论文详情
岩溶缝洞储集体已成为中国西部海相油气藏的重要勘探开发目标,地震“串珠”状反射被认为是该类型储集体及其组合在地震成像剖面上最直接的识别与检测标志。常规地震时间和深度偏移成像处理,利用平滑平缓的均方根速度体或层速度体对缝洞反射进行偏移归位处理,虽经多轮次的偏移速度调整,但依然不能保证每一个“串珠”反射都能达到最佳的收敛与归位。为此提出一种基于连续速度替换的地震聚焦成像技术,利用缝洞绕射归位对偏移速度的高敏感性,通过不同速度偏移归位时能量聚焦强度与绕射形态平直性,实现每一个缝洞储集体“串珠”反射部位最优偏移速度的准确检测。利用新的带有地层与每个缝洞建模的偏移速度模型,经偏移后每个缝洞体都取得最佳的收敛归位效果,同时获得缝洞等效偏移速度,模型与实际资料均展示其与钻探井的缝洞充填速度呈线性正相关。实际资料缝洞体的聚焦偏移成像处理结果表明,在整个三维数据体的每一个缝洞体“串珠”状反射上,不论是单个型“串珠”反射,还是组合型“串珠”反射,“串珠”能量明显增强、边界更加清晰、聚焦性更为突出,偏移速度相对低的“串珠”与钻探井钻遇的放空漏失、油气高产的有利缝洞储集体有极高吻合率,展示了本文方法的有效性和适用性。
Karst fracture-cavern reservoirs have become important targets for marine oil and gas exploration in western China.Bead-like seismic reflections are the most recognized characteristic of a karst reservoir detected on a seismic migrated profile.In conventional prestack time migration (PSTM) and prestack depth migration (PSDM) seismic imaging,the smooth root mean square (RMS) and interval velocity body are used for reflection migration of the fracture-cavern reservoir.Although the migration velocity is adjusted,conventional methods are still not able to provide the best reflection convergence and bead-like images.In this paper,a seismic focusing imaging technique based on continuous velocity replacement is proposed to accurately detect the optimal migration velocity of each bead-like feature in a fracture-cavern reservoir.The technique uses the sensitivity of fracture-cavern reflections,which are the focused energy intensity and straightness morphology of diffraction formed by different velocities in the migration data,to find migration velocity.The best convergent effect for fracture-cavern reservoirs after migration was obtained using the new migration velocity model.Both the model and the actual data showed that the equivalent migration velocity for each fracture cave was linearly positively correlated with the filling-velocity in the drilling wells.The focusing imaging of the fracture-cavern reservoir from the real data showed that the bead energy was enhanced,the boundary was clear,and the focus was more prominent for single and combined bead reflections in the entire volume of 3D data.The beads with low migration velocity have a high coincidence rate with leakage in the well and are favorable reservoirs with high rates of oil and gas production.This demonstrates the effectiveness and applicability of the method presented in this paper.
国家科技重大专项课题“不同缝洞储集体地震识别与预测技术”(2016ZX05014-001)、中国石化科技攻关项目“碳酸盐岩复杂缝洞型储层流体识别研究”(P15152)共同资助。