Post Well Pore Pressure Analysis Facilitated by Managed Pressure Drilling

Abstract

Real-time managed pressure drilling (MPD) data is analysed post drilling for the purpose of identifying ‘formation pressure events’ which are quantified to define the actual wellbore formation pore pressure (PP) profile.

MPD software allows the operator to maintain a desired bottomhole pressure (BHP) by application of surface backpressure (SBP) at the choke manifold. The system closely monitors; flow in, flow out and BHP within the closed system to identify minor influxes to the wellbore which are controlled before they can propagate in size by automatic application of SBP. Utilisation of MPD technology in combination with downhole pressure monitoring, allows for a series of micro-influxes to be analysed to map a formation PP profile.

MPD facilitates the analysis of the PP by performing dynamic PP testing. The PP can be accurately determined by reduction of BHP until a miniscule influx is detected in a controlled manner by MPD.

MPD allows BHP to be maintained close to the perceived PP. Maintaining this BHP will result in a diminishing overbalance when drilling into overpressured zones. The diminished overbalance will result in a micro-influx which will be identified by MPD and controlled by application of SBP, while knowledge of the PP is obtained.

Acquisition of data from micro-influx events induced or otherwise, documents the PP regime as it is drilled allowing post well interpretation to build a detailed picture of the PP. A case study is presented which illustrates how a number of PP events can be analysed post well to map the PP of a hydrocarbon bearing reservoir.

This paper illustrates how application of MPD not only provides enhanced safety benefits from a well control perspective by early kick detection, but allows the operator to gather critical formation pressure data, as the formation pressure profile is mapped while drilling.