Changbei is a marginal tight gas field located in Yulin, China. Historically similar fields had been developed with fractured vertical wells. To improve well productivity and reserve recovery, a new concept of long dual horizontal wells (2 × 2,000m legs) has been developed to recover the gas reserves more cost effectively. The initial drilling campaign had proved to be challenging due to:
Bit balling while drilling the 12¼ hole section
Difficulties in landing of the 9 5/8" production casing accurately, due to drilling of coals just above top of QA reservoir and geological uncertainties
Unstable carbonaceous claystone or coal across the long horizontal reservoir sections
High Non-Productive Time (NPT) due to failures of downhole equipment and drillpipe
High drilling costs as a result of the above stated problems
To make the field development a success, the Changbei wells team had formed a performance improvement team, which turned around the wells performance with DTL, LEAN and Performance Improvement Staircases. As a result, the wells costs and drilling times have been halved. The team has since maintained their drive for continued drilling performance improvement and made drilling operations a successful story.
This paper will discuss the key successful factors for Changbei horizontal drilling. It will first of all introduce the dual lateral horizontal well design. This will be followed by a summary of the drilling problems encountered from the initial drilling campaign. The paper will then address how the various tools such as DTL, LEAN (a step-change performance improvement methodology) process, RTOC and Performance Improvement Plan (PIP) have been applied effectively to drive down the drilling times and wells costs, with the application of selected localized products and services.
It will also illustrate how to manage changes during horizontal wells drilling campaign with two case studies including change of the drilling strategy and the re-drill of one of the horizontal legs in well CB8-3.