The development of effective scale squeeze inhibitors in carbonate reservoirs is still a big challenge, especially with the increasing environmental constraints. For tight carbonate reservoirs, formation damage is one of the major considerations as it can be caused due to fines mobilization, carbonate reservoir dissolution and collapse, and scale inhibitor compatibility issues. For the development of any product for squeeze application, the product must also demonstrate good inhibition performance, long squeeze life and accurate residual analysis at low concentrations as well as being suitable for improved placement techniques if required.
Many scale inhibitors are either irreversibly retained in chalk reservoirs due to uncontrolled precipitation reactions or are poorly adsorbed with both processes resulting in short treatment lifetimes. Some new, readily detectable, polymeric scale inhibitor chemistry, containing a special functional amine group to have a good affinity to the chalk reservoir, was developed to provide a balance between irreversible and poor retention and thus provide effective squeeze life.
The results of a comprehensive testing program, including compatibility, formation dissolution, dynamic tubing blocking, static adsorption and core flood tests will be presented, that will highlight the design and development of a polymeric scale inhibitor suitable for tight carbonate reservoirs while meeting the environmental requirements for application in the UK and Scandinavia.
The new polymer has been shown to demonstrate excellent retention and release characteristics while also being non-damaging to carbonate reservoir material. The impact of calcium tolerance, pH and molecular chemistry will be discussed with regard to the design and performance of the new polymer when compared to some environmentally friendly phosphonate chemistry and other polymeric scale inhibitors.
This paper will demonstrate a logical design procedure to develop an environmentally acceptable polymeric scale inhibitor product whose chemistry has been optimised for squeeze application in tight carbonate reservoirs. In addition, discussions on the mechanisms of scale inhibitor retention and formation damage with regard to selection, design and optimization of suitable scale squeeze inhibitors in tight carbonate reservoirs will be addressed.