基于地震正演精细外推地层油气藏边界——以溱潼凹陷帅垛—陈家舍区带戴南组一段为例

Fine Extrapolation of Stratigraphic Oil-Gas Reservoir Boundary Based on Seismic Forward Modeling:A Case Study of the First Member of Dainan Formation in Shuaiduo—Chenjiashe Belt,Qintong Sag

溱潼凹陷地层油气藏由于圈闭复杂,含油条带较窄,根据地震波反射特征追踪的地层尖灭线与实际地层尖灭线往往存在较大误差,导致钻探成功率不高。通过对地层不整合尖灭的地质模型正演得到地震模型,对比各种地震属性在识别地层油气藏边界中的优势与不足,优选出识别效果较好的平均波谷振幅属性和平均瞬时相位属性。对不同频率下一系列模型分析,得到不同频率、不同夹角(不整合面与地层夹角)的地层尖灭点与地震剖面上尖灭点间的误差,通过拟合建立不整合面和地层的夹角与地层尖灭点误差的函数关系,实现了夹角外推定量计算。综合利用地震属性半定量刻画与地震正演模型夹角外推定量计算,精细刻画地层圈闭的边界。

Because the traps are complicated and the oil?bearing zones are relatively narrow in the stratigraphic oil?gas reservoirs of Qintong sag,there are big differences between the stratigraphic pinchout line obtained from seismic reflection tracing and the actual one,which results in the difficulties in stratigraphic oil?gas reservoir boundary identification and low success rate of drilling.A seismic model obtained from the forward modeling of a stratigraphic pinchout model,the advantages and disadvantages of various attributes in the seismic model are analyzed for the stratigraphic reservoir boundary identification,and the average trough amplitude and average instantaneous phase are selected due to their good recognition effects.The error between stratigraphic pinchout points with different frequency and included angles(i.e.the included angle between unconformity surface and stratum)and the pinchout points on the seismic sections can be obtained through analyses of a series of models at different frequencies.A functional relationship between the included angle and the error of stratigraphic pinchout point is established through matching and then the quantitative calculation of the included angle extrapolation can be realized.The boundaries of stratigraphic traps are characterized detailedly by the integrated use of semiquantitative description of the seismic attributes and quantitative calculation of the included angle extrapolation with seismic forward modeling.