论文部分内容阅读
薄片鉴定、流体包裹体分析、埋藏演化史与有机质热演化史分析、膏岩层脱水及黏土矿物转化分析等研究表明:河西务构造带古近系沙河街组四段储集层经历了碱性→酸性→碱性→弱酸性→弱碱性的成岩环境演化过程;成岩作用演化序列为:压实作用→长石溶蚀和(或)石英加大→碳酸盐胶结和(或)硬石膏胶结→少量碳酸盐胶结物溶解→少量黄铁矿胶结。利用“反演回剥”的原理,以铸体薄片资料为基础,计算了各关键成岩作用对储集层面孔率的贡献量,并利用面孔率—孔隙度的函数关系,结合机械压实校正,定量地恢复了不同成岩特征储集层的实际孔隙度演化史。根据孔隙度演化史与油气成藏史匹配关系,河西务构造带沙四段储集层第1期油气成藏时期储集物性较好,孔隙度高达20%左右。第2期油气成藏时期,北部区块储集层碳酸盐胶结强烈,孔隙度急剧降低至7%左右,不利于油气充注补充;而南部区块储集层碳酸盐胶结作用弱,孔隙度仍以大于10%为主,有利于油气充注补充和成藏,成为有利勘探目标。
The analysis of thin slices, analysis of fluid inclusions, burial evolution and thermal evolution history of organic matter, gypsum formation dehydration and clay mineral transformation analysis indicate that the reservoirs of the fourth member of Shahejie Formation of Hexi Xizu tectonic belt experienced alkaline → Acidic → alkaline → weakly acidic → weakly alkaline diagenetic environment. The diagenetic evolution sequence is: compaction → feldspar dissolution and / or quartz enlargement → carbonate cementation and / or anhydrite cementation → A small amount of carbonate cement dissolved → a small amount of pyrite cement. Based on the data of cast thin slab, the contribution of each critical diagenesis to the porosity of the reservoir is calculated by using the principle of “inversion back stripping”. By using the function of porosity and porosity, The actual porosity of the different diagenetic reservoirs has been recovered by quantitative correction. According to the matching relationship between the evolution of porosity and the history of hydrocarbon accumulation, the reservoirs in the first reservoir of Shahejie Formation of Hexiwuwu structural belt have good reservoir property and porosity up to about 20%. In the second stage of hydrocarbon accumulation, the carbonate in the northern block is strongly cemented, and the porosity is drastically reduced to about 7%, which is unfavorable to the recharge of oil and gas. The carbonate cementation in the southern block is weak, The porosity is still more than 10%, which is favorable for recharge and accumulation of oil and gas, which has become a favorable prospecting target.