石臼坨凸起陡坡带东三段扇三角洲砂体成岩作用定量表征

QUANTITATIVE CHARACTERIZATION OF THE DIAGENESIS OF Ed_3 FAN-DELTA SANDBODIES IN THE STEEP SLOPE BELT OF SHIJIUTUO UPLIFT

为了明确成岩作用对石臼坨凸起陡坡带东三段扇三角洲砂体的控制作用,利用岩心观察、铸体薄片、扫描电镜、阴极发光、岩石物性测试及包裹体等多种资料,分析了研究区砂体成岩演化规律、成岩作用强度和成岩改造孔隙度并利用"反演回剥法"以成岩演化序列为约束,根据铸体薄片中各种自生矿物和溶解孔隙的面积百分比,定量计算压实作用后各期成岩作用强度。研究结果表明:研究区东三段扇三角洲砂体目前处于中成岩B期,成岩演化序列为压实作用→早期碳酸盐胶结→长石、岩屑、碳酸盐胶结物溶蚀/高岭石胶结→石英加大→晚期碳酸盐胶结;压实作用导致目标样品面孔率损失率为34.86%,成岩早期菱铁矿胶结和晚期含铁碳酸盐矿物胶结导致面孔率损失率为12.29%,以高岭石为主的黏土矿物胶结导致面孔率损失率为42.68%,溶蚀作用使得面孔率增加率为22.21%;沉积物源中高刚性颗粒含量有助于原生孔隙的保存,以中酸性火成岩碎屑为主的易溶成分是溶蚀作用发生的主要对象;物源是形成优质储层的先决条件,后期酸性流体对易溶组分的溶蚀有效改善了砂体物性。定量表征成岩演化过程,明确物性差异主控因素并有效恢复砂体孔隙度演化史,对指导渤海海域内深层油气勘探具有重要意义。

In order to make clear of the controlling action of the diagenesis on the controlling Ed3 fan-delta sandbodies in Shijiutuo Uplift,with the help of the core observation,cast thin section,scanning electron microscope,cathode luminescence and petrophysical property test,inclusion data and so on,the diagenetic evolution law,diageneticintensity and its stimulated porosity were analyzed,by means of ＂invertingand back stripping methods＂and constrained by the diagenetic evolution sequence,according to the areapercentages of the autogenous minerals anddissolved pores in the cast thin sections,the diagenesis intensity for each period after the compaction was calculated quantitatively. The study achievements show that Ed3 fan-delta sandbodies in the study area arecurrently in the middle diagenetic stage B,which the diagenetic evolution sequence is compaction→early carbonate cementation→feldspar,debris,carbonate cementation dissolution/kaolinite cementation→quartz secondary increase→late carbonate cementation; the compaction results in theloss rate of the target sample＇s planar porosityup to 34. 86%,the early diagenetic siderite cementation and the late cementation of the ferruginous carbonate minerals cause the loss rate of the planar porosity by 12. 29%,the clay mineral cementation with the kaolinite as the main mineral leads to the planar porosity loss rate up to 42. 68%,the new increased planar porosity by the dissolution is up to 22. 21%; the high-rigid particle content in the sediment source contributes to the preservation of the original pores,the dissolvable components taking the acidic igneous rock clastics as the main partare the principal object of the dissolution;the material source is the precedent condition of accumulating the high-quality reservoir,the dissolution of the soluble components in the latter period of the acid fluid can effectively improve the physical properties of the sandbodies. The quantitative characterization of the diagenetic evolution,clear understandings of the main controlling factors on the physical property difference and the effective restoration of the sandbody porosity evolution history are of great significance to guide the explorationof the deep oil and gas in Bohai Bay.