Importance

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Abstract

A well drilling system for drilling with gaseous drilling fluid, particularly natural gas, in a closed circulation path including an enclosure or bell nipple mounted on a wellhead between the wellbore and a rotary control head for the drillstem. The enclosure redirects the flow of cuttings laden gaseous drilling fluid being circulated out of the well and includes a plurality of fire extinguishing fluid injection nozzles arranged to inhibit or extinguish fire within the enclosure and the rotary control head. Drill cuttings are separated from the gaseous drilling fluid in a pressure vessel which includes separator baffles and a drill cuttings port and valve arrangement for dumping samples and substantial quantities of drill cuttings collected within the pressure vessel during operation of the system. The enclosure and fire extinguishing system may be used in conjunction with operations using conventional liquid drilling fluids and conventional liquid-solids separation equipment. Methods for monitoring pressure surges in the wellbore to control or minimize deviation from a predetermined pressure condition included monitoring fluid flow rate and pressures of drilling fluid flowing into and from the well and controlling the rate of insertion of a drillstem into the well to minimize pressure surges.

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First Claim