Acreage and Potential Factors in Allocation
- Eugene A. Stephenson (University of Missouri, School of Mines and Metallurgy)
- Document ID
- Society of Petroleum Engineers
- Transactions of the AIME
- Publication Date
- December 1937
- Document Type
- Journal Paper
- 172 - 182
- 1937. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 5.2 Reservoir Fluid Dynamics, 1.6 Drilling Operations, 2.4.3 Sand/Solids Control
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The writer apologizes for presenting this very elementary analysis of oneaspect of proration, but a search of the literature failed to disclose anyconcrete illustrations of the effect of various proration formulas upon theallowable oil produced by tracts of different sizes. Many engineers havedoubtless made somewhat similar calculations and are fully acquainted with theresults.
The various allocation formulas that are in use are based on one or more of thefollowing factors: (1) wide-open well potential, (2) potential through anorifice, (3) uniform well allowable, (4) acreage, (5) sand thickness, (6)bottom-hole pressure, (7) productivity index, and (8) volumetric displacement.Of these, the unrestricted potential formula, or open-flow test, and theuniform well allowable are commonly regarded by engineers as those least likelyto give each producer his proportionate share of the oil or gas, as representedeither by acreage or by sand thickness, or both, except when the wells arelocated on tracts of large size.
Unless the mechanical equipment that may be used during the potential test andthe method of taking the test are both specified, the net result of thepotential formula is to practically force the operators to use specialequipment and adopt special procedures prior to and during the potential test,so as to secure the largest possible allowables. Much ingenuity and skill havebeen devoted to this problem, but the general effect is to permit excessiveallow ables for very small tracts, and stimulate unnecessary drilling.
It is interesting to compare some of the high yields from the Wilcox horizon atOklahoma City with each other, as an illustration of the effect of anallocation factor based solely on potential (Table 5']. One of the glaringinstances is a well on a 72-acre lease, which had produced, as of September1936, at the rate of almost 3,000,000 bbl. per acre. This is at least twice asmany barrels as could have been present under the property if the reservoir hadconsisted of a tank of oil 200 ft. deep and 72 acre in area.
Numerous combinations of acreage, potential, bottom-hole pressure, sandthickness, etc., have been proposed and are in use in various fields.
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