Effects of micrite microtextures on the elastic and petrophysical properties of carbonate reservoirs  

微晶结构对碳酸盐岩地震弹性与储层物性特征变化规律的影响（英文）

作　　者：Pan Jian-Guo Deng Ji-Xin Li Chuang Wang Hong-Bin Zhang Hu-Quan Zhao Jian-Guo Tang Gen-Yang 潘建国;邓继新;李闯;王宏斌;Zhang Hu-Quan;赵建国;唐跟阳(中国石油勘探开发研究院西北分院;油气藏地质及开发工程国家重点实验室(成都理工大学);成都理工大学地球物理学院地球物理系;Research Institute of Petroleum Exploration & Development-Northwest,Petro China;中国石油大学(北京)油气资源与探测国家重点实验室)

机构地区：[1]Research Institute of Petroleum Exploration&Development-Northwest,PetroChina,Lanzhou,730020,China [2]State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,CUT,Chengdu 610059,China [3]College of Geophysics,Chengdu University of Technology,Chengdu 610059,China [4]State Key Laboratory of Petroleum Resources and Prospecting,CUP(Beijing),Beijing 102249,China.

出　　处：《Applied Geophysics》2019年第4期399-413,559,共16页应用地球物理（英文版）

基　　金：supported by the National Natural Science Foundation of China(Nos.41774136 and 41374135);the Sichuan Science and Technology Program(No.2016ZX05004-003)

摘　　要：Apparent differences in sedimentation and diagenesis exist between carbonate reservoirs in different areas and affect their petrophysical and elastic properties.To elucidate the relevant mechanism,we study and analyze the characteristics of rock microstructure and elastic properties of carbonates and their variation regularity using 89 carbonate samples from the different areas The results show that the overall variation regularities of the physical and elastic properties of the carbonate rocks are controlled by the microtextures of the microcrystalline calcite,whereas the traditional classification of rock-and pore-structures is no longer applicable.The micrite microtextures can be divided,with respect to their morphological features,into porous micrite,compact micrite,and tight micrite.As the micrites evolves from the first to the last type,crystal boundaries are observed with increasingly close coalescence,the micritic intercrystalline porosity and pore-throat radius gradually decrease;meanwhile,the rigidity of the calcite microcrystalline particle boundary and elastic homogeneity are enhanced.As a result,the seismic elastic characteristics,such as permeability and velocity of samples,show a general trend of decreasing with the increase of porosity.For low-porosity rock samples(φ<5%)dominated by tight micrite,the micritic pores have limited contributions to porosity and permeability and the micrite elastic properties are similar to those of the rock matrix.In such cases,the macroscopic physical and elastic properties are more susceptible to the formation of cracks and dissolution pores,but these features are controlled by the pore structure.The pore aspect ratio can be used as a good indication of pore types.The bulk modulus aspect ratio for dissolution pores is greater than 0.2,whereas that of the intergranular pores ranges from 0.1 to 0.2.The porous and compact micrites are observed to have a bulk modulus aspect ratio less than 0.1,whereas the ratio of the tight micrite approaches 0.2。碳酸盐岩储层是油气勘探的重要储层类型,不同地区的碳酸盐岩储层在沉积、成岩过程都存在着明显的差异,这种差异是引起其物性及地震弹性性质变化的的主要因素。为认识这种机制,在本文中我们对取自塔里木盆地不同地区碳酸盐岩储层不同层位的98块样品进行了岩石学特征、岩石微观结构特征、物性特征和地震弹性特征识别分析,并研究了样品物性对地震弹性性质的影响及其变化规律。研究结果表明,碳酸盐岩样品物性与地震弹性性质整体变化规律受微晶方解石结构特征的控制,而传统的岩石结构及孔隙结构分类不能完全反应上述特征的变化。依据形态特征可将样品微晶结构分为多孔微晶、紧密微晶体和致密微晶三种类型,随着上述三种微晶中晶体边界紧密缝合接触的程度增加,其微晶晶间孔隙度与孔喉半径逐渐减小,同时方解石晶体颗粒边界刚度特征与弹性均匀性的逐渐增强,致使样品渗透率与速度等地震弹性特征表现出随孔隙增大而逐渐减小的总体趋势。对于以致密微晶为主的低孔隙度样品(孔隙度φ<5%),微晶孔隙对样品孔隙及渗透率贡献较小,同时微晶弹性性质接近岩石基质,致使岩石宏观物性特征与弹性性质受裂隙、溶蚀孔隙等的影响更为明显,样品物性与地震弹性性质的特征表征孔隙结构的控制作用。孔隙纵横比对孔隙类型也具有明显的指示作用,溶蚀孔隙的体积模量纵横比高于0.2,粒间孔体积模量纵横比介于0.1~0.2之间,多孔微晶与紧密微晶体积模量纵横比小于0.15,而致密微晶的体积模量纵横比接近于0.2。研究结果可为碳酸盐岩储层的分类以及相关储层的岩性及烃类地震检测提供依据。

关 键 词：carbonate rock micrite microtextures rock physical properties petrophysical properties pore aspect ratio 

分 类 号：P618.13[天文地球—矿床学]