Heavy Oil Field Development Revitalized through Horizontal and Lateral Re-Entry Wells
Authors: Popa Andrei S. , Cassidy Steve 
Published: October 2014

Heavy oil assets represent a significant component of Chevron's portfolio with a continuous potential growth given the well understood recovery mechanism and established processes for reservoir management. Technology advancements such as horizontal drilling and completions enable ingenious and lucrative re-development projects to achieve maximum recovery. This paper describes the success of the reservoir management practices used in one of the company's heavy oil reservoirs to revitalize production and arrest the decline through use of horizontal well drilling and high angle lateral re-entry wells. Deployed in 2013, the new workflow using artificial intelligence enabled a significant step change in the selection outcome of horizontal infill and well re-entry candidate selection. Using this methodology increased production output was realized and it is expected to achieve recovery factors as great as 75% in some of the nine producing sands of the reservoir.

With over 20, 000 wells drilled and more than 100 years of production history, the Kern River Field presents an interesting and attractive challenge for reservoir management, identification of widespread development opportunities, and continued optimization. Located in Kern County, California, the heavy oil reservoir consists of nine productive sands, with additional stratigraphic complexity introduced by the braided stream depositional setting. The field is currently produced by steam injection, and the primary production mechanism is gravity drainage.

Initial development of the field consisted of vertical well drilling with pattern development as dense as 5/8 acres. The field reached a peak production in 1997 followed by a steep 6% decline driven by a rapidly shrinking number of new recompletion and expansion opportunities. With the introduction of horizontal wells in 2006 and lateral re-entry completions in 2012, the production decline curve flattened and today the decline rate is around 2 %.

Prior to 2013 the full field 3D reservoir model was the primary tool used for the identification and selection of horizontal well drilling. While initially successful, the hard cut-off filtering criteria lead to a quick exhaustion of the candidate pool and threatened the future of the program. In December 2012 an intelligent approach to well selection identification was introduced using fuzzy quality maps. This approach expanded the pool of candidates tenfold with more than 600 well locations identified.

Building on the quality maps created for the horizontal well identification program, and integrating Voronoi mapping for reserves, engineers were able to identify high potential areas to place lateral re-entry completions. Initial performance review conducted revealed that the lateral re-entry wells identified and drilled in 2013 had a drastic increase in production. In some cases after lateral re-entry production increased from less than 1 bopd to more than 50 bopd at peak.

The examples presented in this paper showcase not only the reservoir management practices but also the use of technology to extract the maximum value from mature heavy oil fields. Due to the success of these programs, the workflows are now being expanded to other Chevron heavy oil fields the San Joaquin Valley.