Horizontal separator for treating under-balance drilling fluid

Claim 1

A closed separator for separating the components of under-balanced drilling fluid returning from a well to produce separate streams of solid cuttings, gas, oil and water, when present in the fluid, comprising: an elongated, horizontal, cylindrical pressure vessel having a side wall and curved heads which together form a closed internal chamber, said vessel having first and second ends; inlet means for introducing the fluid through an aperture into the upper portion of the vessel chamber at its first end; cuttings outlet means, positioned at the bottom of the chamber at its first end, for removal of solid cuttings; a first weir extending upwardly from the bottom and transversely of the chamber, said first weir being slanted away from the first end head and being sealed to the vessel sidewall, said first weir having its top rim spaced below the inlet means aperture, the bottom end of the first weir being positioned close to the first end head on the downstream side of the cuttings outlet means; the first weir, side wall and first end head combining to form a first upstream compartment of downwardly diminishing cross-sectional area, said compartment being shaped to funnel settling cuttings down to the cuttings outlet means; means, connected with the cuttings outlet means, for withdrawing solid cuttings therethrough; gas outlet means for removing gas from the upper end of the chamber; water outlet means, downstream of the first weir, having an aperture for removing water that has settled to the bottom end of the chamber; and oil outlet means, downstream of the first weir, having an aperture for removing oil; said water outlet aperture being located below the oil outlet aperture.