Abstract
Formation damage due to calcite deposition is currently an issue in the five sedimentary basins producers of hydrocarbons in Colombia. At this moment, over 100,000 BOPD are in risk due to this kind of damage. A lab-scale correlation is developed which contemplates thermodynamic and hydrodynamic parameters for predicting the Calcium Carbonate formation tendency in Sandstones. An experimental methodology to recreate the continuous deposition of CaCO3 was implemented using Berea sandstones, scalating different production rates and varying the physicochemical composition of the formation water, reproducing accurately the concentrations of the ions Ca++ of Colombian oilfields (consisting currently the biggest issue in this sort of formation damage). The used methodology consisted in a factorial experimental design, which allows the optimal combination of thermodynamic parameters (represented by the Ca++ concentration) and hydrodynamic parameters (represented by injection rates), along a series of rock-fluid interaction experiments which exhibited a permeability impairment of approximately 80%. The correlation was developed using a specialized software. The proposed correlation predicts the permeability impairment with an 80% adjustment of experimental data. This correlation is valid for low permeability values (less than 150 mD), field-scale velocities between 1 and 10 ft/day, and contemplates regular values of Ca++ ions concentration for Colombian oilfields. Furthermore, the correlation was validated with experimental data obtained at several flow rates (between 1 and 3 cc/min), several temperatures (150 -250°F) and several concentration of Ca++ ions (250-650 ppm). This proposed correlation is the basis to develop a deterministic model, which quantifies the depth, severity and production losses related to this phenomenon.
