Purpose of Vacuum Degasser in Drilling: Cost Savings, Risk Reduction, and Operational Benefits
When drilling a well, every piece of equipment on the solids control system has a job. Shale shakers remove large cuttings. Desanders and Desilters take out fine solids. Centrifuges recover barite. But one device often misunderstood is the Vacuum Degasser. What is its real purpose? Why do rig operators spend money on it? This article explains the purpose of a vacuum degasser in drilling from a practical, business‑oriented perspective: how it saves money, reduces risks, and improves overall drilling efficiency. AIPU Solid Control vacuum degassers are used as the reference example.
1. The Single, Overarching Purpose
The fundamental purpose of a vacuum degasser in drilling is to remove entrained and dissolved gases from drilling fluid. That is the technical answer. But from an operational and financial viewpoint, the purpose is to prevent the costly and dangerous consequences of gas‑cut mud.
Gas‑cut mud is drilling fluid that contains small gas bubbles. These bubbles are not large enough to be a “kick,” but they are large enough to cause serious problems. A vacuum degasser eliminates these bubbles so the mud returns to its designed density and properties.
2. The Four Main Operational Purposes
Let us break down the “purpose” into four specific operational goals that directly affect rig performance.
Purpose #1: Maintain Hydrostatic Pressure and Well Control
Drilling fluid exerts hydrostatic pressure against the formation. Gas bubbles lower the fluid’s density, which reduces that pressure. If the pressure drops below formation pore pressure, formation fluids can flow into the well – a kick. If not controlled, a kick becomes a blowout.
What the vacuum degasser does: It removes gas bubbles, restoring mud density to its original value. This maintains the designed safety margin against kicks.
AIPU advantage: AIPU vacuum degassers achieve ≥95% gas removal efficiency, quickly restoring mud weight.
Purpose #2: Prevent Mud Pump Cavitation and Damage
Mud pumps are positive displacement pumps. They are designed to pump liquid, not gas. When gas bubbles enter a pump cylinder, they collapse violently under compression. This cavitation erodes liners, damages valves, and can break power ends.
What the vacuum degasser does: It removes gas before the mud reaches the pump suction, eliminating cavitation.
Cost impact: Pump liner life can double from 800 to 1,600 hours. Valve life increases similarly. On a deep well, this saves tens of thousands of dollars.
Purpose #3: Improve Downstream Solids Control Performance
Desanders, desilters, and centrifuges all rely on the density difference between solids and liquid. Entrained gas reduces the effective density of the liquid phase, making separation less efficient. As a result, fine solids are not removed properly, and more solids recirculate.
What the vacuum degasser does: By removing gas, it restores the density differential, allowing hydrocyclones and centrifuges to work at their designed efficiency.
Result: Cleaner mud, less bit and pump wear, fewer solids‑related problems downhole.
Purpose #4: Protect Personnel from Toxic Gases
Formation gases often include hydrogen sulfide (H₂S). H₂S is lethal even at very low concentrations. It can escape from gas‑cut mud at the shale shakers or in the mud pits.
What the vacuum degasser does: It extracts H₂S from the mud and directs it through a closed vent line to a flare ignitor (such as AIPU’s APFI series), where it is safely burned. Personnel are never exposed.
Safety impact: This is not a cost saving – it is life saving.
3. What a Vacuum Degasser Is NOT For
To fully understand its purpose, know what it does not do:
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It does not handle large gas kicks – that is the job of a mud gas separator (MGS).
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It does not remove solids – that is for shakers, desanders, desilters, and centrifuges.
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It does not replace a mud agitator or shearing pump.
The vacuum degasser is a continuous gas‑polishing device for normal circulation, not an emergency kick separator.
4. Where It Fits in the System – Location Tells Purpose
The placement of the vacuum degasser in the solids control sequence reveals its purpose:
Flowline → Shale shakers → Vacuum degasser → Desander → Desilter → Centrifuge → Suction pit → Mud pumps
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After shakers: Large cuttings are removed first so they do not clog the degasser.
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Before desander/desilter: Gas is removed before fine solids separation, because gas interferes with hydrocyclones.
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Before mud pumps: Degassed mud reaches the pump suction, preventing cavitation.
If a degasser is placed elsewhere, its main purposes are defeated. AIPU engineers can help design the correct tank layout.
5. Financial Impact: What a Vacuum Degasser Saves
Let us put numbers to the purpose. Based on field data from AIPU users:
A vacuum degasser typically pays for itself within the first few hundred drilling hours.
6. Regulatory and Environmental Purpose
In many jurisdictions, environmental and safety regulations require operators to minimize gas emissions and prevent H₂S exposure. A vacuum degasser connected to a flare ignitor provides:
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Controlled combustion of methane (reducing greenhouse gas emissions compared to venting)
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Safe disposal of H₂S (preventing toxic release)
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Compliance with OSHA, EPA, or local HSE rules
AIPU vacuum degassers can be supplied with H₂S‑resistant steel (316L or 2205 duplex) and ATEX/IECEX certifications to meet the strictest regulations.
7. How the Purpose Is Achieved – Brief Mechanism Recap
To appreciate the purpose, it helps to know the mechanism:
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Gas‑cut mud enters the degasser.
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A rotor or baffles spread it into a thin film.
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A vacuum pump lowers pressure to -0.02 to -0.04 MPa.
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Under vacuum, dissolved gas comes out of solution and bubbles expand.
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The vacuum pump removes the gas through a vent line.
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Degassed mud returns to the tank.
Efficiency: ≥95% for AIPU models.
8. AIPU Vacuum Degassers – Models That Fulfill the Purpose
AIPU Solid Control offers vacuum degassers designed for different rig sizes and gas conditions. All share the same purpose: removing gas efficiently and reliably.
AIPU APLCQ300 – Vertical Centrifugal
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Compact footprint, ideal for tight spaces.
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300 m³/h mud capacity, 30 m³/h gas removal.
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Main motor 22 kW, vacuum pump 1.1 kW.
AIPU APZCQ Series – Tank‑Mounted
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Designed for high‑flow land and offshore rigs.
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Capacities from 240 to 360 m³/h.
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Main motors 15–37 kW, vacuum pumps 2.2–5.5 kW.
AIPU APVD Series – Float‑Controlled
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Energy‑efficient, automatic operation.
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Ideal for low‑power or environmentally sensitive sites.
All AIPU degassers feature:
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Three‑layer marine anti‑corrosion coating.
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H₂S‑resistant steel option for sour gas.
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ATEX / IECEX certification option.
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Customizable electrical systems (any voltage/frequency).
9. Common Questions About the Purpose
Q: Can I drill without a vacuum degasser?
A: Yes, but you will suffer from lower mud density, shorter pump life, poor solids control, and higher safety risks. It is technically possible but economically and operationally unwise.
Q: Is a vacuum degasser the same as a mud gas separator?
A: No. The MGS handles large gas kicks; the vacuum degasser continuously removes fine bubbles during normal circulation. Both serve different purposes, and most rigs need both.
Q: How do I know if my mud needs degassing?
A: Signs include: mud weight lower than calculated, pump cavitation noise, foaming on the mud pit surface, or gas detector alarms. Even without visible bubbles, gas may be present.
Q: Does the degasser work with oil‑based mud?
A: Yes, but vacuum should be kept at the lower end (-0.02 MPa) to avoid vaporizing light hydrocarbons. AIPU degassers have adjustable vacuum control.
10. Conclusion: The True Purpose Is Risk‑Adjusted Drilling
The purpose of a vacuum degasser in drilling is not just to remove gas. It is to enable safe, efficient, economical drilling by eliminating the hidden hazard of gas‑cut mud. Without a degasser, you accept lower mud density, damaged pumps, poor solids control, and toxic gas risks. With a degasser – especially a reliable AIPU unit – you drill faster, cheaper, and safer.
AIPU Solid Control has been building vacuum degassers for over 20 years. With deliveries to more than 30 countries and over 300 system‑equivalent units shipped, AIPU understands the purpose and delivers the performance.
Do not let gas cut your profits. Install an AIPU vacuum degasser.