南海神狐海域非均质性天然气水合物储层的分频反演

南海北部陆坡神狐海域天然气水合物钻探结果显示，这一区域水合物储层具有纵横向分布不均质性、规模小且变化快的特点，使得精确评价水合物资源量面临诸多困难。根据井震数据分析了水合物分布特点，利用分频反演方法对该区水合物的空间分布进行预测。分频反演是利用测井和地震资料，采用支持向量机（SVM）的方法研究不同探测频率下的振幅响应（AVF），将AVF作为独立信息引入反演，建立起测井和地震波形间的非线性关系，充分利用地震中全频带信息，实现高分辨率的反演结果。采用该方法进行预测的结果与实际钻井情况非常吻合，验证这一技术适用于预测非均质性天然气水合物空间分布。基于预测结果并结合区域地质特征综合分析表明：水合物分布不均匀的主控因素除温压条件外，晚中新世之后的频繁构造运动使较深部的热解气沿着断层、气烟囱向上运移，形成厚块状“流体运移通道型”天然气水合物藏，而浅部沉积物中以扩散方式在渗透性良好的储层形成薄层状天然气水合物藏。

Frequency-divided inversion method of heterogenous natural gas hydrates reservoir in the Shenhu area,South China Sea

Drilling results suggest that natural gas hydrates in the Shenhu area of the northern continental slope of South China Sea are obviously heterogenous in both vertical and horizontal directions, which brings about great difficulties to evaluate accurately the amount of hydrate resources. Based on integrated well-seismic data analysis for gas hydrates distribution characteristic, using frequency-divided inversion of SVM method in this research to predicted the hydrate spatial distribution in the area. Frequency –division inversion which is using logging and seismic data, application the method of support vector machine (SVM) under different frequency versus amplitude response (AVF), introduced the AVF as independent information, establish the nonlinear relationship between well logging and seismic waveform, make full use of the whole frequency band in the seismic, thus high resolution inversion results are obtained. The inversion results are in good agreement with the facts disclosed by drilling wells in this paper. Therefore, the method is believed feasible to the prediction of thickness heterogeneity. The research results also revealed that the mainily factors which control the thickness heterogeneity of gas hydrates include not only temperature-pressure conditions. Tectonic movement was frequent since late Miocene in the study area and deep pyrolysis gas shall be transported up along the vertical channels such as gas chimneys and faults, which is to form thick layer of “leakage type gas hydrate deposits fluid transported”, at the same time, the biogas generated by microorganisms will be accumulated in the thin layers of seabed sediments to form the “autochthonously generated and self-stored diffusion type” gas hydrates reservoir.