Riserless Drilling With Casing: Deepwater Casing Seat Optimization

Kotow, Kenneth J.

doi:10.2118/127817-ms

Cited by 6 publications

References 6 publications

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Drive Down Costs at Surface: Eliminate Contingency Strings in Deepwater

Nunzi¹,

Molaschi

Beattie

et al. 2010

All Days

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As the expense of deepwater drilling increases, efforts to eliminate or reduce non-productive time (NPT) can have a significant effect on overall costs. Current standard practices for installing surface casing strings involve multiple trips to first drill the hole section, and then run casing, land the wellhead, and cement. In many instances these casing seats are set shallower than is optimal due to anticipated hazards such as shallow gas or water flows and wellbore stability issues. Although with the current deepwater drilling model these practices are safe and reasonably efficient, they can limit the depth at which the casing can be set, as compared to the optimal depth with respect to pore pressures and fracture gradients. The use of current proven Casing While Drilling (CWD) techniques has effectively reduced NPT in several key areas including: flat-time reduction, shallow hazard mitigation, minimized/eliminated lost circulation, and improved cement placement and bond. Additionally, CWD provides the opportunity to push casing seats deeper, thus potentially eliminating contingency strings. Current CWD methods have not been applied to subsea surface casing applications, primarily because of the challenge of simultaneous drilling-in and landing the high pressure wellhead without damaging the seal surfaces on the wellhead housings. Additionally, many wellhead running tools are not designed to carry drilling torque. This paper discusses the benefits associated with drilling-in the surface casing in a subsea application. Introduced is a new CWD method and enabling technology that can significantly improve this phase of deepwater drilling operations. The complete process of drilling-in and running casing, landing the wellhead, and cementing can be achieved in a single trip. The benefits of CWD and features of the new technology are presented. When compared with current deepwater "best practice" models, an immediate 25% time savings is achievable. This technology also enables the utilization of less expensive floating rigs for cost reduction by batch drilling and setting of surface casing.

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Drive Down Costs at Surface: Eliminate Contingency Strings in Deepwater

Nunzi¹,

Molaschi

Beattie

et al. 2010

All Days

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Exploiting Shallow Formation Strengths to Deepen Riserless Casing Seats

Kotow¹,

Pritchard

2020

SPE Drilling &Amp; Completion

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Summary A significant improvement in deepwater well integrity can be accomplished by deepening the structural casing to have a dual functionality. This exploits the rapid growth of formation strength in the shallow first 1,000–2,000 ft below the seafloor. This first casing string in the deepwater well design would, firstly, support the axial and bending loads of the wellhead, blow out preventers, riser, and subsequent casing strings, as is the current practice, and secondly, provide sufficient casing shoe strength to mitigate the shallow drilling hazards. The basis for this recommended well design change has been the sporadic drilling performance in the execution of deepwater drilling operations, especially for exploration and appraisal wells, which has included some significant catastrophic well failures. The placement of the structural casing significantly deeper than current practice allows the well design to have larger casing diameters in the deeper well sections. This significantly improves deepwater well integrity by decreasing circulating friction. The current practice in the riserless section is to place casing seats above the identified shallow drilling hazards. The study reviews and evaluates the feasibility of setting the subsequent riserless casing strings according to the pore pressure and fracture gradient environment. This requires fewer casing strings to reach the planned well depths, which results in larger casing annuli across the deeper narrow pore pressure/fracture gradient (PP/FG) environment than in current deepwater well designs. This increase in annular space reduces the circulating friction across these sections, decreasing the loss of circulating/well kick cycles that are problematic and can prevent drilling from continuing to planned well depths. This study evaluates the effect of deepening the structural casing for the improvement of well integrity. The feasibility of various drilling methods and technologies required to deepen the structural casing, including conventional drilling, jetting, casing drilling, and reaming, are reviewed and evaluated. The method proposed for this deepening is the application of casing drilling technology. Its principles and merits are reviewed as it would be applied in a subsea environment in mitigating shallow drilling hazards and facilitating the deepening of the structural casing. Finally, the value of this proposal is evaluated in terms of meeting well objectives, improving well integrity, and reducing well construction time.

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Qualitative and Quantitative Analysis of the Stability of Conductors in Riserless Mud Recovery System

Qin

Chen

et al. 2022

Energies

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Riserless Mud Recovery (RMR) technology, as an emerging and efficient drilling method, is advantageous to reduce the shallow flow hazards and the number of casings. The wave current effect is one of the reasons limiting the application of RMR technology in deep and ultra-deep water, and fewer quantitative and qualitative analyses of the effect of the current are made on the stability of conductors. This paper investigates the influence of the overturning moment generated by the continuous subsea internal wave flow and the soil resistance to the conductor. The numerical simulation software ABAQUS is used to study the effects of sea state recurrence period, seabed soil properties, conductor material, driving depth in the mud, and conductor wellhead height on the stability of the conductor, and the influence weights of the factors affecting the stability of the conductor are analyzed using the weight analysis algorithm of extreme learning machine-mean impact value (ELM-MIV). Finally, the qualitative and quantitative analyses affecting the stability of the conductor are carried out, which provide reference values for the application of the RMR technology.

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Riserless Drilling With Casing: Deepwater Casing Seat Optimization

Cited by 6 publications

References 6 publications

Drive Down Costs at Surface: Eliminate Contingency Strings in Deepwater

Drive Down Costs at Surface: Eliminate Contingency Strings in Deepwater

Exploiting Shallow Formation Strengths to Deepen Riserless Casing Seats

Qualitative and Quantitative Analysis of the Stability of Conductors in Riserless Mud Recovery System

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