Abstract Completion and production data presented for three wells in the Oakville areaof Live Oak County, Texas, which were completed near the gas-oil or water-oilcontact, indicate that coning may not be as prevalent a cause of failure insuch cases as is commonly assumed. Failure in the cases discussed is indicatedto be due instead to:erosion of the formation,flowing out of mudfilter cake, orfailure of the cement. An open-hole gravel-pack type ofcompletion procedure is proposed for preventing failures of this kind bypreventing movement of all solid material in the space in which completion ismade. Various combinations of layers of gravel, sand, and cement are utilizedfor this purpose. Experimental results and theoretical discussion as to the applicability ofgravel pack completion are included. Introduction This paper is primarily a study of the reasons for failure of oil-wellcompletions near the gas-oil or oil-water contact, and suggests a procedure forincreasing the efficiency of this type of completion. The value of improvement in completion effectiveness near the gas or water zoneis not confined, however, to wells of relatively thin oil columns. Thick oilcolumns become thin as depletion progresses. It would seem to follow that theminimum distance from the gas or water zone at which completion can be made ina new well indicates the limit to which depletion may be carried in a wellhaving an oil column of any initial magnitude. Only four ways can be postulated in which high gas-oil or water-oil ratio caninitially occur if the zone exposed for production is within the oilcolumn:Failure of the cementing material.Vertical coning.Failure along the boundary between the cement and the wall of thewell.Failure of the formation comprising the wall of the well. Cementing materials such as portland cement and plastics have reached a highstage of development. Failures of this type are probably due almost always toextraneous causes such as mud contamination rather than to faulty cementingmaterial. Vertical coning can and obviously does occur. However, the usual occurrence ofthin impermeable streaks in sand sections and the success with which open-holedrill-stem tests can be made near the gas-oil contact suggest that over-alleffective vertical permeability, and in turn vertical coning, is less prevalentthan frequently is assumed. Much has been written on failure by flowing out of the mud filter cake betweencementing material and the formation. A filter cake is always present if, priorto cementing, mud has come in contact with a permeable formation at pressuresexceeding the pressure head of the fluid it contains. T.P. 2094