碳酸盐岩微观测试技术对比与应用——以济阳坳陷乐安油田潜山为例

Comparison and Application of Carbonate Rock Microscopic Test Technologies:A Case of Buried Hill in Le’an Oilfield at Jiyang Depression

微观测试结果能反映很多油藏信息。目前关于微孔缝的镜下测试技术不断丰富,但仍缺少对微孔缝最全面的微观分析。为了便于对比各类测试技术,以济阳坳陷乐安油田草桥潜山区域为典型代表实例,先采用不同的精细微观专项测试技术对孔缝储集空间特征进行分析,具体包括微溶孔电子探针成分分析、扫描电镜、薄片和阴极发光测试等技术,然后总结了通过各种不同的微观测试技术观察到的现象及规律。具体结果和得出认识如下:通过电子探针成分分析技术,能够分辨出灰岩微溶孔内诸如有机质、方解石、黄铁矿、白云石、石膏等成分;薄片内可见灰岩含油段砾间砾内孔洞发育,溶蚀孔洞边部有轻微方解石化;通过扫描电镜分析,能够分辨出代表区块的白云岩结晶孔比灰岩溶蚀孔大两个以上数量级,能通过晶间孔或溶蚀孔推断岩石的脆性以及是否易于压裂;通过岩样阴极发光测试,能够区分出共有几期成分不同的孔洞充填物;通过扫描电镜和压汞都可以得到孔喉大小,比较两项技术,扫描电镜得到的是局部纳米级的孔喉直径,而压汞测试得到的是单块样品微米级孔喉半径。从应用对象来看,前者适合对应到矿物的孔喉,后者更适合开发区块的孔喉对比研究。

The microscopic test results can reflect abundant oil reservoir information.Currently,there is a growing number of microscopic testing technologies for micro-pores and fractures,but there is still a lack of the understanding of micropores.In order to compare various test techniques,Caoqiao buried hill of Le’an oilfield in Jiyang depression is taken as a typical study case,different fine microscopic specialized test techniques are used to analyze the characteristics of pore and fracture storage spaces,including the composition analysis of micro dissolved hole electron probe,scanning electron microscope,thin slice,and cathodic-luminescence tests.The microscopic characteristics and statistical laws of micro dissolution pores are specifically described.There are some new findings:organic matter,calcite,pyrite,dolomite,gypsum,and other components are found in the electron probe composition of micro dissolution pores of limestone.In thin sections,pores can be found between and inside gravels in limestone oil layers,and there is some calcite at the edges of dissolution pores.The dolomite is mainly composed of inter-granular pores.Through scanning electron microscopy(SEM)analysis,it is found that the crystalline pores of dolomite representing the block are two or more orders of magnitude larger than the dissolution pores of limestone.The brittleness of the rock and whether it is easy to fracture can be inferred through inter-granular pores or dissolution pores;By conducting cathodo-luminescence tests on rock samples,it is possible to distinguish several stages of pore filling materials,which are different in composition.Both SEM and mercury intrusion porosimetry can measure pore-throat sizes.Comparing the two techniques,SEM can measure local nanoscale pore-throat diameter,while mercury intrusion porosimetry can measure the micrometer scale pore-throat radius of a rock sample.From the perspective of application objects,the former is suitable for the pores and throats of minerals,while the latter is more suitable for the comparative research of pores and throats in oil exploitation blocks.