Analytical Modelling of Gas Production From Hydrates in Porous Media

Abstract

Gas hydrates are being considered as an alternative energy resource of thefuture since they exist in enormous quantities in permafrost and offshoreenvironments. However, gas production potential from hydrate reservoirs throughdifferent production schemes has not been fully investigated yet. This workintroduces a simple analytical model for simulating gas production from hydratedecomposition in porous media by a depressurization method. We consider the heat transfer to the decomposing zone, intrinsic kinetics ofhydrate decomposition, and gas-water two-phase flow as the three primarymechanisms involved in hydrate decomposition in porous media. In this study, the relative importance of these mechanisms is compared over a realistic rangeof the physical properties. It is shown that for the cases studied, the effectof two-phase flow is significantly smaller than the heat transfer and theintrinsic kinetics of hydrate decomposition. Considering the rate-controllingmechanisms, an analytical model is developed to predict the performance ofdecomposition of gas hydrates in porous media. The model is used to performsensitivity studies to investigate the feasibility of commercial gas productionfrom hydrate reservoirs. The results suggest that significant quantities of gascan be produced from gas hydrate reservoirs where the hydrate overlies the gaszone. Such reservoirs have been found in the permafrost regions of Siberia, Alaska, and Canada. Introduction The enormous natural gas reserves associated with the in situ gas hydratesin permafrost regions and offshore environments of the earth is expected to bean energy resource of the future. The gas could be produced from the hydratedissociation by depressurization, thermal stimulation, solvent injection, or acombination of these methods. The potential for gas production from hydratereservoirs through different production techniques is still uncertain and underinvestigation. One method of investigation is with the help of mathematicalmodels. For a mathematical model to be representative, it should include theimportant mechanisms. In a depressurization scheme considered in this study, three important mechanisms are involved: intrinsic decomposition of the hydratethat results in reduced temperature; heat flow towards the cooled zone thatprovides the necessary energy for further decomposition; and, flow of thedecomposed gas and water through the porous rock.

Heat Transfer Analysis of Methane Hydrate Sediment Dissociation in a Closed Reactor by a Thermal Method

“…Due to this potential resource, the problems associated with production of natural gas hydrate have become of greater interest to the more and more countries [7,8]. Heat transfer, as one of the three main mechanisms of hydrate production, has an increasingly significant influence on hydrate safety and efficient exploitation [9]. One of the key requirements of any production technique is to provide the heat necessary for the endothermic reaction of hydrate decomposition, which is determined by heat transfer [10], so the heat transfer analysis of hydrate-bearing sediments is a controlling factor for all production techniques.…”

Numerical Simulation of the Depressurization Process of a Natural Gas Hydrate Reservoir: An Attempt at Optimization of Field Operational Factors with Multiple Wells in a Real 3D Geological Model

“…This simulator includes the Kim-Bishnoi kinetic parameters that can describe heat of dissociation and hydrate thermodynamic stability which is the core mechanism for hydrate simulation [30]. Compared with other software that can be adapted to describe hydrate reservoirs, its accuracy and suitability to represent production performance from hydrate deposit in porous media has been validated by many researchers (e.g., [29,31,32]). TOUGH + HYDRATE, originated and developed at the Lawrence Berkeley National Laboratory was the first available model to simulate hydrate reservoirs, it can take in four mass components (i.e., inhibitors, water, hydrate, and methane) partitioned between four possible phases (ice, water, gas and hydrate,) and fully couple reservoir heat transfer and mass to simulate the non-isothermal dissociation process, as described by Moridis [33].…”

Sensitivity Analysis of Parameters Governing the Recovery of Methane from Natural Gas Hydrate Reservoirs

“…Its suitability to represent methane production from gas hydrates in porous media and has been examined by other authors who validated it against other comparable software [14][15][16][17]. Table 1.…”

“…The equilibrium pressure equation is determined by regression from experimental data compiled by Sloan and Koh [27] (see Figure 1): (17) and:…”

“…On the other hand, the relative permeability and capillary pressure were obtained from Hong [17] who modified the equations of Van Genuchten [28] and Parker et al [29] to incorporate the presence of a hydrate phase.…”