MATHEMATICAL-MODELING OF FORMATION HEAT-TREATMENT PROCESS

A novel matrix stimulation concept, formation heat treatment (FHT), wh ich involves the application of intense heat around the near-wellbore region for the treatment of water blockage and clay related formation damage in water sensitive formations previously was developed and pres ented in the literature. The FHT process involves the application of i ntense heat around the wellbore using a downhole heater. The heat is c onveyed to the near-wellbore region using an inert gas flowing through a downhole heater. To understand the heat transfer and fluid-flow cha racteristics of the FHT process, a transient two-dimensional mathemati cal model has been developed and is presented in this paper. The model is based on coupling the momentum and energy-balance equations for th e wellbore gas with the surrounding porous formation. The presence of the heater across the net pay (sandface) is taken into account in the energy equation as a localized volumetric heat source. A control-volum e based finite-difference scheme is used to solve the model equations on a staggered grid. Parametric studies indicate that by injecting a s uitable quantity of gas through the tube and annulus, and by adjusting the power input to the downhole heater, the temperature near the well bore can be favourably controlled.