沉积微相在致密砂岩可压裂性分析中的应用——以鄂尔多斯盆地陇东地区延长组7段为例  

The application of sedimentary microfacies on the fracability of tight sandstone reservoir in Chang 7 member of Longdong area in the Ordos Basin

作　　者：王冠民[1] 祝新怡 刘海[2] 陈帅 石晓明 胡津 WANG Guanmin;ZHU Xinyi;LIU Hai;CHEN Shuai;SHI Xiaoming;HU Jin(School of Geosciences,China University of Petroleum(East China),Qingdao 266580,Shandong,China;Changqing Underground Technology Operation Company of Chuanqing Drilling Engineering Co.,Ltd.,Xi'an 710018,Shaanxi,China;Beijing Engineering Corporation Limted,Beijing 100024,China)

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]川庆钻探工程有限公司长庆井下技术作业公司,陕西西安710018 [3]中国电建集团北京勘测设计研究院有限公司,北京100024

出　　处：《地质力学学报》2024年第6期893-905,共13页Journal of Geomechanics

基　　金：国家自然科学基金项目(41972131)。

摘　　要：沉积特征差异是控制储层非均质性的关键因素之一,利用沉积微相来分析储层的非均质性通常是油气田开发和储层甜点预测的重要手段,也可以尝试用其评价致密砂岩储层的可压裂性。以鄂尔多斯盆地陇东地区延长组7段(长7段)的致密砂岩为研究对象,在通过岩芯、测井等资料识别不同沉积微相类型基础上,利用全岩X射线衍射(XRD)分析、铸体薄片观察得到致密砂岩样品的矿物成分和结构参数,并结合岩石力学实验,采用脆性指数和三轴抗压强度的比值来表征岩石的可压裂性。将致密砂岩的沉积微相、成分结构和可压裂性进行对比分析后得到以下认识:长7段致密砂岩主要发育水下分流河道和席状砂2种沉积微相,不同沉积微相之间的矿物成分、结构存在明显差异;与席状砂相比,水下分流河道砂体的平均粒径更大,分选更好,碳酸盐矿物和黏土矿物含量更低,杂基含量更少;可压裂性指数与砂岩的石英含量、碳酸盐矿物含量、粒度分布标准偏差具有正相关性,与长石含量、平均粒径具有负相关性。灰色关联分析表明碳酸盐矿物含量、粒度分布标准偏差、粒径是影响长7段致密砂岩可压裂性的最主要因素,整体上席状砂的可压裂性指数要高于水下分流河道砂,更易于压裂。由于砂岩颗粒的粒度分布标准偏差、粒径受沉积微相控制,碳酸盐矿物含量受砂岩厚度直接控制、受沉积微相间接控制,故在致密砂岩油气储层压裂的实际工程中可以依据沉积微相差异来判断致密砂岩的可压裂性变化,简化可压裂性的评价流程。[Objective]Sedimentary differences are the key factor in controlling reservoir heterogeneity.Analyzing reservoir heterogeneity through sedimentary microfacies is crucial for oil and gas field development and sweet spot prediction,and it also informs the evaluation of fracturing in tight sandstone reservoirs.There are many types and complex lithologies of unconventional oil and gas reservoirs in the Ordos Basin as well as many factors controlling reservoir fracability.At present,mechanical experiments are used to comprehensively characterize the fracturing property;however the research cost is high and the experimental process is complicated,making it unnsuitable for large-scale oilfield development and use.Therefore,this study attempted to analyze and compare the fracability of tight sandstones with different sedimentary microfacies from the perspective of sedimentary microfacies controlling the lithology and reservoir development to provide a reference for oilfield development plans.[Methods]Taking the compact sandstone of Chang 7 member of Yanchang Formation in the Longdong area of Ordos Basin as the research object,the different types of microfacies are identified through the data of core and cast slice,the mineral composition and structural parameters of rock samples were obtained by X-ray diffraction(XRD)analysis,and rock mechanics experiments were conducted to quantitatively described the fracturing property.[Results]The results are as follows:(1)Two sedimentary microfacies,namely underwater distributary channel and sheet sand,mainly developed in Chang 7 Member of Yanchang Formation in the study area.Among them,the single sand body thickness of the underwater distributary channel is greater than 2 m,the sheet sand is mostly a medium thin and thick sand mudstone interlayer,and the single sand body thickness is generally less than 2 m.(2)The composition and structure of the two sedimentary sandstone microfacies are obviously different:the content of carbonate minerals,clay minerals,and heterobases in the shee

关 键 词：延长组 致密砂岩 可压裂性 沉积微相 水下分流河道 席状砂 

分 类 号：TE121[石油与天然气工程—油气勘探]