Simulation of Gas Production and Seafloor Subsidence during the Development of Natural Gas Hydrates in the South China Sea,Energy & Fuels

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Simulation of Gas Production and Seafloor Subsidence during the Development of Natural Gas Hydrates in the South China Sea
Energy & Fuels ( IF 5.2 ) Pub Date : 2024-04-24 , DOI: 10.1021/acs.energyfuels.4c00700
Xuefeng Li ₁ , Baojiang Sun ₁ , Hao Li ₁ , Huaqing Liu ₂ , Dejun Cai ₂ , Xiansi Wang ₂ , Xiangpeng Li ₂

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In the process of developing offshore hydrate reserves, the stability of the subsea formations emerges as a crucial determinant, exerting a significant influence on the feasibility of prolonged extraction. Addressing the challenge of seafloor subsidence induced by pressure reduction during extraction, a numerical simulation method was employed that integrates multiphase seepage, heat transfer, and mechanical considerations. It delves into the dynamic evolution of mechanical parameters in shallow seabed formations, considering the depth-dependent changes. An in-depth analysis is conducted to discern the impact of reservoir permeability, hydrate saturation, and geothermal gradient on both formation subsidence and the overall efficiency of the extraction process. Key findings highlight that the permeability of the reservoir plays a pivotal role in enhancing the extraction efficiency. Extracting from high-permeability reservoirs not only yields greater gas production but also avoids significant subsidence compared to that from low-permeability counterparts. Furthermore, higher hydrate saturation levels are found to substantially contribute to the increased gas production. The cohesive effects of the hydrates further elevate the stability of the surrounding strata near the wellbore. When dealing with reservoirs characterized by higher geothermal gradients, the expanded range of hydrate decomposition results in a heightened formation subsidence. Consequently, the ratio of gas-extraction-induced subsidence exhibits a discernible downward trend. The results of this research provide valuable theoretical insights, serving as a reference for effectively controlling risks during the process of the depressurization extraction of natural gas from shallow offshore reserves.

中文翻译：

南海天然气水合物开发过程中产气量和海底沉降模拟

在开发海上水合物储量的过程中，海底地层的稳定性成为关键的决定因素，对长期开采的可行性产生重大影响。为了解决提取过程中压力降低引起的海底沉降的挑战，采用了集成多相渗流、传热和机械考虑的数值模拟方法。它深入研究了浅海海底地层力学参数的动态演化，考虑了与深度相关的变化。通过深入分析，了解储层渗透率、水合物饱和度和地温梯度对地层沉降和开采过程整体效率的影响。主要发现强调，储层的渗透率在提高开采效率方面发挥着关键作用。与低渗透油藏相比，高渗透油藏的开采不仅可以提高天然气产量，而且可以避免严重沉降。此外，发现较高的水合物饱和度水平大大有助于增加天然气产量。水合物的粘结作用进一步提高了井眼周围地层的稳定性。当处理地温梯度较高的储层时，水合物分解范围的扩大会导致地层沉降加剧。因此，抽气引起的沉降比率呈现出明显的下降趋势。研究结果提供了有价值的理论见解，为有效控制浅海储量减压开采天然气过程中的风险提供了参考。

更新日期：2024-04-24

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