This paper describes a recent Directional Coiled Tubing Drilling (DCTD) job that was completed for an independent operator in the Appalachian Basin. The objective was to access target zones identified adjacent to a recently drilled, vertical well using a lateral sidetrack. The target thickness was around 15ft so accurate depth control was critical. It was also considered essential that the entire reservoir section be drilled underbalanced to minimise formation damage. The challenge was to deliver a productive horizontal sidetrack in an effective and cost-efficient manner. The field development strategy required costs to be kept to a minimum, but the use of high-tech equipment was essential to delivering the production improvements. A 3.2 inch DCTD Bottom Hole Assembly (BHA) and a specialised DCTD engineering software package were enabling technologies. A multi-disciplinary approach was adopted to plan and execute the sidetrack. This approach required inputs to the planning process from all stages in delivering the well, which included: 3D seismic, well trajectory planning, drilling engineering, completions. This project was ultimately successful in that a dry hole was re-entered and sidetracked to create a productive well, thereby validating the technology and multi-disciplinary approach of the team. The lessons learned from this operation can be used to optimise the planning of future wells and maximise the value of re-entering marginal wells and fields.

A set of 5 wells were to be drilled with directional Coiled Tubing Drilling (CTD) on the North Slope of Alaska. The particular challenges of these wells were the fact that the desired laterals were targeted to be at least 6000ft long, at a shallow depth. Almost twice the length of laterals that are regularly drilled at deeper depths. The shallow depth meant that 2 of the 5 wells involved a casing exit through 3 casings which had never been attempted before. After drilling, the wells were completed with a slotted liner, run on coiled tubing. This required a very smooth and straight wellbore so that the liner could be run as far as the lateral had been drilled. Various methods were considered to increase lateral reach, including, running an extended reach tool, using friction reducer, increasing the coiled tubing size and using a drilling Bottom Hole Assembly (BHA) that could drill a very straight well path. All of these options were modelled with tubing forces software, and their relative effectiveness was evaluated. The drilling field results easily exceeded the minimum requirements for success. This project demonstrated record breaking lateral lengths, a record length of liner run on coiled tubing in a single run, and a triple casing exit. The data gained from this project can be used to fine-tune the modelling for future work of a similar nature.

Summary A set of five wells were to be drilled with directional coiled tubing drilling (CTD) on the North Slope of Alaska. The particular challenges of these wells were the fact that the desired laterals were targeted to be at least 6,000 ft long, at a shallow depth, almost twice the length of laterals that are regularly drilled at deeper depths. The shallow depth meant that two of the five wells involved a casing exit through three casings, which had never been attempted before. After drilling, the wells were completed with a slotted liner, run on coiled tubing (CT). This required a very smooth and straight wellbore so that the liner could be run as far as the lateral had been drilled. In this paper, we focus on one of the two wells on which triple casing exit was performed. However, the same considerations and results apply to the other wells on which the same technology has been used. Various methods were considered to increase lateral reach, including running an extended reach tool, using a friction reducer, increasing the CT size, and using a drilling bottomhole assembly (BHA) that could drill a very straight well path. All of these options were modeled with tubing forces software, and their relative effectiveness was evaluated. The drilling field results easily exceeded the minimum requirements for success. This project demonstrated record-breaking lateral lengths, a record length of liner run on CT in a single run, and a triple casing exit. The data gained from this project can be used to fine-tune the modeling for future work of a similar nature.