Abstract Gas hydrate reservoir properties provide critical information on the controlling mechanisms of gas hydrate formation and accumulation in natural depositional environments. They also are essential to understanding and accurately predicting gas production characteristics. However, the properties of fine-grained reservoirs that host hydrates are poorly studied. Guangzhou Marine Geological Survey acquired a comprehensive set of logging-while-drilling (LWD) logs, in situ tests, and lab measurements from 2015 to 2018 in the W11-17 fine-grained, gas hydrate reservoir of the Shenhu on the South China Sea. Porosity, hydrate saturation, and gas saturation were derived from neutron porosity, nuclear magnetic resonance (NMR), and electrical resistivity logs of SH-W17 and SHSC-4J1 wells and compared with lab measurements of pressurized cores. Units A to C contain three hydrate-concentrated intervals, with a maximum thickness of 32 m and an average hydrate saturation of 0.32 ±0.05. The hydrate saturation was estimated using resistivity and NMR models. Units D and E were inferred to be approximately 20 m thick, free-gas layers containing gas hydrates. Compared to hydrate saturation, the estimations of gas saturation from resistivity and NMR models are less reliable with a range of 0.05–0.4 due to the coexistence of gas hydrates and free gas. Permeabilities estimated from the NMR log agree well with those from neuron porosity in non-hydrate bearing intervals but are slightly higher in hydrate-bearing intervals. By incorporating the lab measurements and in situ tests into the NMR pore-size analysis, the permeability of water-bearing sediments in the hydrate intervals in the SHSC-4J1 well can be constrained to the range of 0.002–0.1 md, with 0.015 md being our best estimate. The NMR pore-size geometries indicate gas hydrates appear to preferentially fill bigger pores within fine-grained reservoirs, which exhibit a similar behavior to coarse-grained reservoirs. Our resistivity and relative permeability modeling indicate that the growth of gas hydrates within pore spaces is characterized by pore-filling and cementation behaviors.

中文翻译：

---

南海北坡神狐天然气水合物生产试验场测井和室内测量估算的细粒天然气水合物储层性质

摘要 天然气水合物储层性质为自然沉积环境中天然气水合物形成和聚集的控制机制提供了关键信息。它们对于理解和准确预测天然气生产特征也是必不可少的。然而，对含有水合物的细粒储层的性质研究甚少。广州海洋地质调查局于 2015 年至 2018 年在南海神狐 W11-17 细粒天然气水合物储层中获得了一套全面的随钻测井 (LWD) 测井、现场测试和实验室测量数据. 孔隙度、水合物饱和度和含气饱和度来自 SH-W17 和 SHSC-4J1 井的中子孔隙度、核磁共振 (NMR) 和电阻率测井，并与加压岩心的实验室测量结果进行比较。A～C单元包含3个水合物富集层段，最大厚度为32 m，平均水合物饱和度为0.32±0.05。使用电阻率和核磁共振模型估计水合物饱和度。单元 D 和 E 被推断为大约 20 m 厚的含有天然气水合物的游离气层。与水合物饱和度相比，由于天然气水合物和游离气共存，电阻率和核磁共振模型对天然气饱和度的估计不太可靠，范围为 0.05-0.4。根据核磁共振测井估算的渗透率与非水合物层段中神经元孔隙度的渗透率非常吻合，但在含水合物层段中略高。通过将实验室测量和原位测试结合到 NMR 孔径分析中，SHSC-4J1井水合物层段含水沉积物的渗透率可以限制在0.002-0.1 md范围内，0.015 md是我们最好的估计。核磁共振孔径几何结构表明，天然气水合物似乎优先填充细粒储层中较大的孔隙，这与粗粒储层表现出相似的行为。我们的电阻率和相对渗透率模型表明，孔隙空间内天然气水合物的增长以孔隙填充和胶结行为为特征。