Variable Circulation Rate Sub for Delivering a Predetermined Straight through Flow

Abstract

A housing is integrated into a tubing string having a straight through passage and a lateral wall exist. Inside the passage is a flow responsive member with an applied preload force. Flow corresponding to a predetermined differential pressure in the housing will not move the valve member so all flow will go straight through in a downhole direction. As flow increases, the preload bias is overcome to align the passage through the housing and openings in the valve member with wall openings. As flow into the housing increases, more lateral wall opening area is aligned with the passage to increase circulation flow while holding through flow downhole constant. Dropping a ball on the valve member blocks through flow and allows opening of total bypass passages. The ball can be removed by blowing it through the seat or otherwise failing or disintegrating it.

Description

FIELD OF THE INVENTION

[0001] The field of the invention is downhole circulation subs and more particularly subs that vary circulation rate to hold a predetermined straight through flow responsive to incoming flow and with a capability to be selectively placed in full recirculation or automatic recirculation modes.BACKGROUND OF THE INVENTION

[0002] In drilling operations it is sometimes necessary to deliver a predictable flow rate to a mud motor, directional drilling equipment or the bit. Automatic systems have been developed to accomplish this task but they are complex and very expensive to install and operate. One example of such a system that sequentially opens and closes surface mounted choke valves is described in WO2015 / 179408 beginning at paragraph 53. Systems with similar complexity are described in U.S. Pat. No. 7,353,887. On the other hand, very basic systems that detect fluid loss during drilling and which rely on differential pressure measurements are revealed in U.S. Pat. N...

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