利用多方位能量梯度差识别碳酸盐岩溶洞储层

由于溶洞型储层在纵向和横向上均具有较强的非均质性,采用常规手段进行识别难度较大。本文针对溶洞型碳酸盐岩储层所特有的串珠状地震反射特征,提出了基于最小二乘拟合算法的地震能量梯度估算法,该法的基本流程为:①选择或指定一个估算方向和估算半径;②以目标点为中心,在估算半径范围内沿估算方向确定采样点,并由所有采样点的序号组成x变量,所有采样点上的地震振幅组成y变量;③利用最小二乘法对x变量和y变量构成的y=f(x)进行线性拟合,求取截距和梯度;④将线性拟合所获得截距和梯度之积作为目标点的地震能量梯度值。与其他方法相比,该法更稳定,更能突出溶洞体的能量变化特征。应用效果表明,基于最小二乘拟合算法的地震能量梯度估算法对碳酸盐岩缝洞异常体的识别效果较好,可提高碳酸盐岩储层识别的效率和精度。

Carbonate cavern reservoir identification based on multi-azimuth energy gradient difference

It is very hard to identify carbonate cavern reservoirs by conventional methods because of their strong longitudinal and transverse heterogeneity.According to the bead-like seismic reflection response, the seismic energy gradient estimation based on least-square fitting is concluded in the paper.The estimation procedure is as follows：① Selecting or assigning a estimated direction, and defining the estimated radius;② Taking the target as the centre, confirming sample points along the estimated direction in the range of estimated radius, and variants x are made from the sequence number, the variants y are from the amplitudes of all the sample points;③ Applying linear ftt on by least squares to obtain the intercept and gradient.④ Taking the arithmetic product of the intercept and gradient from the linear ftt as the seismic energy gradient of the targets.Comparing with others, this method is more stable, and obtains more obvious energy variation of the bead-like seismic reflection.Applications have shown the efficiency and accuracy of carbonate fracture-cave abnormal body identification by the seismic energy gradient estimation based on least-square fitting.