Highly deviated and horizontal wells present challenges for many types of coiled tubing (CT) interventions. Surface measurements that feed into theoretical and predictive models for critical downhole parameters are reasonably accurate in vertical wells. However, in highly deviated and horizontal wellbores the models are less reliable. This is especially true with regards to understanding downhole forces as the significantly increased uneven drag on the coil, due to wellbore interaction, can cause buckling and erratic stick-slip behavior. Data gathered via new CT technology has indicated that inaccuracies in the interpreted downhole load measurement can be as high as 20-200 percent. In operations that require tight control (e.g. setting weight on shifting tools and packers), inaccuracy of calculated downhole forces in extended laterals can lead to an increase in service quality incidents. With the industry targeting deeper horizontal wells it is becoming increasingly clear that predictive models alone are insufficient to fully understand the dynamic behavior of CT string and its interaction with the wellbore.
Victor Lyashkov is a Schlumberger senior intervention production engineer at the Houston Conveyance and Surface Equipment technology center. He has broad field, management, and engineering experience in well interventions and has worked in Western Siberia, the United Kingdom, the United Arab Emirates and the United States. Lyashkov holds an MSc in mechanical engineering from Bryansk State Technical University.
Richard Morrison is a Schlumberger engineering project manager for the ACTive product line. He joined Schlumberger in 2006 as a mechanical engineer in new product development. He was the lead mechanical engineer on the ACTive Tension & Compression project from 2007 to 2011 when it commercialized, after which he stepped into his current role. Morrison holds a Bachelor’s degree in mechanical engineering from University of Nevada as well as a Master’s degree in mechanical engineering from Arizona State University.
Fernando Baez joined Schlumberger in 2000 and is currently the intervention diagnostic domain manager for well intervention services in the Middle East. In his current role, he leads the workflows for interpretation of real-time downhole measurement systems with CT and slickline. Baez received his MSc degree in mechanical engineering (honors) from Universidad de los Andes, Colombia, in 1999.
Critical Real-Time Measurements for CT Intervention
The need for measurements during CT operations is not new. Memory tools have been used during CT interventions to better understand downhole conditions, but they add additional runs to the intervention and lack the real-time component. Mono- and hepta-cables have been successfully installed in CT and used for production logging for over a decade. However, installing e-Line CT on mono- or hepta-cables exerts additional CT weight that can result in additional drag forces, further intensifying the stick-slip effect in deviated wells. This effect is the suspected cause of multiple unexpected failures during attempts to convey certain wireline downhole tools such as a flow scan imager and calipers. These tools are sensitive to compressive loads, limited to logging applications that impose restrictions in flow rates, and sometimes incompatible to fluids used in well interventions. In