鄂尔多斯盆地黄土塬区三维地震资料处理解释的地质模型

鄂尔多斯盆地南部黄土塬区地表黄土层厚度变化大, 对地震能量的吸收不均, 因此, 对该地区地震资料进行处理时静校模型构建困难, 资料成像难度大, 被认为是地球物理勘探的禁区。以往的地震资料解释分歧大, 多认为地震剖面上同相轴不连续的原因是地震采集技术不过关造成资料品质差, 因而制约了地球物理资料的深度应用。华北油气分公司“十二五”期间在该地区开展了大面积三维地震勘探, 获得的地震资料剖面上存在杂乱反射和同相轴不连续等现象, 这给该地区岩性圈闭和低幅构造解释带来了困难。近年来, 在盆地区域地质研究的基础上建立了正确的地质模型, 认为区域性走滑断层对地层连续性、地质体完整性的破坏是造成同相轴复杂的重要原因, 从而能够客观评价地震资料品质, 对地震资料重新处理后成像效果得到大幅改善, 对重新处理后的资料进行解释后识别出了不同级序断裂以及伴生的裂缝体系。认为: 燕山运动形成的走滑断裂十分发育, 它们是盆地南缘中生界特别是三叠系致密油成藏及富集的主控因素。地质模型的正确建立奠定了黄土塬区地质物探一体化研究的基础, 利用裂缝地震响应特征和地震属性开展断缝体的三维地震雕刻, 形成了一套确定断缝体样式、组合、响应、期次、边界的技术, 完善了黄土塬特殊地表条件下地震资料处理和解释的方法流程, 据此发现了致密油藏高产目标, 打开了中国石化鄂尔多斯盆地南部黄土塬区的油气勘探新局面。

It is difficult to construct an accurate model for static correction and seismic imaging owing to heterogeneous wave absorption related to loess thickness change at the surface of the loess tableland, the southern Ordos Basin, and discontinuous seismic reflections were once supposed to be caused by poor data quality acquired.North China Oil and Gas Company performed extensive 3D seismic surveys in this region in the 12th five-year plan, but it is hard to interpret lithologic traps and low-relief structures due to chaotic and discontinuous reflections.According to the geologic model established after regional geologic research, regional strike-slip faults, instead of seismic acquisition, are supposed to be an important contributor to poor data quality and complicated reflections because these faults break stratal continuity and geobody integrity.Seismic interpretation using reprocessed data with significantly improved imaging quality shows well-developed strike-slip faults of different grades and associated fracture system generated by the Yanshan movement, which dominated tight oil accumulation and enrichment in the Mesozoic Erathem, especially in the Triassic System, in the south marginal basin.The geologic model lays the foundation for the integrated study of geology and geophysics in the loess tableland.We use seismic responses of fractures and seismic attributes for 3D characterization of fractured units, including their style, association, responses, period, and boundary.Based on the methodology and workflow of seismic data processing and interpretation in the surface conditions of loess tableland, high-yield tight oil accumulations were discovered, which opened new ground for hydrocarbon exploration by Sinopec in the loess tableland, the southern Ordos Basin.