高、低产煤层气井AVO正演特征及其识别

利用鄂尔多斯盆地东缘地区煤层气勘探阶段的钻井与测井资料,获得该地区煤层气井主力储层5煤层与围岩的岩性特征及弹性参数,并应用基于zoeppritz方程的线性近似公式进行射线追踪模拟,以研究该区高、低丰度煤层气储层5煤层AVO响应特征。该区XX-3井煤层气高产井与XX-11低产井的AVO分析表明：高产气井的振幅随偏移距的增大存在明显的减弱现象,且其顶板负相位反射振幅呈现较强的负截距异常和正梯度异常,底板正相位反射振幅呈现较强的正截距异常和负梯度异常;而低产气井的AVO现象不明显,代表煤层顶底板反射波振幅梯度曲线异常变化较小。在该区地质条件下建立的识别高、低产煤层气井的AVO响应特征识别方法,可为煤层气试井质量提供新的判识手段。

AVO Forwarding Features and Recognition in High and Low Yielding CBM Wells

Using CBM exploration stage drilling and well logging data in the eastern margin area of the Ordos Basin, lithologic characteristics and elastic parameters of CBM main reservoir No.5 coal seam and surrounding rocks in the area have been obtained. Based on Zoeppritz＇s equations have carried out ray tracing simulation to study the AVO responding characteristics of high and low abundance CBM reservoir No.5 coal seam in the area. The AVO analyses of XX-3 high yielding and XX-11 low yielding wells have demonstrated that： the high yielding well AVO increasing exists obvious weakening phenomenon, and its roof negative phase reflection amplitude presents stronger negative intercept anomaly and positive gradient anomaly, floor positive phase reflection amplitude presents stronger positive intercept anomaly and negative gradient anomaly; while the low yielding well AVO phenomenon is not clear, represents lesser variation of coal roof and floor reflection amplitude gradient curve anomaly. The high and low yielding CBM wells AVO responding characteristics recognition method established under the area＇s geological condition can provide CBM test well quality new judging means.