南海常压与超压气水过渡带岩电特征与气藏结构

Petroelectric characteristics and gas reservoir structure of the gas-water transition zone between normal pressure and overpressure in the South China Sea

于俊峰,吴其林,晁彩霞,林懿瑜,詹子钦,赖焕明

广东石油化工学院石油工程学院，广东 茂名 525000 中海石油（中国）有限公司湛江分公司，广东 湛江 524057

School of Petroleum Engineering, Guangdong University of Petrochemical Technology, Maoming 525000, China Zhanjiang Branch of CNOOC Ltd., Zhanjiang 524057, China

碎屑岩气藏的常压与超压气水过渡带的岩电特征不同，常压与超压气水过渡带也影响气藏结构。文中利用南海地区钻井岩电资料及勘探实践资料，通过分析了过渡带气水关系成因与岩电标志得出：常压气藏常规储层的测井电阻率曲线基本呈两段式，超压气藏气水过渡带测井电阻率曲线呈明显的三段式。气水过渡带岩电特征的差异体现了碎屑岩气藏结构模式：常规储层的常压气藏气水界面清楚，没有明显的过渡带，气层以气水界面为界；常规储层的超压气藏过渡带长，过渡带含气饱和度也较高，应该在段内取点作为气水界面；含致密砂岩透镜体的超压气藏受致密砂岩透镜体影响，气藏结构跟砂岩透镜体的顶面形状相关。该结论有别于以往以常规气藏气水界面作为超压气层底界的认识，可以更准确地判识气藏结构与评价气藏储量。

The petroelectric characteristics of the gas-water transition zone between normal pressure and overpressure are different in clastic gas reservoirs, and the structures of gas reservoirs affected by them are also different. Based on drilling data, petroelectric data and exploration practice in the South China Sea area, this paper analyzes the causes of gas-water relationship and the petroelectricity signs in the transition zone, and points out that the logging resistivity curves of normal gas reservoirs are basically two-stage, while the logging resistivity curves of gas-water transition zone in overpressure gas reservoirs are obviously three-stage. The difference of petroelectric characteristics in the gas-water transition zone has universal significance for indicating the structural model of clastic rock gas reservoir. The normal pressure gas reservoir of conventional reservoir has clear gas-water interface, no obvious transition zone, and the gas reservoir is bounded by gas-water interface. The superpressure transition zone of conventional reservoir is long, and the gas saturation of transition zone is high, so the point should be taken as the gas-water interface in the section. The overpressure reservoir with tight sandstone lens is affected by the sandstone lens, and the reservoir structure is ralated to the top shape of sandstone lens. This conclusion is different from the previous understanding that the conventional gas-water interface is used as the bottom boundary of overpressured gas reservoir, which plays an important role in more accurate identification of gas reservoir structure and evaluation of gas reservoir reserves.

10.6056/dkyqt202104013