Damage Tolerance of Well-Completion and Stimulation Techniques in Coalbed Methane Reservoirs

Abstract

Coalbed methane (CBM) reservoirs are characterized as naturally fractured, dual porosity, low permeability, and water saturated gas reservoirs. Initially, the gas, water, and coal are at thermodynamic equilibrium under prevailing reservoir conditions. Dewatering is essential to promote gas production. This can be accomplished by suitable completion and stimulation techniques. This paper investigates the efficiency and performance of the openhole cavity, hydraulic fractures, frack and packs, and horizontal wells as potential completion methods which may reduce formation damage and increase the productivity in coalbed methane reservoirs. Considering the dual porosity nature of CBM reservoirs, numerical simulations have been carried out to determine the formation damage tolerance of each completion and stimulation approach. A new comparison parameter, named as the normalized productivity index Jnp(t) is defined as the ratio of the productivity index of a stimulated well to that of a nondamaged vertical well as a function of time. Typical scenarios have been considered to evaluate the CBM properties, including reservoir heterogeneity, anisotropy, and formation damage, for their effects on Jnp(t) over the production time. The results for each stimulation technique show that the value of Jnp(t) declines over the time of production with a rate which depends upon the applied technique and the prevailing reservoir conditions. The results also show that horizontal wells have the best performance if drilled orthogonal to the butt cleats. Long horizontal fractures improve reservoir productivity more than short vertical ones. Open-hole cavity completions outperform vertical fractures if the fracture conductivity is reduced by any damage process. When vertical permeability is much lower than horizontal permeability, production of vertical wells will improve while productivity of horizontal wells will decrease. Finally, pressure distribution of the reservoir under each scenario is strongly dependent upon the reservoir characteristics, including the hydraulic diffusivity of methane, and the porosity and permeability distributions in the reservoir.

Challenges During Shallow and Deep Carbonate Reservoirs Stimulation

“…Jahediesfanjani and Civan [7] assessed the effect of formation damage on the production from coal bed methane (CBM). They found out the invasion of the drilling, completion, clean-up fluid has great impact on the damage of CBM.…”

Proper Orthogonal Decomposition-Based Method for Predicting Flow and Heat Transfer of Oil and Water in Reservoir

“…The aims of some reservoir engineering problems [1][2][3][4][5][6][7], such as optimal control of reservoir production and history matching, are to determine the optimal parameter sets (well controls or physical properties). Several methodologies [8][9][10][11][12][13][14][15][16][17][18] including ensemblebased optimization methodologies, quadratic interpolation, and gradient-based methodologies have been applied to determine the optimal parameter sets.…”

Computer Modeling of Coal Bed Methane Recovery in Coal Mines

“…Unlike conventional reservoirs, flow phenomena in coal seams are quite complex, mainly due to the heterogeneous nature of coal and possible impact of rocks destruction caused by mining activity [1]. Examples of activities influencing the rock structure include hydraulic fracturing of coal [2] or shale [3], underground coal gasification [4], explosive fracture and permeability enhancements [5,6], and mining of coal.…”