逆时偏移技术在土库曼斯坦地区的应用

Reverse time migration for the Block X in Turkmenistan

逆时偏移的实现主要包括三个步骤:首先利用双程波动方程对震源波场进行正向外推;然后对接收波场进行反向外推,每外推一步应用成像条件进行求和,得到局部成像数据体;最后将所有炮集的逆时偏移结果进行叠加,得到最终的叠前深度偏移成像结果。GeoEast-Lightning软件具有以下特点:(1)适用于多种基准面的偏移;(2)完善的高精度、高效率逆时偏移算法;(3)可抽取灵活多样的成像道集;(4)GeoEast-Lightning独创的自治并行模式极大地提高了并行计算效率和操作的方便性。通过GeoEast沿层速度建模及网格层析速度建模软件的综合应用,建立了土库曼斯坦某地区合理、准确的层速度模型。利用逆时偏移技术较好地解决了该区由于膏(盐)层速度横向变化引起的成像归位不准确,构造不落实的问题,取得了较好的勘探效果。

Reverse time migration(RTM)contains three steps:First,source wavefield are forwardly extrapolated by the two-way wave equation.Then receiver wavefield is reversely extrapolated,and a local imaging data volume is created using imaging conditions to summate at every step extrapolation.Finally the imaging of all the source gathers is stacked together to get the final prestack depth migration.GeoEast-Lighting software has following advantages:A.Being suitable for migration of different datum;B.A complete set of accurate and efficient reverse-time migration algorithms;C.Being able to flexibly extract the imaging gathers;D.Very high-efficient parallel computation and easy operation thanks to the original autonomic parallel model.With the comprehensive applications of horizon-based velocity modeling and grid tomography velocity modeling provided by GeoEast,accurate interval velocity models are created for the Block X in Turkmenistan.RTM technology achieves preferably accurate imaging of salt beds with lateral velocity variation for the future hydrocarbon development.