A closer look at SRB souring in porous media: Higher-order finite difference scheme in radial coordinate

Microorganisms have different benefits including bioremediation of aquifers contaminated with the non-aqueous liquid phase, microbial EOR, and bacterial degradation of asphaltenes. Despite these profits, a special kind of bacteria named Sulfate Reducing Bacteria (SRB) causes H2S generation which is toxic and also results in equipment erosion and corrosion. The injected water approaches the production well in a radial form geometry. However, less is known about the H2S generation and movement in the radial coordinate. In this study, we investigated SRB souring in aquifers and oil reservoirs using a reactive numerical simulation of multicomponent and multiphase radial flow. The operator-splitting method was utilized to model this dispersion-dependent phenomenon. Furthermore, a higher-order finite difference approach was adopted to more accurately model SRB souring by avoiding the numerical dispersion. The results of the proposed approach were verified with the existing analytical radial solution by applying the simplifying assumption of the analytical radial solution. Also, the effect of numerical and physical dispersions was evaluated and it was highlighted that under certain conditions numerical dispersion can be confused with the physical one. Moreover, a comparison of the H2S profile in the radial coordinate with linear geometry showed significant differences which should be considered in SRB souring studies. This difference highlights the necessity of radial grid refinement around the wells in full-field reservoir simulation to attain more accuracy. The study of SRB souring during water injection in an oil reservoir also illustrates the same pattern as souring in aquifer but the oil presence delays mixing between sea and formation water and postpones H2S generation. The findings of this work provide a better understanding of nearwellbore SRB souring during water injection in porous media.

Automated summary

This study used reactive numerical simulations to investigate the generation of H2S by microorganisms in aquifers and oil reservoirs. The results showed significant differences in the distribution of H2S in the radial coordinate compared to the linear coordinate, highlighting the need for radial grid refinement in reservoir simulation. The presence of oil also delayed the generation of H2S. These findings enhance our understanding of microbial souring during water injection in porous media.