南海W油田弱地震反射区断层多级优势成像及识别研究

南海W油田ZH₃Ⅱ主力油组位于弱地震反射区, 断层识别困难, 严重影响该区可动用储量评价及开发方案制定。为此, 研究设计了针对弱地震反射区的断层多级优势成像及识别的攻关思路。首先, 研究发现低频段信号对弱地震反射区的地层格架识别精度较高, 据此提出了针对大断层识别的低频地震信号增强解释性优化处理流程, 有效改善了弱反射区地震成像品质, 大断层识别精度大幅提高, 有效指导区域断层解释; 然后, 基于相位对地层产状变化敏感的特点, 针对微小断层刻画, 以逐级识别的思路, 在大断层识别成果的基础上应用断面波线性分离与去噪和相位筛选等方法, 生成相位指示相干数据体, 有效提高弱地震反射区微小断层的空间可识别度, 解决了传统本征值相干对垂向断距小的断层识别能力不足的问题, 有效落实了微小断层的空间分布。研究结果表明, 在南海W油田开展的断层多级优势成像及识别研究大幅度提高了弱地震反射区的断层识别精度, 其成果成功指导了油田的可动用储量评价及开发设计工作。

The main oil-layer group ZH₃Ⅱ in oilfield W, the South China Sea, is located in a weak-reflection area.How to image and identify multi-scale faults of weak responses is crucial to the evaluation of producing reserves and development planning.As low-frequency signals indicate stratigraphic framework, a target-oriented processing workflow is proposed to improve data quality and enhance low-frequency signals for major fault identification.Accurate major fault identification is instructive to regional fault interpretation.Based on phase sensitivity to the change of formation occurrence, phase-indicated coherence is formulated to improve minor fault detection after linear separation and denoising for major fault-surface reflections as well as phase selection.This type of coherence is better than eigenvalue coherence in spatially identifying those faults with small vertical fault distance.The application of multi-scale fault imaging and identification method to oilfield W in the South China Sea shows greatly improved accuracy of fault detection in the weak-reflection area.Research results offer technical support to the evaluation of producing reserves and development planning in the oilfield.