鄂尔多斯盆地姬塬油田东部长82油层组储层酸敏特征及主控因素

摘要

基于X-射线衍射、扫描电镜、薄片鉴定以及酸敏实验等测试分析手段,对鄂尔多斯盆地姬塬油田东部长82油层组储层酸敏性进行分析.结果表明:储层黏土质和钙质胶结严重,非均质性强,主要的酸敏矿物为绿泥石和方解石/铁方解石,储层酸敏性主要以改善型—弱酸敏型为主;酸敏实验中,部分原始大孔隙样品出现减孔现象,主要是部分绿泥石包膜及针叶状晶体溶蚀、崩落所致,实验中Fe(OH)3沉淀及凝胶体在短时间内对储层酸敏性影响有限,方解石/铁方解石的溶解能有效补偿Fe(OH)3沉淀及凝胶体对储层的影响;在碳酸盐胶结物富集区,CaF2沉淀是储层物性变差的直接因素,总体呈现出盐酸对储层的改善程度要好于土酸;酸敏矿物较发育于水下分支河道微相,并呈现出近物源区绿泥石胶结物含量较高、远物源区方解石/铁方解石胶结物含量较高的分布特征;酸敏矿物的含量、类型、分布受沉积物源、沉积微相以及成岩作用等控制,特别是有机质热解-脱羧作用在成岩过程中与溶蚀作用、交代作用相伴生,对酸敏矿物的形成、类型及赋存状态具有重要影响.%Based on XRD,SEM,slice image and acid sensitivity experiment,the acid sensitivity of reservoir of Chang-82 oil-bearing interval in the eastern Jiyuan oilfield of Ordos Basin was analyzed.The results show that the acid sensitivity of reservoir of Chang-82 oil-bearing interval is dominated with amendment-weak sensitivity;clay and calcareous cements of reservoir are serious,the heterogeneity is strong,and the main acid sensitivity minerals are chlorites and calcite minerals;the relative large porosities of some samples are reduced by the spallation of partial coniferous chlorite and chlorite film,which blocks the porosities and throats in the acid sensitivity experiment;meanwhile,the effects of the precipitation of ferric hydroxide (Fe(OH)3) and gel on the reservoir physical properties are limited,and the corrosion of calcareous cement compensates the negative effects on reservoir;whereas,the calcium fluoride (CaF2) is the direct factor to the damage of physical properties in acid sensitivity experiment,indicating that the hydrochloric acid is more suitable for the reservoir improvement than mud acid;the underwater distributary channel is the suitable place for the development of acid mineral,including that the chlorite and calcite/ferrocalcite,and the chlorites cement with high content distribute well near the provenance,while the distribution of a relative high content of calcites/ferrocalcites is far away from provenance;the contents,types,and distribution of acid mineral are controlled by sedimentary provenance,sedimentary microfacies and diagenesis,especially the thermolysis and decarboxylation of organic material in Chang-82 oil-bearing interval occur along with the dissolution and metasomatism during the diagenetic stage,having an important influence on the formation,types and the existence condition of acid mineral.