Coupled geochemical and compositional wellbore simulators: A case study on scaling tendencies under water evaporation and CO2 dissolution

Abstract

Inorganic deposits are the result of mineral precipitation due to changes in pressure and temperature along water flow and one of the main causes of production decline in the Oil & Gas Industry, as water is usually inherent to any oil/gas production. These deposits may be present in the reservoir, wellbore, and processing facilities. Literature suggests that evaporation of water can significantly increase (if not be the main cause of) mineral precipitation and consequently scale deposition for a gas condensate well. This work aims to determine if evaporation can also play a similar role for an oil well. New achievements towards an integrated platform (called UTWELL, for wellbore simulation) are addressed; however, emphasis is given to the effects of a newly added evaporation model in the case of an offshore oil production well showing calcite precipitation. Results demonstrate that evaporation is only relevant for very small water cuts (<1%), which are characteristic of early stages of production, leading to increased ionic strength and mineral precipitation (calcite and halite). Since scale inhibitors might not be effective for this specific scenario, an alternative solution with dilution water injection is proposed and analyzed. It is estimated that, for 0.1% water cut, the injection of a dilution water flowrate triple that coming from the reservoir can practically eliminate any precipitation in the wellbore. It is also shown that UTWELL is able to match results from commercial multiphase-flow simulator OLGA with the advantage of more physically meaningful aqueous density calculation and the availability of mineral precipitation (absent in the commercial simulator). Although showing similar results for little water content (<1%), total liquid flowrate is 4% lower than when using OLGA for a 50% water cut due to its poor aqueous density calculation, and 8% lower compared with previous version of UTWELL after multiple improvements to the model.