Ca-DTPMP nanoparticles-based nanofluids for the inhibition and remediation of formation damage due to CaCO3 scaling in tight gas-condensate reservoirs

The oil productivity of tight gas-condensate reservoirs can be affected by the precipitation/deposition of inorganic scales such calcium carbonate (CaCO3), which leads to a reduction mainly in permeability and porosity of the porous media. Therefore, the main objective of this study is to develop for the first time a nanofluid based on the interaction between active nanoparticles such as Ca-diethylenetriamine pentamethylene phosphonic (Ca-DTPMP) and remaining synthesis fluid (RSF) obtained from the synthesis process, to simultaneously inhibit and remove the formation damage due to the precipitation/deposition of CaCO3 scales. The synthesis of the Ca-DTPMP nanoparticles was performed varying the phosphonate concentration between 0.01 and 0.5 M. The obtained nanoparticles were characterized through N2 physisorption at −196 °C for obtaining the surface area (SBET), field emission scanning electron microscopy (FESEM), and dynamic light scattering (DLS) measurements. The mean nanoparticles size of the obtained materials ranged between 36 and 69 nm and was lower for the nanoparticles synthesized with a lower concentration of DTPMP. Nanofluids containing the synthesized nanoparticles of Ca-DTPMP were prepared with RSF solutions in deionized water as a carrier fluid for different Ca-DTPMP/RSF ratios of 10, 50, 200 and 500. The ability of the nanoparticles and nanofluids to inhibit the CaCO3 scaling was evaluated in batch-mode experiments at 70 °C by measuring changes in the calcium ion (Ca2 +) concentration in the solution. The nanofluid with better performance was that prepared with 50 mg/L of Ca-DTPMP/0.3 nanoparticles and a Ca-DTPMP/RSF ratio of 10, with an inhibition efficiency of 67%. Further, coreflooding tests were carried out using the nanofluid with better performance from the batch - mode experiments. Displacement tests were conducted under tight gas-condensate reservoir conditions at a temperature of 110 °C (230 °F) and confining and pore pressures of 34.47 MPa (5000 Psi) and 6.89 MPa (1000 Psi), respectively. Inhibition and remediation of CaCO3 scaling were evaluated. The nanofluid was soaked in the porous media for 8 h. Based on the results of the relative permeability and oil recovery curves, it is possible to conclude that the synthesized nanofluid promotes the inhibition and removal of the formation damage due to CaCO3 inorganic scales. The nanofluid injection leads to an increase of the oil permeability of 57% in comparison with the base system, suggesting that the nanofluid acts as inhibitor agent, as remediation treatment, and as stimulation product of oil wells. Also, the treatment showed a perdurability of more than 60 pore volumes and increasing of oil recovery of 4 and 24% regarding the base and the damaged systems, respectively.