鄂尔多斯盆地姬塬油田东部长8_2油层组储层酸敏特征及主控因素

Acid Sensitivity Characteristics of Reservoir and Main Controlling Factors of Chang-8_2 Oil-bearing Interval in Eastern Jiyuan Oilfield of Ordos Basin,China

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,CaF_2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 andcalcite 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.