Effect of novel chelating agent seawater based system on the integrity of sandstone rocks

The objective of sandstone acidizing the objective is to reduce the skin around the wellbore. This process may affect the stability of the formation and may decrease the efficiency of the stimulation job. One of the main problems related to rock integrity is sand production. Sand causes erosion of surface and down hole equipment. The objective of this work is to introduce DTPA (diethylene tri-amine pentaacetic acid) to sandstone acidizing. Moreover, use mechanical properties estimated based on acoustic measurements to address the impact of the new formulation on the integrity of Bandera and Berea sandstone cores after stimulation. In this study, DTPA and EDTA (ethylene di-amine tetra-acetic acid) chelating agents at high pH diluted with seawater combined with potassium carbonate were used to acidize Bandera and Berea sandstone cores. Core flooding system was used to acidize the sandstone samples. Non-destructive tests were conducted to evaluate the effect of injected solution volume on the rock integrity. The samples were scanned using Computed Tomography (CT) to detect any precipitations after using the seawater based chelating agents. The results showed that DTPA and EDTA chelating agents at pH of 11 diluted using sea water injected at rate of 5 cm³/min into 2-inch Bandera and Berea sandstone cores at temperature of 250^oF enhanced the permeability ratio. Furthermore, increasing the fluid injected pore volumes raised the permeability improvement ratio of the sandstone cores. CT-number of the treated samples decreased which means no precipitations formed inside the cores. Elastic moduli of the cores after the acidizing showed that the integrity of the samples was not affected and no sand production is expected under the flooding conditions. The obtained results of this work will provide the engineers with sandstone acidizing seawater based fluids that will not affect the rock integrity after stimulation.