水平井约束的叠前深度偏移技术及应用

Horizontal well constrained prestack depth migration technology and its application

页岩气储层致密、分布连续,为了提高页岩气井的储层钻遇率和页岩气井的产量,页岩气开发中的井型设计普遍采用水平井。因此,井位部署和钻井设计都需要高精度预测页岩气气藏的埋藏深度和储层的地层倾角,对地震资料的成像精度提出了很高的要求。针对常规井约束叠前偏移速度模型优化方法只能利用水平井垂直段资料做约束的缺陷,基于地质模型约束和垂向速度分析的速度优化方法能高效率更新速度模型的特点,重点研发设计了能充分利用水平井垂直段和水平段资料共同约束的各向异性速度模型构建技术,并建立了一系列相应的处理流程。结果表明:水平井约束的叠前深度偏移技术在四川盆地页岩气区块的实际应用中,成像清晰、波组特征保持良好、成像归位合理,成像深度与钻井深度吻合度高,成像剖面的地层倾角与钻井所得的地层倾角一致,是解决页岩气储层精确成像的关键技术,也是解决页岩气勘探水平井轨迹高精度设计的重要支撑技术。

Shale gas reservoirs are generally tight and distribute continuously. To enhance reservoir encountering rate and producUon rate of shale gas wells, horizontal wells are the common well type design for the development of shale gas reservoirs. To satisfy the well deployment and drilling design of horizontal wells, the burial depth of shale gas reservoirs and the formation dip of reservoirs shall be predicted precisely and the imaging accuracy of seismic data is highly required. The data of vertical section in horizontal well is the only constraint to the optimization of conventional well constrained prestack migration velocity model, and the velocity model can be updated efficiently by using the velocity optimization method which is based on geologic model constraint and vertical velocity analysis. For these reasons, an anisotropic velocity model constructing technology which is jointly constrained by vertical and hori- zontal sections of horizontal well was designed and developed, and a series of treatment process was established correspondingly. The horizontal well constrained prestack depth migration technology is successfully applied in the shale gas blocks in the Sichuan Basin with clear image, well preserved wave group characteristics and rational imaging homing. The imaging depth is highly coincident with the drilling depth, and the formation dip in imaging section is accordant with that of well drilling. To sum up, this technology is the key technology for accurate imaging of shale gas reservoirs, and the important supporting technology for the high-precision trajectory design of horizontal wells which are used for shale gas exploration.