Genetic types and distribution of shallow-buried natural gases

作     者：Gao Yang Jin Qiang Zhu Guangyou Gao Yang 1 , Jin Qiang 1 and Zhu Guangyou 2 1 College of Geo-resources and Information, China University of Petroleum, Dongying, Shandong 257061, China 2 Petroleum Exploration and Development Institute, PetroChina, Beijing 100083, China

作者机构：College of Geo-resources and Information China University of Petroleum Dongying Shandong 257061 China Petroleum Exploration and Development Institute PetroChina Beijing 100083 China 

出 版 物：《Petroleum Science》 (石油科学（英文版）)

年 卷 期：2010年第7卷第3期

页      面：347-354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] 

主　　题：Primary biogas secondary biogas oil-degraded biogas low-mature gas genetic type gas identification gas accumulation distribution 

摘      要：Great volumes of shallow-buried （〈2,000 m） natural gases which are mainly composed of biogases and low-mature gases have been found in the Mesozoic-Cenozoic sedimentary basins in China. Many shallow gas reservoirs in China are characterized by coexistence of biogas and low-mature gas, so identifying the genetic types of shallow gases is important for exploration and development in sedimentary basins. In this paper, we study the gas geochemistry characteristics and distribution in different basins, and classify the shallow gas into two genetic types, biogas and low-mature gas. The biogases are subdivided further into two subtypes by their sources, the source rock-derived biogas and hydrocarbon-derived biogas. Based on the burial history of the source rocks, the source rock-derived biogases are divided into primary and secondary biogas. The former is generated from the source rocks in the primary burial stage, and the latter is from uplifted source rocks or those in a secondary burial stage. In addition, the identifying parameters of each type of shallow gas are given. Based on the analysis above, the distributions of each type of shallow gas are studied. The primary biogases generated from source rocks are mostly distributed in Quaternary basins or modem deltas. Most of them migrate in watersoluble or diffused mode, and their migration distance is short. Reservoir and caprock assemblages play an important role in primary biogas accumulation. The secondary biogases are distributed in a basin with secondary burial history. The oil-degraded biogases are distributed near heavy oil pools. The low-mature gases are widely distributed in shallow-buried reservoirs in the Meso-Cenozoic basins.