Determining Seismic Attributes of Amplitude Versus Offset Analysis in Order to Identify Gas-Bearing Layers Using Inversion of Shuey Approximation

This research used prestack seismic data in Penobscot to detect gas-bearing layers using AVO analysis. AVO technique is not easy based on Zoeppritz equations then this work applied Shuey approximation to calculate gradient (G) and intercept (Rp) parameters using least square and Tikhonov solutions. Model covariance matrix was calculated for least square and Tikhonov technique to obtain the variance of estimation of Rp and G. The variance of estimation of least square method is 0.24 and 15.08 for RP and G, respectively. Also, it is equal to 0.08 and 0.14 for Rp and G in Tikhonov solution. Therefore, the results of Tikhonov are more reliable than least square solution. Multiplication of intercept and gradient showed the strong and positive values in gas layers. The reflection coefficient of shear wave identified gas-bearing layers by a positive value. The difference of P-wave and S-wave profile appeared relatively high negative values in time range of 2000 to 2020 ms. L30 well which was drilled in cross line 1153 showed that there is gas accumulation in time range of 2000 to 2036 ms. Therefore, AVO attributes could identify gas-bearing layers.