永进油田西山窑组砂岩储层尖灭线的地震识别技术

Seismic recognition techniques for sandstone reservoir pinch-out line in Xishanyao formation in Yongjin Oilfield

永进油田属于典型的地层-岩性油气藏,此类油气藏砂体范围的准确预测是勘探成功的关键,而砂体尖灭线的识别直接影响砂体范围圈定的精度。尖灭点识别的方法较多,但直接用剖面解释的方法存在较大误差,而基于调谐厚度的方法存在应用条件的限制问题,基于瞬时谱分析的地震属性方法则存在分辨率的问题。通过建立不同地质模型进行正演研究与分析,优选出识别砂体尖灭点效果较好的上覆地层下波谷幅值属性。理论测试表明,该属性比剖面直接解释和瞬时相位识别的尖灭点更接近真实位置。在实际应用过程中,考虑到研究区目的层分辨率低、不同砂组相互叠置等问题,结合谱分解技术,沿上覆地层下波谷同相轴提取了分频数据体的下波谷幅值属性,通过切片能清晰地识别出永进油田西山窑二、三砂组主力油层的尖灭线,且计算结果与实际井资料相符,为该区域砂体范围刻画提供了可靠依据。研究方法对同类地层-岩性油气藏的尖灭点识别有一定的借鉴作用。

Yongjin Oilfield is a typical stratigraphic-lithologic reservoir and it is very important to predict the range of sandbodies accurately.The identification of pinch-out boundary would affect the delineated range of sandbodies directly.For the recognition of pinch-out points,the interpretation on seismic profiles exists large error,the method based on tuning thickness is restricted by application conditions,and the seismic attributes method based on instantaneous spectrum analysis is difficult to achieve satisfied resolution.By conducting forward modeling for different models,the attribute of reflection trough amplitude beneath overlying layer is optimized to recognize the location of pinch-out point.Theoretical tests show that the location of pinch-out points recognized by the trough amplitude is closer to the real location compared with seismic profile and instantaneous phase.In the process of actual application,the complexity of low resolution and the stacking of different sand group in objective layer are taken into account;the amplitude attribute slice along with the reflection trough event from frequencydivided cube is extracted by spectral decomposition.It can clearly identify the point-out boundary of major reservoirs of the second and third sand groups in Yongjin Oilfield and the calculation results are corresponding to actual well data,which provides a favorable basis for the characterization of the distribution of sand bodies.