Electrical surface activated downhole circulating sub

Details Electrical surface activated downhole circulating sub Electrical surface activated downhole circulating sub

1999-08-20

2002-02-26

Neuder, William (Department: 3672)

Wells

With electrical means

Electrical motor

C175S232000, C175S234000

Reexamination Certificate

active

06349763

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates generally to downhole circulation subs. More particularly, this invention relates to the use of an electric motor to drive a downhole circulation sub.
Retrieval of oil and other hydrocarbons form below ground typically includes drilling a borehole, also known as a wellbore, in the Earth. As drilling technology has advanced, these boreholes may be drilled off of vertical, sometimes even sideways or horizontal. In this way, an operator can reach a formation that contains the desired substance. Thus, the terms “upper” and “lower”, or “above” and “below” as used herein are made with respect to a position in the borehole, and may not necessarily reflect whether two elements are above or below each other in an absolute sense.
FIG. 1
includes rock formation
100
surrounding a borehole
110
. Borehole
100
is formed by the cutting action of drill bit
125
attached to rotating drill string
120
. Drill string
120
also includes a circulating sub
170
.
A variety of drill bits
125
are known, but a common feature is that each contains ports or nozzles on its face to direct drilling mud
130
(also known as drilling fluid) flowing through drill string
120
. The drilling mud
130
exits the drill bit as shown by arrows
160
. This mud not only cools the face of the drill bit, but also carries to the surface a substantial amount of shavings and cuttings
140
that result from the drilling action. These cuttings are carried up to the surface from downhole along an area between the drillstring and the borehole wall known as the annulus
150
. At the surface, the drilling mud is then cleaned, filtered and recycled for repeated use.
One problem occurs when the ports or nozzles on the face of the drill bit
125
become blocked or otherwise impeded from spraying drilling mud out the face of the drill bit
160
. This prevents or substantially slows the flow of mud to the surface, resulting in the rock cuttings falling to the bottom of the wellbore. It also results in a pressure build-up in the mud contained in the drill string. The increase in pressure can damage equipment uphole such as pumps. To minimize this problem, it is known to provide a circulating sub
170
that provides an alternate route
165
for drilling mud flow when the mud is unable to exit drill bit
160
properly.
Referring to
FIG. 2
, a known circulating sub
200
is called a ball-drop circulating sub. It includes a cylindrical valve sleeve
210
having holes or ports
220
. At its lower end is a lip
230
that reduces the inner diameter of the cylindrical valve sleeve
210
. The circulating sub housing surrounds valve sleeve
210
and also includes ports
225
. Shoulder
260
is positioned for abutment against the lower portion of valve sleeve
210
, as explained below. Between valve sleeve
210
and drill string
120
are o-rings
240
-
242
and a shear pin
250
. Ball
270
is shown falling in mid-travel from the surface before lodging in area formed by lip
230
.
During normal operation (i.e., when mud is properly flowing
160
through the drill bit
125
), drilling, mud
130
flows through the center of circulating sub
200
as shown by arrows
280
. However, upon a blockage in the flow of mud, a ball
270
is shot from the surface down to ball-drop circulating sub
200
. Ball
270
lodges against lip
230
, preventing the flow of mud
130
along flow path
280
. Pressure built up in the mud column exerts itself against ball
270
and causes shear pin
250
to break. Valve sleeve
210
drops down until stopped by shoulder
260
. This aligns ports or holes
220
and
225
. Drilling mud
130
then escapes circulating sub
200
and follows mud path
165
(shown in
FIG. 1
) to the surface. This lifts the rock cuttings above the circulating sub
200
to the surface. However, the ball-drop circulating subs have a number of problems. For example, because the ball
270
originates at the surface, it can take up to thirty minutes from the time the mud flow stops through a drill bit to the time the circulating sub redirects the flow. In addition, this design is a one-time actuation and cannot be reset.
Other circulating subs having various problems, such as U.S. Pat. No. 5,465,787, are also presently known.
SUMMARY OF THE INVENTION
A preferred embodiment of the present invention features a downhole circulation sub having an electric motor associated with a valve poppet. The valve poppet moves from a first position to a second position in response to force from the electric motor, causing drilling fluid flowing through the circulation sub to switch its path of travel from a first route generally downwhole to a second route generally uphole. In its second position, the valve sleeve may engage a valve plug. Further, the valve poppet may be placed back in its first position by operation of the electric motor. The circulation sub is designed so that this movement of the valve sleeve from its first to its second position, and back again, may be carried out repeatedly.
Another aspect to the invention is a method of redirecting the flow of drilling fluid in a circulation sub. This aspect of the invention includes actuating an electric motor to apply force to a connected valve sleeve, moving the valve sleeve from a first position inside a housing to a second position by actuation of the electric motor, preventing by movement of the valve sleeve to the second position the flow of fluid past a lower end of the circulation sub, and directing by the movement of the valve sleeve to the second position the flow of fluid through ports positioned between the valve sleeve and an annulus. The first position is typically an upper position with respect to a wellbore, and the second position is a lower position.
Thus, the present invention comprises a combination of features and advantages which enable it to overcome various problems of prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings.


REFERENCES:
patent: 3907046 (1975-09-01), Gaylord
patent: 4129184 (1978-12-01), Parker
patent: 4373582 (1983-02-01), Bednar et al.
patent: 4632193 (1986-12-01), Geczy
patent: 5465787 (1995-11-01), Roth

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