Successful Implementation of Resurgent Relative Permeability Modifier (RPM) Technology in Well Treatments Requires Realistic Expectations

Abstract

Abstract Industry interest in relative permeability modifier (RPM) treatments for water control is revived. However, as in the past, a majority of the treatments are applied to wells with extremely high water cuts (95% and greater) - with the unrealistic expectation that use of such agents will substantially reduce percent water cut or even prevent (shut off) unwanted water flow altogether. Recent field experience with newly-developed RPM-based treatments is leading to clearer definition of the proper applications necessary to overcome the existing barriers to success which include, but are not limited to, treatment penetration depth, treatment placement, formation permeability and wettability characteristics, pre- and post-treatment reservoir fluid flow mechanisms, and a history of skepticism. With these aspects in mind, this paper points to the largely unrecognized economic benefits that can be realized through creative and strategic deployment of low-risk or risk-reducing RPM-based technologies in multi-well scenarios. Examples include oil and gas producer matrix treatments, especially in high permeability and clean sands. Introduction It is estimated that, on average, every barrel of oil produced in the U.S. is accompanied with nine barrels of water in the U.S. Current water production worldwide is estimated at more than 300 million barrels per day - with a water-to-oil ratio of perhaps at least four-to-one1. In addition, regulatory requirements governing disposal of produced water are becoming more stringent. Water production compromises the profitability of all oil and gas producing wells. Decreased well productivity and increasing operating expenses are among the inherent problems associated with excessive water production. Water handling costs range from less than 5 cents to more than $4 per barrel of water produced, thus costing the industry billions of dollars per year. The need for effective water management technologies in the industry becomes more apparent as fields mature, as operations move into marginal fields, and as environmental restrictions become more stringent. Numerous attempts have been made over the years to control water production. Mechanical intervention such as bridge plugs and a variety of cement systems have been successfully applied once the water source has been identified. Other successful options include the use of polymeric blocking gels, silicate gels, phenol-formaldehyde gels and plugs. It is important that each of these methods be applied only after the water source is identified and the problem zone isolated to prevent the inadvertent placement of the chemicals in the hydrocarbon rich sectors of the formation. Locating the water source can be expensive and time consuming and at times include speculation and luck in diagnosing the water pathway. Misapplying a treatment, particularly, if the water source is misdiagnosed and the treatment is injected into a hydrocarbon rich interval, can have disastrous effects on production and possibly cause the operator to lose the well. One approach to water control that does not inadvertently reduce hydrocarbon production is to use products that selectively respond to water without impairing hydrocarbon production. These products offer several advantages including the ability to bullhead treatments without fear of restricting hydrocarbon recovery, in the ideal case. This advantage also negates the need to pinpoint the exact location of water entry since these products only respond in water rich intervals. Another advantage of the selective products is that most are easily removed in the event that their response impairs hydrocarbon recovery. There are several products that have some degree of water selectivity. One class of products is the relative permeability modifier (RPM).2–7 The RPM products have been used to reduce water permeability in wells having either high permeability water-producing streaks or water-coning problems.8,9 Historically, these products have performed very inconsistently.10 As a consequence of this inconsistent behaviour, the industry has lost confidence in this approach to water management.