桑托斯盆地盐下CO聚集条件及对油气成藏影响

Accumulation Conditions of CO and Its Influence to Pre-salt Oilfields, Santos Basin

贾怀存 康洪全 李明刚 程涛 侯波

JIA Huaicun KANG Hongquan LI Minggang CHENG Tao HOU Bo

中国海洋石油国际有限公司, 北京 朝阳 100026

CNOOC International Limited, Chaoyang, Beijing 100026, China

巴西桑托斯盆地盐下层系是近几年世界油气勘探的热点地区，但盐下已发现的油气田中普遍含有CO。通过对CO含量、CO碳同位素和伴生氦气同位素分析，明确桑托斯盆地盐下油气田中的CO成因类型主要为幔源无机成因。从CO成因类型出发，结合对桑托斯盆地盐下已发现油气田中CO含量与基底断裂展布关系，提出紧邻基底大断裂的油气田中CO含量往往高于远离基底断裂的油气田。同时，通过对桑托斯盆地盐下典型油气田中的CO形成条件和聚集成藏特征分析后，认为火山活动和晚期活化的基底断裂是桑托斯盆地盐下CO聚集成藏的主要控制因素，其中火山活动为CO的聚集成藏提供气源条件，晚期活化的基底断裂为CO聚集成藏提供了有利通道条件。受后期大量幔源CO源源不断地注入影响，油气藏中的油气组分发生蒸发分馏作用，并形成高含CO的凝析气顶和下部的稠油油环。

In recent years, the pre-salt sequence of Santos Basin is the focused exploration area, but CO is generally found in the pre-salt oil fields. After analysis of CO content, carbon isotope and helium isotope, the generation type of CO in Santos basin pre-salt layers is inorganic mantel. Based on generation type and the comprehensive analysis of the correlation of CO content with basement faults distribution, we found that fields closed to faults are generally high in CO content. Meanwhile, the analysis of generation factors and accumulation elements of CO in the typical fields displays that volcano activities and basement faults are the controlling factors for the accumulated CO gas cap. And the volcano provides CO source, faults acting as migration pathways. Affected by a large amount of inflow of continuous CO, evaporation and diffluence occurred in oil and gas composition and generated gas cap of high CO content.

10.11885/j.issn.1674-5086.2018.12.04.01