琼东南盆地渗漏型天然气水合物识别与差异成藏特征

Identification and the differential accumulation of leakage-typed gas hydrate in the Qiongdongnan Basin, northern South China Sea

  • 摘要: 南海北部琼东南盆地中央凹陷带松南低凸起之上的研究区的管状渗漏通道内普遍发育渗漏型天然气水合物,岩芯中可见块状、脉状以及结核状等产状水合物发育。为了探究渗漏型天然气水合物的综合识别方法以及不同渗漏型水合物矿体成藏是否存在差异,结合地震、测井以及岩芯资料,开展了多类型含水合物储层识别以及流体渗漏分布研究。研究表明,渗漏型水合物综合识别方法中,地震反射同相轴上拉以及方差地震属性异常指示了流体渗漏通道的存在;侧向和感应电阻率曲线分离,电阻率成像图上见高亮和高角度变形层理,为渗漏型水合物测井响应。根据水合物钻探和地震解释结果,划分了3个与渗漏型水合物相关的水合物矿体,其中的1个水合物矿体钻遇了砂质高饱和度扩散型水合物。砂体发育导致水合物矿体的流体渗漏强度明显减弱,砂体既作为良好的储层,也是储能泄压载体。未发育砂体的水合物矿体中,渗漏通道内渗漏型水合物发育显著,远离渗漏通道,水合物钻探显示差。砂体和渗漏通道是琼东南盆地渗漏型天然气水合物差异成藏的主控因素。

     

    Abstract: Leakage-typed gas hydrates occurs in the form of block, vein, nodule in the core and are developed widely in tubular leakage passage in the Songnan low uplift in the central depression of the Qiongdongnan Basin in the northern South China Sea. To explore a comprehensive identification method for the leakage-typed gas hydrate and their differences in the accumulation for various ore bodies of leakage-typed gas hydrate. Identification for multiple types of gas hydrate reservoirs and fluid leakage distribution were studied combining seismic, logging well drilling, and borehole data. In the comprehensive identification methods, seismic reflection phase axis pull-up and variance seismic attribute anomalies indicate fluid leakage channels; the separation of lateral and induced resistivity logging curves, the bright and high-angle deformation layers seen in the resistivity image are the logging responses of leaky hydrates. Based on the borehole data and seismic profiles, three gas-hydrate ore bodies related to leakage gas hydrates were identified, and one of them encountered high-saturation diffusion gas hydrates in sandy sediment. The deposition of sand bodies significantly weakened the fluid leakage intensity of the hydrate ore bodies, during which sand sediments served as good reservoirs, and also energy storage with pressure relief. In hydrate ore bodies without developed sand bodies, seepage-type hydrates are significantly developed in seepage channels, while far away from the seepage channels, the hydrate drilling indication is poor. However, in the absence of sand sediment, leakage gas hydrates well developed in the leakage channels, while far away from the channels, the hydrate drilling indication is poor. Therefore, sand bodies and the leakage channels are the main controlling factors for the differential accumulation of leakage-typed gas hydrate in the Qiongdongnan Basin.

     

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