疏松砂岩储层预测与油气检测技术在Albertine地堑的应用

Application of reservoir prediction and hydrocarbon detection for unconsolidated sand in Albertine rift valley

Albertine地堑位于东非裂谷西支,属于中新生代陆内裂谷盆地.主力含油层段为疏松砂岩储层,由于孔隙物性较好且随埋深变化较大,疏松砂岩地震响应特征复杂,储层预测及油气检测难度大.通过岩石物理统计及井旁地震的时频域分析,有针对性的选用了基于泊松阻抗的储层预测技术和基于瞬时谱异常的油气检测技术.在储层预测方面,利用泊松阻抗参数降低孔隙度等岩石骨架因素对岩石弹性效应的影响,提高疏松砂岩和泥岩的区分敏感度,并针对研究区缺失大角度叠前资料的问题,在实际应用中利用两角度弹性阻抗反演方法实现了泊松阻抗参数的计算;在油气检测方面,利用储层含油气呈现的低频端瞬时谱能量增加的特征,借助匹配追踪时频分解算法,计算了低频端的瞬时能量梯度属性,有效预测了疏松砂岩的含油气异常范围.在N油田取得了较好的应用效果,指导了评价井位的部署,预测结果得到了钻井的验证.

Albertine rift valley is located in the western rift of East Africa,which belongs to Mesozoic and Cenozoic continental rift basin. The main oil-bearing intervals are unconsolidated sandstone reservoirs. Due to the good porosity and variance with depth,the seismic reflection characteristic of the sand reservoir is complex and it is difficult to make the reservoir prediction and hydrocarbon detection using the normal amplitude attributes. Based on the rock physics analysis and the time-frequency analysis of borehole side seismic trace,this paper uses the Poisson Impedance to predict reservoir and uses the instantaneous spectrum anomaly to detect hydrocarbon. The Poisson Impedance can reduce the negative effect of porosity to the rock elasticity,and raise the sensitivity of the discrimination between sand and shale. However,there are only two angle partial stack seismic data,the common Poisson impedance estimation method using three angle prestack seismic data is not useful. Based on the two-angle elastic impedance formula, the Poisson Impedance parameter is estimated using two-angle elastic impedance inversion in the real reservoir prediction application.Based on the anomalous instantaneous energy in low frequency band of hydrocarbon-bearing reservoirs,the low-frequency instantaneous energy gradient attribute is calculated by match pursuit timefrequency decomposition algorithm. The low frequency instantaneous energy gradient attribute predicts the hydrocarbon area effectively.The techniques have achieved good application effect in N field,which guided the position of the evaluation well,and the prediction results have been verified by drilled well.