Sand screen with integrated sensors

Details Sand screen with integrated sensors Sand screen with integrated sensors

2002-12-18

2004-02-03

Bagnell, David (Department: 3672)

Wells

Processes

With indicating, testing, measuring or locating

C166S227000

Reexamination Certificate

active

06684951

ABSTRACT:

TECHNICAL FIELD
The present invention relates to sand screens for use in the production of hydrocarbons from wells, and specifically to an improved sand screen having integrated sensors for determining downhole conditions and actuators for modifying the sand placement efficiency or controlling the production profile during the life of the reservoir.
BACKGROUND OF THE INVENTION
Many reservoirs comprised of relatively young sediments are so poorly consolidated that sand will be produced along with the reservoir fluids. Sand production leads to numerous production problems, including erosion of downhole tubulars; erosion of valves, fittings, and surface flow lines; the wellbore filling up with sand; collapsed casing because of the lack of formation support; and clogging of surface processing equipment. Even if sand production can be tolerated, disposal of the produced sand is a problem, particularly at offshore fields. Thus, a means to eliminate sand production without greatly limiting production rates is desirable. Sand production is controlled by using gravel pack completions, slotted liner completions, or sand consolidation treatments, with gravel pack completions being by far the most common approach.
In a gravel pack completion, sand that is larger than the average formation sand grain size is placed between the formation and screen or slotted liner. The gravel pack sand (referred to as gravel, though it is actually sand in grain size), should hinder the migration of formation sand.
FIG. 1
illustrates an inside-casing gravel pack
10
. A cased hole
8
penetrates through a production formation
6
that is enveloped by non-producing formations
2
. The formation
6
has been perforated
4
to increase the flow of fluids into the production tubing
14
. If formation
6
is poorly consolidated, then sand from the formation
6
will also flow into the production tubing
14
along with any reservoir fluids. A gravel pack
12
can be used to minimize the migration of sand into the tubing. A successful gravel pack
12
must retain the formation sand and offer the least possible resistance to flow through the gravel itself.
For a successful gravel pack completion, gravel must be adjacent to the formation without having mixed with formation sand, and the annular space between the screen and the casing or formation must be completely filled with gravel. Special equipment and procedures have been developed over the years to accomplish good gravel placement. Water or other low-viscosity fluids were first used as transporting fluids in gravel pack operations. Because these fluids could not suspend the sand, low sand concentrations and high velocities were needed. Now, viscosified fluids, most commonly, solutions of hydroxyethylcellulose (HEC), are used so that high concentrations of sand can be transported without settling.
Referring to
FIGS. 2
a
and
2
b,
the gravel-laden fluid can be pumped down the tubing casing annulus, after which the carrier fluid passes through the sand screen and flows back up the tubing. This is the reverse-circulation method depicted in
FIG. 2
a.
The gravel is blocked by a slotted line or wire wrapped screen
16
while the transport fluid passes through and returns to the surface through the tubing
18
. A primary disadvantage of this method is the possibility of rust, pipe dope, or other debris being swept out of the annulus and mixed with the gravel, damaging the pack permeability. Alternatively a crossover method is used, in which the gravel-laden fluid is pumped down the tubing
18
, crosses over the screen-hole annulus, flows into a wash pipe
20
inside the screen, leaving the gravel in the annulus, and then flows up the casing-tubing annulus to the surface, as shown in
FIG. 2
b.
For inside-casing gravel packing, washdown, reverse-circulation, and crossover methods are used as shown in
FIGS. 3
a,
3
b,
and
3
c.
In the washdown method, the gravel
22
is placed opposite the production interval
6
before the screen
16
is placed, and then the screen is washed down to its final position. The reverse-circulation and crossover methods are analogous to those used in open holes. Gravel
22
is first placed below the perforated interval
4
by circulation through a section of screen called the telltale screen
24
. When this has been covered, the pressure increases, signaling the beginning of the squeeze stage. During squeezing, the carrier fluid leaks off to the formation, placing gravel in the perforation tunnels. After squeezing, the washpipe is raised, and the carrier fluid circulates through the production screen, filling the casing-production screen annulus with gravel. Gravel is also placed in a section of blank pipe above the screen to provide a supply of gravel as the gravel settles.
In deviated wells, gravel packing is greatly complicated by the fact that the gravel tends to settle to the low side of the hole, forming a dune in the casing-screen annulus. This problem is significant at deviations greater than 45° from vertical. Gravel placement is improved in deviated wells by using a washpipe that is large relative to the screen because this causes a higher velocity over the dune in the annulus between the screen and the casing by increasing the resistance to flow in the screen-wash-pipe annulus.
Another form of sand control involves a tightly wrapped wire around a mandrel having apertures, wherein the spacing between the wraps is dimensioned to prevent the passage of sand.
FIGS. 4 and 5
illustrate such a sand screen
10
. The primary sand screen
10
is a prepacked assembly that includes a perforated tubular mandrel
38
of a predetermined length, for example, 20 feet. The tubular mandrel
38
is perforated by radial bore flow passages
40
that may follow parallel spiral paths along the length of the mandrel
38
. The bore flow passages
40
provide for fluid through the mandrel
38
to the extent permitted by an external screen
42
, the porous prepack body
58
and an internal screen
44
, when utilized. The bore flow passages
40
may be arranged in any desired pattern and may vary in number in accordance with the area needed to accommodate the expected formation fluid flow through the production tubing
18
.
The perforated mandrel
38
preferably is fitted with a threaded pin connection
46
at its opposite ends for threaded coupling with the polished nipple
34
and the production tubing
18
. The outer wire screen
42
is attached onto the mandrel
38
at opposite end portions thereof by annular end welds
48
. The outer screen
42
is a fluid-porous, particulate restricting member that is formed separately from the mandrel
38
. The outer screen
42
has an outer screen wire
50
that is wrapped in multiple turns onto longitudinally extending outer ribs
52
, preferably in a helical wrap. The turns of the outer screen wire
50
are longitudinally spaced apart from each other, thereby defining rectangular fluid flow apertures Z therebetween. The apertures Z are framed by the longitudinal ribs
52
and wire turns for conducting formation fluid flow while excluding sand and other unconsolidated formation material.
As shown in
FIG. 5
, the outer screen wire
50
is typically 90 mils wide by 140 mils tall in a generally trapezoidal cross-section. The maximum longitudinal spacing A between adjacent turns of the outer wire wrap is determined by the maximum diameter of the fines that are to be excluded. Typically, the aperture spacing A between adjacent wire turns is 20 mils.
The outer screen wire
50
and the outer ribs
52
are formed of stainless steel or other weldable material and are joined together by resistance welds W at each crossing point of the outer screen wire
50
onto the outer ribs
52
so that the outer screen
42
is a unitary assembly which is self-supporting prior to being mounted onto the mandrel
38
. The outer ribs
52
are circumferentially spaced with respect to each other and have a predetermined diameter for establishing a prepack annulus
54
of an appropriate size for receiving the annular prepack body

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