Numerical Analysis on Gas Production Efficiency from Hydrate Deposits by Thermal Stimulation: Application to the Shenhu Area, South China Sea

Abstract

Gas hydrates have been attracted a great deal of attention because of their potential as an energy substitute and the climate implications. Drilling and sampling research on the hydrate deposit in the Shenhu Area on the northern continental slope of the Southern China Sea was a big breakthrough for hydrate investigation in China, but as a new potential energy source, how the gas can be effectively produced from hydrate deposits has become a hot research topic. Besides depressurization heat stimulation is regarded as another important means for producing hydrate-derived gas, however, the production efficiency and economic feasibility of producing gas by heat stimulation have not been clearly understood. In this paper, a simplified model for predicting gas production from hydrate deposits by heat stimulation is developed. The model ideally neglects the effects of heat convection and pressure regime in the sediments for simplicity. We compute the heat consumption efficiency and gas energy efficiency of gas production from hydrate deposits by heat stimulation, only considering effect of hydrate dissociation due to heat input. This model is for predicting the maximum production efficiency. By studying the hydrate reservoirs and significant parameters collected from drilling and sampling researches, we calculate the production potential of the Shenhu hydrate deposits and investigate the production efficiency and feasibility. Our research shows that the maximum amount of OPEN ACCESSEnergies 2011, 4 295 cumulative gas production at Shenhu is ~509 m 3 per meter in three years. The production potential is much lower than the industrial criterion for marine production. In our discussion the numerical simulations show that a practical potential of the gas production is merely 25 m 3 /m in 3 years and contribution of thermal stimulation is very small in joint-production schemes. We conclude that production cost is quite high and the economic value of producing gas from the hydrate through a vertical well is not attractive, even though the production by heat stimulation theoretically has a very high heat consumption rate and energy efficiency.Keywords: gas hydrate; heat stimulation; numerical analysis; Shenhu area Nomenclature:c p = heat capacity of sediment c g = heat capacity of gas c w = heat capacity of water P = system pressure ΔP=pressure difference in thermal production simulation Q = total heat consumption, T H Q Q Q = +Q T = heat consumption for raising sediment temperature Q H = heat consumption for decomposing hydrate Q C = net combustion heat of methane gas Q r =release rate of gas from hydrate deposit q g = gas flux q w = water flux R DH = heat consumption efficiency of hydrate dissociation R CH = energy efficiency of thermal hydrate exploitation r = distance to vertical well r d = dissociation radius r w = radius of vertical well, r w = 0.10 m r max = maximum radius of cylindrical domain simulated, r max = 10 m Δr = grid step in radius direction of cylindrical domain, Δr = 0.01 m S H = hydrate saturati...

Effects of Formation Dip on Gas Production from Unconfined Marine Hydrate-Bearing Sediments through Depressurization

“…Shenhu area is located in the Baiyun Sag, Pearl River Mouth Basin (PRMB) of the northern slope of the SCS (Figure 1). Geological, geophysical, geothermal, and geochemical investigations had suggested that Shenhu area is a beneficial district for the formation of NGH [18,24,26]. Gas hydrate samples were collected during a recent scientific expedition conducted by the China Geological Survey in this area in May 2007 and September 2015 [5,19,20,45].…”

“…In order to seek the most economically and technically feasible method for gas production from the HBS, numerical simulation for its economic, convenient, and flexible response to complex geological problems was considered as the best way to achieve this objective. Based on the available geological data in Shenhu area of the SCS, Zhang et al [22] investigated the gas production performance by using two parallel horizontal wells to depressurize the HBS; Li et al [13,23] and Su et al [24][25][26] fully investigated the gas production potential and efficiency through depressurization and the combination of depressurization and 2 Geofluids thermal stimulation, respectively, employing both vertical and horizontal wells. Their results indicated low gas production rates and unsatisfied gas/water ratios because of low intrinsic permeability of the HBS and permeable overburden and underburden formations.…”

Numerical simulation of Class 3 hydrate reservoirs exploiting using horizontal well by depressurization and thermal co-stimulation

“…However, the production simulation carried out by Moridis and Reagan only lasted about 1500 days in industry level [18]. Su et al [20] and Myshakin et al [21] employed the depressurization and thermal stimulation method to investigate vertical well hydrates dissociation, and found that the gas released rate was too small to reach industry-scale commercial production. Li et al attempted to produce gas by depressurization and the pull and hull method in horizontal well, but the results were not as satisfactory as expected [19,[22][23][24].…”

Evaluation of Gas Production from Marine Hydrate Deposits at the GMGS2-Site 8, Pearl River Mouth Basin, South China Sea

“…The application of the vertical well [28], the single horizontal well [25], and the dual horizontal well [15] technologies in the hydrate reservoir at the Shenhu Area were investigated. Evaluations of the gas production from hydrate reservoir by depressurization [29], thermal stimulation [30], the huff and puff method [26], and depressurization in conjunction with warm brine stimulation [31] were also studied. However, up to now, there was little literature about the evaluation of gas production from the hydrate reservoir in the Dongsha Area.…”