Home / News / Company News / Foam Drilling Know How

Foam Drilling Know How

Apr. 07, 24

Foam drilling is a drilling technique that involves the use of a polymer foaming agent, water, and compressed air. Foam is composed of a continuous liquid phase that surrounds and traps the gaseous phase. Its main characteristics are a relatively low density and extremely high viscosity. This combination of properties gives foam a major advantage over mist and dry air drilling.

Drilling with foam combined with compressed air is applied in multiple ways to facilitate drilling operations.

High velocity foam – air misting

When drilling consolidated rock with compressed air, large dust clouds will blow out from the borehole.

Injecting a small stream of water into the air line can effectively suppress dust, protecting both operator health and drilling equipment. Adding soap solution (0.5 – 1.5% dilution) keeps well walls clean and prevents small water-bearing fissures from clogging, as well as avoids damp drill cuttings accumulating above the drilling bit. The soap solutions used are generally biodegradable surfactants: they can be purchased as professional drilling additives, or cost-effective common liquid dish soap and cold-water laundry detergent.

With foam assistance, stable drilling can be realized under lower upward air velocity. The foam keeps the borehole clean, and bubbles can carry cuttings out at low flow speeds.

Low velocity foam – stable foam column

Steadily inject mixed polymer drilling mud (35-40 Marsh funnel seconds) and drilling foam (0.5–1.5% dilution) into air supply with controllable flow, then a slowly rising stable foam column will form to lift cuttings out of the hole. This foam will not erode formations and consumes minimal air, so small air compressors can drill large-diameter holes in soft strata.

Inside the hole forms a continuous rising foam bubble column with texture similar to aerosol shaving foam. Foam overflows from the hole top in wave-like shapes, carrying rock debris stripped by the drill bit. Excess air mixed with insufficient foam will break the foam column and only produce sparse foam outflow. High-quality stable foam is thick when squeezed between two palms and can separate the skin of both hands, forming dense bubble clusters with strong consistency. If standing water accumulates in the hole, foam texture will change, with larger bubbles generated after dilution.

Core Advantages of Foam Drilling

Foam drilling enables drilling of larger boreholes that cannot be directly completed with air compressors of limited capacity. It is an efficient construction method that requires very little compressed air and a small amount of water. New drill crews need a period of practice to master this technique.

Foam drilling is adopted when water inflow is expected during drilling. To realize efficient cuttings transport, the annular velocity shall be maintained at a relatively low level (~100 ft/min). Meanwhile, foam drilling requires lower compression power compared with dry air drilling and mist drilling.

Standard foam drilling design requires a minimum downhole foam quality of around 60% and annular velocity of 100 ft/min. The foam quality inside the wellbore can be adjusted by controlling annular backpressure.

All JCDRILL drilling rigs are equipped with independent foam pumps. The foam pump injects diluted foam mixture into the compressed air pipeline at low flow rates to generate foam bubbles inside boreholes. Driven by a hydraulic motor, our foam pumps support multiple flow and pressure specifications to match different project requirements.

Previous: CWD600T Crawler Mounted Water Well Drilling Rig

Next: How Does Surface Drilling Work?

HOT PRODUCTS

NEWS