Old platforms are not well known for extended-reach drilling (ERD) operations mainly due to rig and hydraulics limitations. ERD wells demand robust rig capabilities, good hydraulics systems, and equipment reliability. In addition, the well profile, rotary steerable system (RSS), measurement-while-drilling (MWD) and logging-while-drilling (LWD) tools, surveying, and new technologies are extremely important to the success in drilling an ERD well. RSS and drillpipe selection are important factors for hydraulics optimization. Surveying techniques are also important for time saving and improved efficiency. An ERD well in the North Sea Statfjord field was kicked off in the 17 ½-in. section from the openhole cement plug through a 50-m window between the 20-in. casing shoe and 13 3/8-in. casing stump, ensuring a smooth well profile and reduced doglegs compared to the whipstock window exit. The 17 ½-in. section was drilled and landed at a 79° inclination using point-the-bit RSS technology, and the 12 ¼-in. section was drilled in two runs as planned using the point-the-bit RSS withstanding more than 550 h down hole. The 9 5/8-in. liner was run and floated successfully in the ~6000-m section. Strict adherence to surveying techniques and quality control processes proved very helpful to meet Operator technical requirements. The 8 ½-in. section was drilled and landed on top of the reservoir with an inclination decrease from 88° to 35°. New MWD technology was successfully used in drilling the 6-in. section. These latest technologies as well as employing appropriate techniques help to drill ERD wells on aged platforms like those in the Statfjord field. This paper will describe the planning and execution phases of a challenging ERD well drilled in the Statfjord field.
Using a concentric underreamer is a widely used technique for efficient wellbore construction. Most underreamers are fitted with lock-out systems to provide a means of drilling out the shoe-track with the cutters closed before enlarging the tool below casing. Several underreamers also provide a system to lock the tool closed after reaching TD to enable full flow while POOH for best possible cleaning. However, a major limitation these systems have in common is the underreamer cannot be reactivated once closed and the tool must be placed at top BHA due to the activation method. To increase reamer efficiency/BHA flexibility, a new hydro-mechanical system has been developed that makes it possible to perform multiple activation/deactivation of the underreamer by manipulating the flow rate in a short sequence allowing infinite open/close cycling for selective underreaming and more flexible placement opportunities within the BHA. The concept does not require any form of device to be pumped down the drill string. The system also increases the potential to save rig time on the activation/deactivation sequence. Through the field testing stage, it has been proven that the system works as designed under difficult drilling conditions. It delivers operator value by having the flexibility to selectively activate/deactivate and save rig time. The majority of runs have been on complex rotary steerable BHAs together with MWD/LWD systems and does not interfere with those tools’ operating range. All criteria set in the comprehensive field testing plan have been met to qualify the reamer as a viable downhole tool system. Several case studies will be presented to document successful operation of the on-demand surface controlled system with details about operator benefits including downhole flexibility, cost savings and increased safety.
In recent years, slot recovery to drill more wells in brownfields has posed different challenges due to extensive and time consuming Plug and abandonment (P&A) and casing cut and pull operations [SPE 173954]. In 2013, For the first time on Statfjord Field, a ruggedized point the bit rotary steerable system (RSS) and Gyro while drilling (GWD) were used to sidetrack off cement plug in 17 ½-in hole section through a narrow window (80m) between 20-in casing shoe and 13 3/8-in casing stump. This reduced risk and saved time by sidetracking and drilling the section in one run. In similar scenarios on previous wells, mud motors had been used to kickoff and sidetrack from a cement plug between the casing shoe and casing stump. Two runs were always required to complete the sections; first run with a dedicated sidetracking assembly (motor BHA) and a second run with a drilling assembly (RSS BHA). After this success another attempt was made in 2014 where 17 ½-in section was sidetracked and drilled to TD through 40m narrow window between 20-in casing shoe and 13 3/8-in casing stump in high well collision risk environment. Significant time and cost saving was achieved on this project. In 2015 a challenging well was planned where kick off had to be done through 37m window and close to six producers. Due to high risk of collision and no possible option of whipstock exit, new Point the bit RSS technology was employed to kick off in high magnetic interference environment and drill the section in one run. With the ruggedized point the bit RSS and GWD service, it was possible to constantly monitor direction and inclination in real time and thereby tracking the trajectory progress in the loose formations at shallow depth. This allowed to guard against dropping back to the mother bore and hitting the 13 3/8-in casing stump. Sidetracking in open hole from cement plug also increased formation strength at 20-in casing shoe and saved time/cost compared to whipstock exit. During execution all three wells were sidetracked successfully from motherbores in the first attempt and drilled to section TD in one run saving significant rig time and cost. This paper discusses the planning and execution phases of these three successful reentry wells drilled on Statfjord Field, one of the largest field on North Sea Continental Shelf (NCS).
fax 01-972-952-9435. AbstractThe value of multi-lateral well technology is increasing for the Statfjord field. This first cased multi-lateral well was drilled from the last vacant slot on the three Statfjord platforms. At the same time, limiting the production decline is increasingly dependent on successful drainage of remainiig oil pockets by WII1 drilling.This paper presents a case histo~covering the drilling and completion of the multi-lateral well C-23 on the Stadjord field. The well was drilled with two horizontal branches in the Brent reservoir, 1765 m and 2394 m long respectively. The two horizontal wellbores both penetrate the Tarbert and the Ness formation in the same direction, with a distance between each branch of only 80 m. Both laterals have 7" cemented liners in the reservoir. The lateral has been perforated in the Tatbert formation using a snubbing unit.The following list outlines tie main issues that will be described in the paper: q The commercial and technical just~lcation for drilling a multi-lateral well on the Statfjord field and the tectilcal requirements in each lateral.q Key issues in the planning phase. q The importance of establishing a dedicated team together with the service companies covering all disciplines.q The drilling phase, focusing on general well design, well profile, drilling technology (including the use of a rotary steerable system), running and cementing of 9 5/8" and 7" liners, as well as time schedule.q Design and requirements for the junction at 2376 mMD. Special emphasis will be put on the most critical phases, incIuding the solid whipstock exchange and re-establishing communication to the main bore.q Running and cementing the 2421 m long 7" liner in the lateral, and the use of a proprietary tough cement.q Completion design and production strategy.
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