Numerical simulation of the simultaneous flow of methane and water through dual porosity coal seams during the degasification process

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5715407

King, G

Described in this study are the mathematical and numerical developments for a series of finite difference models which simulate the unsteady state behavior of coal seam degasification wells. Included in this series are models capable of predicting the performance of vertical drainage wells and horizontal drainage wells drilled from a shaft bottom. For the vertical wells the models allow for the simulation of post-fracture performance. The hydraulically induced fractures can be specified as either infinite or finite (constant) conductivity. The natural fracture system of the coal seam, the face and butt cleat, is identified as a porous network and assigned effective permeability and porosity values representative of coal. A time-dependent diffusion/sorption model is included to describe the phenomenon of gas desorbing from the coal matrix and diffusing into the porous network. The coal seam is then modeled as a dual porosity reservoir using a pseudosteady state approach. Unique to the models developed in this study is the dual mechanism transport of gas. In this treatment gas is assumed to be traveling under the influence of two fields: a concentration field and a pressure field. The combination of these two flow mechanisms yields a pressure, saturation, and composition dependence slippage factor. The models have been used to evaluate the many parameters associated with the methane drainage process, in order to determine those which most significantly affect production. Where possible these parameters, along with their effects, are put into dimensionless form, and type curves for predicting recovery, based on these dimensionless groups, are presented.

• Research Organization: Pennsylvania State Univ., University Park (USA)
• OSTI ID: 5715407
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
012000 -- Coal
Lignite
& Peat-- Mining
03 NATURAL GAS
030900* -- Natural Gas-- Artificial Stimulation
Plowshare-- (-1989)
ALKANES
COAL DEPOSITS
COAL SEAMS
DEGASSING
DIFFUSION
EQUATIONS
FAILURES
FINITE DIFFERENCE METHOD
FLOW MODELS
FLUID FLOW
FRACTURED RESERVOIRS
FRACTURES
GEOLOGIC DEPOSITS
HYDRAULIC FRACTURES
HYDROCARBONS
ITERATIVE METHODS
MATHEMATICAL MODELS
METHANE
MINERAL RESOURCES
NATURAL GAS WELLS
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
PERMEABILITY
POROSITY
PREDICTION EQUATIONS
PRESSURE DEPENDENCE
QUANTITY RATIO
RECOVERY
RESOURCES
SORPTION
TIME DEPENDENCE
UNSTEADY FLOW
WELLS