Understanding Liquid Loading Will Improve Well Performance
Robert Sutton, Thursday, June 16th, 2016 (San Juan College, School of Energy)
The key take-away: Illustrate that complex well geometries increase the critical velocity requirement and that failure to account for this can result in loss of both production and reserves.
Operators of natural gas wells have long used the Turner equations to calculate critical gas velocity to keep gas wells unloaded. The original Turner method was developed for vertical wells with analysis performed using wellhead conditions. However, this methodology is only applicable to high pressure, vertical wells with a simple completion geometry. Modern well design most often employs complex geometries including slant, s-shaped and horizontal well paths as operators seek to reduce costs and the environmental footprint while maximizing the production rate potential. These geometries require special consideration when estimating critical velocity. Wells produced below the critical velocity will develop a static liquid column which can damage the reservoir and impede well productivity. Proper diagnosis of this problem will improve well performance and ultimate recovery.
The purpose of this presentation is to provide an overview of historical techniques for detecting liquid loading and to provide modification to the classical Turner method that address contemporary well designs. The discussions will include recent advances which address the proper evaluation point based on reservoir and well conditions. The talk will also compare the modified Turner methods to the use of multiphase flow pressure drop models for predicting liquid loading and will demonstrate the superiority of using a modified Turner’s method to determine critical velocity. Flow loop videos are used to illustrate the result of producing below the critical velocity. Potential improvements will be quantified through field examples for conventional, unconventional and horizontal well applications.
Rob Sutton is a petroleum consultant in Houston, Texas. He started his 35 year career with Marathon Oil Company in their Gulf Coast Offshore District in 1978. He moved to Marathon's Denver Technology Center in 1985 where he worked in the Reservoir Management Department and developed Marathon's in-house nodal analysis software. He moved with the technology organization to Houston in 2001 and retired from Marathon in 2014.
Rob received a BS in Petroleum Engineering from Marietta College. He also holds an MS in Petroleum Engineering from the University of Louisiana at Lafayette. He has authored 27 papers for SPE along with 10 journal publications. He wrote the chapter on oil PVT correlations in the recently updated Petroleum Engineering Handbook as well as coauthored a chapter in Gas Well Deliquification. Rob received SPE’s 2014 Production and Operations Award.
Rob was an SPE Distinguished Lecturer for the 2012-13 lecture season.