The Effect of Casing Perforations on Well Productivity
- Morris Muskat (A.I.M.E)
- Document ID
- Society of Petroleum Engineers
- Transactions of the AIME
- Publication Date
- December 1943
- Document Type
- Journal Paper
- 175 - 187
- 1943. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 1.6.10 Running and Setting Casing, 2.4.3 Sand/Solids Control, 2.2.2 Perforating, 5.4.2 Gas Injection Methods, 4.1.5 Processing Equipment
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Analytical calculations have been carried out on theeffect of casing perforations on the productivity of wells, and formulas havebeen derived for general types of perforation patterns. The numericalcalculations, however, show that the resultant well productivity is essentiallyindependent of the perforation pattern, but is determined mainly by the totalperforation density. thus, for example, for a density of three perforations perfoot of casing the well productivity will be cut to one third of that of theuncased well for a perforation radius of 1/8 in., and to approximately one halfof a perforation radius of 1/4in., regardless of the detailed manner in whichthe perforations are distributed over the casing surface. the analytical theoryis also extended to included wells completed with slotted liners. it is showthat the reduction in productivity due to such liners will be relativity smallas compared with that due to perforated casings.
The increasingly important role being played byproductivity factors of wells in determining well potentials and in the generalevaluation of producing formations lends interest to the analysis of all thevarious factors that may influence the productivity of a well. In recent papersthe results have been given of theoretical studies made to determine the effecton the productivity factors of a well of the gas-oil ration of the productionand the connate water within the sand. These have served to show that both ofthese factors may, under suitable conditions materially reduce the effectiveproductivity factors below those that would be anticipated on the assumptionthat the wells produce homogeneous fluids.
In this paper will be presented the results of theanalysis of an entirely different factor influencing the productivity of awell.This refers to that resulting from the increased use of the methodof completing wells by setting casings opposite all of the productive strataand then gun-performing the particular zones of immediate interest. Thepractical success of this method of completion would appear to be an answer tothe question as to whether it seriously reduces the well productivity ormaterially cuts down the ultimate oil recovery that may be derived from theproducing section.
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