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The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription.

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The water-alternating-steam process (WASP) uses alternating slugs of steam n a d water injected ov r more than one (cycle to recover oil.The process was applied to I:he vertical expansion (VE ) sands in the pilot area of Section 13D, West Coalinga Field, to stop wasteflood Steam production and to improve vertical conformance of injected steam. By replac-ing a part of steam with unheated water, the pro-cess also reduced fuel consumption and improved the steamflood economics. Prior to the WASP application, steam breakthroug'n in the VE sands caused well sanding, cutting of downhole tubulars, and high temperature fluid handling problems.To alleviate these problems pumps had to be raised in feive wells and one well had to be shut in, reducing oil production from both the VE sands and the lower waterflooded zones. A WASP field tes:t, based on a numerical simulation study, was implemented in July of 1988 with alternating slugs of water and steam, each injected over four months. The WASP eliminated steam production, allowing pumps to be lowered in the five producing wells and one shut-in well to be returned to pro-duction.The Oil production remained constant through the fir:3t cycle and increased during the second cycle of WASP. The sales oil (total pro-duction minus oil used to generate steam) increased -References and Illustrations at end of papee 84-1 due to the saving of generator fuel during the water leg of each WASP cycle. Encouraged by the test results, the WASP is continuing in the pilot area.It is presently applied to another steamflood area in West Coalinga Field and considered for two other areas in the San Joaquin Valley. om Steam injection was first used in the late 50's to recover high viscosity oils. This EOR method has become increasingly popular during the past 30 years and now accounts for over one million barrels per day of oil production worldwide, about half coming from heavy oil fields of the U.S.' Despite the success of steam in improving the re-covery of viscous oils, there are characteristic problems associated with its use: steam gravity override and steam channeling.Steam gravity override results from the large density difference between the injected steam and in situ fluids. It reduces the reservoir vertical conformance and leads to early steam breakthrough at production wells. If high permeability channels are present in the reservoir, steam can propagate through them, also leading to early steam breakthrough and poor vertical conformance. These are undesirable events because they reduce the ultimate steamflood oil re-covery and cause such well Production problpmq agi