A comparative evaluation of vertical and horizontal drainage wells for the degasification of coal seams
A two-phase, single well numerical simulator capable of modeling the performance of either vertical wells, or horizontal wellbores drilled from a vertical shaft, has been developed. For the vertical wells, the model allows for the prediction of post-fracture performance. The hydraulically induced fractures can be specified as either infinite conductivity or finite (constant) conductivity, so that conventional, as well as massive treatments, can be modeled. For the horizontal boreholes the problem is idealized as N infinite conductivity boreholes distributed uniformly around a vertical shaft and extending radially outward. The problem is then reduced by considering a symmetric element defined by theta /SUB sym/ . The value of theta /SUB sym/ is solely dependent on the value of N. This symmetric element can then be modeled in radial coordinates by placing a single horizontal borehole along theta=O, and a no flow boundary along theta=theta /SUB sym/ . For coal seams, the formation to be modeled is a dual porosity reservoir. The natural fracture network of the coal seam (the butt and face cleat) has been assigned an effective porosity and permeability. A time dependent, quasi-steady state sorption term has been included to describe the phenomenon of gas desorbing from the formation matrix to the fracture network. All the equations generated by the model are solved simultaneously by the fully implicit, NewtonRaphson procedure. Both the numerical and mathematical developments are presented in detail. The model has been used to sift through the many parameters associated with the two production schemes 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.
- OSTI ID:
- 6179796
- Report Number(s):
- CONF-8409104-
- Journal Information:
- Soc. Pet. Eng. AIME, Pap.; (United States), Vol. SPE13091; Conference: 59. annual Society of Petroleum Engineers of AIME technical conference, Houston, TX, USA, 16 Sep 1984
- Country of Publication:
- United States
- Language:
- English
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Numerical simulation of the simultaneous flow of methane and water through dual porosity coal seams during the degasification process
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Related Subjects
COAL SEAMS
DEGASSING
HYDRAULIC FRACTURING
MATHEMATICAL MODELS
NATURAL GAS
DESORPTION
BOREHOLES
DIRECTIONAL DRILLING
DRAINAGE
HYDRAULIC CONDUCTIVITY
HYDRAULIC FRACTURES
METHANE
NEWTON METHOD
PERMEABILITY
POROSITY
UNDERGROUND MINING
ALKANES
CAVITIES
COAL DEPOSITS
COMMINUTION
DRILLING
ENERGY SOURCES
FAILURES
FLUIDS
FOSSIL FUELS
FRACTURES
FRACTURING
FUEL GAS
FUELS
GAS FUELS
GASES
GEOLOGIC DEPOSITS
HYDROCARBONS
ITERATIVE METHODS
MINERAL RESOURCES
MINING
ORGANIC COMPOUNDS
RESOURCES
012000* - Coal
Lignite
& Peat- Mining