Factors Controlling Hydrocarbon Accumulation in Jurassic Reservoirs in the Southwest Ordos Basin, NW China  

作　　者：LIU Xin WANG Feng LIU Baojun TIAN Jingchun SHANG Ting MA Jiong ZHANG Zhongyi ZHANG Xiaolei 

机构地区：[1]Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,Chino [2]Exploration&Development Research Institute of PetroChina Changqing Oilfield Company,Xi'an 710018,China [3]National Engineering Laboratory for Exploration and Development of Low Permeability Oil&Gas Fields,Xi'an 710018,China [4]Key Laboratory of Nuclear Resource and Environment(Ministry of Education),East China University of Technology,Xanchang 330013,China [5]Production Logging Center,China Petroleum Logging Co.Xi'an 710200,China

出　　处：《Acta Geologica Sinica(English Edition)》2020年第2期467-484,共18页地质学报（英文版）

基　　金：National Science and Technology Major Projects(Grant No.2016ZX05050,2017ZX05001002-008);CNPC Major Projects(Grant No.2016E-0501).

摘　　要：The sedimentary, paleogeomorphological and reservoir characteristics of the Jurassic Yan’an Formation in the southwestern Ordos Basin, northwestern China, were studied by means of casting thin sections, scanning electron microscopy, inclusion analysis and identification of low-amplitude structures. A model for reservoir formation is established, and the controlling effects of sedimentary facies, paleotopography, low-amplitude structures and formation water on oil reservoirs are revealed. There are significant differences in the sedimentary characteristics, structural morphology and paleowater characteristics between the reservoirs above the Yan 10 Member and those in the Yan 9 to Yan 7 Members. The Yan 10 Member contains fluvial sediments, whereas the Yan 9 to Yan 7 members contain delta-plain anastomosing-river deposits. The distribution of high-permeability reservoir is controlled by pre-Jurassic paleogeomorphology and sedimentary facies. Some of these facies exhibit high porosity and high permeability in a lowpermeability background. The main hydrocarbon accumulation period was the late Early Cretaceous, filling was continuous, and the charging strength altered from weak to strong and then from strong to weak. The Yan 10 reservoir is mainly controlled by the paleogeomorphology: hydrocarbons migrated upward at a high speed through the unconformity surface, and accumulated in the favorable traps formed by paleogeomorphic structural units, such as gentle slopes or channel island. Furthermore, groundwater alternation in these areas was relatively stagnant, providing good reservoir preservation conditions. The reservoirs in the Yan 9 and higher members are controlled by the sedimentary facies, lowamplitude structure and paleowater characteristics. Hydrocarbons migrated through the three-dimensional delivery system, influenced by favorable sedimentary facies and high-salinity groundwater, then accumulated in the favorable low-amplitude structural traps that formed during the hydrocarbon production period.

关 键 词：inclusion analysis LOW-AMPLITUDE structure hydrocarbon accumulation JURASSIC Yan'an Formation SOUTHWESTERN ORDOS BASIN 

分 类 号：P618.13[天文地球—矿床学]