Design and Assessment of Channeling Control Systems for Enhanced CO₂ Storage in Fractured Reservoirs

Area of Science:

• Petroleum Engineering
• Reservoir Engineering
• Enhanced Oil Recovery

Background:

• Traditional Water Alternating Gas (WAG) injection in fractured heterogeneous reservoirs suffers from poor mobility control and unstable displacement fronts, leading to severe gas channeling.
• Continental fractured reservoirs present unique challenges for conventional enhanced oil recovery (EOR) techniques due to complex heterogeneity.

Purpose of the Study:

• To design and evaluate a novel CO2-responsive gel-assisted WAG system for enhanced channeling control in fractured reservoirs.
• To optimize the gel concentration and tapered WAG ratio for improved oil recovery and reduced gas channeling.

Main Methods:

• Development of a CO2-responsive gel (M-Gel) for in situ fracture plugging.
• Evaluation of M-Gel injectivity and plugging efficiency in grade I-III fractures under simulated reservoir conditions.
• Optimization of M-Gel-assisted WAG parameters using orthogonal experiments on a reservoir model with grade I fractures.
• Microscopic visualization model displacement experiments to assess residual oil reduction.

Main Results:

• M-Gel demonstrated excellent injectivity and achieved up to 80% plugging efficiency in grade I fractures.
• The optimized system, with a tapered WAG ratio (3:1 to 1:1) and 0.5 wt% M-Gel, significantly inhibited gas channeling.
• Gas breakthrough time was delayed, interlayer utilization improved, and low-permeability layer utilization increased from 9.6% to 21.4%.
• The overall recovery factor reached 60.8%, with reduced residual oil observed in microscopic pore throats.

Conclusions:

• The designed enhanced channeling control system effectively combines gel-induced fracture plugging with WAG flow field regulation.
• This synergistic approach suppresses gas channeling in heterogeneous fractured reservoirs, leading to substantial improvements in crude oil recovery.