Origin of the Silurian Crude Oils and Reservoir Formation Characteristics in the Tazhong Uplift

作     者：YANG Haijun LI Sumei PANG Xiongqi XIAO Zhongyao GU Qiaoyuan ZHANG Baoshou 

作者机构：Research Institute of Exploration and Development Petrochina Tarim Oilfield Company Korla Xinjiang 841000 China The National Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum Changping Beijing 102249 China 

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

年 卷 期：2010年第84卷第5期

页      面：1128-1140页

核心收录：

学科分类：0820[工学-石油与天然气工程] 070903[理学-古生物学与地层学(含：古人类学)] 0709[理学-地质学] 07[理学] 08[工学] 082002[工学-油气田开发工程] 

基　　金：supported by the China National 973 Key Research and Development Project(Grant No. 2006CB202308) the National Natural Science Foundation of China(Grant No.40973031 and 40772077/ D0206) 

主　　题：Silurian isotope biomarker mixed-source oil 

摘      要：The Silurian stratum in the Tazhong uplift is an important horizon for exploration because it preserves some features of the hydrocarbons produced from multi-stage tectonic evolution. For this reason, the study of the origin of the Silurian oils and their formation characteristics constitutes a major part in revealing the mechanisms for the composite hydrocarbon accumulation zone in the Tazhong area. Geochemical investigations indicate that the physical properties of the Silurian oils in Tazhong vary with belts and blocks, i.e., heavy oils are distributed in the TZ47-15 well-block in the North Slope while normal and light oils in the No. I fault belt and the TZ16 well-block, which means that the oil properties are controlled by structural patterns. Most biomarkers in the Silurian oils are similar to that of the Mid-Upper Ordovician source rocks, suggesting a good genetic relationship. However, the compound specific isotope of n-alkanes in the oils and the chemical components of the hydrocarbons in fluid inclusions indicate that these oils are mixed oils derived from both the Mid- Upper Ordovician and the Cambrian-Lower Ordovician source rocks. Most Silurian oils have a record of secondary alterations like earlier biodegradation, including the occurrence of ＂UCM＂ humps in the total ion current （TIC） chromatogram of saturated and aromatic hydrocarbons and 25-norhopane in saturated hydrocarbons of the crude oils, and regular changes in the abundances of light and heavy components from the structural low to the structural high. The fact that the Silurian oils are enriched in chain alkanes, e.g., n-alkanes and 25-norhopane, suggests that they were mixed oils of the earlier degraded oils with the later normal oils. It is suggested that the Silurian oils experienced at least three episodes of petroleum charging according to the composition and distribution as well as the maturity of reservoir crude oils and the oils in fluid inclusions. The migration and accumulation model