INVESTIGATION OF THE IMPACT OF SALINITY ON ASPHALTENE PRECIPITATION DURING WAG-CO2 INJECTION FOR A MALAYSIAN LIGHT OIL

This project aims to study the impact of low and high injection water salinity on asphaltene precipitation during WAG-CO2 injection. Dynamic core flooding experiments were conducted with injection water salinity of 5000ppm and 35000ppm at 1:1 WAG ratio.
Dynamic core flooding experiments were conducted using Berea sandstone core as formation representative. Dulang Malaysian light crude sample with 0.39 % wt initial asphaltene content was used. 2 runs of experiments were conducted using low and high salinity of injection water at 5000ppm and 35000ppm. Secondary water flooding were conducted followed by WAG-CO2 injection. WAG-CO2 injection procedure from Jiang et al.(2010) will be use as a reference in this research. In WAG injection scheme, a 0.25PV half slug size of CO2 is injected followed by 0.25PV half slug size of injection water for a total of 6 alternate cycles.
All experiment parameters were fixed at 2500psia overburden pressure and 98oC with an injection rate of 0.4cc/min (for secondary water flooding and WAG injection) and 2000psi injection pressure. The effluent oil was collected for every cycle of WAG injection (total of 6 samples). Asphaltene precipitations in the core were determined from the change in asphaltene content of effluent oil. The effects of asphaltene precipitation in the core sample were observed from initial and final porosity and permeability measurement of the core sample.
The experiment results concluded that higher brine salinity will give a higher oil recovery, lower asphaltene precipitation and lower porosity & permeability reduction.