Although in nearly 200 field treatments of producing oil wells polymers have effectively reduced the WOR, not all such wells polymers have effectively reduced the WOR, not all such wells with a high water cut are candidates for polymer treatment. This paper discusses the probable working mechanisms of polymers and presents guidelines for selecting wells to be treated. Introduction The use of polymers to reduce water production in high-watercut oil-producing wells has proved highly successful in many areas of the Mid-Continent region. This process is an outgrowth of the use of polymers to adjust permeability profiles for water polymers to adjust permeability profiles for water injection wells. It has been used in nearly 200 wells to date and has resulted in a water-oil-ratio (WOR) decrease of 60 to 90 percent in most wells. In many cases, oil production has been substantially increased. The flow of polymer solutions through porous media has been a subject of intense research over the past decade. A thorough review of this subject has been given by Savins and therefore will not be repeated here. Polymers are of interest to the petroleum industry because they are useful in secondary petroleum industry because they are useful in secondary recovery and in the improvement of injection profiles in waterflooding. The behavior of polymer solutions in porous media has been controversial and several mechanisms have been proposed as an explanation of polymer behavior. Perhaps more than one mechanism is operative, depending on conditions. We believe that the basic behavior of the polymers is independent of the process, but the techniques of using polymers and the way they are applied in different processes do vary. The treatment of producing wells with polymer solutions is a unique process to reduce the WOR by selectively reducing water production without greatly hindering oil flow. As the polymer solution is injected into the formation, it tends to seek out and flow into the higher-permeability water zone. For this reason, deeper penetration is obtained with the polymer than is possible with conventional nonselective plugging agents. For producing wells, when the treatment is successful, the response is usually rapid and dramatic and occurs in a matter of days. In contrast, with water injection wells and polymer flooding, the results of a polymer treatment may not be evident for 6 to 12 months or even longer. How Polymers Work Before discussing the details of how polymers work, we shall outline the salient features of this process. This paper is aimed at those persons unfamiliar with the process and is not intended to be technically precise. The terms "resistance factor" and "residual precise. The terms "resistance factor" and "residual resistance factor" have been defined elsewhere. Although these terms are applicable as defined, we also use them in a general sense, as shown in the following discussion and in Fig, 1. Because of its viscosity, a polymer solution would be expected to offer a given resistance to flow in a rock. The actual or total resistance to flow offered by some polymers, however, is some 5 to 20 times this expected resistance. The total resistance is important in polymer floods and injection wells, but is effective in producing wells only until the solution is returned producing wells only until the solution is returned to the wellbore. Core tests show, however, that after a polymer treatment, even after hundreds of pore volumes of brine have been produced, enough polymer is retained in the rock to provide a residual resistance that will reduce the brine flow by as much as 60 to 95 percent. JPT P. 143

Polymers can effectively reduce the wateroil ratio in producing oil wells and, in many cases, can significantly increase oil productio] This use of polymers is relatively new to the Rocky Mountain Region but has been"used successfully in more than 200 wells in the Mid-Continent area. Although a complete shut-off of water production cannot be expected, most of the treatments have resulted in a decrease in water-oil ratio of 50 to 90 per cent.Not all high water-cut producers are candidates for polymer treatment. Care needs to be exercised when selecting wells to be treated Selection can be made on the basis of well and reservoir data. Use of flow tests in formation cores can aid in well selection as well as improve the prediction of results of the treatment,The purpose of this paper is to discuss the probable working mechanism of polymers and present the guidelines useful in selecting candidates for treatment. Field results are used to substantiate these guidelines and show the economics of this type of treatment. A summary of treatments shows the application and *References and illustrations at end of paper. results of polymer use in the Rocky Mountain area.

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. This paper was prepared for the Oklahoma City SPE Regional Meeting, to be held in Oklahoma City, Okla., March 24–25, 1975. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract Recent developments in job design have improved the success of polymer treatments for water control. The purpose of this paper is to briefly discuss the need for polymer as a secondary recovery tool, materials, polymer effects, treatment designs, and field results. New treating designs have made it possible to tailor the treatments to fit the reservoir conditions. These designs have provided very successful treatments as shown by the field results. Moreover, the tailored treatments provide better application to individual provide better application to individual problems such as coning or channeling. problems such as coning or channeling Introduction The addition of water soluble polymers to increase the effectiveness of waterflooding is a well established concept. Polymers have also been useful in controlling water problems in producing wells. The successful use of polymers to control water problems in polymers to control water problems in producing wells and injection wells has been producing wells and injection wells has been demonstrated in many areas of the Mid-Continent. The growing need for increased domestic production has increased efforts to seek improved production has increased efforts to seek improved production methods. production methods. The necessity for improved secondary recovery methods is evident when reviewing the production for Oklahoma, Kansas, and Texas in production for Oklahoma, Kansas, and Texas in Table 1. Nearly 70% of the oil in Oklahoma is produced by secondary recovery which is produced by secondary recovery which is proportionally much greater than Texas or Kansas. proportionally much greater than Texas or Kansas. oil produced by secondary recovery in Texas and Kansas was 31% and 23.6% respectively. An average of 41% of the production from these three states comes from flooding operations. As shown in Table 1, the injected to produced fluid ratio is not very efficient, ranging from 13:1 to 20:1. These values are near the economic limit of several years ago. A recent article indicates new prices may increase the recovery efficiency by 10% from 31.6% to 41.6%. This will increase the economic limit for the water/oil ratio. The article indicates for one field the economic limit for the water/oil ratio as 16:1 at an oil price of $2.61/bbl, 26:1 at $4.21/bbl, and 58:1 at $9.21/bbl. With increased oil prices and greater water/ oil ratios, the economic incentive to reduce water/oil ratios and to increase oil production is greatly enhanced. Thus, proper production is greatly enhanced. Thus, proper utilization of polymers to control water in injection wells or producing wells will be more beneficial.