HEAT-TREATMENT FOR CLAY-RELATED NEAR WELLBORE FORMATION DAMAGE

During drilling and completion, the primary mechanisms of near-wellbor e formation damage include pore throat constriction, water blocking, p lugging with drill solids and mud products, and loading of the reservo ir with drilling or completion fluids. Among these mechanisms, some of the most severe ones encountered in elastic reservoir applications ar e the pore throat constriction due to clay swelling, and water blockin g resulting in a reduction in the relative permeability to hydrocarbon s. A novel matrix stimulation concept which involves the application o f intense heat for the treatment of water blockage and clay related fo rmation damage in water sensitive formations is presented in this pape r. Bench-scale heating tests were carried out on water sensitive sands tone cores to determine the effect of heat on effective permeability, fluid saturation, and mineralogy (i.e., degradation of in situ mineral s). Results indicated that heat treatment at 600 degrees C can improve air permeability of a damaged core by about 51% above the initial per meability. Dramatic permeability increases of 764% and 988% above the initial reservoir permeability occurred at 800 degrees C for the cores taken from the gas-and oil-bearing formations, respectively.