In September 2010 a decision was made to expand the current Mars field development with a second 24 slot TLP structure in a water depth of 3000 ft. This new development includes higher pressured deeper pays below the existing brown field Mars pays. The new structure will install wells with multiple casing strings across stacked sand packages that are both depleted and virgin pressured ranging from 10,500 ft to 23,000 ft TVD in depth. This in combination with other challenges such as extremely tight annuli clearances, depletion zones greater than 5000 psi, multiple stacked sands at varying degrees of depletion, and risk of borehole stability failure/ballooning presents a unique set of zonal isolation challenges that requires proactive novel approaches and design strategies. Zonal isolation is a regulatory requirement and a key component of project success in order to secure maximum field recovery and future wellbore utilization within the estimated field life.Zonal isolation methodology and design does not have a single focus but explores all parameters that affect placement and isolation while not losing focus on striving operational simplicity. This paper discusses the engineering approach to zonal isolation requirements in a highly challenging environment utilizing a step wise methodology with increasing complexity and also elaborates on how this approach led to the identification and ultimately the development of new technologies.Design methodologies will be discussed as well as resulting technologies identified as a "must haves" for development to ensure maximum probability of zonal isolation success. Technologies discussed will include reverse cementing tools, 50 (ϩ) year seals for stage collars, and connection requirements. Statement of Requirements (SORs), basic tool descriptions, and preliminary results of these developments will also be included. Discussions on why certain placement techniques or approaches were not integrated into the zonal isolation project plan will also be discussed. OverviewNumerous design challenges must be managed to ensure wellbore objectives, lifecycle wellbore integrity, robust future utility and top quartile execution performance is achieved for Mars B Olympus direct vertical access (DVA) wells. New regulatory requirements and design conditions have led to the required use of
New regulatory requirements and design conditions introduced in recent years have led to the use of higher strength tubulars in the majority of Deepwater wells in the Gulf of Mexico. To achieve the new design requirements, the use of non-conventional casing sizes, grades and weights different than those traditionally used and available in the industry are required. The use of thicker wall tubular has consequently resulted in geometrical constraints and tighter annuli clearances in the wellbore driving new connection design requirements and selection criteria to meet overall well objectives. The new design conditions require innovative connection design to meet or exceed the collapse strength of pipe body rating. As part of the Shell Mars B project, the Olympus TLP DVA team championed the development and qualification of multiple connection types to meet the project requirement and for overall portfolio usage. As the number of connections to be designed and qualified is substantial, a pragmatic and systematic testing philosophy and strategy was developed for the Mars-B project TLP DVA wells. This paper provides a high level overview of the connection selection challenges, the systematic process adopted to streamline connection development, testing and qualification. It will also discuss some of the challenges in connection design to meet well requirements and qualification process. The scope includes static connection design for strings installed below the subsea well head, as well as, dynamic connection design on strings that are installed in the water column. Both connection designs require sealability qualification and assurance. Dynamic connections require additional fatigue design and qualification. Rigorousness of sealability and fatigue testing is appropriate to the environment of which it will be subjected throughout the well and the 50 year field life.
The Mars-B project is Shell's sixth GOM TLP development and demonstrates Shell's commitment to GOM. The Mars-B project is aiming to unlock resources over the next 50 years through the deployment of a new 24 slot TLP structure (Olympus TLP) and additional subsea infrastructure for the West Boreas/South Deimos fields. The Olympus DVA rig is a novel platform drilling rig designed specifically to meet the execution requirements of complex Olympus DVA well designs. The well design and associated equipment must accommodate the 50 year design life, the longest design life of a TLP in Shell's history. This is the first development to incorporate post-Katrina environmental design loads and new regulatory design requirements. Project challenges include numerous technical challenges pertaining to well designs for 24 DVA wells targeting over 50 horizons spanning 10, 500 ft TVD to approximately 25, 000 ft TVD encompassing both highly depleted brown field and deeper virgin pressure formations. The Olympus DVA well trajectories range from near vertical to high angle extended reach both through sediments and through salt penetrations. Rig and surface facilities must be designed to address multiple challenges present to ensure well and facility integrity, reservoir isolation and desired well construction objectives are met. This requires successful development and deployment of novel technologies and world class systems. The design requirements have resulted in an evolution of traditional well designs which in turn drives novel rig and surface facilities requirements. A high level overview of the design challenges and the resulting surface equipment requirements will be discussed. This includes rig equipment requirements to meet the specified execution directives, the development of an innovative drilling riser concept, added systems optimization to increase safety and overall execution efficiency.
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