Multilaterals are often cited as technology that can be implemented to maximize reservoir-recovery rates. However, few operators have been willing to put multilaterals into practice. The most frequently cited reason for not considering multilaterals is risk. Without access to data to show otherwise, it is difficult to overcome this industry perception of risk toward multilateral technology (MLT). This often leads to decisions not to run the technology on the basis of anecdotes of failed installations that occurred more than a decade ago with technology and circumstances far removed from what would be seen today. To move toward addressing this problem, the authors present a study of data from 22 years of actual multilateral-well applications, examining the true reliability of the technology.
In this study, the records of one multilateral service provider have been analyzed from more than 800 actual multilateral installations, and success and failure rates have been determined. The reliability of multilaterals has been compared with the reliability rates of other wellbore-completion and -construction technologies.
In the context of this study, reliability has been defined as the ability to successfully construct and complete a multilateral junction. Failure has been defined as the loss of either the lateral, main bore, or junction (and therefore access to both legs). Where failures have occurred, a study to determine root cause(s) has been undertaken.
MLT, which was first implemented by Alexander Grigoryan in 1953, came into modern practice in the 1990s. Although it is not failure-free, the reliability of multilateral wells has improved remarkably during the past 22 years. This improvement in reliability has occurred as the complexities of multilateral installations have increased. This paper shows that successful completion rates of multilateral junctions have improved from slightly more than 87% for the period of 1995 to 1999 (with more than 100 junctions completed) to slightly more than 98% for the period of 2010 to 2015 (with more than 220 junctions completed). This improvement is the result of continuous planning, development of and adherence to procedures, management of change, communication, and continuous improvement.
This is the first known study of multilateral reliability that encompasses a large body of data during a significant time period. The results presented should enable operators to make fact-based decisions about the reliability of MLT and about whether this technology should be considered for implementation into resource-development plans.