Open Access

ARTICLE

Numerical Simulation on Depressurization-Driven Production of Class I Hydrate Deposits with Transition Layer and Perforation Modes Optimization

Yajie Bai^1,*, Jian Hou^2,3, Yongge Liu^2,3
1 Petroleum Exploration and Production Research Institute, SINOPEC, Beijing, 102206, China
2 Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum (East China), Ministry of Education, Qingdao, 266580, China
3 School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, 266580, China
* Corresponding Author: Yajie Bai. Email:
(This article belongs to the Special Issue: Integrated Geology-Engineering Simulation and Optimizationfor Unconventional Oil and Gas Reservoirs)

Energy Engineering https://doi.org/10.32604/ee.2025.063198

Received 08 January 2025; Accepted 28 March 2025; Published online 18 April 2025

Abstract

Natural gas hydrate widely exists in the South China Sea as clean energy. A three-phase transition layer widely exists in low permeability Class I hydrates in the Shenhu offshore area. Therefore, taking into account the low-permeability characteristics with an average permeability of 5.5 mD and moderate heterogeneity, a 3-D geological model of heterogeneous Class I hydrate reservoirs with three-phase transition layers is established by Kriging interpolation and stochastic modeling method, and a numerical simulation model is used to describe the depressurization production performance of the reservoir. With the development of depressurization, a specific range of complete decomposition zones appear both in the hydrate and transition layers. The entire decomposition zone of the whole reservoir tends to outward and upward diffusion. There is apparent methane escape in the three-phase transition layer. Due to the improvement of local permeability caused by the phase transition of hydrate dissociation, some methane accumulation occurs at the bottom of the hydrate layer, forming a local methane enrichment zone. The methane migration trends in reservoirs are mainly characterized by movement toward production wells and hydrate layers under the influence of gravity. However, due to the permeability limitation of hydrate reservoirs, many fluids have not been effectively produced and remain in the reservoir. Therefore, to improve the effective pressure drop of the reservoir, the perforation method and pressure reduction method were optimized by analyzing the influencing factors based on the gas production rate. The comparative study demonstrates that perforating through the free gas layer combined with one-time depressurization can enhance the effective depressurization and improve production performance. The gas production rate from perforating through the free gas layer can be twice as high as that from perforating through the transition layer. This study can provide theoretical support for the utilization of marine energy.

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Keywords

Class I hydrate; transitional layers; heterogeneity; depressurization; numerical simulation; perforation mode

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