Coiled Tubing Resin Squeeze to Mitigate Water Production in Offshore Gravelpack Wells

Abstract

Abstract Increasing water production in offshore wells creates many problems to operators. These problems include declining oil rate, scale buildup, water handling and processing, and equipment corrosion. Coiled tubing workover for water shutoff offers a low cost alternative as compared to recompleting the well using a rig for offshore operators. This paper reviews Mobil's research and field experience with the design and field implementation of resin squeeze to mitigate high water production in offshore wells. Two field case studies for offshore gravelpack wells in Mobil's Gulf of Mexico and Nigeria operations are discussed in this paper. An engineering computer model originally developed for polymer gel solutions is used for treatment design. The model predicts changes in injection pressure and bottom hole temperature during resin squeeze by coiled tubing. The computer model is a PC-based model that couples both the wellbore and reservoir hydraulics and temperature changes using empirical reaction kinetic equations. The viscosity increase of the resin with time due to reaction is captured in the empirical equations. The PC model can also be used for other reacting polymer gel systems for either near wellbore or in-depth gel placement. Introduction Liquid resins such as phenolic and epoxy can be effective in shutting off unwanted gravel packed zones and perforations. Historically resin was used to plug and abandon wells. The most common use is plastic plugback with phenolic resin. Resin is also being used as a remedial cementing agent for near-wellbore profile modification and plugging off unwanted gravelpack and perforation intervals. Several oil companies have used epoxy, furan, and phenolic resins for these purposes. The advantages of using resin over conventional or microfine cements are:superior chemical resistance;effective penetration into gravel packs and small channels behind casing; andinsensitivity to wellbore fluids during placement. Mobil has used resins successfully for shutting off water or steam breakthrough in heavy oil gravelpack wells and for CO2 profile modification in CO2/water injectors. The field treatment design and case histories have been discussed before. The development of our resin technology has resulted in a method for selective placement of resin and a low temperature epoxy system for fixing CO2/water injectors. Our experience shows that candidate selection, chemical formulation design, and placement method are the keys to a successful polymer or resin treatment. In this paper, the method of coiled tubing placement is used for offshore gravelpack production wells. This placement technique for resin is not commonly used because of the fear of resin setting up inside the coiled tubing, high friction pressure due to resin viscosity, cleanup of equipment, and cost of resin. However, liquid resin is best used for gravelpack wells. Coiled tubing placement provides an economically viable selective placement method for water shut-off. References 10 and 11 have also cited the use of coiled tubing placement and temperature modeling of aqueous polymer solutions for water and gas shut-off. Their temperature model requires running the wellbore and reservoir model independently. Our model is the first PC-based commercial temperature and flow model coupling the wellbore and reservoir with empirical viscosity models for reacting polymer solutions or resins. Two field case studies using coiled tubing resin placement in gravelpack producers are discussed in this paper. P. 869^