摘要
东河砂岩是塔中40油田的主要产层,根据岩性不同,由上至下可分含砾砂岩段和均质砂岩段,两段储层的储集物性相差很大,其中均质砂岩较好.通过岩心观察、储层岩石学、成岩作用和孔隙演化等多种特征研究,认为含砾砂岩段为临滨亚相的产物,均质砂岩段为前滨亚相的产物,这是两段储层物性相差大的重要原因之一.在岩石组份上,含砾砂岩中碳酸盐胶结物的含量比均质砂岩高得多,通过细致的微观特征分析,认为这种碳酸盐胶结物可能是埋藏过程中粘土矿物蒙脱石向伊利石转化,析出的钙、镁、铁等离子与碳酸根离子反应所产生;这些碳酸盐胶结物后被溶蚀形成现今的储层.含砾砂岩段储层较差可能是由于其沉积于临滨环境,原始孔隙度较低,成岩改造后相对更致密,在溶蚀过程中,溶蚀流体通过少,胶结物被溶蚀的少所形成.沉积相和成岩作用中的胶结作用、溶蚀作用是东河砂岩储层发育的主要控制因素.
Donghe sandstone is the main oil-producing formation in Tazhong 40 oil field. According to different lithology, it can be divided into conglomeratic sandstone member and homogeneity sandstone member descendingly. Their reservoir properties are different significantly, which of homogeneity sandstone member are better. Mean porosity of the former is 8.65% and its mean permeability is 13.43 × 10-3 μ m2. Mean porosity of the latter is 15.61% and mean permeability is 130.74 × 10-3 μ m2. With observations on thin sections of rocks and cores, analysis of samples and data, which shows that basic geological features of the members are different:(1)Textural maturity of conglomeratic sandstone member is higher than conglomeratic sandstone member, but mean content of carbonate cements is much lower.(2)Conglomeratic sandstone member is result of shoreface subfacies, while homogeneity sandstone member is foreshore subfacies.(3)Cementation of conglomeratic sandstone member is developed and corrosion is not developed.
These are the main reasons why the reservoir properties of the members are so different. Based on the study of micro-characteristics of caststone thin sections, scanning electron microscope and so on, and integrated analysis of oxygen and carbon isotope data of carbonate cements and so on, the carbonate-cements are possibly considered to be from reaction between ions (such as Ca2+, Mg2+, Fe3+) and the ion of CO33- which are separated out from the process of clay montmorillonite converting to illite during buried procedure. Having analyzed diagenesis types and diagenesis, we can concluded that reservoir properties of conglomeratic sandstone member are bad probably because it is deposited in shore face environment which brought about low primary porosity, much compact after diagenetic processes, quite small corrosion fluids passing through the reservoirs and small corroded cements in the course of corrosion. The porosity of homogeneity sandstone member is as high as about 40%. Although it is decreased due to later diagenesis, its residual pores are still quite big, which is helpful for corrosion fluids to corrode carbonate cements. Therefore the porosity of homogeneity sandstone member are quite good. Sum up, sedimentary fakes are basis for forming good-quality reservoirs, and late-diagenesis, especially corrosion, are important for reservoir formation, while carbonate cementation is the main factor to destroy reservoirs. To look for the zones of foreshore subfacies and the zones of corrosion growth is an important basic work for exploring Donghe sandstone formation.
出处
《新疆地质》
CAS
CSCD
2003年第4期440-444,共5页
Xinjiang Geology
关键词
碳酸盐胶结物
次生孔隙
控制因素
东河砂岩
两类储层
油气层
Donghe sandstone
two sorts of reservoir
carbonate-cements
secondary pore
key controlling factor
