The potential for microbially induced calcite precipitation to support wellbore sealing and zonal isolation in the hydrocarbon industry

Steinacher, Fabian

Thesis

The potential for microbially induced calcite precipitation to support wellbore sealing and zonal isolation in the hydrocarbon industry

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Creator

Steinacher, Fabian

Rights statement

Strathclyde Thesis Copyright

Awarding institution

University of Strathclyde

Date of award

2021

Thesis identifier

T16056

Person Identifier (Local)

201661048

Qualification Level

Doctoral (Postgraduate)

Qualification Name

Doctor of Philosophy (PhD)

Department, School or Faculty

Abstract

Today many countries have set ambitious climate goals towards a carbon net-zero future to reduce the impact of climate change on society and our planet. Global targets in greenhouse gas emissions have led to new innovation in research and practice in the fields of civil and geotechnical engineering developing alternative low carbon technologies that are resilient to climate change. This PhD thesis explores the potential for deployment of one such technology in the field of petroleum engineering. The PhD explores the low carbon biomineral sealing technology, Microbially induced carbonate precipitation (MICP) which uses the bacteria Sporosarcina pasteurii to precipitate calcium carbonate and evaluates its potential for sealing wellbores in the hydrocarbon industry. Three experimental campaigns were conducted in this thesis. In the first, the potential for bacteria growth using an alternative yeast-based nutrient media was explored. S. pasteurii is commonly grown using brain heart infusion which is an expensive beef product with a high carbon footprint. The second campaign explored the effect of increased temperature and pressure on bacteria ureolysis. To apply MICP in the oil industry, the bacteria must be able to withstand elevated temperature and pressure combinations found at-depth. A small number of experiments to determine the potential for thermal ureolysis at much higher temperatures were also conducted. Finally, in the third campaign, experiments were conducted to seal sandstone well-cores at three temperature and pressure combinations found in the North Sea. The experimental results presented in this thesis demonstrate the following key points:(1) S. Pasteurii have the potential to grow in alternative low-cost, low-carbon, yeast-based waste-stream products (2) pressure alone has no significant impact on ureolytic activity(3) temperature does affect ureolysis. The optimal temperature for high and sustained ureolytic activity was around T = 60°C with ureolytic activities around 13 mM urea hydrolysed/min( 4) at 70°C and above MICP is not applicable (5) thermally decomposed urea in a pilot experiment showed visible thermal degradation of urea above > T = 120°C , hence, for high temperatures thermally induced carbonate precipitation might be a feasible alternative (6) bio-grouting of heterogenous sandstone well-cores under in-situ wellbore pressure and temperature conditions could establish a CaCO:3 biomineral seal with permeability reductions of 5 to 6 orders of magnitude - reaching a minimum value of k = 4.0 E-18 m2 (4 μD) after 18 MICP treatment cycles (7) two fundamental nucleation processes in the formation of CaCO₃ biominerals were identified; random nucleation followed by chaotic growth and highly ordered spherulitic growth.The results from this thesis provide new insights into the potential for MICP as a novel sealing technology within the hydrocarbon industry. Results show that MICP could be successfully deployed at depths up to ~1120 m (depending on the local geothermal gradient). MICP it is far more penetrable than traditional cements, as a result it may prove highly valuable for sealing well cement sheaths, fractured caprocks and as an additional wellbore barrier element (WBE)to seal production and stimulation horizons prior to plugging and abandonment.

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