The urgent demand for high quality imaging data,especially high-precision geological structure,is a key problem in the development of YKL gas field.Because of missing near-offset data and low fold of seismic data,well-seismic misfit for structural depth prediction in this region can`t meet the exploration requirement if we only use conventional velocity modeling.Therefore,well-controlled anisotropy grid-tomography technique was adopted to conduct velocity modeling layer-by-layer.Based on precise choosing the reasonable markers and building the initial velocity model in the selected area,we use known logging data to calculate anisotropic parameters within this region.Then we eliminate the influence of large set for stable formation velocity on gas reservoir depth,and from shallow to deep layer by layer inversion on marker layer,update iterative anisotropic parameters,velocity and depth migration imaging until the predicted depth errors from well log and seismic data for each marker layer to be reduced.In addition,it has been confirmed by 3 drilling wells that the misfit between the predicted structural depths respectively from the final seismic migration results and logging depth measurements in this gas reservoir are all within 5m.So we can draw a conclusion that our technique can significantly improve the imaging accuracy for structure and fracture of gas reservoir so as to reduce the risk of production drilling.%YKL气藏开发迫切需要高品质地震成像资料的支撑,尤其是要求有高精度的构造成像资料.由于该区块三维地震勘探资料存在缺失近炮检距、覆盖次数低等不利因素,因此,常规单一的速度建模方法难以解决该区井震误差大的问题.为此,针对性地提出并联合应用了井控各向异性网格层析和逐层速度建模技术.在选好区内标志层、建好初始速度模型的基础上,利用区内多口已知井信息求取各向异性参数,先消除浅部大套稳定地层速度对气藏深度的影响,再由浅到深逐层对标志层反演,更新迭代各向异性参数、速度及深度成像,直至各标志层的井震误差降低到规定范围内.3口验证井的应用结果显示,实际资料最终成像成果的气藏构造深度预测值与实钻井深度误差均在5m内,气藏构造成像的精度得到了显著提高,断裂成像也得到明显改善,降低了开发钻井的风险.
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