Factory-Model Approach Improves Performance of Coiled-Tubing Drillout

Abstract

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 191689, “Factory-Model Approach for Successful Coil-Tubing-Unit Drillout Operations in Unconventional Wells,” by Jesus Barraza, SPE, and Chris Champeaux, SPE, Chevron; Heath Myatt, SPE, and Kyle Lamon, C&J Energy Services; Ryan Bowland, Spartan Energy Services; Troy Bishop, SPE, and Jerry Noles, SPE, Coil Chem; and Rocky Garlow, RGC Consulting, prepared for presentation at the 2019 SPE Hydraulic Fracturing Technology Conference and Exhibition, The Woodlands, Texas, USA, 5–7 February. The paper has not been peer reviewed. As drilling and fracturing operations improve, there is a need to adapt current coiled-tubing (CT) drillout processes to a more fit-for-purpose approach applicable in any area, regardless of lateral length, number of plugs, and reservoir target. This paper presents a factory-model approach to improving CT drillout performance that has been used successfully for more than 3 years and has become standard practice. The paper includes detailed discussion of the methodology used to create a successful, repeatable, and operationally safe process; field case studies and results; and engineering, design, and implementation of new technologies to improve the process. Introduction CT practices have become increasingly effective in plug drillout operations by reducing the operational cost, environmental exposure, and time to production. Techniques for no-wiper or short trips and plug milling, added benefits from extended-reach bottomhole assemblies (BHAs), and improved fluid-system monitoring methods have helped enhance overall performance. However, there are still components within each of these techniques that can be evaluated. Background and Methodology Results of a thorough evaluation of the CT drillout process revealed that the factors with the greatest influence on improving performance included the following: Wellbore trajectory Plug type CT size BHA selection Fluid-rheology quality assurance/quality control (QA/QC) Real-time modeling Communication Wellbore trajectory is an important factor because it has a major effect on the ability of a CT unit to reach plug-back total depth. High tortuosity in the lateral section can cause plug parts and sand to settle on the low side of the wellbore, making adequate cleaning of the hole by increasing overall friction difficult. Proper plug type and design serve two purposes: to provide a barrier between stages during hydraulic-fracturing operations and to be easily removed from the wellbore during drillout. Ideally, a fully composite plug should be selected because the lower specific gravity of the material aids in removal. The proper CT size can lead to a more-successful drillout because it allows for higher pump rates, leading to better hole cleaning. Additionally, larger outer-diameter CT (23/8 in. or greater) ensures sufficient weight on bit (WOB) in the toe of longer laterals to reduce friction pressure and protect against helical buckling.