面向深层复杂地质体油气勘探的地震一体化技术

中国深层油气资源潜力巨大,是未来油气勘探开发的现实领域。塔里木、四川和鄂尔多斯等盆地的海相深层碳酸盐岩是最重要的油气突破领域。以岩溶缝洞型、礁滩孔隙型、白云岩孔隙型和裂缝型为典型的4类特殊储层,具有构造圈闭复杂、储层多样、地表复杂、地下埋藏深、温压高、构造复杂和勘探目标尺度小、非均质性等特点,这导致了地震波场复杂、地震信号弱、信噪比低、分辨率低及地震各向异性强等诸多地球物理难题,极大地增加了此类油气藏勘探高精度地震成像与储层预测的难度。常规物探技术,即单一的采集或处理解释技术,即便是先进的技术但由于缺乏系统的配套措施,也难以有效解决问题。因此,面对此类深层复杂构造地质体的勘探,必须采用地震采集、处理、解释一体化的思路系统性地开展综合研究,从复杂地表、复杂地质条件下的高质量地震采集入手,采用以深度域RTM成像为核心的地震成像处理,综合利用叠前、叠后地震属性开展沉积相带、储层与流体预测研究,精细刻画多尺度储集体,才能有效解决复杂地质体描述与目标落实问题。为此重点介绍面向深层复杂地质体,以叠前RTM深度成像和叠前反演为核心的地震一体化新技术,主要包括“小宽高”高密度地震采集技术,“小平滑面”速度建模与叠前深度成像技术以及“五维数据”叠前方位各向异性裂缝检测、叠前反演等关键技术;展示了一些成功的应用案例,验证了地震一体化技术的有效性。在实际应用中,围绕地震一体化技术开展工作,必须根据地质模型进行正演模拟和岩石物理分析,通过模型试验、野外现场试验科学优选适合的方法和参数,以达到方法技术应用效果和效益的平衡。

 China's deep oil and gas resources have high potential and will be the target of oil and gas exploration and development in the future.Among them,the marine deep carbonate rocks in the Tarim,Sichuan,and Ordos basins are the most important oil and gas exploration targets.The four types of special reservoirs,namely karst fracture-caves,reef-bank pores,dolomite pores,and fractures,generally exhibit the following characteristics:complex structural traps,reservoir diversity,complex surfaces,large burial depths,high temperature and pressure,complex structures,small scale,and heterogeneous exploration targets.Consequently,during seismic exploration,complex seismic wavefields are obtained,with weak seismic signals and low signal-to-noise ratio and resolution.This makes high-precision seismic imaging and reservoir prediction difficult.Conventional geophysical exploration techniques,that rely on a single acquisition or processing interpretation technique,can hardly be carried out effectively.Therefore,seismic acquisition,processing,and interpretation need to be integrated.After high-quality seismic acquisition under complex surface and geological conditions,seismic imaging processing based on depth-domain RTM imaging was performed,and prestack and poststack seismic attributes were jointly utilized to research the sedimentary facies zones,perform reservoir and fluid prediction,and carry out a fine delineation of multi-scale reservoirs.This way,the description of complex geologic bodies and detection of targets could be achieved.In this study,we focused on an integrated seismic technology relying on prestack RTM imaging in the depth domain and seismic prestack inversion as the core,including seismic acquisition with “small trace distance,small bin,wide azimuth,wide band,high coverage,high shot and trace density”,velocity modeling and prestack depth imaging with a “small smooth surface”,and prestack azimuthal anisotropy fracture detection using five-dimensional data and pre-stack inversion.Results of an application using real data confirmed the effectiveness of the proposed technology.A forward simulation and a rock physical analysis were implemented based on a geological model,and suitable methods and parameters were optimized through model and field tests to achieve a balance between the application and production benefits.