A procedure have been developed and tested for measurement and evaluation of water-oil relative permeability characteristics from unconsolidated core samples; in an unsteady state displacement experiment. In this work a simple core flooding experiment was designed, with emphases on the rate of injection, critical velocity, brine-rock compatibility, pressure response of the core sample and net over burden. This procedure proposed here besides being fast and cheap, presents the advantages of permitting the displacement to be conducted at pre-determined rates more typical to that of the reservoirs.
This research work is in response to: (1) the need of practical experimental evidence to justify the use of unsteady state method in preference to other methods. (2) The need to obtain relative permeability data from unconsolidated formation of the Niger Delta, which could be used to correlate other un-cored formation in the region.
The samples for this analysis were taken from seven (7) different locations representing the depositional belt of Niger Delta. Their porosity and permeability ranges from 18-34% and 100-20,000md respectively. These unconsolidated and friable sand stones are susceptible to deformations, grain re-arrangement, grain losses and surface drainage. The severity of these occurrences were minimized by drilling the plugs with liquid nitrogen, mounting the plugs with tin sleeve and protecting both ends of the plugs with a pair of screen of 100 and 135 us mesh size.
Also, it was possible to avoid potential problem of EOR'S such as fines mobilization, precipitation, scaling, clay swelling and compatibility of other chemical flooding agents.
This method involves performing low rate displacement of brine with oil and oil with brine and measurement of liquid permeability at irreducible – water and residual – oil end point saturation.
Except for the added provision of stopping, restarting and reversing the flood after end point have been reached, the pressure drop across the core is measured externally, between the inlet and out let of the system.
The measurement and analytical interpretation of the experimental variable, using a combination of the modified Darcy equation and our developed semi-empirical model make for quick calculation of relative permeability from the unconsolidated core samples.