Speaker
Description
Cement plug is a crucial barrier material for ensuring long-term integrity of depleted wells, either where CO2 has been sequestered or in permanently abandoned wells [1]. However, some of the drilling mud used prior to the cementing operation often remain due to wetting properties of the base mud [2]. The remaining drilling mud might therefore contaminate the cement and can be detrimental to permanent plugging and abandonment as it might not only affect the intrinsic properties of the cement (mechanical strength, porosity, permeability) but also the properties of the cement-casing interface (bonding, hydraulic sealing). Eventually this can induce leakage paths such as microannuli (crack between cement and casing).
In this study, we investigate the effect of oil-based drilling mud (OBDM) contamination on the sealing properties of cement and cement-casing interface, on a macroscopic and a mesoscopic scale.
Different fractions of OBDM are dispersed in a neat Portland G cement. First, the mechanical properties of contaminated cements are monitored under relevant downhole conditions, high pressure and high temperature (HPHT): in the liquid state we used a rheometer with a HPHT cell to evaluate the slurries flow properties and an ultrasound cement analyser (UCA) to assess the setting time. In the hardened state we used the UCA, to monitor cement strength. The compressive strength of the cement tends to decrease with the OBM contamination, while the viscosity increases significantly indicating a deterioration in its pumpability.
Secondly a tailor-built plug integrity experimental set-up [3], which allows us to simulate cement placement and curing, and to assess plug integrity by inducing a differential pressure and monitoring the resulting flow rate, is used to assess the overall integrity of the contaminated cement and casing through their effective permeability.
Finally at the mesoscale we used nuclear magnetic resonance (NMR) [4] to follow oil phase evolution during cement hardening and analyse the relationship with the resulting macroscopic properties of the contaminated cement.
References
[1] T. Vrålstad, A. Saasen, E. Fjær.; T. Øia, J.D. Ytrehus; M. Khalifeh, Plug & abandonment of offshore wells: Ensuring long-term well integrity and cost efficiency, J. Pet. Sci. Eng. 173 (2019), 478–491.
[2] N. Arbad and C. Teodoriu, A Review of Recent Research on Contamination of Oil Well Cement with Oil-based Drilling Fluid and the Need of New and Accurate Correlations, ChemEngineering 4 (2020), 2-28.
[3] N. Opedal, A.N. Corina and T. Vrålstad, Laboratory Test On Cement Plug Integrity, ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. Madrid, Spain, June 17, 2018. 10.1115/OMAE201878347.
[4] P. Coussot, Progress in rheology and hydrodynamics allowed by NMR or MRI techniques, Experiments in Fluids 61 (9) (Sep. 2020).
| Participation | In-Person |
|---|---|
| Country | Norway |
| Energy Transition Focused Abstracts | This abstract is related to Energy Transition |
| MDPI Energies Student Poster Award | No, do not submit my presenation for the student posters award. |
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