川西二叠系火山碎屑岩储层特征及发育有利区

火山岩是四川盆地重要的有效储集体,中石化在川西地区部署的YS1井钻遇厚层火山岩,气显示强烈,为盆地内火山岩勘探新区域。基于对已有钻井资料分析,综合研究区域地质背景,从岩性组合方式、储集空间类型、地化特征和储层孔隙演化等方面开展川西地区火山碎屑岩储层基本特征研究。研究区火山岩的形成与峨眉山地幔柱活动具有一定关联,岩石类型复杂,储层储集性能非均质性强,具高孔低渗特征,为一套裂缝-孔隙型储层。火山角砾岩为主要储集岩类,储集空间以残余气孔、基质微孔、次生溶孔为主,见少量构造裂缝和冷凝收缩缝。同生成岩阶段,挥发逸散、脱玻化作用和冷凝收缩作用促使气孔、玻屑孔和收缩孔缝发育,但热液充填作用使孔隙度大幅度降低；表生成岩阶段,构造破裂和风化淋滤作用小幅改善储层储集性能；埋藏成岩阶段压实作用、充填作用和溶蚀作用对储层进行改造,最终储层残余面孔率4%左右。YS1井区、广汉、知新场和龙宝梁地区为储层发育有利区。

Pyroclastic reservoir characteristics and favorable reservoir zone of Permian in Western Sichuan

Volcanic rock is an important and effective reservoir in Sichuan Basin, thick volcanic rocks were encountered in well YS1 showed strong gas display in western Sichuan depression, new areas for volcanic rocks within the basin were explored. The drilling data and regional geological setting were taken from well YS1, the characteristics of pyroclastic reservoir in western Sichuan were analyzed by lithologic association pattern, type of reservoir space, geochemical characteristics and reservoir pore evolution. The formation of volcanic rocks was related to the mantle plume activity in Emeishan, the complex rock type of volcanic rock reservoir lead to the reservoir property is highly heterogeneous. The fracture-pore type reservoir have high porosity and low permeability. The main reservoir rock is volcanic breccia. Residual pores, matrix micropore and secondary erosion pore are the main reservoir space, structure crack and condensing crack besides. Gas pocket, devitrification pore, shrinkage hole and stich were formed during the syngenetic stage by volatile releasing, devitrification and condensation shrinkage, but the porosity was greatly reduced by hydrothermal filling. The reservoir performance improved by tectonic disruption and weather eluviation over the period of the course of the exodiagenes. During the burial diagenesis stage, the reservoir retrofit of compaction, packing action and dissolution. The result reflects the residual face rate of reservoir is about 4%. Well YS1 area, Guanghan area, Zhixinchang area and Longbaoliang area are the favorable reservoir zones in Western Sichuan.