An Evaluation of Polyacrylamides for Reducing Water Production (includes associated papers 6561 and 6562 )
- D.D. Sparlin (Continental Oil Co.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- August 1976
- Document Type
- Journal Paper
- 906 - 914
- 1976. Society of Petroleum Engineers
- 4.3.1 Hydrates, 2.4.3 Sand/Solids Control, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 2.2.2 Perforating, 4.1.2 Separation and Treating, 4.2 Pipelines, Flowlines and Risers, 5.1 Reservoir Characterisation, 4.1.5 Processing Equipment, 1.6.9 Coring, Fishing, 5.2 Reservoir Fluid Dynamics, 1.8 Formation Damage, 2.7.1 Completion Fluids, 5.3.1 Flow in Porous Media
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While laboratory tests show that polyacrylamides can decrease permeability to water while only slightly decreasing permeability to oil, there is much confusion about why this occurs. This study focuses on determining which properties are most important for reducing permeability to water and how they relate to successful field treatments.
Polyacrylamide polymers have been used for years to reduce water production in oil wells and for mobility control in injection wells. The unique property of polyacrylamides that makes them attractive for reducing the water production from oil wells is their ability to reduce the permeability to water of a porous media with only a minor effect on the permeability to oil. This has been demonstrated by many laboratory tests, but some field results have been disappointing. A description of 19 polyacrylamide treatments of producing wells within Continental Oil Co. over the past several years is shown in Table 1. Results of some jobs were excellent. For instance, Job 11 resulted in nearly a tenfold increase of oil production rate and 4,000 bbl of additional oil. However, only seven jobs were economically successful. Although the number of successful jobs is discouraging, several that did not pay out did reduce water production significantly but did not improve oil production. Jobs 4, 11, 18 and 19 were all run in the same field and formation; but t he first two were very successful and the others failed. To remove some confusion from this technology, this study was conducted on polyacrylamides currently being used in the field for water control. The differences between the polymers and the importance of these differences in treating various types of formations were studied. We attempted to define where polymers most likely will reduce water production and improve oil production as well as where they should not be used. This study led to several conclusions that are important to improving the success ratio of future polymer treatments in producing wells.
Commercial Water-Control Polyacrylamides
Currently available commercial polyacrylamides can be divided into five types as shown in Table 2. These polymers are provided in dry powdered form or concentrated in a water-and-oil emulsion. In its dry form, the polymer is dissolved in water at the wellsite by various means. An advantage of the emulsion polymers is that they will dissolve readily and uniformly in water, thus facilitating control of the polymer concentration during a job. However, the emulsion polymers are usually more expensive than dry polymers. The average molecular weights and activities listed in Table 2 were provided by the polymer suppliers as typical of the polymer analyses. The higher molecular-weight polymers generally yield higher-viscosity solutions in the same water. The activity numbers indicate the relative number of reactive sites or degree of hydrolysis in the polymer. Nonionic polyacrylamides usually have less than 10-percent activity. An anionic polyacrylamide will be compatible only with fresh-water or soft-water brines, while nonionic polymers are compatible with a wide variety brines. Table 3 gives some chemical analyses of various polyacrylamide samples.
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