Case Study - Constant Bottom Hole Pressure of Managed-Pressure Drilling Utilization to Maintain Wellbore Instability in East Java Drilling Operation, Indonesia

Abstract

Conventional open-to-atmosphere mud returns systems present a challenge when attempting to obtain energy resources that have previously been deemed economically or technically impossible to drill due to narrow drilling windows. A narrow drilling window significantly reduces the possibility of drilling to targeted depth effectively and efficiently from cost and safety perspectives. However, it is not always the pore pressure and fracture pressure gradients that define the drilling window, as has been observed in a field in East[MA(1] Java Province, Indonesia. In this instance, the actual drilling window lay between the wellbore instability and mud losses pressure gradients. Having the bottom hole pressure lower than the wellbore instability pressure would risk collapse of the wellbore, resulting in stuck pipe, or worse, a fishing job and requirement to sidetrack the well. Thus, a steady bottom hole pressure within that window was deemed critical to successfully drill to the section target depth. The application of Managed Pressure Drilling (MPD) was selected to drill the narrow drilling window and has resulted in being able to successfully drill to the targeted depth without wellbore collapse.

Data acquired from system-recorded drilling parameters enabled analysis of the wellbore condition and adjustment of parameters leading to a successful operation. Calculated friction pressure, ECD trend line, flow behavior and most importantly surface back pressure were compared as analysis subjects.

The utilization of MPD equipment, including Rotating Control Device (RCD) and Automated MPD Choke Manifold, enables surface back pressure to be applied to create the required bottom hole pressure sufficient to maintain wellbore stability within the narrow drilling window. With real-time results being applied on site, as described further in this paper, drilling hazards related to wellbore instability were significantly minimized, if not completely eliminated.