U.S. patent application number 12/845666 was filed with the patent office on 2011-02-03 for method of servicing high temperature wells.
Invention is credited to Jared Jensen, Stewart Layden.
Application Number | 20110024120 12/845666 |
Document ID | / |
Family ID | 43514008 |
Filed Date | 2011-02-03 |
United States Patent
Application |
20110024120 |
Kind Code |
A1 |
Jensen; Jared ; et
al. |
February 3, 2011 |
METHOD OF SERVICING HIGH TEMPERATURE WELLS
Abstract
A method of servicing high temperature wells. A cooling chamber
is secured in end to onto a wellhead of a high temperature well. A
hot tubing string is raised from the high temperature well into the
cooling chamber. A cooling fluid is injected into the cooling
chamber to cool the hot tubing string prior to handling.
Inventors: |
Jensen; Jared; (Red Deer,
CA) ; Layden; Stewart; (Red Deer, CA) |
Correspondence
Address: |
CHRISTENSEN, O'CONNOR, JOHNSON, KINDNESS, PLLC
1420 FIFTH AVENUE, SUITE 2800
SEATTLE
WA
98101-2347
US
|
Family ID: |
43514008 |
Appl. No.: |
12/845666 |
Filed: |
July 28, 2010 |
Current U.S.
Class: |
166/302 |
Current CPC
Class: |
E21B 36/001 20130101;
E21B 33/068 20130101 |
Class at
Publication: |
166/302 |
International
Class: |
E21B 36/00 20060101
E21B036/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2009 |
CA |
2,674,703 |
Claims
1. A method of servicing high temperature wells, comprising:
securing a cooling chamber onto a wellhead of a high temperature
well; raising a tubular member from the high temperature well into
the cooling chamber; injecting a cooling fluid into the cooling
chamber to cool the hot tubing string prior to handling.
2. The method of claim 1, wherein the cooling chamber is defined by
a stack of spools attached in end to end relation onto the
wellhead.
3. The method of claim 1, wherein the tubular member has a
temperature of at least 100.degree. C. prior to entering the
cooling chamber.
4. The method of claim 1, wherein the tubular member is cooled to a
temperature of less than 50.degree. C. in the cooling chamber.
5. The method of claim 1, wherein the tubular member is
continuously raised through the cooling chamber.
6. The method of claim 1, wherein the cooling chamber has a cooling
fluid input and a cooling fluid output for circulating cooling
fluid through the cooling chamber.
7. The method of claim 1, wherein injecting the cooling fluid
comprises maintaining the pressure of the cooling fluid in the
cooling chamber at a pressure that avoids overbalancing the
well.
8. The method of claim 1, wherein the cooling fluid is in direct
contact with the tubular member.
9. The method of claim 1, wherein the tubular member is raised
during a snubbing operation.
Description
FIELD
[0001] The present method was developed to service high temperature
wells without requiring them to be cooled prior to servicing.
BACKGROUND
[0002] There are currently a number of energy companies producing
oil in Northern Alberta regions using steam-assisted gravity
drainage (SAGD) recovery methods. As its name implies, SAGD
production uses steam to elevate the temperature of the bitumen or
heavy crude in the formation. Once the viscosity is reduced to a
sufficient level, the fluids will freely flow, by gravity, to the
well where they can be pumped to the surface. Temperatures
typically encountered in SAGD operations are generally between
200.degree. C. and 300.degree. C. and pressures are generally
between 2000 kPa 5500 kPa. Other wells aside from SAGD wells may
also operate under similar high temperature and high pressure
conditions. For example, with the toe heel air injection method
(THAI) of producing bitumen, the temperature may be in excess of
600.degree. C.
[0003] Conventional well servicing operations require that both the
well temperature and the well bore pressure are reduced before work
can proceed. In SAGD wells, the temperature of a particular well is
reduced by shutting down the steam injection in the vicinity of the
well to be worked over. Of course, once the steam is shut down,
production in all of the neighbouring wells ceases until the
reservoir temperature gets back up to producible levels. This is a
lengthy process and it may end up being several months until the
well is back in production. There are, therefore, considerable
costs incurred with a well servicing operation; the cost of
reheating the formation to producible levels as well as the loss of
production during this period. In some cases, a number of wells are
positioned in close vicinity to one another so as to support each
other in heating the formation. In the event that one of these
wells require servicing a number of wells could be affected by the
prerequisite to cool one of the group's members. Again, several
months of seriously impacted production could result; not to just
one well, but to numerous wells.
[0004] What is required is a method to safely perform servicing
operations on high temperature wells while they are operating
within their normal temperatures and pressure ranges.
SUMMARY
[0005] There is provided a method of servicing high temperature
wells, comprising the steps of securing a cooling chamber onto a
wellhead of a high temperature well; raising a tubular member from
the high temperature well into the cooling chamber; and injecting
the cooling chamber with a cooling fluid to cool the hot tubing
string prior to handling.
[0006] According to different aspects, the cooling chamber is
defined by a stack of spools attached in end to end relation onto
the wellhead. The tubular member may have a temperature of at least
100.degree. C. or 200.degree. C. prior to entering the cooling
chamber. The tubular member may be cooled to a temperature of less
than 50.degree. C. in the cooling chamber. The tubular member may
be continuously raised through the cooling chamber. The tubular
member may be raised during a snubbing operation. The cooling
chamber may have a cooling fluid input and a cooling fluid output
for circulating cooling fluid through the cooling chamber.
Injecting the cooling fluid may comprise maintaining the pressure
of the cooling fluid in the cooling chamber at a pressure that
avoids overbalancing the well. The cooling fluid may be in direct
contact with the tubular member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features will become more apparent from the
following description in which reference is made to the appended
drawings, the drawings are for the purpose of illustration only and
are not intended to be in any way limiting, wherein:
[0008] FIG. 1 is a side elevation view of a wellhead with a stack
of spools forming a cooling chamber.
[0009] FIG. 2 is a top plan view in section of the cooling
chamber.
DETAILED DESCRIPTION
[0010] The method will now be described with reference to FIGS. 1
and 2.
[0011] It is possible to maintain pressure and work on the well by
cooling the tubular member, such as a tubing string or coiled
tubing string, and pulling the tubular member through a closed BOP.
The tubular member is cooled by a cool fluid or gas being pumped
through a cooling chamber situated between the wellhead and the
snubbing unit. For the purposes of this application, it will be
understood that "fluid" means any substance, such as a liquid or
gas, that can flow. For the purposes of this application, a high
temperature well is considered anything with a temperature above
that which can be safely handled by workers, such as 50.degree. C.
However, the method is designed primarily for use with high
temperature wells that have a temperature of at least 200.degree.
C.
[0012] Referring to the embodiment depicted in FIG. 1, a SAGD well
10 is shown with a number of spools 12 bolted onto the wellhead 14.
Referring to FIG. 2, spools 12 have an internal diameter that forms
a cooling chamber 15. The cooling chamber 15 is large enough to
receive the tubular body 16 as it is pulled through. While spools
12 are shown, it will be understood that other bodies could be used
to form the cooling chamber, such as a large pipe, or other body
that is large enough and has a cavity. Referring again to FIG. 1,
the spools 12 are stacked end to end and allow the tubing string to
pass through their centers. The height of the spool stack is
determined by the amount of cooling required to bring the tubing
string down to a temperature that can be handled safely. For
example, temperatures above 50.degree. C. are likely too hot to
safely handle by workers. If more cooling is required to reach a
safe operating temperature, more spools 12 may be stacked together
give a larger area of tubing exposed to the cooling fluid or
gas.
[0013] Above the stack of spools 12 is a snubbing unit 18. The
snubbing unit blow out preventer stack 20 is bolted to the top most
spool and keeps the pressure in the well from escaping to the
atmosphere. The snubbing unit 18 provides a means of raising or
lowering the tubing string in and out of the well while it is under
pressure.
[0014] On each of the lowermost and uppermost spools 12, there is a
port 22 so that a suitable gas or liquid can be pumped into the
cooling chamber. The fluid is pumped into one port 22, flows up or
down the stack of spools and out of the other port 22. The pressure
is maintained on the outgoing line so that the fluid pressure in
the spool stack is equal to or higher than the well pressure. This
prevents the fluid from escaping down the well. The fluid enters
into the spool system at a lower temperature than the tubing string
and serves to cool it as it passes through the stack of spools. A
number of variables can be adjusted to change the amount of
cooling--the fluid used, the temperature of the fluid, the height
of the spool stack, the speed at which the tubing string is pulled
through the spool stack 12, and the flow rate of the fluid. By this
means, tubing can be cooled as it is removed from the well by the
snubbing unit 18. The pressure is maintained by the BOP system 20
and the well can be serviced without having to cool the well down.
As the hot tubing string is extracted through the wellhead 14, it
is exposed to the flow of cooling gas in the spool stack. The
extraction rate of the tubing as well as other variables can be
adjusted so that the tubing string comes out of the BOP 20 at a
temperature that can be safely handled by the personnel on the
snubbing unit.
[0015] In a preferred embodiment, the removal of production tubing
results in intermittent movement of the tubing string as the
various lengths are removed. Preferably, the cooling occurs quickly
enough that the tubing string is cooled as it is pulled up through
spools 12. This is particularly important if used with coiled
tubing string, as it is pulled continuously.
[0016] In the depicted embodiment, the cooling chamber is open to
the annulus of the well. In a preferred embodiment, a gas, such as
nitrogen gas, may be pumped into the cooling chamber at the bottom
port 22, and extracted at the top port. The nitrogen gas is pumped
in at a pressure that is slightly higher than the wellbore
pressure, and is allowed to escape through the top port 22. This
creates a nitrogen gas buffer at the top of the wellbore. While
there will generally be some gas that escapes downhole because of
the higher pressure and the mixing of fluids, the rate of flow in
and out of the cooling chamber may be monitored to ensure that this
is minimized to an acceptable level. If it is found that an
unacceptable gas is being diverted downhole, the pressure may be
adjusted to reduce this. Other gases may be used, such as carbon
dioxide, although nitrogen is preferred for economic reasons. For
safety reasons, the gas should be an inert gas. While the fluid may
be at any temperature below the target temperature, a colder fluid
will accelerate the cooling process. However, excessively cold
temperatures may cause certain components to freeze. To balance
these concerns, a suitable temperature for the cooling fluid has
been found to be within 3 or 4 degrees of 5.degree. C.
[0017] In this patent document, the word "comprising" is used in
its non-limiting sense to mean that items following the word are
included, but items not specifically mentioned are not excluded. A
reference to an element by the indefinite article "a" does not
exclude the possibility that more than one of the element is
present, unless the context clearly requires that there be one and
only one of the elements.
[0018] The following claims are to be understood to include what is
specifically illustrated and described above, what is conceptually
equivalent, and what can be obviously substituted. Those skilled in
the art will appreciate that various adaptations and modifications
of the described embodiments can be configured without departing
from the scope of the claims. The illustrated embodiments have been
set forth only as examples and should not be taken as limiting the
invention. It is to be understood that, within the scope of the
following claims, the invention may be practiced other than as
specifically illustrated and described.
* * * * *