U-Tube Wells - Connecting Horizontal Wells End to End Case Study: Installation and Well Construction of the World's First U-Tube Well

Abstract

Abstract Although wellbores have been intersected before - both through planned intersections for the purpose of well control and through unplanned wellbore collisions - they have not been intersected for the purpose of actually joining their wellpaths to effectively create one smooth continuous conduit from one surface location to another. There is just one exception: the very large conduit between England and France! The purpose of this paper is to review the planning and execution of what is believed to be the world's first planned successful joining of two such horizontal wells, with a slotted liner to casing connection in between them. Introduction This paper gives a review of the scope of this project and of its desired outcome. The review will include a description of the plans for the wells including their trajectories and depths. Also included is a discussion of pre-planning activities with emphasis on the technology that was expected to make the planned intersection a success. This paper will discuss testing the specialized equipment needed to enable the intersection, mock ranging tests necessary to know the positions of the wells relative to each other, and the accuracy achieved through modified use of magnetic ranging techniques. Finally, rigsite operations will be reviewed, problems encountered will be discussed, and the lessons learned pertinent to similar efforts in the future will be disclosed. Project Goals and Objectives As with any trial or development of new technology, clear goals, objectives and expectations must be identified prior to design and implementation. It was clear from the onset that this was to be a producing well, and, as such, sand control was a concern. The intersection of the two wellbores was strictly for science and had no value to the actual production of the originally planned wellbore. The value obtained was the knowledge of what could be accomplished, so that future implementation of the technology could be considered for strategic planning purposes. Following this line of thought, the goals of this project were laid out as follows:Apply current directional drilling technology to see if two horizontal wellbores could be intersected end to end. Success was defined as intersecting the two wellbores with the drill bit and being able to enter the wellbore of the second well with the drilling assembly.Run standard steel casing through the intersection to prove that the two wellbores could be linked with solid tubulars. Success was defined as being able to run regular 7-in. casing through an 8 3/4-in. intersection point without getting the casing stuck in the hole.Join the two casing strings with a connection technique that eliminated sand production. It was agreed that the connection technique used on this first well would be as simple as possible. If this initial trial was successful, future work could be done on a more advanced connection technique. Reservoir Description / Surface Location The location selected for the trial of this technology was on land in an unconsolidated sandstone reservoir. The reservoir was only 195 m true vertical depth (TVD). The original field development plan called for several horizontal wells to be drilled under a river running through the field. It was decided that one of these horizontal wells would be an excellent location to test out this technology, as only one additional well would need to be drilled and connected to the currently planned well. Since one well was already planned to be drilled from one side of the river, a second surface location was selected on the opposite side of the river. This arrangement placed the two surface locations approximately 430 m from each other.