One of the main challenges that today’s drilling operation faces is uncertainty in formation pressures. Excessive overbalance between the Equivalent Circulating Density (ECD) and formation pressure causes unnecessary, often detrimental formation breakdown, while underbalance drilling increases the risk of drilling kicks which can lead to catastrophic blowouts at the worst case scenario. Due to the uncertainty in formation pressures, managing the ECD becomes quite challenging and difficult. The ECD presents a significant drilling parameter particularly in wells that have a narrow window between the fracture gradient and pore-pressure gradient. Therefore, as early as possible knowledge of pore pressures, is highly sought after by the operating company.
Formation pressure while drilling (FPWD) technology has proved over the past few years to provide accurate formation pressures during drilling. Apart from the use of formation pressures to calculate fluid gradients, mobilities and identify tight zones, it has also found its usefulness in ECD management.
This paper presents a case study from an onshore horizontal well in the Middle East, which discusses the successful application of FPWD in ECD management. Due to the lack of reservoir formation pressure data, a heavier mud than necessary was used to drill the reservoir section to avoid risk of formation fluid influx. However, accurate measurements of pore pressures in real time recorded from a FPWD tool indicated lower pore pressures than expected. Consequently, based on that real time data, decision was made to significantly reduce the ECD, which resulted in improved hole cleaning, performance, increased rate of penetration, among other benefits.