莺歌海盆地中深层高温高压河道砂岩储层含气性检测新方法

莺歌海盆地中深层河道砂岩含气储层受高温高压和强非均质性等地质条件的影响,导致其AVO地震响应特征类型多变,利用常规的P(AVO拟合截距)、G(AVO拟合斜率)、P×G、P+G等属性已不能有效识别该区储层的含气范围,亟待寻找适合该地区的、有效的储层含气性检测方法。为此,通过基于Shuey近似公式的单井AVO正演模拟技术和基于蒙特卡洛随机正演的AVO模拟技术,探讨了该区含气储层的AVO类型和含气性检测方法。研究结果显示,该区含气砂岩表现为第Ⅰ、第Ⅲ、第Ⅳ等3类AVO地震响应特征;然后提出采用标量泊松比反射率属性作为该区含气性检测的敏感属性因子,并模拟计算出了标定系数,进而得到了新的储层含气性检测方法。现场应用效果表明:1新方法预测结果与实际钻井结果相吻合;2新方法的运用效果明显优于常用的P、G、P×G、P+G等流体敏感属性因子;3有效应用新方法的关键在于储层AVO地震响应特征研究、敏感参数筛选和标定系数计算。结论认为,新方法在该区具有较好的推广应用价值。

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.