Gas production from a silty hydrate reservoir in the South China Sea using hydraulic fracturing: A numerical simulation

Abstract

The low permeability of silty hydrate reservoirs in the South China Sea is a critical issue that threatens safe, efficient, and long‐term gas production from these reservoirs. Hydraulic fracturing is a potentially promising stimulation technology for such low‐permeability reservoirs. Here, we assess the gas production potential of a depressurization horizontal well that is assisted by the hydraulic fracturing using numerical simulation according to field data at site SH2 in this area. In addition, the number of horizontal wells drilled is discussed if commercial production is to be performed at this site. The results show that the production potential can be significantly stimulated at the early production stage by adopting hydraulic fracturing in this reservoir due to a better depressurization effect. However, the increase in gas recovery gradually decreases with the continuous dissociation of gas hydrates, and the evolution trend is similar to that in a reservoir without stimulation during later periods of gas production because the dissociation front gradually moves away from the fractures. From the perspective of production potential, using a horizontal well scheme assisted by the hydraulic fracturing technology for gas recovery from a hydrate deposit can sharply reduce the number of operation wells, shorten the drilling operation time, and boost the economic efficiency. The horizontal well scheme may be an effective way to increase the gas yield if the application of quickly deployed horizontal wells and hydraulic fracturing techniques in such hydrate reservoirs greatly increases in the near future.

Experimental Study on the Propagation Characteristics of Hydraulic Fracture in Clayey-Silt Sediments

“…They concluded that the permeability improvement, which raised the average gas production rate by one order of magnitude, might be more reliable than the aggressive depressurization on the gas recovery enhancement. Hence, enhancing the permeability to assist depressurization is necessary [21][22][23][24][25].…”

Numerical simulations of depressurization‐induced gas production from hydrate reservoirs at site GMGS3‐W19 with different free gas saturations in the northern South China Sea

“…Natural gas hydrate (NGH) is regarded as one of the most promising alternative energy resources that is widely distributed in permafrost zones and oceanic sediments. The NGH reservoirs are generally divided into four classes: Class 1 (the free gas layer above which the hydrate-bearing layer exists), 1 Class 2 (hydrate formation overlies a mobile water zone), 2 Class 3 (only one hydrate formation without any underlying zone of mobile fluids), 3,4 and Class 4 (reservoirs with low hydrate saturation and unconfined geological strata near the seafloor, hydrates in fractures, etc). 5 The percentages of the above four types of reservoirs in nature are expected to be 14%, 5%, 6%, and 75%, respectively.…”

Thermal Diffusion Characteristics in Permafrost during the Exploitation of Gas Hydrate

“…This temperature change will dramatically affect the efficiency of hydrate production [27,28]. It may conduct the wellbore instability, sand production ( Figure 2), and methane leakage [26,[29][30][31]. The temperature range of hydrate layers in Messoyakha gas field, Mount Elbert gas hydrate well (Alaska), Malik gas hydrate site (Canada), and Qinghai-Tibet Plateau were about 8~11°C [32], -8~10°C [33,34], -20~-1°C [6,12,33], and -0.1~-5°C [35], respectively, which are different from the traditional petroleum temperature.…”