Pressure analysis of low permeability gas reservoir using variable flow rates and turbulence
Rate variation, q(t), usually declining during testing, is considered as a continuous function of time. It is assumed that the function q(t) can be approximated by a polynomial of some degree, n. A significant majority of low permeability wells, both unfractured and fractured, was analyzed using the conventional transient pressure buildup test. Application of this technique to wells faced with wellbore storage, even a small amount, can be time-consuming and may not provide accurate answers. Wellbore storage and its effect on the transient regime duration distorts early time data. Such early time data could range between a couple of hours to even days and weeks. This constraint makes long-term data necessary and does not allow the interpretation of early transients reflective of near-wellbore conditions. The use of this interpretation technique can reduce the test duration to only that required for a standard drawdown or buildup test. This technique will also allow the estimation of the stabilized deliverability potential without flowing the well until stabilization is reached. The mathematical model simultaneously incorporates the effect of non-Darcy flow and a variable expressed as a continuous function of time. A Cartesian plot and a linear and multiple regression computer program were used to process test data and to provide an estimate for the values of the non-Darcy flow coefficient, skin factor, and formation permeability. Two actual field cases for drawdown and one simulated example for buildup were presented. Both actual field cases exhibited extensive turbulent flow. Emphasis was placed on the early transient behavior, before the effects of the outer boundary are noticeable at the wellbore.
- Research Organization:
- Louisiana Tech Univ., Ruston, LA (USA)
- OSTI ID:
- 7032497
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
030300* -- Natural Gas-- Drilling
Production
& Processing
COMPUTER CALCULATIONS
DATA ANALYSIS
FLOW RATE
FLUID FLOW
MATHEMATICAL MODELS
MEASURING METHODS
NATURAL GAS WELLS
PERMEABILITY
PRESSURE MEASUREMENT
PRESSURIZING
RESERVOIR PRESSURE
STORAGE
TESTING
TIME DEPENDENCE
TRANSIENTS
TURBULENT FLOW
WELL PRESSURE
WELLHEADS
WELLS