Analysis of short‐ and long‐term system response during gas production from a gas hydrate deposit at the UBGH2‐6 site of the Ulleung Basin in the Korean East Sea

Abstract

This study is a continuation of an investigation into the feasibility of long‐term production from a marine hydrate accumulation that has the properties and conditions of the UBGH2‐6 (UBGH2, Ulleung Basin Gas Hydrates 2; 2 is the number of the scientific expedition) site at the Ulleung Basin in the Korean East Sea. The 12.7 m‐thick system is in deep water (2157 m), but at 140 m below the seafloor. It is characterized by alternating hydrate‐free clays and muds and hydrate‐rich sand layers. The layered stratigraphy and the presence of mud layers favours the use of vertical wells rather than horizontal wells for production. The analysis indicates that production from such a hydrate accumulation is technically feasible, but the gas production rates are generally low. Water production accompanying gas production from this deposit appears manageable under all the scenarios investigated in this study, however, the water‐to‐gas ratio is high. Subsidence at the ocean floor at the end of a 14 day test is quite limited. However, there is significant uncertainty in the predictions of the geomechanical system's behaviour because they are not based on measured system properties but only on estimates/assumptions from analogues. The long‐term production potential of the reservoir at the site investigated here appears challenging because of the limited effectiveness of dissociation and large water production, in addition to substantial subsidence.

Numerical Simulations in Support of a Long-Term Test of Gas Production From Hydrate Accumulations on the Alaska North Slope: Water Production and Associated Design and Management Issues

“…As indicated earlier (and as has been pointed out by Moridis et al. , ), production from hydrates from any given accumulation is evaluated using two criteria: (a) the absolute criterion, involving either (i) maximization of Q mT and of the overall CH 4 production potential for a given water production or (ii) minimization of Q wW and Q wTB for a given gas production, depending on where the focus of the study is, and (b) the relative criterion, describing the instantaneous or cumulative water-to-gas ratios ( R Qwm or R Mwm , respectively) that describe the amount of (unwanted) water associated with the CH 4 production. Obviously, after satisfying the absolute criterion, a promising production target is associated with minimization of the relative criterion.…”

“…We evaluated the production potential of the hydrate deposit in HU-B (the only dissociating accumulations in the subsurface; HU-C and HU-D (included in the simulation domain) were unaffected for the duration of the simulation) by using two production criteria , : an absolute criterion and a relative criterion. Because water production is the main focus of the study, the absolute criterion is reversed from what we have used in other production studies and is now satisfied by a low water production potential (i.e., low Q wW , M wW , R wR , R mAT , R Qwm , and R Mwm values) over the duration of the study. High water production is undesirable not only because it may indicate significant water inflows from the boundaries and inefficient depressurization and is inevitably associated with higher production costs associated with water lift and disposal.…”

Numerical Simulation of Improved Gas Production from Oceanic Gas Hydrate Accumulation by Permeability Enhancement Associated with Geomechanical Response

“…Four methods can be used for gas recovery from hydrate-bearing sediments, including depressurization [4,5], thermal stimulation [6], inhibitor injection [7], and CO 2 -CH 4 replacement [8][9][10][11]. National programs exist in many countries to research and produce natural gas from gas hydrate deposits in order to discover the commercialization possibility of methane hydrate resources, leading to various studies on the Alaska North Slope [12][13][14][15], the Mallik site in Canada [4,16,17], the Black Sea [18,19], the Krishna-Godavari basin in India [20,21], the Ulleung basin in Korea [22,23], the Nankai Trough in Japan [24][25][26], and the South China Sea [27][28][29] and Qilian Mountain [30] in China.…”

Preface to the special issue section honouring Professor P. Raj Bishnoi

“…Bollineni and Daraboina [ 17 ] investigate the use of clathrate formed from tetra‐n‐butyl ammonium chloride (TBAC) and methane for the treatment of produced water from oil and gas operations. Moridis et al [ 18 ] present an analysis of the system response during gas production from a hydrate deposit in the Korean East Sea. Dai et al [ 19 ] report improved performance of an adsorption–hydration hybrid process, with a fixed bed of activated carbon, to capture CO 2 at hydrate formation conditions.…”