Casing While Drilling Level 2 as Mitigation for Shallow Gas and Loss Circulation Hazards in Surface Section

Abstract

Casing while drilling Level 2 was introduced to mitigate problems in the surface section of Mutiara and Pamaguan Field in East Kalimantan. These two fields have historical shallow gas and loss circulation hazards in surface section. Following a blowout incident in Pamaguan in 2012, new policy was introduced for drilling the surface section in Mutiara and Pamaguan. A pilot hole must be drilled, and additional surface casing shall be set. Although considered safe, longer drilling days and vulnerability to repeated loss circulation made this method inefficient. A new approach to mitigate the problem was proposed by introducing casing while drilling Level 2 in 2020 drilling campaign. Many papers already discussed about the effectiveness of casing while drilling to mitigate loss circulation. However, a limited number of papers discuss casing while drilling to mitigate shallow gas. Costeno et al, 2012, discussed the use of casing while drilling to mitigate shallow gas. However, the risk of shallow gas was low and there was no shallow gas record during the execution. This paper specifically discusses about utilizing casing while drilling (CWD) technology to mitigate not only loss circulation, but also shallow gas risks during surface hole interval. Both hazards occurred in several wells during job execution and CWD with its plastering effect has managed to drill troublesome surface hole safely, thus making it the better alternative to achieve efficient drilling in comparison with the previously used pilot hole method.