Multilateral Work-Overs: A New Possibility with Coiled Tubing

Abstract

Abstract The number of fields that are being developed, or re-developed, using multi-lateral wells to enhance the effective drainage from minimal surface facilities is increasing. Some of these types of wells have complex Level 3, or higher, junctions but the vast majority are still Level 1 junctions. Often drilling and other damage can be imposed on the various exposed leg well bores, as in the case of a Level 1 junction, while the other branches of the well are being drilled. This formation near well bore damage can, in the extreme, lead to a re-evaluation of the field development strategy as there has been no intervention method available to enter the various branches and perform effective stimulation or clean-up and, therefore, achieve the full production potential from the well. This paper describes a new Bottom Hole Assembly (BHA), enabling a new method to workover multilateral wells using coiled tubing. The BHA and its method of navigating through multi-lateral wells makes the assumption a smart and/or selective entry completion is not installed in the well. Therefore, the onus is on the BHA to intelligently navigate through a junction(s) whether it is an open hole or cased hole. The BHA's operational success however, is dependent on the geometry of the junctions. Examples from case studies performed in Canada Venezuela will be used to explain how the geometry is critical for successful operation of the tool. In addition, these case studies will explain what type of workovers have been tested and proven and what further possibilities exist. Introduction This paper describes a new bottom hole assembly (BHA), and a lateral entry guidance system (LEGS), herein referred to as the LEGS BHA. The LEGS BHA is a through tubing device and in its current form it is small enough to pass through the completion tubing and function in diameters of typical casings or liners. The BHA can cope with many completion types, however, operational considerations must be made for success. As a result it is now possible to perform workover treatments in well bores that were previously impossible to treat or in a manner which is more cost effective. This paper begins with a brief description of how the tool functions1. Next the completion type, geometry of the junction, and treatment fluid parameters will be reviewed to determine the iMPact these parameters have on the success of the job. Lastly, case histories of completed jobs will be cited to add practical, on the job realism to the discussion. LEGS BHA Function The LEGS BHA is an intelligent robotic device. The BHA controls its own actions depending on the environment in which it finds itself. When the BHA is at the entrance to a lateral, and activated, it will adjust its shape to point directly into the lateral. The BHA will perform the necessary movements without any assistance from the operator, other than its reliance on the supply of hydraulic power. In addition, if the BHA is pointing into the lateral it will communicate this information to the operator at surface.