A new gas-bearing detection method for medium and deep channel sand reservoirs under high temperatures and high pressures in the Yinggehai Basin

The AVO seismic response characteristics of the medium and deep channel sand reservoirs in the Yinggehai Basin are very complicated because of the specific geological setting with high temperature, high pressure, and strong heterogeneity, etc. Thus it becomes difficult to predict the gas-bearing property of these reservoirs in this study area by means of those common seismic AVO attributes like P intercept, G gradient, P+G and P×G products. In view of this, the forward AVO modeling by use of both Shuey's equation and the Monte Carlo random approach was applied to discuss the AVO types and the gas-bearing prediction methods. The simulated results demonstrated three AVO response effects in this area, i.e. No. I, III and IV, then the scalar Poisson's ratio reflectance was proposed as an identification factor for the gas-bearing property and the calibration coefficient was figured out. Thus, a new gas-bearing prediction method was obtained. Field application shows that this method is of value to be further promoted by the following satisfactory findings. First, the prediction results agree well with the actual drilling ones. Second, the new prediction method shows obvious advantages over the common analysis of seismic AVO attributes. Third, the key to the effective application of this method lies in the research of AVO seismic response characteristics of the reservoir, sensitive parameter screening, and calibration coefficient calculation. © 2016, Natural Gas Industry Journal Agency. All right reserved.