Experimental Investigation of Noble Viscoelastic Surfactant and Chelating Agent for Heavy Oil Enhanced Oil Recovery in High‐Pressure–High‐Temperature Carbonate Reservoirs

Abstract The success of chemical enhanced oil recovery (cEOR) is significantly dependent on the type of reservoir and its pressure and temperature conditions. The recovery of heavy oil from carbonate reservoir using cEOR method is still challenging because of its highly complex internal structures and high pressure–high temperature (HPHT) conditions. This research work is the first account of the use of AGA‐97 (viscoelastic surfactant [VES)) along with a chelating agent diethylene triamine penta acetic acid (DTPA) for their application in cEOR method in heavy‐oil‐carbonate reservoirs. Several core flooding experiments were carried out to ascertain the effectiveness of the VES AGA‐97 and chelating agent for cEOR method. The effect of VES on viscosity and interfacial tension was also studied with varying concentration, temperature, and time. The thermal stability of VES was analyzed with the help of thermogravimetric analysis, nuclear magnetic resonance (NMR) and Fourier‐transform infrared spectroscopy. VES AGA‐97 was found to have high thermal stability in short‐term aging. The static adsorption and dynamic adsorption of VES AGA‐97 was studied with the help of total organic carbon analysis. After all the analysis, it was found that VES AGA‐97 and DTPA can be effectively used for cEOR method in carbonate reservoir at HPHT conditions, and the total additional oil recovery of 5.82–9.64% may be achieved.