Origin and Distribution of Grain Dolostone Reservoirs in the Cambrian Longwangmiao Formation,Sichuan Basin,China

作     者：SHEN Anjiang HU Anping PAN Liyin SHE Min 

作者机构：Petrochina Hangzhou Research Institute of Geology Hangzhou 310023 Zhejiang China Key Laboratory of Carbonate Reservoirs CNPC Hangzhou 310023 Zhejiang China 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2017年第91卷第1期

页      面：204-218页

核心收录：

学科分类：081803[工学-地质工程] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：granted by the National Major Science and Technology Projects (grant No.2016ZX05004002) PetroChina Major Science and Technology Projects (grant No.2014E-32) PetroChina Science and Technology Projects (grant No.2016B-0402-01) 

主　　题：Sichuan Basin Longwangmiao Formation grain dolostone meteoric dissolution buried dissolution origin of reservoir distribution of reservoir 

摘      要：Dolostones in the Cambrian Longwangmiao Formation have become one of the most significant gas exploration domains in China. Over a trillion cubic meters of gas reservoirs have been discovered in the Gaoshiti-Moxi area; however, the origins and distribution of the dolostone reservoirs are not well understood. This work discussed the geology and geochemistry of the dolostone reservoirs in the Longwangmiao Formation to determine their origin and distribution. Two understandings are acquired： firstly, a carbonate ramp provided excellent conditions for grain beach deposition, while the presence of a hypersaline lake was favorable for the contemporaneous dolomitization of grain beach deposits. Petrographic and geochemical evidence further confirm that the Longwangmiao dolostone was formed during the contemporaneous stage. Secondly, the reservoir characteristics indicate that the grain beach sediments provide material basis for the development of the Longwangmiao dolostone reservoirs. Reservoir dissolution simulation experiments show that the porosity of the reservoirs was formed by dissolution during contemporaneous and burial stages. The dissolution pores formed during the contemporaneous stage were controlled by sequence interfaces. The large scale dissolution vugs formed during the burial stage subsequently spread along the pre-existing porosity and fracture zones. This study therefore identified that the development of grain dolostone reservoirs in a shallow water ramp under arid climatic conditions generally met the following conditions：（1） reefal beach deposits lay a foundation for reservoir development;（2） superficial conditions are an important determining factor for reservoir porosity; and（3） burial conditions provide environment for porosity preservation and modification.