N油田A油组钙质隔夹层地质特征及成因分析

在油田开发过程中，隔夹层控制油气水运动规律，对于寻找剩余油具有重要控制作用。本文以N油田TF组2段A油组为研究对象，通过薄片、岩心测试、测井、碳氧同位素等资料综合分析，研究其钙质隔夹层的分布特征、岩石学特征、物性特征、测井识别特征，并从沉积环境、物质来源、成岩作用相结合的角度分析钙质隔夹层的成因。研究表明，A油组纵向上发育的三套钙质隔夹层主要发育在前滨滩坝沉积微相，顶钙与底钙的岩性以砂质生屑质灰岩为主，中钙为钙质砂岩；三套钙质隔夹层中生物碎屑主要以腕足、腹足、有孔虫为主，含少量棘皮、瓣鳃、红藻、介形虫、苔藓虫等；成岩作用主要为胶结作用，胶结物类型包含早期方解石胶结物、中期铁方解石胶结物、晚期铁白云石胶结物；碳氧同位素分析表明，隔夹层中碳主要来自于沉积过程中的海水，同时有少量来自于大气淡水和有机酸，Ca²⁺主要来源于生物碎屑，其次为钙长石溶解、铝硅酸盐矿物的水化作用。

Geological Characteristics and Genesis Analysis of Calcareous Intercalation Layer of Oil Group A in N Oilfield

In the process of oilfield development, the interlayer controls the law of oil and water movement, which plays an important role in controlling the remaining oil. In this paper, the oil group of the second section of the TF formation in the N oilfield is taken as the research object. Through the comprehensive analysis of the thin section, core test, logging, carbon and oxygen isotope, the distribution characteristics, petrological characteristics, physical properties and measurement of the calcareous interlayer are studied. The study shows that three sets of calcareous interbeds are developed vertically in the A oil group. The lithology is mainly composed of terrigenous clastic bioclastic limestone, followed by calcareous quartz sandstone, and the bioclastic is mainly composed of brachiopods and gastropods, with a small amount of echinoderms, foraminifera, flaps and gills, red algae, ostracods, bryozoans, etc. It mainly develops in foreshore beach bar deposits. The diagenesis is mainly cementation, and the cement type includes early calcite cement, medium-term iron calcite cement, and late iron dolomite cement. Carbon and oxygen isotope analysis shows that carbon mainly comes from seawater during deposition, while a small amount of it comes from atmospheric fresh water and organic acid. Ca²⁺ mainly comes from biological debris, followed by calcium feldspar dissolution and hydration of aluminosilicate minerals.