Led by Senior Drilling Fluid Engineer Simulacrum
About this course
Underbalanced drilling inverts the central assumption of conventional drilling: instead of maintaining the hydrostatic column above formation pressure, the bottomhole pressure is held deliberately below it — the formation flows while drilling. The benefits are substantial when the reservoir is suitable: zero formation damage, no lost circulation in fractured or depleted zones, increased rate of penetration, and real-time reservoir evaluation from the produced fluids. The engineering challenge is equally substantial: the well is live throughout drilling, requiring entirely different surface equipment, pressure management, and well control procedures.
Four simulacra contribute. The Senior Drilling Fluid Engineer Simulacrum leads — UBD fluid systems (gas, foam, mist, aerated mud) and the pressure management that makes the operation possible are squarely their discipline. The Senior Reservoir Engineer Simulacrum assesses the reservoir for UBD suitability. The Senior Instrumentation & Control Engineer Simulacrum covers the real-time downhole and surface data systems. The Senior HSE Engineer Simulacrum covers the specific hazards of working with a flowing well during drilling.
Led by Senior Reservoir Engineer Simulacrum
The question
When is underbalanced drilling the right approach — and when is it not? This module places UBD on the pressure spectrum between conventional overbalanced drilling and managed pressure drilling, develops the four benefits of underbalance (damage reduction, ROP increase, differential sticking elimination, lost circulation avoidance) with the physical mechanisms behind each, then covers the reservoir suitability assessment and the four UBD fluid systems — gas, mist, foam, and aerated mud — ranked by the degree of underbalance each can achieve.
Outcome
The student can distinguish UBD from MPD and conventional drilling, assess a reservoir for UBD suitability, and select the appropriate UBD fluid system for a given well scenario with justification. (UBD fundamentals — when, why, and with what)
Sub-units
Led by Senior Drilling Fluid Engineer Simulacrum
The question
The equipment that makes UBD possible — the rotating control device that seals the annulus around the rotating drill string, the choke manifold that replaces mud weight as the primary pressure control tool, and the surface separation system that handles live hydrocarbons during drilling. This module covers passive and active RCDs, manual and automated choke systems, four-phase separator sizing, flare and gas handling design, nitrogen generation, the three UBD operational methods, and the multiphase flow regimes in the annulus — including why slug flow is the regime most dangerous to equipment and pressure control.
Outcome
The student can describe the RCD and choke manifold functions, explain how the choke controls BHP during UBD, describe the surface separation system sizing basis, and identify the four multiphase flow regimes and explain why slug flow is operationally problematic. (UBD equipment and multiphase flow)
Sub-units
Led by Senior Instrumentation & Control Engineer Simulacrum
The question
In conventional drilling, well control means killing a kick by weighting up the mud. In UBD, the well is already flowing by design — conventional kill procedures do not apply. This module develops the target BHP window concept, the dynamic pressure changes during connections and trips, the UBD-specific well control procedures (progressive choke closure, bullhead kill, and the decision to resume or convert), gas injection systems and their continuous adjustment, cuttings transport in gas and foam systems, and the real-time data acquisition that makes precise pressure management possible.
Outcome
The student can describe the target BHP window and the dynamic events that perturb it, explain the UBD well control procedure and how it differs from conventional well control, and describe the minimum velocity concept for hole cleaning in gas systems. (UBD pressure management, well control, and monitoring)
Sub-units
Led by Senior HSE Engineer Simulacrum
The question
A UBD operation brings live hydrocarbons to surface as the normal operating condition — not as an emergency. This module covers the drill string design requirements (sour service compliance, RCD element life management), surface separation sizing and the gas boot for slug flow damping, casing and cementing requirements (why cement integrity is more critical in UBD than conventional drilling), and the safety framework specific to UBD operations — continuous hydrocarbon presence, H₂S exposure risk, RCD stored-energy hazards, and the regulatory and environmental requirements including supplementary flaring permits.
Outcome
The student can describe the drill string and casing requirements specific to UBD, explain why cement integrity is more critical in UBD wells, identify four UBD-specific hazards, and describe the regulatory requirements for a UBD operation. (UBD surface systems, drill string, and safety)
Sub-units
Led by Senior Drilling Fluid Engineer Simulacrum
The question
A UBD programme is a different operational concept from a drilling programme with lighter mud. This module develops the structured planning process: reservoir assessment through equipment specification through the pressure management plan and its decision tree for contingencies. It then works through six common UBD problems (excessive inflow, insufficient underbalance, cuttings accumulation, RCD failure, choke plugging, foam collapse) with their diagnostic signatures and responses, followed by three case studies from actual UBD operations. The module closes with horizontal UBD, the MPD-to-UBD transition path, and closed-loop automated systems.
Outcome
The student can design a UBD programme for a given well scenario including fluid system, equipment, pressure management plan, and contingency decision tree, and diagnose and prescribe the response to the six common UBD operational problems. (UBD programme design and troubleshooting)
Sub-units