埕北低断阶沙二段原油特性及油源分析

埕北低断阶区沙二段是大港油田近年来重点勘探层系之一,研究目标层段原油特点及油源对比分析对油气勘探具有重要的意义.研究表明,原油物理性质总体表现出高成熟原油特征,具有四低一高的特点,即低密度,低黏度,低胶质＋沥青含量、低含硫量及高含蜡量.原油地球化学性质和原油生物标志特征整体反映出生油母质形成于湖相沉积弱还原环境,具有丰富的藻类贡献,也表现出高成熟油特征.通过原油的物理四性分析和层系间油岩生物标志特征对比研究,分析认为其油气来源为两个方面：主要方面来自歧口凹陷和歧南次凹两大生油凹陷的双向供油,另一方面油气来自沙二段烃源岩的自生自储和沙三段的高成熟烃源岩.

Analysis of Crude Oil Characteristics and Oil-source Correlation of the Sha-2 Member of Shahejie Formation in the Chengbei Low Step Fault

The Sha-2 Member of Shahejie Formation in the Chengbei low step fault is one of the key exploration targets of Dagang Oilfield in recent years. It is significant for oil and gas exploration to analyze the characteristics of the crude oil in the target horizons and conduct oil-source correlation. The study results shows that the crude oil generally exhibit high mature oil characteristics in physical property, with the characteristics of four low and one high, including low density, low viscosity, low gel and asphalt content, low sulfur content and high wax content. The crude oil geochemical properties and the characteristics of the crude oil biomarkers indicates that the source materialls deposited in the lacustrine weak reduction environment, reflecting high contribution of algae, with high mature oil characteristics. Study of four physical characteristics of the crude oil and correlation of biomarker characteristics be- tween oils and source rocks, it is concluded that the oil and gas were sourced mainly from two ways, one was from the bidirectional oil supply from Qikou Sag and Qinan Sag, the other was from self-generation and self-reservoiring Sha-2 Member and high mature source rocks of Sha-3 Member.