Application of Managed Pressure Drilling Successfully Navigating Narrow Drilling Window Enabling Opportunity for Offshore Depleted Reservoir

Abstract

Extending field productivity within the reservoir which is currently facing natural decrease from virgin pressure is common challenge in mature field development. The depleted reservoir changes formation properties such as pore pressure and fracture pressure when the drilling window becomes narrower promotes further challenges.

As the reservoir pressure window becomes narrow, implementation of conventional drilling technique may induce common drilling problems, such as loss circulation, kick, differential sticking and so on. An alternative method known as Managed Pressure Drilling (MPD) which actively controls the annular hydraulic pressure while drilling, making connections, and tripping operation was implemented in this operation.

At the beginning of the 8.5in. section, extensive drilling window of 6.33ppg observed based on the subsurface information and preliminary study. The challenges appear when the well had just been drilled in less than for 2,300ft where the drilling window significantly reduced to 0.93ppg as a result of pore pressure ramp up. Meanwhile, fracture pressure point decreases at the same section which result in narrow drilling window of the 8.5in hole. At this condition, the utilization of conventional drilling methods promotes high risk of inviting undesirable conditions such as loss and kick. Without MPD implementation, it is considered impossible to reach target depth successfully.

Weatherford MPD system computes precise ECD model based on real-time drilling parameters and downhole condition. Surface Back Pressure is exerted during pipe connection to keep the well overbalance until target depth achieved. 

This paper describes MPD utilization as unconventional method to overcome drilling hazard related to pressure depletion and extend technical limits for prolonged and developed field. The publication is expected to unlock further advancement in Indonesia developed field with similar approach by other operators.