ABSTRACT

Experimental studies on secondary and tertiary recovery processes in tight oil formations require a set of scaling criteria to scale them up to field dimension for either optimizing field production or designing displacement experiments. In this study, scaling criteria have been developed and validated to evaluate performance of waterflooding and immiscible CO₂ flooding in tight formations by performing three-dimensional (3D) sandpacked displacements. Experimentally, waterflooding and immiscible CO₂ flooding processes have been conducted with the 3D physical model, respectively. Continuous CO₂ flooding results in a relatively low oil recovery with 33.8% of original-oil-in-place after 1.20 pore volume of CO₂ injection. Theoretically, mathematical formulas have been developed for the corresponding processes on the basis of dimensional and inspectional analyses. Mass transfer from CO₂ to oil by dissolution and diffusion has been considered in the inspectional analysis; for relaxation of the scaling criteria, gravitational force, viscous force, and dispersion and diffusion have been considered critical factors. The moderate water and CO₂ injection rates (i.e., 2.0 cm³/min and 200.0 cm³/min for water and CO₂, respectively) are ensured to result in a transverse diffusion-dominated flow, further simplifying the scaling group. The relaxed scaling group has been subsequently validated with the experimental measurements. Capillary force and geometric factors are found to be negligible when scaling up the 3D physical model to the prototype. There exists a reasonably good agreement between laboratory measurements and simulation results of a field production. By using the validated scaling criteria, displacement experiments in the 3D physical model can be properly designed to simulate waterflooding and immiscible CO₂ injection in a targeted tight formation so as to design and optimize the field-scale exploitation processes.