Abstract

The implementation of Managed Pressure Drilling (MPD) equipment into a drilling operation or rig integration requires planning to establish appropriate procedures, guidelines, training, familiarization, as well as equipment placement and modifications to the drilling package when necessary. Often the drilling group initiating the use of MPD underestimates the time required for planning to integrate the system into their conventional drilling program and practices. As a result, they underutilize the full potential of the MPD system, instead focusing only on a single component of enhanced well control; early kick detection.

The real advantage of MPD systems are well documented in literature, and during influx management situations only becomes evident to those operators choosing to fully integrate the system, procedures and planning, into all operational activities such as drilling, tripping, circulating to kill or trip weight fluid, and cementing. The MPD system can help determine the pore pressure and fracture pressure window and quickly implement remedial action if the window is exited, be it increasing Equivalent Mud Weight (EMW), spotting Loss Circulation Material (LCM) or circulating out small influxes.

Though the rig contractor is often responsible for well control, typically the operator runs simulations prior to, and during drilling, based on the estimated and actual Leak Off Tests (LOT) to define a working conventional matrix for kick tolerance in each section. It has long been understood that many of the well control simulations and assumptions are grossly conservative, resulting in figures which are unrealistic forcing operators to set casing strings early to abide by in-house guidelines and standards.

MPD has begun to challenge this paradigm through pre-job simulations, followed by validation with real-time influxes and circulations, facilitating proper influx modeling. The ability to build this flexibility into influx management practices, when using MPD, reduces time spent dealing with small influxes, over-pressured zones which can easily be depleted, as well as reduce secondary events such as stuck pipe, plugged nozzles, lost BHAs and even lost hole sections. The MPD Operations matrix defines influx volumes and surface pressures the MPD system and Mud Gas Separator (MGS) can safely manage. The pressures are defined based on equipment limitations during normal operations and influx management control. The influx modeling results show expected surface pressures and flow rates through the MGS based on various kick intensities and volumes.

BG Egypt is one of a handful of operators that planned and used MPD to its full potential, circulating out influxes with success while drilling an extreme High Pressure-High Temperature (e-HPHT) well offshore Egypt. This paper outlines the steps taken to develop an MPD Operations matrix, as well as calculations required for surface equipment to ensure proper sizing, pressure limits, and equipment safety factors. Finally, it includes a comparison of a real-time influx circulated through the MPD system to that of a modeled data.

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