A Novel Method of Removing Emulsion Blockage after Drilling Operations Using Thermochemical Fluid

Abstract

Summary A novel approach to exploit heat and pressure generated from the exothermic reactions of the aqueous solution of thermochemical reactants, in removing emulsion blockage induced by oil-based mud (OBM) has been investigated. The proposed technology essentially concerns raising the temperature and pressure of the formation above the kinetic stability of emulsions using thermochemical fluid (TCF). From the batch experiments, to assess the energetics of the thermochemical reaction, it was observed that the temperature of the system could be raised above 170°C at a pressure of 1,600 psi. The chemical can be effectively applied under different operating temperatures Tr = 20, 40, 55, and 100°C without significant effect on the heat and pressure generation. The specific energy per unit volume of the reaction is equivalent to ≈370 MJ/m3 within the operating conditions. OBM was prepared and used as the damaging fluid. A TCF was injected into the damaged core sample for cleaning. Permeability and porosity change of the treated core was tested using nuclear magnetic resonance (NMR) to monitor the efficiency of the TCF injection. Ultimately, injecting 1 pore volume (PV) of the TCF removed approximately 72% of the OBM-based emulsion from the core sample. In addition, permeability of the core sample increased from 120 to 800 md, while the porosity increased from 20 to 21.5% after treatment. Moreover, the pressure profile, observed during the flooding experiment, showed that no precipitation or damage was induced during the TCF flooding. Therefore, it is envisaged that the in-situ heat generation can mitigate the emulsion blockage problem and offer advantages over the existing methods considering environmental friendliness and damage removal efficiency.