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钙质夹层是控制剩余油形成与分布的主要因素之一。辽河盆地大民屯凹陷沈95区块钙质夹层十分发育,利用丰富的岩心、测井资料,识别并探讨了钙质夹层的分布规律及成因。研究表明:本区钙质夹层是早期无铁碳酸盐与晚期含铁碳酸盐胶结形成的两期夹层;早期钙质夹层主要分布于泛滥平原亚相、三角洲平原亚相;晚期钙质夹层主要发育于三角洲前缘亚相,且一般位于砂泥岩接触带,厚层砂岩顶底部碳酸盐胶结物较中部高。早期钙质夹层是沉积期、成岩早期,蒸发作用使富钙孔隙水中的钙质沉淀形成的;晚期钙质夹层是在有机酸作用下,Ca2+、Mg2+在烃源岩(泥岩)中溶解,再于储集岩(砂岩)中沉淀形成的。根据夹层的分布规律可以更有效地挖掘剩余油。
Calcareous dissemination is one of the main factors controlling the formation and distribution of residual oil. Calcareous interbeds in Shen 95 block of Damintun depression in Liaohe Basin are well developed. By using abundant core and logging data, the distribution and origin of calcareous interbeds are identified and discussed. The results show that the calcareous intercalations in this area are two intercalated layers of early iron-free carbonate and late-stage iron-bearing carbonate cements. The early calcareous intercalations are mainly distributed in floodplain subfacies and delta plain subfacies. Late calcareous intercalations Mainly developed in the delta front subfacies, and generally located in sand and mud contact zone, thick sandstone bottom carbonate cement higher than the middle. The early calcareous interbeds are sedimentary period. In the early stage of diagenesis, the evaporation caused the calcareous precipitation in the calcium-rich pore water. In the later stage of calcareous intercalation, Ca2 + and Mg2 + were dissolved in the source rocks Precipitated in reservoir rocks (sandstone). According to the distribution of the interlayer can be more effective in mining residual oil.