Excessive water production results in reduced well productivity, increased costs associated with produced water treatment and handling, and premature well abandonment. This paper discusses well treatments with relative permeability modifying (RPM) polymers- - polymers that are capable of selectively reducing the permeability to water of the rocks onto which they adsorb. The principal results of experimental and simulation studies, conducted with the goal of linking the basic physical mechanisms of the process to the development of operational rules for treatment design, are reported. The application of these understanding-based rules for candidate and chemical selection has led to a successful RPM application in an Italian gas field. for chemical and candidate well selection for
water production control treatments4. We also report a successful application of these criteria Excessive water production from oil and in an RPM polymer treatment of a gas well in gas wells is a widespread problem that can Southern Italy. sometimes be reduced by re-completing the well or by intervening with cement or polymer gel treatments. These solutions, however, RESULTS require identification and isolation of the Selecting the chemical watered-out layer and are not always feasible: To clarify the factors that govern the examples include microlayered formations and effectiveness of polymer treatments we have gravel-pack completed wells. investigated the nature of the polymer-rock The use of RPM§ agents is an attractive interactions and the impact of rock lithology option in these cases. The RPM chemical can and wettability5. be injected (bullheaded) into all open intervals The polymer-rock interactions have been to reduce the permeability to water1,2,3. One of investigated by means of adsorption isotherms the most common RPM treatments employs and kinetics for polymers of varying structure solutions of water-soluble, high molecular (biopolymers, polyacrylamide, and other weight polymers that adsorb onto the surface synthetic co- and terpolymers), charge of the porous rock, changing its flow (cationic, anionic and non-ionic), and properties. The main advantages of this molecular weight (5*105 5*106 Dalton). The method are: tests were carried out on reservoir sands and · Low cost (limited quantities of cores of varying lithology and wettability. chemical are used, and the treatment does not require zone isolation) The following guidelines have been derived · Low risk (the polymer reduces water from these studies6,7: permeability without plugging the · Adsorption is governed by the formation) electrostatic interactions between rock · Low environmental impact and polymer (cationic polymers are The execution of these treatments in
