Underbalanced drilling inverts the usual safety logic. The well is deliberately allowed to flow, and the control comes from surface equipment rather than from hydrostatic pressure. Everything depends on the rotating control device, the separation system and the ability to shut in quickly, which is why equipment specification and procedures matter more than in conventional drilling.

The circulating medium is chosen by the pressure reduction needed and the hole cleaning required. Dry air gives the lowest bottomhole pressure and the best penetration rate in hard dry rock but cannot handle water influx; mist handles small volumes of water; foam carries cuttings well at low densities; aerated mud gives moderate reduction with better control. Water production usually drives the choice.

The reservoir benefit is real but conditional. Avoiding overbalance avoids filtrate invasion and solids damage, which matters in damage-sensitive reservoirs. But underbalanced drilling can also damage formations through other mechanisms, including spontaneous imbibition when the well goes overbalanced during connections, so maintaining underbalance continuously is part of the benefit.

By the end of this training, participants will be able to:

• Explain underbalanced drilling concepts, objectives and benefits.
• Select candidate wells and assess the value case.
• Compare air, mist, foam, aerated and gasified fluid systems.
• Specify nitrogen generation and compressor requirements.
• Specify surface equipment, including rotating control devices and separation systems.
• Calculate hydraulics and hole cleaning for compressible fluids.
• Manage well control in underbalanced operations.
• Apply snubbing and pressure containment for tripping under pressure.
• Assess reservoir and formation damage considerations.
• Apply operating procedures and HSE requirements for continuous surface flow.

The course is instructor-led. Fluid system selection and hydraulics are covered with calculations and comparisons, and equipment and procedures with schematics, specifications and field procedures. Participants plan underbalanced operations for given wells and work through operational scenarios. The course is aligned with recognised well control practice and does not award accredited certification.

Organisations sending participants to this training will:

• Apply underbalanced drilling where it adds real value.
• Reduce formation damage in sensitive reservoirs.
• Improve penetration rate in hard rock and reduce differential sticking.
• Specify equipment and procedures that keep underbalanced operations safe.
• Meet the HSE and regulatory requirements of flowing-while-drilling operations.

Participants will:

• Understand underbalanced drilling methods and their selection.
• Be able to specify fluid systems and surface equipment.
• Be able to calculate compressible fluid hydraulics.
• Understand well control in underbalanced operations.
• Be able to plan and supervise underbalanced operations.

• Drilling engineers
• Drilling supervisors and company representatives
• Reservoir engineers assessing formation damage
• Underbalanced service company personnel
• HSE staff supporting drilling operations
• Well engineers working damage-sensitive reservoirs

Upon successful completion of this training course, delegates will be awarded an official Certificate of Completion issued by the Petroleum Engineers Association (PEA), an ISO 9001:2015 certified training organization. The certificate carries 10 Credits and formally records the total learning hours completed.

Each certificate is signed by the Course Facilitator and the CEO of the Petroleum Engineers Association, and serves as verifiable proof of professional training that delegates can present to employers and professional bodies worldwide.