Abstract
A methodology for enhancing the performance of relative permeability modifier (RPM) treatment presented here utilises a technique of injecting chemicals sequentially into the affected wells. This technique considers injecting a single RPM into matrix reservoir cannot occupy all the reservoir pores, because as RPM injected it will form a constant film on the reservoir rock grains that may plug small pores and reducing the effective size of larger pores. Therefore the RPM displacement will not be piston like and consequently the RPM treatments have shown low to moderate success. The aim of this method is to obtain a high dispersion rate of RPM polymers onto the reservoir rock grains to improve the performance of RPM treatments.
In this study we examined two injection methods; namely single and sequential injections. For the single chemical injection, three chemicals were tested each individually in Berea plugs having water permeabilities ranging from 5.5 to 18.5md and porosities from 14.1 to 19.6%. Thereafter three of these chemicals were injected successively into a Berea sample having water permeability of 34md and porosity of 20.4%.
The experiment results revealed that injecting chemicals sequentially is more effective method for conformance control in matrix reservoir than the single chemical injection method. For instance, for the first and second water alternate oil (WAO) cycles, the residual resistance factor to water Frrw obtained by this method was 5 and 2.5 times higher than the Frrw acquired by the single chemical injection method. The measured residual resistance factor to oil Frro using the sequential method was less than two, which is considered to be the upper limit for conformance control in matrix reservoirs. Accordingly injecting chemicals sequentially method can be applied to enhance RPM performance in matrix reservoirs.
