松辽盆地龙虎泡地区高台子油层成岩作用研究

Diagenesis study for Gaotaizi reservoir in Longhupao area of Songliao Basin

高台子油层为龙虎泡地区主要含油层,储层岩性以含泥粉砂岩为主。通过岩心观察和化验分析对其成岩作用研究表明:压实作用使原始孔隙减少,不利于储集空间的保存;胶结作用和溶蚀作用同步进行,早期胶结作用抑制压实作用强度,胶结物后期溶解可有效改善储层物性。根据蒙脱石、高岭石、伊利石等黏土矿物特征及演化阶段推断储集岩成岩作用已达到晚成岩阶段中期。另外,研究区高台子油层主要为三角洲前缘相沉积,岩石碎屑颗粒间孔隙被泥质充填,加之后期大量自生黏土矿物生成,使岩石碎屑颗粒间孔隙以小孔为主,孔隙结构复杂,沉积作用与成岩作用共同决定了高台子油层中孔、低渗特征。

Gaotaizi reservoir is the principle oil-bearing reservoir in Longhupao area with muddy siltstone as major reservoir lithology. Diagenesis study conducted through core observation and laboratory analysis indicates that the original porosity was reduced by compaction which was adverse to conservation of reservoir space; cementation and dissolution were synchronous; early cementation suppressed compaction strength, and later cement dissolution can improve reservoir physical property. Clay mineral characteristics such as montmorillonite, kaolinite and illite, and the evolutionary stage have inferred that the diagenesis of Gaotaizi reservoir rock has entered the mid-late diagenetic period. Moreover, Gaotaizi reservoir in the study area mainly belongs to delta front facies where intergranular pores were filled with mud. The pore structure was complicated by generation of numerous authigenic clay minerals in later period thus resulting in small intergranular pores. The sedimentation and diagenesis had worked together and defined Gaotaizi reservoir to be medium porosity and low permeability.