低渗油藏中相对高渗储层特征及其主控因素——以鄂尔多斯盆地志丹地区上三叠统延长组长10_1为例

Characteristics and control factor of the relatively high permeability reservoir in the low permeability oil gas pool: A case study of Chang 10_1 oil layer of upper Triassic Yanchang Formation in Zhidan area, Ordos Basin

相对高渗储层研究是低渗油田勘探开发的方向标。以2007年鄂尔多斯盆地志丹地区新发现的延长组长101含油层系为研究对象,通过岩心观察,结合室内铸体薄片、物性资料、X衍射、扫描电镜、压汞资料等的综合分析,对相对高渗储层特征及其控制因素进行研究。结果表明,研究区长101相对高渗储层以中粗粒—中粒含浊沸石长石砂岩为主,砂岩成分成熟度相对较高;胶结物主要以绿泥石膜和浊沸石为主;成岩作用主要表现为次生溶蚀作用;孔隙以浊沸石溶蚀孔、长石溶蚀孔和残余粒间孔为主。控制研究区相对高渗储层的因素主要有3个方面:三角洲平原亚相分流河道微相控制储层的分布及储层原始物质的组成,绿泥石膜的存在使原生粒间孔隙得以保存和次生溶蚀作用中浊沸石、长石溶孔优化了储层的储集性能。

The relatively high permeability reservoir is the exploration and development direction of the low permeability oilfield. A new oil-bearing layer, i.e., Chang101 oil layer of Triassic Yanchang Formation, was found in Zhidan area of Ordos Basin in 2007. It has been proved by practice that the study area has a good exploration prospect. Based on core observation and all kinds of analytical means, such as cast thin sections, physical properties, X-ray diffraction, SEM and capillary pressure curve, the authors studied the characteristics of the relatively high permeability reservoir and its control factors. The results show that the relatively high permeability reservoirs are made of medium-coarse or medium feldspar sandstones which have relatively high compositional maturity. The ce-ments are mainly chlorite film and laumontite, and the diagenesis mainly finds expression in secondary dissolution. Pore types are so-lution opening and inter-granular opening. Feldspar solution opening and laumontite solution opening constitute the main types of solution opening. The factors controlling the relatively high permeability reservoir are delta distributary channel microfacies which control the reservoir distribution and its primary material. The chlorite film is favorable for the preservation of primary inter-granular pore, whereas the secondary dissolution of feldspar and laumontite seems to be the key to improving the reservoir property.