Abstract
Mineral scale deposition often occurs not only in surface facilities and well tubing but also in the near well bore reservoir area. Sulphate scale formation is usually the result of poor compatibility between injected seawater and formation brine. Carbonate scales are mainly generated by abrupt pressure and temperature variations to which production fluids are submitted between reservoir and surface and the Simultaneous loss of CO2. The precipitation of both mineral deposits may create significant permeability impairments due to plugging of pore throats and consequently induce large well productivity loss. In most cases, scale formation cannot be avoided and preventive treatments are recommended. One of the most efficient techniques to prevent mineral scale deposition is the squeeze into the formation of a specific scale inhibitor.
This paper presents an integrated methodology applied by IFP in order to define the best chemical inhibitor formulation for a specific squeeze treatment and to optimize its implementation into the corresponding reservoir. Both experimental and numerical approaches are used to select the inhibitors, to evaluate their performance in bulk and in core conditions, and to define the best strategy for the squeeze process. Laboratory tests include classical inhibitor selection methods based on static Jar Tests and dynamic Tube Blocking Tests in order to determine the Minimum Inhibitor Concentration (MIC) to prevent scale formation. The properties of current scale inhibitors, i.e. phosphonates, as well as those of new environmentally friendly products are compared. Core flooding experiments are performed to evaluate inhibitor adsorption/desorption properties at reservoir conditions and the risks of production impairments. Numerical simulations of the treatment are finally performed using a specific reservoir simulator to upscale the squeeze life time of the treatment from the laboratory to the reservoir level.