Abstract
A wide variety of mechanical and chemical technologies have been implemented for controlling unwanted fluid production in hydrocarbon-producing wells. This paper presents the field implementation of a porosity-fill sealant (PFS) system for water and gas shutoff applications. Proper diagnostics and candidate selection process is the key to a high success ratio with this type of treatment. Case histories are presented along with lessons learned from more than 1,000 treatments highlighting the diagnostic stage.
The PFS system is based on a copolymer of acrylamide and t-butyl acrylate (PAtBA) crosslinked with polyethyleneimine (PEI). The PFS system is placed into the formation as a low-viscosity solution that eventually actives at a predicted time to form a three-dimensional (3D) gel structure. The crosslinked gel provides a total shutoff of pore spaces and channels, thus limiting undesired water or gas flow. The PFS is not a selective treatment; thus, zonal isolation might be required. The working temperature range of this system is 40 to 400°F. This system has been successfully tested to withstand a differential pressure of at least 2,600 psi and is resistant to acid, CO2, and H2S environments. The following parameters are discussed: (1) PFS performance testing, (2) design considerations, and (3) case histories.
To date, more than 1,000 treatments have been performed with the PFS system worldwide to address conformance problems, such as water coning/cresting, high-permeability streaks, gravel-pack isolation, fracture shutoff, and/or casing-leak repair. Because of the capability of the PFS system to withstand high-pressure environments, workover operations have been successfully performed in previously treated wells, including acid stimulation, sand control, and frac-pack treatments, among others. Case histories are presented for different types of water production mechanisms and different wellbore completions and reservoir conditions where the PFS system was successfully implemented.
