The extreme under-balanced that results when drilling with air or gas allows large disc-shaped cuttings to break from the formation with the impact of the bit tooth. These cuttings are degraded to dust as the turbulent airlifts them to the surface. Solids control while air drilling (including natural gas and nitrogen) consists of controlling atmospheric pollution, collecting samples, and disposing of cuttings and liquids. Normally there is no recovery or reuse of the air or gas except for a few occasions in natural-gas drilling when the gas is recycled to the gas plant. An elaborate separator/cleaning/recompressing system is required to recycle the gas. It is usually more economical to flare the gas than to recover and clean it (see Figure 1.)

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