川西坳陷二叠系火山岩地质特征及勘探前景

Geological Characteristics and Exploration Prospect of Permian Volcanic Rocks in Western Sichuan Depression

近年来川西坳陷YS1井首次在二叠系钻揭厚大火山碎屑岩储层,测试气水同产;之后邻区YT1井在火山碎屑岩中测试获气22.5×104 m3/d。本文通过对川西二叠系火山岩地质特征研究,明确爆发相与近火山口溢流相上部为有利相带,在川西地区广泛分布,是一个新的勘探领域,具有重要的勘探价值。研究表明,川西二叠系火山岩是“峨眉地幔柱”外带产物,沿深大断裂串珠状中心式喷发;纵向发育3期爆发相-溢流相喷发旋回,岩性主要为(熔结)火山角砾岩、凝灰质角砾岩、(含角砾)凝灰岩等火山碎屑岩,其次为火山熔岩及次火山岩,火山岩相控制影响储层的发育展布,综合预测川西地区发育火山机构面积1754km2,拓展了火山岩的勘探范围,同时具备较好的成藏条件,具有良好的勘探前景和重要的地质意义。

For the first time in recent years,a thick large volcanic clastic rock reservoir in Permian are discovered in YS1 well in the west Sichuan Depression,gas and water are produced simultaneously.After that,YT1 well in adjacent area got 22.5×10^(4)m^(3)/d gas in pyroclastic rock.Based on the study of geological characteristics of Permian volcanic rocks in western Sichuan,it is suggested that the explosive phase and the upper part of the overflow phase near the crater are favorable zones,which are widely distributed in western Sichuan and are a new exploration field with important exploration value.The results show that the Permian volcanic rocks in western Sichuan are the products of the outer belt of the Emei Mantle Plume and erupt in a beaded central type along the deep fault.Three phases of eruption-overflow eruption cycleswere developed vertically.The lithology was mainly volcanic clastic rocks such as(fusible)volcanic breccia,tuffaceous breccia and(breccia-bearing)tuff,followed by volcanic lava and subvolcanic rocks.It is comprehensively predicted that the area of volcanic institutions developing in western Sichuan is 1754km2,which expands the exploration range of volcanic rocks,and has good reservoir formation conditions,which has good exploration prospect and important geological significance.