Compatibility of Diammonium Phosphate (DAP) with Fracturing Fluid Systems for Deep Consolidation of Carbonate Rocks

Acid fracturing is a stimulation technique that creates dissolution in the carbonate rock to enhance productivity; however, it could cause mechanical damage that accelerates fracture closure. Previous studies assessed diammonium phosphate (DAP) as a consolidating agent to maintain the fracture’s cohesion after acid fracturing and enhance its stiffness. In this study, DAP compatibility with a reservoir rock and fracturing fluid additives has been broadly examined. Indiana limestone cores were used to evaluate DAP’s effect on face permeability (regained permeability). Fully penetrating and creating partial wormholes using acid, followed by DAP treatment, was used to assess the changes in the fracture face permeability. It has been observed that using DAP did not lead to plugging of the created wormholes, as indicated by zero pressure drop across the sample. Nevertheless, a 49% regained permeability was measured in the sample with partial wormholes. The compatibility of broken gel systems of typical acid fracturing recipes with 1 M DAP was examined visually and using rheological tests, confirming no precipitation or damage. Indiana limestone and Austin chalk core plug samples were subjected to 1 M DAP alone and two separate mixtures: 1 M DAP with broken gel A and 1 M DAP with broken gel B for 72 h at 70 °C and 1,000 psi, showing no precipitate, color change, or rheological effects. DAP is found to stiffen the specimens and maintain gel integrity and does not plug the wormholes created in the fracture face, emerging as a promising additive for acid-fracturing treatments.