Wells – Processes – With indicating – testing – measuring or locating
Reexamination Certificate
2001-07-31
2003-06-10
Bagnell, David (Department: 3672)
Wells
Processes
With indicating, testing, measuring or locating
C166S250070, C166S250010, C166S066000, C166S374000, C175S025000, C175S048000, C073S152220, C073S152460
Reexamination Certificate
active
06575244
ABSTRACT:
BACKGROUND
This invention relates generally to subterranean boreholes, and in particular to systems for controlling the operating pressures within subterranean boreholes.
Referring to
FIG. 1
, a typical oil or gas well
10
includes a wellbore
12
that traverses a subterranean formation
14
and includes a wellbore casing
16
. During operation of the well
10
, a drill pipe
18
may be positioned within the wellbore
12
in order to inject fluids such as, for example, drilling mud into the wellbore. As will be recognized by persons having ordinary skill in the art, the end of the drill pipe
18
may include a drill bit and the injected drilling mud may used to cool the drill bit and remove particles drilled away by the drill bit. A mud tank
20
containing a supply of drilling mud may be operably coupled to a mud pump
22
for injecting the drilling mud into the drill pipe
18
. The annulus
24
between the wellbore casing
16
and the drill pipe
18
may be sealed in a conventional manner using, for example, a rotary seal
26
. In order to control the operating pressures within the well
10
such as, for example, within acceptable ranges, a choke
28
may be operably coupled to the annulus
24
between the wellbore casing
16
and the drill pipe
18
in order to controllably bleed off pressurized fluidic materials out of the annulus
24
back into the mud tank
20
to thereby create back pressure within the wellbore
12
. The choke
28
is manually controlled by a human operator
30
to maintain one or more of the following operating pressures within the well
10
within acceptable ranges: (1) the operating pressure within the annulus
24
between the wellbore casing
16
and the drill pipe
18
—commonly referred to as the casing pressure (CSP); (2) the operating pressure within the drill pipe
18
—commonly referred to as the drill pipe pressure (DPP); and (3) the operating pressure within the bottom of the wellbore
12
—commonly referred to as the bottom hole pressure (BHP). In order to facilitate the manual human control
30
of the CSP, the DPP, and the BHP, sensors,
32
a
,
32
b
, and
32
c
, respectively, may be positioned within the well
10
that provide signals representative of the actual values for CSP, DPP, and/or BHP for display on a conventional display panel
34
. Typically, the sensors,
32
a
and
32
b
, for sensing the CSP and DPP, respectively, are positioned within the annulus
24
and drill pipe
18
, respectively, adjacent to a surface location. The operator
30
may visually observe one of the more operating pressures, CSP, DPP, and/or BHP, using the display panel
34
and attempt to manually maintain the operating pressures within predetermined acceptable limits by manually adjusting the choke
28
. If the CSP, DPP, and/or the BHP are not maintained within acceptable ranges then an underground blowout can occur thereby potentially damaging the production zones within the subterranean formation
14
. The manual operator control
30
of the CSP, DPP, and/or the BHP is imprecise, unreliable, and unpredictable. As a result, underground blowouts occur thereby diminishing the commercial value of many oil and gas wells.
The present invention is directed to overcoming one or more of the limitations of existing systems for controlling the operating pressures of subterranean boreholes.
SUMMARY
According to an embodiment of the present invention, a method of controlling one or more operating pressures within a subterranean borehole that includes a tubular member positioned within the borehole that defines an annulus between the tubular member and the borehole, a sealing member for sealing the annulus between the tubular member and the borehole, a pump for pumping fluidic materials into the tubular member, and an automatic choke for controllably releasing fluidic materials out of the annulus between the tubular member and the borehole is provided that includes sensing an operating pressure within the tubular member and generating an actual tubular member pressure signal representative of the actual operating pressure within the tubular member, comparing the actual tubular member pressure signal with a target tubular member pressure signal representative of a target operating pressure within the tubular member and generating an error signal representative of the difference between the actual tubular member pressure signal and the target tubular member pressure signal, and processing the error signal to generate a set point pressure signal for controlling the operation of the automatic choke.
The present embodiments of the invention provide a number of advantages. For example, the ability to control the DPP also permits control of the BHP. Furthermore, the use of a PID controller having lag compensation and/or feedforward control enhances the operational capabilities and accuracy of the control system. In addition, the monitoring of the system transient response and modeling the overall transfer function of the system permits the operation of the PID controller to be further adjusted to respond to perturbations in the system. Finally, the determination of convergence, divergence, or steady state offset between the overall transfer function of the system and the controlled variables permits further adjustment of the PID controller to permit enhanced control system response characteristics.
REFERENCES:
patent: 3827511 (1974-08-01), Jones
patent: 3971926 (1976-07-01), Gau et al.
patent: 4253530 (1981-03-01), Sharki et al.
patent: 4440239 (1984-04-01), Evans
patent: 5182703 (1993-01-01), Yamamoto
patent: 5517593 (1996-05-01), Nenniger et al.
patent: 6286602 (2001-09-01), Lemetayer et al.
patent: 6293341 (2001-09-01), Lemetayer
Burkhard Alan
Chang Lingo
Suter Roger
Bagnell David
Bomar T. Shane
Haynes and Boone LLP
M-I L.L.C.
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