Purpose of Vacuum Degasser in Drilling: Cost Savings, Risk Reduction, and Operational Benefits

In oil and gas drilling, the drilling fluid (mud) is a vital resource. It cools the bit, carries cuttings to the surface, maintains hydrostatic pressure, and stabilizes the wellbore. However, as the mud circulates downhole, it picks up drilled solids, gases, and other contaminants. If these contaminants are not removed, the mud loses its properties, equipment wears out faster, and drilling efficiency drops dramatically. The equipment arrangement that solves this problem is called a solids control system. This article provides a complete, standalone introduction to Solids Control Systems: what they are, why they are essential, how they work, and why AIPU Solid Control delivers industry‑leading solutions.

1. Definition: What Is a Solids Control System?

A solids control system is an integrated set of mechanical equipment designed to remove drilled solids (cuttings), gas, and other contaminants from drilling fluid so the cleaned mud can be recirculated back into the well. It is the heart of any modern drilling rig’s mud circulation loop. Without an effective solids control system, the drilling fluid would quickly become contaminated with solids, leading to higher viscosity, reduced penetration rates, increased pump wear, and potentially stuck pipe or lost circulation.

The system typically includes several stages of separation, each targeting progressively smaller particles, from large cuttings down to fine silt and even barite‑sized particles.

2. Why Is a Solids Control System Essential?

Drilling fluid is expensive. A single mud system can cost hundreds of thousands of dollars. Discarding it after one circulation is economically impossible. The solids control system allows the mud to be reused many times by continuously removing the solids that enter it.

Key benefits of a proper solids control system:

• Extends mud life – Clean mud maintains its rheology and density longer.

• Reduces drilling costs – Less need for new mud and chemicals.

• Protects downstream equipment – Mud pumps, centrifuges, and hydrocyclones last longer when fed clean mud.

• Increases penetration rate – Fewer solids in the mud means faster drilling.

• Minimizes environmental impact – Less waste volume and safer disposal.

• Enables well control – Correct mud density is maintained, preventing kicks and blowouts.

3. The Typical Stages of a Solids Control System

A modern solids control system arranges equipment in a specific sequence, from coarse to fine separation. Below are the common stages, using AIPU Solid Control equipment as examples.

Stage 1 – Shale Shaker (First‑Stage Separation)

The returning mud from the well first passes over a shale shaker. This is a vibrating screen that removes large cuttings (typically >75 µm). The shaker is the most critical piece because it removes the bulk of drilled solids before they can break down into smaller, harder‑to‑remove particles.

AIPU example: Hunter‑MG series shale shakers (single, dual, or triple motion) with capacities from 50 to 420 m³/h.

Stage 2 – Vacuum Degasser (Gas Removal)

If formation gases (methane, H₂S, CO₂) are present, a vacuum degasser removes entrained and dissolved gases. Gas bubbles reduce mud density and cause pump cavitation. The degasser applies a partial vacuum to expand and extract the gas.

AIPU example: APLCQ300 vertical degasser (300 m³/h, ≥95% efficiency) or APZCQ series (240–360 m³/h).

Stage 3 – Desander (Medium‑Solids Removal)

The mud then flows to a desander, a set of large hydrocyclones (usually 10‑inch or 12‑inch cones) that remove sand‑sized particles (44–74 µm). The desander protects downstream equipment from abrasive sand.

AIPU example: Hunter S series or APCS series desanders, with capacities from 60 to 360 m³/h.

Stage 4 – Desilter (Fine‑Solids Removal)

After the desander, the mud enters a desilter, which uses smaller hydrocyclones (4‑inch or 5‑inch cones) to remove particles in the 15–44 µm range. The desilter often has a small shaker (mud cleaner) to further dry the separated solids.

AIPU example: Hunter N series or APCN series desilters, with capacities from 60 to 360 m³/h.

Stage 5 – Centrifuge (Ultra‑Fine Solids Control or Barite Recovery)

The final stage is a decanter centrifuge. Centrifuges can perform two roles:

• In unweighted mud, they remove ultra‑fine solids (2–7 µm) to control rheology.

• In weighted mud, they recover barite (specific gravity ~4.2) by separating it from fine drilled solids.

AIPU example: APLW series horizontal decanter centrifuges, with capacities from 35 to 65 m³/h and separation points from 2 to 7 µm.

Stage 6 – Centrifugal Pump (Mud Transfer)

Throughout the system, centrifugal pumps provide the hydraulic power to move mud from tank to tank and to feed desanders, desilters, and centrifuges.

AIPU example: APSB series centrifugal pumps (API 7th edition compatible, interchangeable with MISSION Magnum series).

4. Additional Equipment That Supports the System

Beyond the main separation stages, a solids control system includes several support devices:

Mud Agitators

• Installed inside each mud tank compartment.

• Prevent solids from settling at the bottom.

• AIPU APMA series agitators (5.5–15 kW, dual‑impeller options).

Shearing Pumps

• Hydrate polymers and disperse clays.

• Eliminate “fish eyes” and save bentonite.

• AIPU APJQB series shearing pumps (37–55 kW, 100–155 m³/h).

Jet Mud Mixers (Jet Hoppers)

• Add barite, bentonite, and powdered chemicals.

• Use the Venturi principle to suck powder into a high‑velocity fluid stream.

• AIPU APSLH series jet hoppers (mix up to 315 kg/min barite).

Mud Tanks

• Compartmented steel vessels that hold the mud.

• Sloped or V‑shaped bottoms for easy cleaning.

• AIPU custom mud tanks with three‑layer marine coating.

5. How the System Works Together – A Typical Flow Path

1. Mud returns from the well through the flowline.

2. It enters the shale shaker; large cuttings are removed and discharged to a cuttings box.

3. The overflow mud flows to the degasser compartment; entrained gas is removed.

4. A centrifugal pump sends mud to the desander; medium solids are removed.

5. The mud overflows to the desilter; fine solids are removed.

6. A second pump feeds the centrifuge for ultra‑fine separation or barite recovery.

7. Clean, conditioned mud enters the suction pit, where mud pumps send it back downhole.

8. Mud agitators run continuously to keep solids suspended.

9. Jet mixers and shearing pumps are used when adding new chemicals or weighting materials.

6. Why AIPU Solids Control Systems Are Industry Preferred

AIPU Solid Control has over 20 years of experience in mud solids control and treatment. The company has delivered equipment to more than 30 countries, with cumulative shipments exceeding 300 system‑equivalent products. AIPU holds multiple international system certifications, product certifications, and independent invention patents.

Key Advantages of an AIPU Solids Control System:

✅ Full‑range product line – From shakers to centrifuges, agitators to shearing pumps, AIPU supplies every component needed for a complete system.

✅ Custom engineered – AIPU designs tank layouts, piping, and equipment selection based on your rig’s flow rate, mud type, and space constraints.

✅ Robust construction – Three‑layer marine anti‑corrosion coating, H₂S‑resistant steel options, ATEX/IECEX certifications.

✅ Proven global performance – 30+ countries, 300+ system‑equivalent shipments.

✅ Easy operation and maintenance – Standardized designs, fewer spare parts, clear documentation.

7. Solids Control System for Different Mud Types

• Water‑based mud (WBM): Full system required; centrifuge often used for fine solids removal.

• Oil‑based mud (OBM): H₂S‑resistant steel required for sour service; centrifuge used for barite recovery.

• Synthetic‑based mud (SBM): Similar to OBM; special attention to gas removal.

AIPU provides material upgrades (316L/2205 duplex) for OBM and SBM in sour gas fields.

8. Common Misconceptions About Solids Control Systems

❌ “Only the shale shaker matters.”
False. The shaker is important, but without desanders, desilters, and centrifuges, fine solids will build up and ruin the mud.

❌ “A mud cleaner replaces a separate desander and desilter.”
Partially true, but a mud cleaner combines a desilter with a small shaker – it still requires upstream gas removal and downstream centrifugation for complete treatment.

❌ “Centrifuges are only for weighted mud.”
Incorrect. Centrifuges are equally important in unweighted mud to remove ultra‑fine solids that hydrocyclones cannot catch.

9. How to Select the Right Solids Control System for Your Rig

When designing or upgrading a solids control system, consider:

1. Maximum mud circulation rate (m³/h or GPM) – determines equipment sizes.

2. Mud type (water‑based, oil‑based, synthetic) – affects material selection.

3. Solids loading – high‑penetration rate wells need larger capacity.

4. Gas risk – requires a vacuum degasser and possibly H₂S‑resistant steel.

5. Space available – onshore vs. offshore dictates tank footprint and equipment layout.

AIPU engineers provide full system engineering, including P&IDs, tank drawings, and equipment specifications.

10. Conclusion

A solids control system is the backbone of any efficient, safe drilling operation. It continuously cleans drilling fluid by removing drilled solids and gas, allowing the mud to be reused many times. A well‑designed system reduces costs, protects equipment, improves penetration rates, and minimizes environmental impact.

AIPU Solid Control offers complete, customizable solids control systems – from individual components (shakers, degassers, desanders, desilters, centrifuges, agitators, shearing pumps, jet mixers, and mud tanks) to fully integrated packages with API and HSE certifications.

When you choose AIPU, you get over 20 years of expertise, global delivery experience, and a commitment to quality that has earned trust in over 30 countries.

Build a reliable solids control system with AIPU – cleaner mud, faster drilling, lower cost.