基于匹配追踪分解的流体活动因子预测煤层气甜点区

煤层气勘探与开发是我国非常规油气资源勘探的热点之一，近年来已取得了较多突破性进展，但煤层非均质性强，吸附态为主的煤层气识别困难，勘探开发风险大，因此在钻井资料较少及叠后地震资料未充分利用的情况下，充分利用地震资料的横向变化特征，精确刻画煤层气“甜点”区分布具有重要意义。常规叠后地震反演能够识别煤层，但无法预测煤层的含气性，而基于地震波衰减理论的流体活动因子能够有效表征储层的渗透性，识别含气煤储层。提出将流体活动因子与高精度匹配追踪算法相结合，充分发掘已有叠后地震数据信息，在高精度地震信号时频分解的基础上，建立含气煤层与地震波衰减的联系，求取流体活动性属性，实现高精度煤层气“甜点”识别。该方法忠实于地震数据，不受构造及层序解释的影响，能客观反映煤层的含气性。理论模型试算和在沁水盆地煤层气勘探中的实际应用证明了该方法的可行性及有效性。

Prediction of CBM sweet spots via matching trace decomposition-based fluid activity factor

The exploration and development of CBM is one of the hotspots in the exploration of unconventional oil and gas resources in China, and a lot of breakthrough on CBM exploration and development have been made in recent years. However, it is difficult to identify CBM with strong coal seam heterogeneity and adsorption state, and it is of great importance to use the lateral advantage of seismic data to predict the sweet spots of CBM reservoirs in case of scarce drilling data and insuffisant use of post-stack seismic data. Conventional post-stack seismic inversion method can identify the coal seams, but cannot predict the gas-bearing property of coal seams. However, the fluid activity factor based on seismic attenuation theory can effectively characterize the permeability of the reservoir and recognize the gas-bearing coal. In this paper, we propose to use the fluid activity as a sign of hydrocarbon content. First, the matching pursuit method was applied for seismic wavefield separation. Then, the fluid activity factor was calculated after building the relationship between the gas-bearing coal and seismic attenuation. Based on the above steps, we can obtain the high-precision distribution of CBM sweet spots. This method is faithful to seismic data and can be applied without the limitations of structural and sequential interpretation, thus can objectively reflect the gas-bearing situation. Theoretic model test and the application of coalbed gas exploration in Qinshui basin prove the effectiveness and feasibility of the proposed method.