鄂尔多斯盆地马岭油田侏罗系延安组储层特征研究

Jurassic Yan’an Formation reservoir rocks in the Maling oil field,Ordos Basin

侏罗系延安组是鄂尔多斯盆地马岭油田的主力油层之一。通过岩心观察、薄片鉴定、扫描电镜观察等,研究马岭油田侏罗系延安组储层特征及其控制因素。结果表明,马岭油田延安组储层纵向上自延10期至延4+5期,其沉积相由辨状河相演化为网状河三角洲相。受沉积相影响,延10至延4+5油层组碎屑岩石英含量逐渐减少、长石含量增加,碎屑岩粒度变细,储层厚度变薄。马岭油田各探区储层物性受物源影响,近物源区如北区、南区、镇原区的储层物性较好。上里塬区位于河流下游区,碎屑岩粒度细,储层物性较差。研究区储层的成岩作用程度较低,压实作用和胶结作用使储层物性变差,溶蚀作用则改善了储层物性。

The Jurassic Yan’an Formation reservoir rocks occur as one of the main oil reservoirs of the Maling oil field,Ordos Basin. The characteristics and controlling factors are discussed on the basis of core,thin section and SEM analysis. Vertically,the Jurassic Yan’an Formation reservoir rocks in the Maling oil field are graded from the Yan 10 oil reservoirs upwards into the Yan 4 + 5 oil reservoirs,and the sedimentary facies has witnessed the evolution from the braided stream facies to the anastomosed river-delta facies. From the Yan 10 oil reservoirs to the Yan 4 + 5 oil reservoirs,the quartz contents in the clastic rocks gradually decrease and the feldspar contents gradually increase. Correspondingly,the grain sizes of the clastic rocks become finer,and the reservoir thickness becomes thinner upwards. The physical properties of the reservoir rocks are generally influenced by the source areas. For instance,the North area,South area and Zhenyuan area near the provenances have good physical properties,while the Shangliyuan area located in the lower reaches of the river has relatively poor physical properties. The reservoir rocks in the study area are now in the lower diagenetic degrees,i. e.,from the early diagenetic stage B to the late diagenetic A. The compaction and cementation lead to the poor physical properties,and the dissolution leads to the good physical properties.