Enhancement of Gas Production From Clayey Silt Hydrate Reservoirs Based on Near Wellbore Artificial Fractures Constructed Using High-Pressure Rotating Water Jets Technology

Abstract

Over 90% of the global hydrate resources are stored in very-low-permeability clayey silt reservoirs. The low permeability significantly restricts the efficiency of gas and water flow into the production well. To enhance gas production efficiency in low-permeability hydrate reservoirs, the high-pressure rotating water jets (HPRWJ) technology is proposed to construct near wellbore artificial fractures (NWAFs) in hydrate reservoirs. The HPRWJ avoid the risks of hydraulic fracturing as well as large-scale reservoir damage, which makes it more suitable for constructing fractures in hydrate-bearing sediments (HBS). In this article, the site SH7 in the South China Sea is studied to evaluate the feasibility of this technology for enhancing gas production of low-permeability hydrate reservoirs by numerical simulation. The results show that the gas productivity is increased by approximately three times by using the HPRWJ technology to construct NWAFs with a depth of 3 m. It is suggested that the proposed technology is a promising method for improving gas production from the low-permeability hydrate reservoirs. Furthermore, the gas production performance is closely related to NWAF depth, NWAF permeability, and NWAF spacing. For the site SH7 in the South China Sea, the NWAF depth, permeability, and spacing are recommended as 3 m, 3D, and 3 m, respectively.

Enhancement of Gas Production from Class 1-Type Hydrate Reservoirs with High-Pressure Rotating Water Jets in Horizontal Well Depressurization Production

“…As a result, the first version of the code is insufficient for predicting large-scale models. In this work, we used a thermodynamic equilibrium model to simulate long-term gas production under on-site reservoir conditions with pT+H v1.0. , The following assumptions were made: (1) Darcy’s law is effective in the model; (2) neglecting the movement of geological media . The control equations of multiphase flow, thermal convection, and conduction processes are given as follows: , …”

“…The gas production performance is primarily determined by JGC’s radius and height . Li et al proposed using the high-pressure rotating water jets (HPWRJ) technology to stimulate the near-well reservoir and when the fracture depth is set to 3 m, the cumulative gas production of the vertical well can be increased by about 3 times . Huang et al.…”

“…Previous research has substantially promoted the near-well stimulation technology in NGH production. However, previous work mainly focused on Class 3-type hydrate reservoirs, which are characterized by nonpermeable layers in both the upper and lower parts of the reservoir and a hydrate layer in the middle; the Class 1-type hydrate reservoir mainly consists of an upper hydrate layer and a lower free gas layer (FGL) (where gas and water can flow freely), and the performance of near-well stimulation technology in Class 1-type hydrate reservoirs is still unclear. − Thus, this work is a continuous investigation of hydrate extraction by horizontal well depressurization combined with HPRWJ technology in Class 1-type hydrate reservoirs. According to the research results of Wan et al, in the Class 1-type hydrate reservoir of the Shenhu Sea area, the horizontal wells deployed at the middle of the three-phase layer (TPL) can achieve the optimal gas-to-water ratio .…”

“…12 Li et al proposed using the high-pressure rotating water jets (HPWRJ) technology to stimulate the near-well reservoir and when the fracture depth is set to 3 m, the cumulative gas production of the vertical well can be increased by about 3 times. 13 Huang et al proposed the use of the axial water jet slotting and grouting (AWJSG) technology to stimulate the near-well reservoir when extracting gas hydrate by vertical well. The results demonstrate the feasibility of the method and the parameter sensitivity analysis is performed.…”

Reservoir Stimulation Technologies for Natural Gas Hydrate: Research Progress, Challenges, and Perspectives

“…Jet breaking originates from coal seam cutting, which increases permeability. In a study on jet breaking to increase production, Li et al 130 proposed the use of high-pressure rotary water jet technology to construct near-well fractures in NGHR. The numerical simulation results showed that the productivity increased by approximately three times when a fracture with a radius of 3 m was set.…”