Production performance analysis of horizontal drainage wells for the degasification of coal seams
The production performances of horizontal drainage wells for the degasification of coal seams have been investigated with a multidimensional, two-phase coal-seam degasification model. The model is written in rectangular coordinates, can handle a number of horizontal wells, and operates in a one-, two-, or three-dimensional (1D, 2D, or 3D) mode. The model accommodates multiple horizontal boreholes originating from a common vertical shaft or horizontal boreholes being drilled from the peripheries of the reservoir. In consideration of the relatively thin but large lateral extent of coal seams, flow dynamics around a horizontal borehole is described in elliptic flow geometry. The nonlinear system of equations generated by the finite-difference approximation is solved fully implicitly with Newton's iteration. A series of computer runs was conducted systematically to demonstrate the relative significance of different reservoir and fluid characteristics on the negative and positive decline features of horizontal drainage wells. Along these lines, the effects of coal-seam properties - such as thickness, porosity, permeability, and sorption characteristics - and horizontal borehole parameters - such as hole diameter, penetration length, and positioning of the borehole - have been isolated to understand the role of each individual parameter on the production performance of horizontal drainage wells. Contrary to the design of a vertical fracture, the orientation of the horizontal borehole with respect to face and butt cleats is controllable. Results of another series of runs are presented for different orientations of horizontal boreholes with respect to the principal directions of the natural fracture network to maximize the recovery of methane from coal seams through horizontal boreholes.
- Research Organization:
- Pennsylvania State Univ. (US)
- OSTI ID:
- 7018429
- Journal Information:
- J. Pet. Technol.; (United States), Vol. 40:5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
03 NATURAL GAS
COAL SEAMS
DEGASSING
METHANE
RECOVERY
BOREHOLES
COAL MINES
DIRECTIONAL DRILLING
DRAINAGE
FINITE DIFFERENCE METHOD
FLOW RATE
GEOLOGIC FRACTURES
GEOLOGIC MODELS
MATHEMATICAL MODELS
PRODUCTION
UNDERGROUND MINING
ALKANES
CAVITIES
COAL DEPOSITS
DRILLING
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
HYDROCARBONS
ITERATIVE METHODS
MINERAL RESOURCES
MINES
MINING
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
RESOURCES
UNDERGROUND FACILITIES
012033* - Coal
Lignite
& Peat- Underground Mining- Mine Environment- (1987-)
030300 - Natural Gas- Drilling
Production
& Processing