A wide variety of mechanical and chemical technologies have been implemented for controlling unwanted fluid production in hydrocarbon-producing wells. Some of the most widely used technologies for water and gas control include temperature-activated gel sealants that involve a wide variety of chemistries. However, as the oil and gas industry explores more complex reservoirs and more environmentally sensitive offshore and land areas, these systems must comply with tougher environmental regulations. Based on these restrictions, many of these chemicals treatments are either banned or are projected to be phased out in the near future because of environmental concerns. This paper presents the development of two environmentally acceptable porosity-fill sealant systems approved for North Sea operations with a “green” rating for water and gas control applications.
The two environmentally acceptable conformance systems discussed are based on (1) colloidal silica and (2) polysaccharides. Both systems exhibit low initial fluid viscosity that allows low injection pressures and deep radial penetration into the reservoir, if necessary. Once the treatment is strategically placed into the formation, it actives by the reservoir temperature 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. These systems are not a selective treatment; thus, zonal isolation might be necessary. Characteristics of these two environmentally acceptable porosity-fill sealant systems are discussed in addition to performance testing and application and design considerations, outlining how proper diagnostics and candidate selection are fundamental to a high success ratio in such treatments.