초록 ▼

A drillstring pressure-modulation valve which is usable in combination with a downhole drilling motor and a drillstring thruster to compensate for changes in pressure drop through the drilling motor which normally occur during drilling. When conditions change during drilling, which in turn changes t

A drillstring pressure-modulation valve which is usable in combination with a downhole drilling motor and a drillstring thruster to compensate for changes in pressure drop through the drilling motor which normally occur during drilling. When conditions change during drilling, which in turn changes the pressure drop through the drilling motor, the drillstring pressure-modulation valve compensates for such changes to minimize the effect of such changes on the operation of the thruster and the resulting WOB created by the thruster. The modulation valve has a feature which allows it to find automatically a balanced preload condition for the main needle valve, the primary functional element within the modulation valve, each time the rig pumps are turned off and then turned on. The modulation valve is fully self-contained, and is assembled as part of the bottomhole assembly. The device senses the no-load pressure drop in the system and sets itself each time the rig pumps are turned on to compensate for any change in the no-load pressure drop experienced below the device which could be attributable to such things as motor wear, bit nozzle plugging, or changes in the flow rate. Accordingly, the hydraulic thrusting force remains constant over a wide range of drilling environments. As the drilling conditions change and the pressure drop in the downhole motor increases, the needle valve shifts to compensate for such additional pressure drop with a resultant small or no effect on the thruster and the resulting WOB created by the thruster located upstream of this modulation valve.

대표청구항 ▼

[ What is claimed is:] [1.] A downhole drilling assembly, comprising:a downhole motor supported on tubing;a bit driven by said motor;a thruster mounted to said tubing which extends in length for application of a desired weight on said bit;a compensating device to compensate for pressure change in sa

[ What is claimed is:] [1.] A downhole drilling assembly, comprising:a downhole motor supported on tubing;a bit driven by said motor;a thruster mounted to said tubing which extends in length for application of a desired weight on said bit;a compensating device to compensate for pressure change in said tubing caused by said bit or said motor to allow proper functioning of said thruster.