塔河奥陶系隐蔽溶洞体地震精细识别

实际钻探结果表明，塔河奥陶系发育T₇⁴强轴屏蔽型溶洞体和强“串珠”屏蔽型溶洞体，部分溶洞体产能较高，初步显示了较大的开发潜力。由于该类储集体埋深大（超过5300m）、地震资料主频较低（约28Hz），地震分辨率为30m（约1/4波长）；同时小型溶洞体尺度小，地震响应较弱，地震异常特征不明显，预测强“串珠”储集体的方法明显不适用，亟需加强预测方法研究。为此，在钻、测井资料解释基础上，针对T₇⁴强轴屏蔽型溶洞体，首次采用主成分分析技术克服强子波匹配不足或匹配过度等稳定性问题，有效剥离T₇⁴强干扰，增强隐蔽缝洞体地震响应特征；针对强“串珠”屏蔽型溶洞体，采用低频模型优化的地质统计学反演去除强“串珠”子波旁瓣干扰，以增强隐藏在强子波旁瓣中的缝洞体的辨识度，精细预测隐蔽溶洞体。结果表明，对溶洞体的纵向辨识能力明显提高，可刻画8m厚的溶洞体，反演结果与钻测井符合率达83%，可靠性较高。

Identification of Ordovician subtle cave reservoirs in Tahe on seismic data

Drilling results shows that Tahe Ordovician formation developed two types of concealed cave reservoirs:one is shielded by T₇⁴ strong reflections,the other is shielded by strong bead-like reflections.Some reservoirs show great potentials with high productiion.Because of their buried depth (more than 5300m),the seismic dominant frequency is rather low (about 28Hz),the seismic resolution is about 30m (1/4wavelength).The size of some caves is small,seismic responses are quite weak,and seismic characteristics of these caves are blurry.Conventional methods are not suitable to identify this kind of caves.To sovle the problem,we develop a new approach with the help of drilling and logging data.For caves shielded by T₇⁴ reflections,the principal component analysis (PCA) is used to remove adjacent strong noise and highlight reflections of caves.For caves shielded by bead-like reflections,the geo-statistics inversion based on low frequency model optimization is use to remove bead-like reflections secondary lobes.The proposed approach is succsessfullly applied to identify Ordovician subtle cave reservoirs in Tahe,8m-thick caves are clearly described.The coincidencerate is up to 83% between inversion results and drilling and logging data,which proves high reliability of the proposed approach.