Rune Godøy’s scientific contributions

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Publications (3)


Revealing Microstructure and Enduring Properties of Settled Barite Extracted from an Offshore Well Two Decades Later – Well Abandonment and Slot-Recovery
  • Conference Paper

April 2024

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33 Reads

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1 Citation

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Barite settling in the annulus behind the casing is an undesired yet common occurrence during the life of a well. Over time, the drilling fluid left in the annulus settles, leaving behind solidified barite that can hinder slot recovery and Plug & Abandonment (P&A) operations by impeding the cut and pull process. During a P&A operation, Equinor acquired settled barite samples from a North Sea well where the casing was held back by these weighting agents, introducing overpull and prolonging the cut and pull operation. A laboratory analysis program that included determination of the particle size distribution, electrokinetic potential of particles (zeta potential), crystallography (XRD), chemical composition (XRF), thermogravimetry analysis (TGA), and microstructure (QEMSCAN) was carried out on these settled barite samples to understand their properties. The results of this study provided valuable insights into the composition and characteristics of the settled material in the annulus. The solidified barite within the annular space exhibited no signs of chemical reactions. XRD analysis confirmed the barite to be the sole predominant solid in the solidified material, aligning with expectations. However, additional analytical techniques, including XRF, QEMSCAN, and Energy-Dispersive X-ray Spectroscopy (EDX) detected interconnections between barite particles, primarily facilitated by iron or quartz particles. Additionally, trace amounts of calcite, iron-oxide, SiO2, and mixed compositions involving Si, S, Fe, Ba, O, and Cl were identified within the solidified material. Scanning Electron Microscopy (SEM) results indicated that the particles exhibit strong compaction characteristics but lacked cementation, retaining some porosity. Notably, the absence of bentonite or other clays was consistently observed in all analyses. Furthermore, the zeta potential measurements of the samples showed a more stable response than the API barite. This study highlights the process of solidification observed in settled barite, suggesting that factors other than chemical reactions may be responsible for this phenomenon. The potential mechanisms contributing to solidification include physical aggregation, compaction, and alterations in surface charge under downhole conditions. This enhanced understanding of the solidification process will contribute to the development of solutions for efficient casing removal and even the utilization of settled barite as a barrier material.


Assessment of Cementitious Composites for High-Temperature Geothermal Wells
  • Article
  • Full-text available

March 2024

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65 Reads

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5 Citations

Materials

High-temperature (HT) geothermal wells can provide green power 24 hours a day, 7 days a week. Under harsh environmental and operational conditions, the long-term durability requirements of such wells require special cementitious composites for well construction. This paper reports a comprehensive assessment of geothermal cement composites in cyclic pressure function laboratory tests and field exposures in an HT geothermal well (300–350 °C), as well as a numerical model to complement the experimental results. Performances of calcium–aluminate cement (CAC)-based composites and calcium-free cement were compared against the reference ordinary Portland cement (OPC)/silica blend. The stability and degradation of the tested materials were characterized by crystalline composition, thermo-gravimetric and elemental analyses, morphological studies, water-fillable porosity, and mechanical property measurements. All CAC-based formulations outperformed the reference blend both in the function and exposure tests. The reference OPC/silica lost its mechanical properties during the 9-month well exposure through extensive HT carbonation, while the properties of the CAC-based blends improved over that period. The Modified Cam-Clay (MCC) plasticity parameters of several HT cement formulations were extracted from triaxial and Brazilian tests and verified against the experimental results of function cyclic tests. These parameters can be used in well integrity models to predict the field-scale behavior of the cement sheath under geothermal well conditions.

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Assessment of Cementitious Composites for High Temperature Geothermal Wells

January 2024

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49 Reads

High temperature (HT) geothermal wells can provide green power 24h a day 7 days a week. Harsh environmental and operational conditions, long-term durability requirements of such wells require special cementitious composites for well construction. This paper reports a comprehensive assessment of geothermal cement composites in cyclic pressure function laboratory tests, field exposures in an HT geothermal well (300-350oC) as well as a numerical model to complement the experimental results. Performances of calcium-aluminate-cement (CAC)-based composites and calcium free cement were compared against reference Ordinary Portland Cement (OPC)/silica blend. The stability and degradation of the tested materials was characterized by crystalline composition, thermo-gravimetric, and elemental analyses, morphological studies, water-fillable porosity, and mechanical properties measurements. All CAC-based formulations outperformed the reference blend both in the function and exposure tests. The reference OPC/silica lost its mechanical properties during the 9-month well exposure through extensive HT carbonation, while properties of the CAC-based blends improved over that period. The Modified Cam-Clay (MCC) plasticity parameters of several HT cement formulations were extracted from triaxial and Brazilian tests and verified against the experimental results of function cyclic tests. These parameters can be used in well integrity models to predict field-scale behavior of the cement sheath under geothermal well conditions.

Citations (1)


... It is based on the atomic percentiles of Ca, Na, Al, and Si obtained from the EDS spot analysis, which were normalized by the Si atomic percentage, i.e., Ca/Si, Na/Si, and Al/Si ratios. Results obtained from past literature were employed to identify the values of these ratios pertaining to the different reaction products found in alkali-activated materials, including C-A-S-H, C(N)-A-S-H, N (C)-A-S-H, N-A-S-H, and C-S-H (Marjanović et al., 2015;Yip et al., 2005;Ismail et al., 2014;Liu et al., 2018;Sugama and Pyatina, 2018;Pacheco-Torgal et al., 2014;Haha et al., 2011). ...

Reference:

Optimization of Alkali-Activated Ladle Slag-Fly Ash Composites Using a Taguchi-TOPSIS Hybrid Algorithm
Assessment of Cementitious Composites for High-Temperature Geothermal Wells

Materials