海外页岩油气纵向地质甜点识别方法

Recognition methods for oversea shale oil and gas vertical geological sweet spot

准确识别页岩油气地质甜点、确定关键识别参数、优选水平井靶点是开展页岩油气研究急需解决的问题。勘探开发实践表明,页岩油气的地质甜点为"甜点体",其纵向上遵循从远景段、有利段、核心段,再到甜点的递进识别过程。本文以北美Eagle Ford组页岩为例,从构造沉积背景确定了浅海-半深海相沉积的下白垩统为远景段;利用野外露头和钻井岩芯,通过层序地层分析明确了Eagle Ford组为晚白垩世的有利页岩发育层;结合测井解释得出了下Eagle Ford段为该组的核心段;同时,提出了自然伽马、有机碳含量、电阻率、含烃饱和度4类测井曲线进行划分核心段和识别纵向甜点段的应用方法。在此基础上,通过观察扫描电镜和薄片资料,分析A、B、C三个亚段生烃能力和储集能力,明确了下Eagle Ford段的B亚段为纵向地质甜点。分析PH、EM、BL三口井初始产量和水平井段钻井轨迹在A、B、C三个亚段的钻遇时间,结果显示B亚段对页岩油气较高产量贡献率最大,是下Eagle Ford段最佳的水平井靶点优选位置。

Accurately identifying the geological sweet spot,confirming the key identification parameters and optimizing horizontal well target position are becoming the urgent issues.The exploration and development shows the geological sweet spot in shale actually means a shale body where oil or gas in high content occupied in.The vertical identification process includes from the prospect segment,to the favorable segment,then to the core segment,and progressively to the sweet spot.Taking the Eagle Ford shale as an example,the research results show that the formation deposited in the basin or continental shelf is the shale prospect segment in Late Cretaceous.According to the sequence stratigraphic characteristics based on the outcrops and the core,the Eagle Ford Formation is as the best favorable layer in the Late Cretaceous.Integrated the logging interpretation including natural gamma（GR）,organic carbon content（TOC）,resistivity（RT）and hydrocarbon saturation（1-Sw）four types curve,the lower Eagle Ford layer was divided as the core segment in the Eagle Ford Formation and finally the Part B in the lower Eagle Ford layer was optimized as the vertical geological sweet spot by the analysis on the hydrocarbon generation and reservoir capability of the Part A,Part B and Part C.The per-well initial production of three wells PH,EM and BL,and the drilling time in Part A,Part B and Part C show that the Part B is the largest contributor for production and to be the best horizontal well target position.