Low-Permeability Gas Well Performance At Constant Pressure
- Paul R. Stewart (Belco Petroleum Corp.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- September 1970
- Document Type
- Journal Paper
- 1,149 - 1,156
- 1970. Society of Petroleum Engineers
- 4.1.2 Separation and Treating, 1.2.3 Rock properties, 5.2.1 Phase Behavior and PVT Measurements, 4.6 Natural Gas, 2.4.3 Sand/Solids Control, 5.1.2 Faults and Fracture Characterisation, 2.2.2 Perforating, 4.1.5 Processing Equipment, 5.7.2 Recovery Factors
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Presented here is an analysis of the long-term production performance of some low-permeability wells in the Big Piney-LaBarge Frontier gas field of Wyoming. A rigorous technique is proposed for predicting the abandonment pressure, and thus the recovery efficiency, of such gas wells.
The petroleum industry's search for new natural gas reserves has progressively led to the development of reservoirs that have been assumed to be too tight to provide a reasonable return on invested capital. The Frontier reservoir in the Big Piney-LaBarge field of Wyoming is an excellent example of a lower-permeability field that, through the use of sophisticated sand-fracturing techniques, is now a profitable operation, with initial recoverable reserves in excess of 3 Tcf.
The Big Piney-LaBarge Frontier gas field is located along the western margin of the Green River Basin in western Wyoming. It is approximately 25 miles long, has a maximum width of 16 miles, and is located on the LaBarge platform, which is basically a large anticlinal structure overridden by thrust faulting from the west. It is the largest gas field in Wyoming, in both size and production rate, currently producing approximately 160 MMcf/D from about 220 wells. Cumulative production to date is more than 550 Bcf. Overall spacing is essentially 320 acres/well, with recent infill drilling programs on 160 acres in selected areas.
The Frontier formation, of Cretaceous age, has been separated into the First, Second, and Third Frontier zones. The average gross interval covered by these zones is 650 ft, with approximately 130 ft of gross sand and 35 t of net sand. All productive zones are commonly combined and produced as one "reservoir".
The zones are very widespread but they are very heterogeneous both laterally and vertically, and vary from fine- to medium-grained, well sorted to conglomeritic, with variable amounts of silt and clay matrix. Eastward, the sands become progressively more silty and tighter. Porosities are rather uniform, but permeabilities are extremely variable, and generally quite low. Over-all average rock and gas properties are as follows:
Effective porosity 16 percent
Water saturation 40 percent
Permeability (absolute) 1 md
Permeability (to gas) 0.5 md
Average perforated depth 7,050 ft (+ 150 ft)
Bottom-hole temperature 165°F
Condensate content 5 bbl/MMcf
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