基于匹配追踪算法的高精度页岩气“甜点”识别

中国页岩气资源开发近年来已取得了许多阶段性进展,但因勘探开采成本高、风险大,因此在钻井资料较少的情况下,充分利用地震资料的横向变化特征,精确刻画页岩气"甜点"区分布具有重要意义。常规叠后地震反演方法能够识别页岩层,但不能有效区分含气页岩层与非含气页岩层,而基于地震波衰减理论的流体活动因子能够有效表征储集层的渗透性,识别含气页岩储层。提出将流体活动因子与高精度匹配追踪算法相结合,在地震信号时频分解的基础上,建立含气页岩层与地震波衰减的联系,求取流体活动性属性,进而实现高精度页岩气"甜点"识别。该方法不受测井资料及构造解释的影响,能客观反映页岩层的含气性,适用于页岩气勘探初期钻探目标评价。理论模型试算和在中国南方复杂构造区海相页岩气勘探中的实际应用表明了该方法的有效性。

High-precision Seismic Prediction of Shale Gas Sweet Spots Based on Matching Pursuit Algorithm

The shale gas resource is abundant in China, and a lot of periodical progress on shale gas exploration and development has been made in recent years. However, as the high cost and risk, it is of great importance to use the lateral advantage of seismic data to predict the sweet spots of shale gas reservoirs with scarce well data. Conventional post-stack seismic inversion method can identify the shale formations, but cannot distinguish the gas-bearing shale from gas-free shale. However, the liquid mobility factor based on seismic attenuation theory can effectively characterize the permeability of the reservoir and recognize the gas-bearing shale. In this paper, we propose to use the liquid mobility as a sign of hydrocarbon content. First, apply the matching pursuit method for seismic wavefield separation. Then, calculate the liquid mobility factor after building the relationship between the gas-bearing shale and seismic attenuation. Based on the above steps, we can obtain the high-precision distribution of shale gas sweet spots. This method can be applied without the limitations of well logs and structural interpretations, thus can objectively reflect the gas-bearing situation, which is suitable for drilling target evaluation at the initial stage of shale gas exploration. Theory model test and the application of marine shale gas exploration in complex structure area of South China demonstrate the effectiveness of the method proposed in this paper.