摘要:
综合利用岩芯资料、铸体薄片、物性资料及相关分析测试资料,对车镇北带砂砾岩成岩作用特征及其对储层物性的影响进行了研究。研究表明:工区砂砾岩储层成岩作用主要有压实作用、胶结作用、溶蚀作用、灰泥重结晶作用和交代作用;成岩环境经历了中性/弱碱性→酸性→碱性→酸性→碱性的变化,相应的成岩作用序列为:压实作用→长石溶蚀/早期石英加大→碳酸盐胶结/石英溶蚀→长石溶蚀/碳酸盐胶结物溶蚀/晚期石英加大→黄铁矿胶结;区内砂砾岩储集物性较差,储集空间以次生孔缝为主;不同亚相岩相和成岩作用的差异使其储集物性有所不同,扇根主要发育颗粒支撑和杂基支撑砾岩,成岩作用以压实和灰泥重结晶为主,物性较差,发育无效储层;扇中亚相溶蚀作用较为发育,储集物性得到很好地改善,有效储层比例较高;扇缘亚相以胶结作用为主,使物性变差,局部溶蚀作用发育,可成为有效储层。
Abstract:
Based on a combination of core information, thin-section identification, an analysis of core properties and related analysis-testing data, the diagenesis of Palaeogene glutenite reservoir and its control on physical property in the north zone of Chezhen sag have been studied. Studies have shown that diagenesis is characterized by compaction, cementation, dissolution, lime-mud matrix recrystallization and metasomatism, the diagenetic environment underwent an evolution of alkalescence→acid→alkalescence→acid→alkalescence, and the corresponding diagenetic evolution sequence is compaction→feldspar dissolution/early quartz overgrowth→carbonate cementation/quartz dissolution→feldspar dissolution/carbonate dissolution/late quartz overgrowth→pyrite cementation. The glutenite reservoirs in research area have low porosity and permeability, and the reservoir space is mainly composed of secondary pores and cracks. The difference in lithofacies and diagenesis of different subfacies results in the difference in physical property. The inner fan is mainly composed of matrix-supported or grain-supported conglomerate,whose diagenesis is characterized by compaction or lime-mud matrix recrystallization, so dry layers develop widely in this kind of subfacies. Dissolution is intense in the middle fan, which effectively improves the reservoirs' property, so the rate of effective reservoir is high in this part. As for the fan marginal subfacies, intense cementation makes the property worse, regional dissolution makes the reservoir effective.
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