TY - THES

T1 - Scoring Well Construction Process and Impact on Well Integrity

AU - Liegenfeld, Andreas

N1 - embargoed until 09-09-2024

PY - 2019

Y1 - 2019

N2 - Maintaining the integrity of a well throughout its whole life cycle is very crucial in well construction and operation. Many risks are waiting along that chain of events to threaten the well’s integrity. Recent studies and research have long tried to link well integrity events to constraints in the well operation phase, with emphasis on stresses and their limits in the cement sheath. However, this thesis aims to have a closer look at the well construction process and how it might impact well integrity events. Through a simple performance assessment of the well construction process, a score between 0 and 100 is assigned to each casing/liner section to asses wellbore quality. Responses and parameters during drilling, final BHA pull, casing-running and cementing were used as input for the scoring process. The performance assessment output of the scorecard is precious in detecting shortcomings in the well construction process to help determine root causes of well integrity events. The scoring results of 29 casing/liner sections on 11 OMV Vienna Basin wells already indicate the tool’s effectiveness in detecting problematic well sections. The lowest-scoring ones face incidents like failing casing pressure tests, proven lack of zonal isolation or cementing losses during cementing. Furthermore, the scorecard’s ability to trouble-shoot problematic well sections has been proved with actual and expected/calculated casing pressure test bleed-off volumes. Gaining knowledge about the performance of the well construction process helps to enhance wellbore quality and avoid future well integrity events. The proposed wellbore scorecard tool only covers and captures what is happening in the well construction process, but to study and understand well integrity along the whole life cycle of the well, a more holistic approach will be necessary. Therefore, a stress model is proposed to understand the impact of well operations on the cement sheath in terms of stresses and failure of the cement. Manufacturing a test cell according to the proposed design to verify the stress model is highly recommended. This piece of work covers one essential part of the holistic approach to better understand well integrity events and aims towards a more environmental-friendly, safer and cost-effective way to operate hydrocarbon wells.

AB - Maintaining the integrity of a well throughout its whole life cycle is very crucial in well construction and operation. Many risks are waiting along that chain of events to threaten the well’s integrity. Recent studies and research have long tried to link well integrity events to constraints in the well operation phase, with emphasis on stresses and their limits in the cement sheath. However, this thesis aims to have a closer look at the well construction process and how it might impact well integrity events. Through a simple performance assessment of the well construction process, a score between 0 and 100 is assigned to each casing/liner section to asses wellbore quality. Responses and parameters during drilling, final BHA pull, casing-running and cementing were used as input for the scoring process. The performance assessment output of the scorecard is precious in detecting shortcomings in the well construction process to help determine root causes of well integrity events. The scoring results of 29 casing/liner sections on 11 OMV Vienna Basin wells already indicate the tool’s effectiveness in detecting problematic well sections. The lowest-scoring ones face incidents like failing casing pressure tests, proven lack of zonal isolation or cementing losses during cementing. Furthermore, the scorecard’s ability to trouble-shoot problematic well sections has been proved with actual and expected/calculated casing pressure test bleed-off volumes. Gaining knowledge about the performance of the well construction process helps to enhance wellbore quality and avoid future well integrity events. The proposed wellbore scorecard tool only covers and captures what is happening in the well construction process, but to study and understand well integrity along the whole life cycle of the well, a more holistic approach will be necessary. Therefore, a stress model is proposed to understand the impact of well operations on the cement sheath in terms of stresses and failure of the cement. Manufacturing a test cell according to the proposed design to verify the stress model is highly recommended. This piece of work covers one essential part of the holistic approach to better understand well integrity events and aims towards a more environmental-friendly, safer and cost-effective way to operate hydrocarbon wells.

KW - Bohrlochkonstruktion

KW - Bohrungsintegrität

KW - Zementation

KW - Drucktest

KW - Bewerten

KW - Zonenisolierung

KW - Well Construction

KW - Well Intgrity

KW - Cementing operation

KW - Pressure Testing

KW - Scoring

KW - Zonal Isolation

M3 - Master's Thesis

ER -