The oil and gas industry has operated in Denver Julesburg (DJ) basin for many decades. Currently in the basin, increasing population density and wellbore complexity have resulted in a heightened visibility of long-term well integrity. Failure can lead to future liabilities, loss of public trust, and a revoked right to operate. Operators must demonstrate commitment to well integrity to continue operating in the basin, yet many still report sustained casing pressure (SCP) on a significant portion of wells. Because SCP corresponds to the open communication of fluids to surface, it is a direct metric of well integrity failure. Regulations require operators to report and remediate instances of SCP on all wells. On average, clients experience one well with SCP for every five drilled.
As a primary well barrier element, the cement sheath is vital to well integrity improvement. Enhanced placement techniques of conventional cements failed to prevent SCP, confirming that failure is derived from post-placement dynamic conditions. The solution must account for pressure and temperature stresses, preventing and mitigating mechanical failures throughout the well life cycle. A flexible and self-healing cement design provides a twofold response that is ideal for wells in areas, such as the DJ basin, with SCP risk.
Mechanical properties are optimized based on the results of a mathematical stress model. Although Portland-based cement systems can be optimized to sustain higher levels of dynamic stresses, it is impossible to avoid a mechanical failure entirely. Therefore, a self-healing function is a critical secondary feature. The self-healing mechanism is designed to activate upon contact with an invading hydrocarbon and can be formulated for any type of hydrocarbon, from high gravity oil to dry gas.
Flexible and self-healing cement has been successfully designed and implemented on approximately 250 wells in the DJ basin with a reduction to 2% instances of SCP. Elimination of SCP provides confidence in long-term well integrity, which is essential to continued operation in the basin.
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Zusammenfassung
Das Ziel dieser Arbeit bestand in der Entwicklung eines langwelligen
Strahlungsthermometers zur berührungslosen Messung von
Oberflächentemperaturen in stationären Gasturbinen während
des Betriebs der Turbinen innerhalb des EU-geförderten Projektes
„Sensors Towards Advanced Monitoring and Control of Gas Turbine
Engines (Acronym STARGATE)“. Im Rahmen der Arbeit wurden die
infrarot-optischen Eigenschaften der Wärmedämmschichten und
der vorhandenen Brenngase am ZAE Bayern bei hohen Temperaturen bis
1600 K und Drücken bis 13 bar bestimmt. Mit Hilfe
dieser experimentellen Charakterisierungen konnte ein geeigneter
Spektralbereich um 10 μm für das langwellige
Strahlungsthermometer identifiziert werden. Entsprechend dieser
Erkenntnisse wurde zunächst ein Laboraufbau mit geeigneten
optischen Bauteilen (Filter, IR-Wellenleiter, etc.) realisiert und
verifiziert. Anschließend wurde ein Prototyp für Messungen in
Gasturbinen während des Betriebs der Turbinen entwickelt und in
einem Turbinenteststand der Firma Siemens AG in Berlin erfolgreich
getestet. Abschließend wurde eine Unsicherheitsanalyse
durchgeführt, die eine erweiterte Messunsicherheit der gemessenen
Temperaturen von etwa ± 30 K ergab.
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