川西龙门山前中三叠统雷口坡组储层特征

Reservoir Characteristics of Middle Triassic Leikoupo Formation in the Frontal Longmenshan Mountain,Western Sichuan Basin

龙门山前—川西的雷口坡组为在拉张构造环境里较为稳定的碳酸盐局限台地沉积。雷三段滩相规模大,其展布与龙门山走向一致,从北到南依次发育有广元上寺浅滩、江油—安县浅滩和洪雅浅滩;雷一段浅滩较发育,也与龙门山走向一致。雷口坡组储集岩为浅褐色块状厚层粉晶—细晶藻屑白云岩、砂屑白云岩,雷三段储层发育,平均孔隙度为6.23%,平均渗透率为0.076mD,储集性好。雷一段储层平均孔隙度为3.10%,平均渗透率为0.030mD,储集性较好。主要的孔隙类型有生物孔隙、粒间溶孔、粒内溶孔、晶间溶孔等,孔喉配置为中、小孔隙配细喉道。硫酸盐热化学还原反应(TSR)有利于次生孔隙的形成。在江油—灌县断裂以东的川西坳陷,是雷口坡组有利储层发育区。

Leikoupo Formation,located between frontal Longmenshan Mountains and western Sichuan Basin,is a more stablec arbonate restricted platform deposited in an extensional tectonics etting.For Leikoupo 3 Member,the shoal facies is widespread;the distribution is consistent with the Longmenshan Mountains’s trike;and three shallow shoals,including Guangyuanshangsi,Jiangyou-Anxian and Hongya,are developed from north to south.For Leikoupo 1 Member,the shoal facies is also pretty developed;the distribution is the same as that of Longmenshan Mountains.R eservoir rock in Leikoupo Formation is composed of light-greym assive and thick powder-to fine-crystal algal clastic dolomitea nd dolarenite,in which Leikoupo 3 and Leikoupo 1 reservoirs ared eveloped,with average porosity and permeability of 6.23% and 0 .076 mD,and 3.10% and 0.030 mD,respectively;the main poret ypes include biopore,and intergranular,intragranular and intercrystalline dissolution pore;the pore-throat assembly is middlea nd small pore with fine throat.In this formation,TSR is very conducive to forming secondary pore.In addition,Leikoupo Formationin east area of the Jiangyou-Guanxian Fault Belt,Western Sichuan Depression,is a favorable region for reservoir development.