Wells – Means for forming filter beds
Reexamination Certificate
2001-01-23
2002-12-03
Suchfield, George (Department: 3672)
Wells
Means for forming filter beds
C166S066700, C166S191000, C166S242100, C166S319000, C166S332100, C166S334400
Reexamination Certificate
active
06488082
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a remotely operated multi-zone packing system used in multi-zone gravel pack, frac pack, and similar applications in oil field wells. Specifically, the present invention allows for remote operation of gravel pack, frac pack, or similar assemblies in multi-zone applications, thus eliminating the requirement to physically relocate a work string to each zone of interest to accomplish various phases of the completion.
2. Description of Related Art
Gravel pack assemblies and frac pack assemblies are commonly used in oil field well completions. A frac pack assembly is used to stimulate well production by using liquid under high pressure pumped down a well to fracture the reservoir rock adjacent to the wellbore. Propping agents suspended in the high-pressure fluids (in hydraulic fracturing) are used to keep the fractures open, thus facilitating increased flow rates into the wellbore. Gravel pack completions are commonly used for unconsolidated reservoirs for sand control. Gravel packs can be used in open-hole completions or inside-casing applications. An example of a typical gravel pack application involves reaming out a cavity in the reservoir and then filling the well with sorted, loose sand (referred to in the industry as gravel). This gravel pack provides a packed sand layer in the wellbore and next to the surrounding reservoir producing formation, thus restricting formation sand migration. A slotted or screen liner is run in the gravel pack which allows the production fluids to enter the production tubing while filtering out the surrounding gravel.
A typical single-zone gravel pack completion is illustrated in FIG.
1
.
FIG. 1
is a schematic cutaway representation showing a perforated wellbore casing
2
with perforations
12
shown extending into a single zone of interest
10
. Within the wellbore casing
2
a tube
4
has been placed on which is attached a screen
6
. The gravel
8
is shown packed into the perforations
12
in the zone of interest
10
and surrounding the screen
6
. The gravel
8
is an effective filter of formation fluids, because the formation sand, which would otherwise flow with the production fluid, is largely trapped at the interface with the gravel
8
.
One specific type of gravel pack procedure is called a squeeze gravel pack. The squeeze gravel pack method uses high pressure to “squeeze” the carrier fluid into the formation, thereby placing gravel
8
in the perforation tunnels
12
of a completed well and the screen/casing annulus. The frac pack method is very similar, except the “squeeze” is carried out at even higher pressures with more viscous fluid in order to fracture the reservoir rock. Consequently, the down-hole assembly used for these two procedures is frequently the same, and the procedures will be discussed as examples interchangeably in this disclosure.
A typical gravel pack or frac pack assembly is presently run into the well on a work string. The work string is commonly a length of drill pipe normally removed from the well once the packing job is complete. The work string assembly contains a means for setting the packer and a crossover tool to redirect the treatment from within the work string into the formation. This is illustrated by
FIG. 2
, which shows a schematic cutaway of a basic frac pack assembly for a single zone of interest
210
application. At the upper portion of the assembly the work string is a single tube or pipe
214
(which is also referred to herein as the inner tubing). Further down the assembly this single tube
214
is attached to and enclosed by a middle concentric tube
216
. The now inner tube
214
and middle tube
216
are integral to the work string and can be moved vertically through the wellbore annulus
202
by manipulation at the rig level. The middle tube
216
is initially attached to or pinned to an outer concentric tube
204
when the assembly is landed in the well. Immediately above the point where the middle tube
216
and the outer
204
begin to interface concentrically are seal points
218
,
230
, providing pressure seals between the middle concentric tube
216
and the outer concentric tube
204
. Once the assembly is landed and set in place, the temporary attachment between the middle tube
216
and the outer tube
204
can be broken, for example by applying tension to a shear pin by pulling the middle tubing
216
upward. The seal points
218
,
230
provide pressure isolation between the middle tubing
216
and the outer tubing
204
even as the work string is moved up and down in the assembly.
Attached to the outer tubing
204
is a hydraulic set packer
220
. When “set,” a procedure that will be described momentarily, the hydraulic set packer
220
provides a complete seal between the outer tubing
204
and the wellbore casing
202
. Below the hydraulic set packer is a fluid crossover port
240
, formed by passages through the inner tubing
214
and the concentric middle tubing
216
, which allows fluid to crossover from the inner tubing
214
through the concentric middle tubing
216
without coming into physical contact with any fluid that may be passing through the annulus between the inner tubing
214
and the concentric middle tubing
216
. A gravel pack port
224
, which is opened and closed with a closing sleeve
226
, which is operated by a shifting tool (not shown), provides communication for fluid exiting the crossover port
240
into the wellbore annulus
202
. This gravel pack port
224
, although shown in the open position, may be initially in the closed position with the closing sleeve
226
sealing the port
224
when the assembly is landed in the well. In the closed position, fluid transported down the inner tubing
214
is diverted by a plug
236
, passes through the crossover port
240
, and is isolated between the hydraulic set packer
220
and a seal
230
located below the port
224
. Thus, pressure can be built up inside this isolated segment of the outer tubing
204
. The packer
220
is hydraulically actuated or “set” by applying fluid pressure until the outer tubing
204
is pressure isolated by the packer's
220
seals within the wellbore annulus
202
.
After the packer
220
is set, the gravel packing or frac packing job can be initiated by opening the gravel pack port
224
by shifting open the closing sleeve
226
. This is typically accomplished by physically manipulating the closing sleeve
226
with a shifting tool (not shown) attached to the exterior of the middle tubing
216
by raising or lowering the work string (which consists of the inner tubing
214
, the middle tubing
216
, and all integral components shown in FIG.
2
). Once the closing sleeve
226
opens the port
224
, the proppant for the gravel pack or frac pack completion is pumped down the inner tubing
214
, through the crossover port
240
, out the gravel pack port
224
, and into the wellbore annulus
202
, as indicated by flow arrows
250
in FIG.
2
. Below the closing sleeve
226
and gravel pack port
224
, the outer tubing
204
comprises a screen or slotted liner
206
, similar to the screen
6
illustrated in FIG.
1
. Therefore, during the “frac job” the proppant is forced into the perforations
212
of the wellbore casing
202
and begins to fill the cavity between the screen
206
and the wellbore casing
202
. The carrier fluid
250
for the gravel, after being filtered by the screen
206
, may be circulated through the annulus between the inner tubing
214
and the concentric middle tubing
216
, which has an open end
232
inside the screen
206
in a single zone of interest application. The fluid
250
goes past a ball
234
near the bottom opening
232
of the middle tubing
216
, which acts as a check valve preventing fluids from back flowing from the annulus between the inner tubing
214
and the concentric middle tubing
216
back into the screen. The circulation of the carrier fluid exits through a port
238
above the seal point
218
.
The gravel pack procedure becomes more comple
Echols Ralph Harvey
Hailey, Jr. Travis T.
Thomas Phillip T.
Carstens David W.
Halliburton Energy Service,s Inc.
Herman Paul I.
Imwalle William M.
Suchfield George
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