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

Historically, running large diameter surface and intermediate casing in the shallow sections of a well with a high build rate and inclination has proven to be very challenging, with a high risk of getting stuck off bottom. At the same time, with limited drilling margins, it has become important to be able to successfully set large diameter casing under these conditions to enable the well to reach target objectives and/or avoid subsurface hazards. A comprehensive analysis reveals that a major contributing factor to the difficulty of running large diameter casing is due to the large end loads resulting from the high inherent stiffness of the casing as it is bent through dog-legs or ledges. Finite element analysis indicated that these forces were high enough to cause the shoe to dig in to softer formations, and that the end forces increased substantially as casing size and weight increased, or as dog-leg severity and inclination increased. A fairly simple solution was identified: a composite flexible shoe run at the bottom of the casing reduced the side loads at the bottom of the casing when running into the hole. Effective communication and cooperation between designer and operator allowed for a product that was thoroughly tested and examined from an operational standpoint to identify risks and address possible failure modes. Smaller tools were also proven out in higher build rate horizontal wells prior to running in a higher cost deepwater environment. Several case histories are presented that demonstrate the ability to run 18, 16, and 14-inch casing smoothly to target depth through build sections with doglegs of more than 4°/100ft, in soft formations, and to inclinations of more than 60° using a composite flexible casing shoe. The ability to reliably set large diameter casing through build sections and into high inclination wellbores expands the envelope of design possibility when planning deepwater wells.

Deepwater operators continually face technical and environmental challenges to drilling and completing wells safely and efficiently. To address both current and future challenges, the industry has leveraged radio frequency identification (RFID) technology to reduce risk, rig time, and nonproductive time (NPT) and to perform operations that traditional tools cannot perform. RFID technology has been integrated into drilling and completions tools to improve performance and reduce risk for offshore operations, such as drilling underreamed holes, spotting lost circulation materials, setting packers, opening stimulation sleeves, and performing subsurface reverse cementing. These tools use RFID tags released from the rig floor to enable downhole hydraulic power units (HPUs) to operate the tools. This paper describes criteria for selecting RFID-enabled tools rather than traditional tools, integration of RFID tools with operations, and value-added features enabled by RFID. Contingency, safety, and risk assessment factors are discussed, along with case studies validating performance and suitability of selected RFID tools. Three case studies describe how RFID solutions for drilling and completions were selected and applied in high-cost environments to address specific challenges and job objectives. Design and bench testing of RFID tools to enable future subsurface reverse cementing operations are also covered. The first case study describes an RFID lower-completion system that was successfully deployed into a southern North Sea extended-reach well. The system enabled remote control of flapper isolation valves and remote operation of stimulation sleeves to access the reservoir, which aimed to eliminate the need for intervention between treatments and ultimately improved fracture cycle time and reduced risk. In the Gulf of Mexico, an RFID drilling underreamer was used to set a liner shoe precisely at the casing point and eliminate a dedicated hole-opening run that would have been needed with traditional underreamers. The 8 1/2-in. hole section was drilled; but losses prevented the mechanical reamer from opening. Therefore, the 650-ft hole section was drilled to TD using the bit only. To eliminate multiple trips to take pressure samples and underream the hole section to 9-7/8 in., an RFID underreamer was placed below the measurement-while-drilling/logging-while-drilling (MWD/LWD) equipment. After pressure measurements were taken, the underreamer was actuated with RFID tags to enlarge the entire 650-ft openhole section with less than a 13-ft rathole. In the last case study, an RFID circulation sub was deployed above other bottomhole assembly (BHA) components, including an RFID underreamer and a conventional ball drop underreamer. This configuration enabled the operator to ream out the 22-in. cemented show track, underream the openhole section, and efficiently clean the wellbore at total depth. Because of BHA and standpipe pressure limitations, the RFID circulation sub was used in a split-flow application to bypass a percentage of the total flow to allow for a higher downhole flow rate. The sub helped to achieve high flow rates, high annular velocity, and turbulent flow, which contributed to better hole cleaning and improved wellbore integrity. Selecting the best tools and technology for specific applications results in streamlined applications and reduced operational risk. The methodology for selection, design, planning, and implementation of RFID drilling and completions tools identifies when RFID technology can be beneficial to deepwater operations.

Reverse circulation cementing is a placement technique that reduces bottomhole equivalent circulating densities (ECDs) and reduces lost circulation risk in wells in which conventional circulation pressures would break down formations. Until now, reverse circulation cementing has been performed only on land or in shallow-water wells in which the annulus was accessible from the surface to pump down. This paper describes the design, development, and validation of technology that enables subsurface reverse circulation. Gaps in technology have made it challenging to transfer reverse-cementing-placement techniques to primary cementing operations in deepwater. To reverse cement a liner, fluids must be pumped down the work string to prevent potential contact inside the riser and blowout preventer (BOP), and then fluids must be injected into the annulus downhole while full circulation continues. A tool system was developed to facilitate this unique flow path, provide alternative methods to set liner hangers, and provide flexibility for contingencies and other operational requirements. The developed subsurface reverse circulation tool system uses radio frequency identification (RFID) technology so that the tools can be operated remotely and repeatedly either by RFID tags or through surface-pressure pulse sequences. Three RFID-activated tools were designed: a circulation tool, a crossover tool, and a downhole flapper. The prototype tool system was first evaluated through bench testing of individual components and then through large-scale rig testing. During the rig trials, the entire system was run into a test well, and a multiday sequence of flow testing validated the function and performance of each tool. After successful testing in rig trials, the subsurface reverse circulation tools (RCT) were deployed in the Appalachia basin field, located in the Northeastern United States. This paper discusses the requirements of a subsurface reverse-circulation-cementing system. It describes the design, development, and validation of technology that enables subsurface reverse circulation. It also describes the prototype system that was built and the field testing results. This new capability enables the cement to be pumped down the work string and then to exit to the annulus at a point above the liner string.

Deepwater operators continually face technical and environmental challenges to drilling and completing wells safely and efficiently. To address both current and future challenges, the industry has leveraged radio frequency identification (RFID) technology to reduce risk, rig time, and nonproductive time (NPT) and to perform operations that traditional tools cannot perform. RFID technology has been integrated into drilling and completions tools to improve performance and reduce risk for offshore operations, such as drilling underreamed holes, spotting lost circulation materials, setting packers, opening stimulation sleeves, and performing subsurface reverse cementing. These tools use RFID tags released from the rig floor to enable downhole hydraulic power units (HPUs) to operate the tools. This paper describes criteria for selecting RFID-enabled tools rather than traditional tools, integration of RFID tools with operations, and value-added features enabled by RFID. Contingency, safety, and risk assessment factors are discussed, along with case studies validating performance and suitability of selected RFID tools. Three case studies describe how RFID solutions for drilling and completions were selected and applied in high-cost environments to address specific challenges and job objectives. Design and bench testing of RFID tools to enable future subsurface reverse cementing operations are also covered. The first case study describes an RFID lower-completion system that was successfully deployed into a southern North Sea extended-reach well. The system enabled remote control of flapper isolation valves and remote operation of stimulation sleeves to access the reservoir, which aimed to eliminate the need for intervention between treatments and ultimately improved fracture cycle time and reduced risk. In the Gulf of Mexico, an RFID drilling underreamer was used to set a liner shoe precisely at the casing point and eliminate a dedicated hole-opening run that would have been needed with traditional underreamers. The 8 1/2-in. hole section was drilled; but losses prevented the mechanical reamer from opening. Therefore, the 650-ft hole section was drilled to TD using the bit only. To eliminate multiple trips to take pressure samples and underream the hole section to 9-7/8 in., an RFID underreamer was placed below the measurement-while-drilling/logging-while-drilling (MWD/LWD) equipment. After pressure measurements were taken, the underreamer was actuated with RFID tags to enlarge the entire 650-ft openhole section with less than a 13-ft rathole. In the last case study, an RFID circulation sub was deployed above other bottomhole assembly (BHA) components, including an RFID underreamer and a conventional ball drop underreamer. This configuration enabled the operator to ream out the 22-in. cemented show track, underream the openhole section, and efficiently clean the wellbore at total depth. Because of BHA and standpipe pressure limitations, the RFID circulation sub was used in a split-flow application to bypass a percentage of the total flow to allow for a higher downhole flow rate. The sub helped to achieve high flow rates, high annular velocity, and turbulent flow, which contributed to better hole cleaning and improved wellbore integrity. Selecting the best tools and technology for specific applications results in streamlined applications and reduced operational risk. The methodology for selection, design, planning, and implementation of RFID drilling and completions tools identifies when RFID technology can be beneficial to deepwater operations.