper Deng 2 member is 2.0%-11.0%,with an average of 4.43%,and the permeability is 0.005-10.000 mD,with an average of 1.19 mD.The porosity of the reservoir in the lower Deng 2 member is 2.00%-6.98%,with an average of 3.64%,and the permeability is 0.0309-2.6000 mD,with an average of 0.9500 mD.(2)The distribution and quality of reservoirs of Deng 2 member in the study area are jointly controlled by the distribution of microbial mound shoal,quasi syngenetic karstification and supergene karstification.High-quality reservoirs are mostly developed in the upper and middle parts of the upper Deng 2 member and the top of the lower Deng 2 member.(3)The lower Deng 2 member in the study area is generally a product of semi cyclical marine transgression,with vuggy-fractured reservoirs only developed in the upper part and reservoir undeveloped in the middle and lower parts.The upper Deng 2 member is mostly a product of regression and semi cycle.No.1 sublayer developed in a secondary transgression background,with thin mound shoal,dominated by porous reservoir.No.2 sublayer developed contiguous mound shoal under regression,with thick reservoirs mainly composed of vuggy reservoirs(mostly typeⅡreservoirs),which is the main gas producing zone in the study area.The No.3 sublayer is overall shallow water platform deposit in the late stage of regression,with well-developed botryoidal-lace shape structures and obvious karst transformation,dominated by karst reservoirs with superimposed fractures and caves(typeⅢreservoirs).