四川盆地川西南地区下二叠统气藏类型及有效缝洞分布规律

GAS RESERVOIR TYPES AND EFFECTIVE FRACTURE-VUG DISTRIBUTION LAWS OF LOWER PERMIAN SERIES IN THE SOUTHWEST AREA OF SICHUAN BASIN

通过对川西南地区下二叠统完钻的２００多口并进行综合研究后认为，形成该区下二叠统储层有效储集空间的主控因素是岩溶、构造和断层等作用。根据这三种控制因素的匹配关系，可将该区下二叠统气藏划分成五种类型：①背斜—下二叠统顶部岩溶—断层型；②背斜—断层型；③下二叠统顶部岩溶—断层型（非背斜背景下）；④断层型（非背斜背景下）；⑤背斜—岩溶型。这五类气藏的有利部位是：第一类是三种控制因素的叠加部位，其中以断层使茅口组四段自身重复的部位为最佳；第二类是在有利的构造部位，以断层断开等一、二段，且上、下盘重复茅二段的地区；第三类是断层断开茅二、三段，且上、下盘重复茅三段的地区；第四类是断层使等二段自身重复的地区；第五类是在茅二段之上岩溶发育带和有利构造部位叠加地区。此外，该区下二叠统有利储层具有如下分布规律，即在纵向上主要集中在茅二段之上，模向上分布在岩溶和构造的叠合区。

t is considered that the main control factors of effective storage spaces of Lower Permian Series in southwest area of Sichuan are the actions of karst,structure and fault by comprehensively researching 200 drilled wells distributed over structures(area)of several tens.In the light of the match relations among the three factors,the gas reservoir of tower Permian Series in the area are divided into five types, i.e.①anticline-karst on the top Lower Permian Series-fault;②anticline-fault;③karst on the top of Lower Permian Series-fault;④fault;⑤anticlinekarst.The favourable positions of the five types of reservoirs are those: The first is the superposition controlled by three factors and the best of it is the fault self-overlaping of member 4 of Maokou formation; The second is the fault broken ground of member 1 and member 2 of Maokou formation and the mamber 2 repeated on upper and lower walls at favourable location; The third is the fault broken ground of member 2 and member 3 of Maokou formation and the member 3 repeated on upper and lower walls; The fourth is the fault self-overlaping of the member 2;The fifth is the development karst belt at the top of the member 2 and the superposition at favourabe location. The favourable reservoirs of tower Permian Series in the area mainly gather at the top of the member 2 in vertical direction and distribute over the superposition of karst and structure in horizontal direction.