Geomechanical impact of bio-competitive exclusion chemical on reservoir rocks.

Peretomode, Ebikapaye

Abstract

This study describes a novel approach known as "bio-competitive exclusion", which uses chemical nitrates as an oilfield chemical to treat reservoir souring and control the activities of sulfate-reducing bacteria. Because of its flexibility and extensive use in oil production, this oilfield treatment method has been regarded as a more cost-effective and environmentally friendly alternative. Oilfield chemical-rock interaction occurs when reservoir rocks are treated with oilfield chemicals for increased oil recovery (EOR) and reservoir souring. This interaction reduces the strength of the formation rock, may cause the production of sand, and has a detrimental effect on oil production and its facilities. A lot of research has focused on the use of Nitrate for reservoir souring control, treatment and oil recovery. However, the deleterious effects of nitrate on the geochemical and geomechanical properties of the rock have not been considered under static and flooding conditions. This work uses a combination of UCS, analytical and PSD tests to experimentally investigate the geochemical and potential geomechanical effects of treating sandstone and carbonate reservoir rocks with a biocompetitive exclusion (BCX) chemical (sodium nitrate) under static and flooding conditions. The flooding approach was adopted to study the effects of varying chemical concentrations on sandstone rock's geochemical and geomechanical properties. For the static saturation test, the results showed there was mineral dissolution and precipitation response, which caused the separation of grain particles, and as a result, decreased the strength of the rock. The core flooding investigation was performed at increasing concentrations of 637.5 ppm, 850 ppm, 1062.4 ppm, and 1275 ppm. The results demonstrate that when nitrate concentration increases, mineral precipitation, and dissolution alter elemental and mineralogical phases, PSD, porosity and permeability, decreasing the unconfined compressive strength (UCS) of the rock. This study has demonstrated that the rate of mineral dissolution or precipitation is a direct function of the rate of porosity change; increasing chemical concentration reduces the rock's UCS. In addition, the experimental study from both static and flooding tests suggests that applying nitrate for sandstone reservoirs should be encouraged but discouraged in its application to carbonate formations due to its potential for sand failure and production.

Citation

PERETOMODE, E. 2023. Geomechanical impact of bio-competitive exclusion chemical on reservoir rocks. Robert Gordon University, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-2571274

• Thesis Type: Thesis
• Deposit Date: Nov 5, 2024
• Publicly Available Date: Nov 5, 2024
• DOI: https://doi.org/10.48526/rgu-wt-2571274
• Keywords: Nitrates; Reservoir souring; Oil reservoirs; Oilfields; Sandstone
• Public URL: https://rgu-repository.worktribe.com/output/2571274
• Award Date: Dec 31, 2023