Challenging Standard Practices: How a Review of Standard Practices Resulted in an Improvement in BHA Reliability

Abstract

Bottom Hole Assembly (BHA) reliability is critical to deliver wells on-time and within budget. Improving reliability is a combined effort between operators and service providers. In the D.J. Basin, well drilling times are between 48-60hours. A 10-hour trip for failure can account for over 20% of well time. Onshore operations have benefited from focusing on performance metrics. To achieve some metrics, drilling procedures have been implemented that may have had unintended consequences. It will be shown how a review and change to standard drilling practices helped improve BHA reliability BHA failures occurred on 35% of wells in the operating area of this project. Although steps were taken, such as third-party inspections of tool builds, trialing various BHA components, and adjusting drilling parameters, failure still occurred. Failures were split between motors, measurement while drilling (MWD) and rotary steerable system (RSS) tools. Motor chunking was present on most BHAs, regardless of vendor. Chunking either caused motor failure or blocking of MWD or RSS components despite filters downstream of the motor. A review of operating practices with the service provider concluded that modifications could reduce on-bottom and off-bottom BHA loads and improve reliability. A series of procedural changes were made to connection practices, back-to-bottom procedures and downlink practices and the results tracked. Increased motor reliability was the main goal and would be determined by post-run observations of chunking evidence. A secondary aim was to reduce other failures that may be caused by mechanical overload. After implementing the procedural changes, the first 11 wells were completed in a single run, with no non-productive time (NPT) for BHA failures and no motor rubber observed in filter subs. Several wells were also able to re-run the RSS resulting in an invoice credit and further cost savings. Although the changes have resulted in a small increase in connection time per well, the pad level time savings from improved BHA reliability offsets that cost. There is also greater confidence that the applied drilling parameters start from a zero-load point. This allows the operator and service company to have more confidence that downhole tools are not being overloaded and gives more opportunity to optimize drilling parameters for performance. This paper will challenge standard practices that target incremental performance gains but may result in seemingly unrelated BHA reliability problems. Modeling drillstring stretch and understanding BHA load conditions has resulted in reliability improvements for the basin that can be applied to similar applications for the operator and the industry.