This paper will describe the scope of the Drilling, Completion, and Subsea construction activities and the approach taken by the BP Atlantis Wells Delivery Team in planning and execution. The BP Atlantis Wells Delivery Team recognized early that in order to efficiently execute all of the drilling, completion, subsea construction, and tie back operations to the producing facility, a very disciplined Project Planning and Scheduling approach would be required. A group of dedicated, competent scheduling professionals were assigned to the Drilling and Completion (D&C) Team and proved instrumental to the successful outcome. The D&C scheduling professionals complemented the other professional schedulers strategically selected for each of the project's necessary functional teams and key construction sites. The D&C Team started gaining competency in true project management through development and recruitment as early as three years (2001) prior to the start of development operations.
Deepwater drilling in the U.S. Gulf of Mexico [GOM] is usually characterized by very narrow pore pressure / formation fracture gradient [PP / FG] windows. In GOM deepwater drilling, firm control over Equivalent Circulating Density [ECD] is required to help ensure these fracture gradients are not exceeded to reduce lost circulation and minimize expensive non-productive rig time. With the high daily operational cost of deepwater drilling, operators are pushed to drill as fast as possible, yet maintain a stable borehole and remain within the pressure bounds of their particular drilling situation. For these reasons synthetic-based drilling fluids [SBM] are commonly used. Occasional hole pack-offs of large cuttings around the BHA during connections precipitated a study by the operator and drilling fluids service provider to thoroughly study the problem and recommend courses of action to help improve hole cleaning efficiency and optimize drilling operations. With the calculations of hole cleaning efficiency levels for various cases studied, accurate ECD predictions were made, and safe operating windows in terms of ROP were identified. These results were then applied on 2 GOM deepwater wells drilled with SBM having water depths between 2800 and 8800 ft. In this paper, the hydraulic studies and the field results are described and recommendations for future deepwater drilling operations are offered. Deepwater Drilling Overview Deepwater drilling operations in the Gulf of Mexico are often conducted with large modern vessels having a high day rate. Operators are pushed to drill as fast and as cheaply as possible and optimization of the drilling process is a constant objective. Typically operators ask the question to drilling fluid service contractors: "How fast can I drill this deepwater well and yet stay out of trouble?". To adequately answer this question, several key factors should be evaluated:High rates of penetration [ROP] in young GOM shalesLow annular velocities in the large-diameter wellbores and in the riserLong finger-like cuttings generated by the PDC bits in SBMDrilling fluid rheological propertiesECD levels below FG predictons or measurements This hydraulic study focused on several key areas:Particle settling rates of long finger-like cuttings under static and dynamic conditionsMinimum circulating time required before breaking connections to ensure no pack-offs around the BHA during connectionsHole cleaning efficiency as functions of particle size and shape, drilling fluid rheological properties, pump rate, and ROPPDC bit cutter sizes Hydraulic Modeling for Deepwater Drilling Applications Key variables. The modeling for vertical / near-vertical deepwater drilling applications is essentially the same as that used previously for high-angle extended-reach drilling applications1,2. Some variables such as drill pipe rotation and drill pipe eccentricity effects are less important while others such as drilled particle dimensions and shape become even more important. A listing of the key variables pertinent to the deepwater hydraulic modeling used in this study is given below:Drilling fluid density [including compressibility factor when using SBM]Drilling fluid rheological propertiesPump outputHole and pipe geometryDrilled particle dimensions and shapeRate of penetration
This case history outlines a recent North Sea Coiled Tubing Drilling Project (CTD). The Project consisted of 2 main phases – Onshore Testing and Offshore Operations. The objective of the Project was to drill a 1000 ft sidetrack from an existing water injection well via a window cut in 7 inch casing. If the operation were to be unsuccessful, the well would be returned to its original configuration. The existing perforations were successfully abandoned using a gel plug and a cement abandonment plug. A separate cement kick off plug was spotted above the cement abandonment plug. A pilot hole was drilled in the kick off plug and a window cut in the casing. Eighty feet of formation was then drilled. Following a bottom hole assembly change access to the window was lost. Subsequent attempts to re-enter the window were unsuccessful. The drilling bottom hole assembly continued past the window into the original wellbore. Attempts were made to re-cement to allow a new window to be cut. These operations were unsuccessful. The Project was terminated after 52 days on location. All cement was underreamed from the well, the perforations treated with an acid wash and the well successfully returned to injection.
Case Study - No abstract available.
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