基于地震波形指示的碳酸盐岩储集体反演方法——以塔河油田中-下奥陶统为例

塔河油田奥陶系碳酸盐岩岩溶储集体埋深大，分布不均，类型复杂，具有较强的非均质性，储集体类型识别一直是该区油气勘探和开发的难题。为此，基于贝叶斯判别理论和马尔科夫链蒙特卡洛抽样算法，实现了一种新型波阻抗反演方法。在储集体类型识别、地震反射特征和岩石物理分析基础上，利用地震波形相似性优选样本井，参照样本空间分布距离和曲线分布特征建立初始阻抗模型。通过建立建议分布与先验信息之间的关系，实现先验解空间的有效采样，同时采用Metropolis-Hastings抽样算法对贝叶斯后验概率分布抽样，从而获得最大后验概率解。将该反演方法应用到塔河油田奥陶系岩溶储集体类型识别中，在反演精度得到明显提高的同时，充分利用了地震波形横向变化特征反映岩溶储集体空间分布位置和横向展布规律，有效识别了岩溶储集体类型，为非均质极强的岩溶缝洞储集体的精细表征提供有力支撑。

Waveform-indication-based seismic inversion of carbonate reservoirs:A case study of the Lower-Middle Ordovician in Tahe oilfield,Tarim Basin

Carbonate karst reservoirs of the Lower-Middle Ordovician in Tahe oilfield feature in large burial depth,irregular distribution,complex reservoir types and strong heterogeneity,thus reservoir type identification is always a challenging during oil and gas exploration and development in the area.This paper documented a new impedance inversion method,i.e.waveform-indication-based inversion,based on Bayesian discriminant theory and Markov Chain Monte Carlo sampling algorithm.The method,based on reservoir type identification,seismic reflection characteristics and petrophysical analyses,can be used to optimize sample wells by observing seismic waveform similarities,and establish an initial impedance model by referring to sampling spacing and curve characteristics.The relationship between proposed distribution and prior information is firstly established to achieve efficient sampling of a priori solution space.A Metropolis-Hastings sampling algorithm is then used to sample the posterior probability distribution,so as to obtain the maximum posterior probability solution.The application of the method in identifying the types of the Ordovician karst reservoirs in Tahe Oilfield shows significant improvement of inversion accuracy and a better utilization of horizontal variation of seismic waveforms to reveal effectively the types and spatial and lateral distribution of the reservoirs,and provides fine characterization of the reservoirs.