Drilling reservoir section in the oilfield located in Far North region is challenged with high risks of mud losses ranging from relatively minor losses to severe lost circulation. Numerous attempts to cure losses with traditional methods have been inefficient and unsuccessful. This paper describes implementation of Managed Pressure Drilling (MPD) and Managed Pressure Cementing (MPC) techniques to drill 6-1/8″ hole section, run and cement 5″ liner managing bottomhole pressure and overcoming wellbore construction challenges. Application of MPD technique enabled drilling 6-1/8″ hole section with statically underbalanced mud holding constant bottom hole pressure both in static and dynamic conditions. The drilling window uncertainty made it difficult to plan for the correct mud weight (MW) to drill the section. The MW and MPD design were chosen after risk assessment and based on the decisions from drilling operator. Coriolis flowmeter proved to be essential in deciphering minor losses and allowed quick response to changing conditions. Upon reaching target depth, the well was displaced to heavier mud in MPD mode prior to open hole logging and MPC. MPD techniques allowed the client to drill thru fractured formation without losses or gains in just a couple of days as compared to the months of drilling time the wells usually took to mitigate wellbore problems, such as total losses, kicks, differential sticking, etc. This job helped the client to save time and reduce well construction costs while optimizing drilling performance. Conventional cementing was not feasible in previous wells because of risks of losses, which were eliminated with MPC technique: bottomhole pressure (BHP) was kept below expected loss zones that provided necessary height of cement and a good barrier required to complete and produce the well. Successful zonal isolation applying MPC technique was confirmed by cement bond log and casing integrity test. Throughout the project, real-time data transmission was available to the client and engineering support team in town. This provided pro-active monitoring and real-time process optimization in response to wellbore changes. MPD techniques helped the client to drill the well in record time with the lowest possible mud weight consequently reducing mud requirements. The MPD system allowed obtaining pertinent reservoir data, such as pore pressure and fracture pressure gradients in uncertain geological conditions.
Technology integration is not complete without ownership. In light of the numerous challenges associated with deepwater plays all over the world, the most recent generation of ultra-deepwater drillships have more thoroughly considered the integration of managed pressure drilling (MPD) technology into the rigs. In the interest of accelerating technology integration of MPD in deepwater environments, essential equipment that enables the technique and its associated methodologies was recently offered for ownership by service companies to drilling contractors. Two (2) state-of-the-art dynamically positioned (DP3) drillships have successfully integrated MPD via ownership into their rig systems. This paper focuses on the process that was undertaken to realize rig integration for these drilling rigs, as well as on the challenges that were faced and the solutions developed to surmount them. More importantly, it discusses the outcome of the pioneering MPD rig integration projects and the lessons that were learned along the way, so that future projects are able to build on them. Lastly, it covers the substantial advantages and benefits that MPD equipment ownership, instead of traditional equipment rental, brings to the service companies, drilling contractors and operators.
This paper will discuss the review, integration assessment, engineering analysis, and process safety analysis carried out prior to installing a managed pressure drilling (MPD) system on a classed floating mobile offshore drilling unit (MODU). MPD techniques have proven cost-effective, reliable, and safe when drilling difficult onshore wells, as well as drilling from MODUs with a surface blowout preventer (BOP). However, the implementation of MPD on deepwater wells has been hampered by industry inertia and questions about reliability, barriers, riser gas management (RGM), and general riser interface issues. This paper will focus on those distinctly different aspects introduced by MPD while drilling from a floating MODU. The primary objective will be to highlight how innovative application of MPD can enhance safety when drilling challenging wells in deep water.Additional insights are provided regarding experience from several MPD installations on deepwater rigs around the world that have been tasked with drilling challenging wells.The process employed in these discussions are mainly centered on the following major categories of MPD equipment and methods:• Installing and operating a rotating control device (RCD) below the ocean's surface, including integration with a riser gas handling device. • Redundancy and fail-safe considerations for valving, both for flow lines and control lines. • Piping, umbilicals, and hoses in the moon pool area. • Nodal safety assessment of the system. • An Operator-Contractor-Service Company 'bridged' well control philosophy.The procedures will recount safety considerations of equipment classifications and system certification for MPD systems used on deepwater rigs.The lessons learned during this project help to establish a baseline for standardizing MPD drilling equipment and systems for global applications. The knowledge gained also was instrumental for the classification society certifying this equipment and system to develop safety and certification requirements aimed at improving MPD safety on deepwater drilling units. This paper will outline the core steps taken to achieve classification of an MPD system for a MODU, as well as enable increased utilization of MPD methods in deepwater wells worldwide. Class and certification can provide greater confidence to offshore operators that they can commission drilling equipment and systems capable of delivering safer, more dependable MPD wells, some of which may be considered un-drillable using conventional methods.
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