水平井地震导向技术探索与应用——以四川盆地复杂地区页岩气井为例

The exploration and application of horizontal well seismic guidance technology:A case study of shale wells in the complex area of Sichuan basin

四川盆地南部志留系龙马溪组页岩层具有埋藏深度大(>3 000 m)、优质页岩段厚度薄、地层倾角变化快、微幅构造和微断裂发育等地质特点,传统地质导向技术难以准确识别纵向上甜点的靶体位置,水平段钻井过程中面临较高的靶体脱靶和出层风险。三维地震资料能够给水平井的侧钻和入靶提供导向,并通过地震资料指导水平段钻进。本文以四川盆地南部复杂地区页岩气水平井地震跟踪为例,介绍基于各向异性叠前深度偏移三维数据体的水平井地震导向技术新思路:以高精度成像资料为基础,考虑区域速度场背景,地质约束速度建模确保精准入靶;同时开展目标区块实时各向异性深度偏移处理,提高储层钻遇率;钻井过程中地震实时跟踪,有效帮助钻井地质导向,为钻井工程提供预警和调整方案。实钻表明:面向开发和工程需求的页岩气复杂构造区水平井地震导向技术,可有效提高水平井的有效储层钻遇率。

The Silurian Longmaxi Formation shale in the south of Sichuan Basin has the geological characteristics of large burial depth(more than 3000 meters), thin thickness of high-quality shale section, rapid change of formation dip angle, and development of micro structure and micro fracture.It is difficult for the traditional geosteering technology to accurately identify the target location of the longitudinal sweet spot.During the drilling process of horizontal section, there is a high risk of target miss target and formation production.The 3 D seismic data can provide guidance for sidetracking and target entry of horizontal wells and guide horizontal drilling.Taking the seismic tracking of shale gas horizontal wells in the complex area of southern Sichuan Basin as an example, this paper introduces a new idea of horizontal well seismic guidance technology based on anisotropic prestack depth migration three-dimensional data volume.Based on high-precision imaging data and considering regional velocity field background, geological constraint velocity modeling ensures accurate target and, at the same time, real-time anisotropic depth migration of target block can be carried out.In addition, real-time seismic tracking during drilling can effectively help drilling geosteering and provide early warning and adjustment scheme for drilling engineering.The actual drilling shows that the seismic steering technology for horizontal wells in shale gas complex structural areas can effectively improve the effective reservoir drilling rate of horizontal wells for development and engineering needs.