Simultaneous Drilling, Completions Concept Hopes To Extend Drilling Distances to 30 km
Authors: Wilson Adam 
Published: May 2018

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 178859, “Long-Reach Well Concept,” by Sigmund Stokka, SPE, Eric Cayeux, SPE, David Gardner, SPE, Steinar Kragset, Hans Petter Lohne, SPE, Erlend Randeberg, Hans Joakim Skadsem, and Bjarne Aas, IRIS; Henrik Kyllingstad, Hole in One Producer; Torgeir Larsen, Wintershall; and Arild Saasen, SPE, Det Norske Oljeselskap and University of Stavanger, prepared for the 2016 IADC/SPE Drilling Conference and Exhibition, Fort Worth, Texas, USA, 1–3 March. The paper has not been peer reviewed.
Current extended-reach-drilling (ERD) well technology limits the well lengths to approximately 12 km, with a horizontal departure of approximately 10 km. This paper presents a concept that enables simultaneous drilling and completion, with an aim to extend well reach substantially and with an ultimate objective of constructing 30-km-long production wells. Longer-reach wells can be used to drain remote reserves using existing production facilities and to provide a means to access reservoirs located beneath environmentally sensitive areas.
Concept Description
The concept introduces a new way of constructing production wells. During drilling, the annulus is closed by packers and the well is drilled to the final target with one hole diameter. A steerable drilling module performs the drilling operation. A dual-wall casing replaces the drillstring and enables the drill cuttings to be transported to surface inside the inner casing. The string does not rotate during drilling but is pulled forward by a multiple-traction system com-posed of traction modules tentatively spaced at 120-m intervals along the drillstring. Tools for well completion, such as sand screens, sensors, and control systems, are integrated into the dual-wall casing.
Fig. 1 shows an illustration of the tool string with two dual-traction units spaced with an intermediate-casing section. Dual-traction units are required to maintain zonal isolation at all times and to enable the string to move smoothly and continuously into the ground as drilling progresses.
System Description
This project investigated two versions of the concept: a casing-drilling system sized for 12¼-in. hole and a liner-drilling version deployed on drillpipe for an 8½-in. hole size. Recently, the project has focused primarily on the liner version. The developed solutions, however, are applicable to both versions.
The liner concept provides a liner-drilling solution able to extend the well from a pre-existing production-casing-shoe depth. The liner assembly that can be deployed will be limited by the depth of the production-casing shoe and, thus, can enable the construction of wells up to perhaps 20 km in length. The liner is deployed using standard drillpipe; therefore, conventional rig equipment can be used for the drilling/completion operations. In contrast, the full production-casing-drilling concept can drill deeper wells but will require considerable modifications to topside facilities.
The main components of the liner system are a pipe-in-pipe circulation system and multiple hydraulically powered traction units to overcome mechanical friction and provide weight on bit. The liner system is deployed on drillpipe using a running tool that channels the mud supply and cuttings returns in addition to connecting data communication between the surface and bottomhole assemblies (BHAs).