Case Study – Successful Real Time Well Pressure Profile Evaluation Achieved by Advanced Managed Pressure Drilling System Through MPD Static Pore Pressure Test and Dynamic FIT/LOT Techniques in Offshore Drilling Operations
Authors: Wang Ping , Singh Harpreet Kaur Dalgit , Palao Felbert , Quang Tuan Nguyen Le , Hong Duc Vu 
Published: October 2024

Drilling a well when there are high uncertainties in pore pressure and narrow drilling windows presents significant challenges. Even though Measurement While Drilling (MWD) technology aids in providing real-time Equivalent Circulating Density (ECD) during drilling operations, it falls short in delivering instantaneous updates on pore pressure and Formation Integrity Test (FIT) / Leak Off Test (LOT) results. Additionally, the minimum pump rate requirement for the MWD tool leads to real-time Pressure While Drilling (PWD) data becoming unavailable when drilling pumps are inactive, and the flow rate falls below the tool's minimal threshold. Consequently, achieving successful drilling results in such wells necessitates a more robust solution encompassing real-time updates and predictions for ECD, along with the concurrent ability to evaluate pore pressure and FIT values in real time.

The Managed Pressure Drilling (MPD) static pore pressure test (SPPT) conducted by intentionally reducing the bottom hole pressure (BHP) below the expected formation pressure with the automated MPD system with the drilling pumps shut off, proves to be valuable to achieve the well objectives. The test can be conducted at any chosen depths of interest, aiding in verifying a real-time lower boundary of the drilling window as well as defining the minimal surface back pressure (SBP) to be applied during MPD operation.

A defined MPD dynamic formation integrity test (DFIT) / MPD dynamic leak off test (DLOT) can be conducted at any desired depth below the casing shoe, which is essential for validating the upper boundary of the drilling window and effectively determining the maximum allowable surface back pressure (MASBP) during drilling operations. With advanced MPD system capabilities, which integrates a closed-loop setup, proprietary data acquisition, intelligent software simulation and automated control, it can provide real-time accurate downhole ECD, regardless of the drilling pumps are on or off, flow rate is high or low and can give instantaneous wellbore pressure control by adjusting the SBP.

The flexibility to conduct SPPT and DLOT / DFIT at any specified depth allows for real-time well pressure profile evaluation, enabling client to optimize drilling ECD during operation, minimize the risk of taking kicks, losses and pipe stuck, and decide whether to continue drilling until the planned total depth (TD) or to case off the well earlier.

The application of MPD in Gulf of Thailand (GOT) offshore drilling campaign demonstrates the value of performing multiple SPPT and DFIT for real-time well pressure evaluation. The comparison between MPD simulated ECD/ equivalent static density (ESD), PWD memorial data, as well as wireline logging results, proved that the advanced automated MPD system can provide reliable, accurate, and continuous down hole pressure data (up to 99.5% - 100% accuracy).

This case study highlights the successful MPD approaches with the combination of multiple tests and advanced MPD system contributed to the success of offshore drilling campaign in GOT.