Scale Inhibition by the Squeeze Technique
- J.K. Kerver (Esso Production Research Company) | J.K. Heilhecker (Esso Production Research Company)
- Document ID
- Petroleum Society of Canada
- Journal of Canadian Petroleum Technology
- Publication Date
- January 1969
- Document Type
- Journal Paper
- 15 - 23
- 1969. Petroleum Society of Canada
- 5.4.1 Waterflooding, 5.6.4 Drillstem/Well Testing, 4.2.3 Materials and Corrosion, 4.3.4 Scale, 5.2 Reservoir Fluid Dynamics, 2.1.3 Sand/Solids Control, 1.6.10 Coring, Fishing, 1.8 Formation Damage, 4.1.5 Processing Equipment, 2.1.1 Perforating, 4.1.2 Separation and Treating, 3 Production and Well Operations, 1.2.3 Rock properties
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The productivity of many wells has been seriously reduced in the pastbecause of scale deposition. In some fields, the produced water is saturatedwith gyp (calcium sulphate) that precipitates in the pores of the reservoirformation sand near the wellbore. Chemical treatments have successfullyrestored productivity for short periods, but deposition of gyp continues tooccur, resulting in a rapid decline in productivity following treatment. In thepast, chemical scale inhibitors were pumped down the annulus to prevent gypscale deposition on the rods and tubing. However, gyp precipitation in theformation and resultant productivity reduction were not prevented.
To effectively prevent gyp from precipitating in a reservoir formation, theinhibitor must be present within the pores of the formation rock. To accomplishthis, an absorbable inhibitor is injected into the formation, where it isadsorbed On the Sand or rock surface. When the well is produced, the inhibitorslowly desorbs into the produced fluids and prevents deposition of gyp in theformation or on the rods or tubing. On the basis of extensive laboratory tests,two chemicals were chosen for field testing. Of ninety wells squeezed one ormore times with these chemicals, only one has become "gypped up" in theformation. The life of the chemical treatment has varied from 2 to 17 months,with an average life of 9 months. Repeated treatments have successfullyprevented gyp deposition for more than 30 months.
PRODUCTIVITIES OF A LARGE NUMBER OF WELLS in a West Texas waterflood wereseriously impaired by gyp (hydrous calcium sulphate) scale deposition in theformation and on the downhole mechanical equipment. The field productiondistrict has been investigating ways of combating gyp scale plugging forseveral years. Although early attempts to remove scale damage were successful,the increasing frequency of treatments and the declining effectiveness led tothe present research investigation. Scale problems are widespread in thepetroleum industry, and the literature discusses the deposition of gyp, calciumcarbonate and other scales as well as
Various methods for treating the problem. This paper presents the results ofboth laboratory and field tests that have been conducted in the development ofmore effective treatments to combat gyp scale plugging Methods for restoringwell productivity were investigated and improved. Preventing the continuedprecipitation of gyp in the pores of the formation sand was a serious problem.A scale inhibitor squeeze technique for preventing gyp precipitation wasdeveloped and successfully applied.
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