Factors that can be optimized in waterfloods of the low permeability reservoir

Oil rates in low permeability sandstone and carbonate rock waterfloods often are unprofitably low. High injection rates seem to be the answer, but unfortunately, due to unsuspected fracturing or pressure parting, large volumes of injection water are frequently lost and untimely water breakthrough often occurs. Ways of recognizing detrimental parting conditions are given and field data are cited which show that formation fracturing or pressure parting occurs at surprisingly low pressure gradients during water injection. While unplanned and uncontrolled parting is only marginal at best, controlled parting can lead to improved rates and profitable recovery efficiency in low permeability reservoirs. Realizing that a moderate degree of fracturing may be needed in many low permeability reservoirs, suggestions are made on how to select optimum injection pressures and injection patterns which take advantage of reservoir properties. (31 refs.)