Characteristics,main controlling factors and densification mechanisms of unconventional tight reservoirs in Triassic Yanchang Formation in southern Ordos Basin,China  

作　　者：Yi-Quan Ma Chen Zhang Yong-Chao Lu Xiang-Ye Kong Ying Guo Yi-Xin Dong Lin Chen Rong Qi Feng-Cun Xing 

机构地区：[1]State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation&Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,610059,Sichuan,China [2]Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of Natural Resources,Chengdu University of Technology,Chengdu,610059,Sichuan,China [3]College of Earth Resources,China University of Geosciences(Wuhan),Wuhan,430074,Hubei,China [4]College of Management Science,Chengdu University of Technology,Chengdu,610059,Sichuan,China [5]Wuhan Center of China Geological Survey,Wuhan,430205,Hubei,China [6]Research Institute of Petroleum Exploration and Development,North China Oil and Gas Company,Sinopec,Zhengzhou,450006,Henan,China

出　　处：《Petroleum Science》2024年第6期3884-3898,共15页石油科学(英文版)

基　　金：supported by Natural Science Foundation of Sichuan Province(2022NSFSC1075);National Natural Science Foundation of China(42072137)。

摘　　要：The key factors controlling the densification of unconventional reservoirs(e.g.,tight oil and gas reservoirs)remain poorly understood and directly affect the distribution of exploitable resources.Here,systematically explored reservoir characteristics,depositional microfacies,and the main factors controlling densification of the tight oil reservoir in the Chang 8 Member(Yanchang Formation,Middle Triassic)in the southern Ordos Basin by thin section analysis,scanning electron microscopy,physical property measurement,X-ray diffraction,and mercury injection.Our results confirm the Chang 8 reservoir as an extremely low permeability tight sandstone reservoir mainly comprising lithic feldspathic sandstone with various primary and secondary pores and fine pore channels.The highest quality reservoir is mainly restricted to the middle and lower parts of subaqueous distributary channel microfacies.Dissolution partly contributed to reservoir formation,but the persistence of early,non-compressed storage space was more important.The compression of plastic rock debris removed a significant amount of porosity,and calcite,kaolinite,and siliceous minerals both fill pores,whereas chlorite cladding of particles protects the pore space.We identified three densification mechanisms:the persistent densification of highly plastic rock debris during burial,calcite cementation and pore filling,and feldspar dissolution and subsequent kaolinite precipitation and siliceous cementation.After their compaction,the Chang 8 Member reservoirs were charged with hydrocarbons.We applied clustering analysis to eight reservoir characteristics(porosity,permeability,median pore-throat radius,maximum pore-throat radius,median capillary pressure,pore discharge pressure,chlorite content,kaolinite content)to quantitatively classify the Chang 8 reservoir into three categories.Type-Ⅰreservoirs have the best conditions for hosting tight oil reservoirs,with~12%porosity,permeabilities of~0.2×10-3μm2,trial oil production rates of>5 m3/d,and,indeed,occur in subaq

关 键 词：Yanchang formation Tight reservoirs Densification process Ordos basin Reservoir evaluation 

分 类 号：TE31[石油与天然气工程—油气田开发工程] P618.13[天文地球—矿床学]