Investigations on the influence of wellbore configuration and permeability anisotropy on the gas production from a turbidite hydrate reservoir of KG Basin

Abstract

Extraction of methane gas from the gas hydrate bearing sediments (GHBS) would primarily depend upon its overall characteristics such as type of the sediments and their stratification, hydrate saturation and morphology, thermo-hydro-mechanical properties (viz., thermal properties, permeability, compressibility), in-situ pressure and temperature conditions prevailing in the reservoir, wellbore configuration (vertical and horizontal), and the process of dissociation (viz., depressurization and thermal stimulation). However, out of these parameters which one(s) would control enhanced gas production from a turbidite hydrate reservoir is a question that needs to be addressed. With this in view, numerical simulations were conducted by employing TOUGH + HYDRATE and considering a clay-dominant turbidite hydrate reservoir, which is a typical of KG Basin, India, and its properties ascertained during the NGHP-02 expedition. This exercise reveals that the vertical wellbore, which is easier to execute as compared to the horizontal wellbore, and depressurization in tandem with wellbore heating would enhance the gas production from the GHBS. In addition, the presence of clay layers has been noticed to impede the dissociation front migration and gas production. It has also been observed that the short-term gas and water production increases and the time required for production of significant gas decreases with an increase in the permeability anisotropy. However, the mass of methane produced has been found to be practically uninfluenced by permeability anisotropy.