SEMI-ANALYTICAL APPROACH OF OPTIMUM VIBRATION FREQUENCY DETERMINATION THAT GIVES MAXIMUM IMPROVEMENT OF RESERVOIR ROCK POROSITY

摘要

Declining production in oil recovery operations is a major concern in the oil industry. Each of commonly applied EOR methods has a number of limitations as well as some undesirable results. Vibration stimulation technologies are an alternative method in improving production and increasing recovery in which the vibration is thought to facilitate production by, in one view of diminishing capillary forces; reducing adhesion between rocks and fluids; or causing oil droplets to cluster into "streams" that flow with the waterflood, and the other view of enlarging pore volume. Various laboratory investigations have been conducted to find out the effect of high and low vibration frequency on the reservoir rock properties. A study of low-frequency waves is of special interest because of the potential for reservoir stimulation by surface-based vibrators. Reservoir resonant frequencies should be selected to get the maximum improvement in reservoir rock properties. The results of the laboratory research show that effect of vibration causes an increase of effective porosity up to 9.17%. Optimum frequency is 15 Hz in all of the experiments. Furthermore, this investigation also tries to seek a semi-analytical equation for optimum frequency based on the laboratory result. The general resultant equation has the format: φ_(av) = A.Sin (ω x f) + φ_o where "A " is constant value, "ω" is constant value, "φ_o" is porosity before vibration (%), "φ_(av)" is porosity after vibration (%) and "f" is frequency (Hz).