FLARE STACK SAFETY SYSTEM AND METHOD OF USE

SYSTEME DE SECURITE DE TORCHERE ET METHODE D'UTILISATION

English Abstract

In the context of an oil or gas well site flare system, a safety system is provided so that in the event of a flammable gas release at the well, the safety system can be activated to extinguish the sources of ignition. Activation of the safety system does not prevent the continued venting or exiting of flare gases from the flare stack. In a system aspect, the safety system comprises a source of purge gas connected to a flare stack and actuator means. When the actuator means is actuated, a flow of purge gas commences from said source into said flare stack while allowing said flammable gases to continue to exit out said flare stack. Other system and method aspects are also provided.

French Abstract

Dans le contexte d'un dispositif de torche pour des sites de sites de puits de pétrole ou de gaz, un système de sécurité est fourni de façon où dans le cas d'un dégagement d'un gaz inflammable au puits, le système de sécurité peut être actionné pour éteindre les sources d'inflammation. Un actionnement du système de sécurité n'empêche pas la ventilation continue ou la sortie de gaz de torche du support de torche. Dans un aspect du système, le système de sécurité comprend une source de gaz de purge raccordée à un support de torche et à un dispositif d'actionnement. Si le dispositif d'actionnement est actionné, un écoulement de gaz de purge commence à partir de ladite source vers ledit support de torche tout en permettant aux gaz inflammables de continuer à sortir du support de torche. D'autres méthodes et d'autres aspects sont aussi fournis.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN
EXCLUSIVE PROPERTY OR PRIVILEGE IS BEING CLAIMED ARE DEFINED AS
FOLLOWS:


1. A flare stack safety system, for connection to a flare line
carrying flammable gases from a well, said well being under pressure, to a
flare
stack, the safety system comprising:

a source of purge gas connected to said flare line; and
actuator means;

wherein said flare line provides for a flow of said flammable gases
from the well to the flare stack at all times, thereby allowing for said well
pressure to
be relieved at all times; and

wherein when the actuator means is actuated, a flow of purge gas
commences from said source into said flare line while allowing said flammable
gases to continue to exit out said flare stack.

2. The system of claim 1 wherein the source of purge gas
comprises a storage vessel containing a purge gas.

3. The system of claim 1 further comprising a purge line
connecting said source of purge gas to said flare line.

4. The system of claim 2 further comprising a purge line
connecting said source of purge gas to said flare line.



5. The system of claim 1 wherein the actuator means comprises a
normally closed purge valve.

6. The system of claim 4 wherein the actuator means comprises a
normally closed purge valve.

7. The system of claim 3 further comprising at least one check
valve mounted in the purge line.

8. The system of claim 6 further comprising at least one check
valve mounted in the purge line.

9. The system of claim 1 further comprising at least one check
valve mounted in the flare line.

10. The system of claim 8 further comprising at least one check
valve mounted in the flare line.

11. A flare stack safety system, for connection to a flare stack
receiving flammable gases from a well, said well being under pressure, the
safety
system comprising:

a source of purge gas connected to said flare stack; and
actuator means;


2


wherein said flare stack safety system provides for a flow of said
flammable gases from the well to the flare stack at all times, thereby
allowing for
said well pressure to be relieved at all times; and

wherein when the actuator means is actuated, a flow of purge gas
commences from said source into said flare stack while allowing said flammable
gases to continue to exit out said flare stack.

12. The system of claim 11 wherein the source of purge gas
comprises a storage vessel containing a purge gas.

13. The system of claim 11 further comprising a purge line
connecting said source of purge gas to said flare stack.

14. The system of claim 12 further comprising a purge line
connecting said source of purge gas to said flare stack.

15. The system of claim 11 wherein the actuator means comprises
a normally closed purge valve.

16. The system of claim 14 wherein the actuator means comprises
a normally closed purge valve.

3


17. The system of claim 16 further comprising at least one check
valve mounted in the purge line.

18. A method of flaring pressurized well gases while preventing
well fires caused by gases or fluids inadvertently discharged around a well,
comprising:

continuously directing the well gases out a flare stack, said flare stack
having an adjacent ignition source;

sensing a gas or fluid leak at the well;

turning off said ignition source adjacent said flare stack;

purging said flare stack by injecting a purge gas into said stack; and
allowing the well gases to exit out said flare stack at all times.

19. The system of claim 1 wherein the flare stack further comprises
a pilot line and the source of purge gas is also connected to said pilot line.

20. The system of claim 11 wherein the flare stack further
comprises a pilot line and the source of purge gas is also connected to said
pilot
line.

21. The method of claim 18 wherein the ignition source comprises
a pilot light fed by a pilot line and the step of turning off the ignition
source is
accomplished by purging the pilot line with a purge gas.

4

Description

CA 02465735 2004-04-29
1 "FLARE STACK SAFETY SYSTEM AND METHOD OF USE"
2
3 FIELD OF THE INVENTION
4 The field of present invention relates generally to flare systems used
at oil and gas drilling sites and, more particularly, to flare stack safety
systems for
6 use during snubbing operations, well testing and other well completion
operations.
7
8 BACKGROUND OF THE INVENTION
9 During the insertion of piping and tools into live well bores, and the
extraction of piping and tools from live well bores, known as "snubbing", it
is
11 conventional that a flare stack is often burning nearby, to receive gases
from the
12 well and thereby relief the well pressures that are present during the
snubbing
13 operations.
14 However, at times failures occur in pressure control systems due to
equipment malfunction or, more commonly, human error. During such an event,
16 large plumbs of flammable gas may escape from the pressure control
equipment
17 and/or blow out from the well and drift towards the flare stack -
occasionally with
18 disastrous results such as a well fire initiated by the flare system.
19 Flare stacks for oil and gas operations tend to be fairly simple systems
that are devoid of anything but the simplest controls. Typically, an ignition
source
21 such as a pilot flame is provided at the outlet of the flare stack and is
left on
22 constantly so that, in the event that flammable gases are vented to the
flare stack,
23 the ignition source will start combustion of such vented gases. Thus,
during normal

CA 02465735 2004-04-29
1 operations, the flare stack or at least portions thereof towards the outlet
end are
2 fairly warm. Additionally, even if the fuel for the pilot flame is shut off,
the remaining
3 fuel (typically propane) in the line to the pilot still has enough pressure
to keep the
4 pilot flame burning for a few minutes.
A further complicating factor is that during workover and completion
6 operations is it generally not desirable to shut off the flow of gases to
the flare
7 system when the pressure control equipment has failed. Shutting off the flow
of
8 vented gases, from the well to the flare stack, would only exaggerate the
well
9 pressure that would be desirable to relieve. However, such a continued flow
of
gases through the flare stack would also allow the flare to continue burning,
long
11 after the fuel to the pilot flame is shut off and the pilot flame itself
has extinguished.
12 What is needed is a safety system which will eliminate the danger of
13 ignition of escaping flammable vapors, by the flare stack system, while
still allowing
14 the flow of vented gases out through the flare stack.
16
17 BRIEF DESCRIPTION OF THE DRAWINGS
18 Figure 1 is a schematic representation of one embodiment of a flare
19 stack safety system;
Figure 2 is a schematic representation of a second embodiment of a
21 flare stack safety system;
22 Figures 3a and 3b are perspective views of the embodiment of Figure
23 1; and
2

CA 02465735 2004-04-29
1 Figure 4 is a schematic representation of a third embodiment of a flare
2 stack safety system.
3
4 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figures 1, 3a and 3b show one embodiment of a flare stack safety
6 system 10. A main flare line 12 carries flammable gases from the well to a
flare
7 stack 14 for combustion. The flare line 12 enters the flare stack 14
substantially
8 near the bottom. The flare stack 14 has an ignition source 16 to initiate
the
9 combustion of the gases. The ignition source 16 can be electronic, a pilot
light or
pilot flame operated with a fuel gas, or any other equivalent ignition source.
In this
11 embodiment the ignition source 16 is a pilot flame created by a burner 18
supplied
12 with fuel gas through a pilot line 20 .
13 A purge line 22 connects a storage vessel 30 to the flare line 12 just
14 prior to the junction of the flare line 12 with the flare stack 14. The
purge line 22
branches and also connects to the pilot line 20. Preferably, check valves 24,
26
16 are mounted in the purge line 22 such that when actuator or purge valve 32
is
17 opened, flow commences from storage vessel 30 into the flare line 12 and
pilot line
18 20. Check valves 24, 26 are illustrated schematically as a spring-loaded
balls and
19 prevent gas from entering purge line 22.
The purge valve 32 is preferably a quick opening valve. The purge
21 valve 32 is left in the normally closed position during normal operations.
A suitable
22 valve would be a butterfly valve or ball valve. Alternatively the purge
valve 32 could
3

CA 02465735 2004-04-29
1 be a pressure activated valve that can be opened from a variety of locations
on the
2 well site.
3 Storage vessel 30 typically carries a non-combustible pressurized
4 inert gas, preferably nitrogen. Another suitable non-combustible gas would
be C02.
In this embodiment, storage vessel 30 further comprises bottles of nitrogen 34
6 connected to lengths of pre-charge piping 36. The pre-charged piping 36
stores the
7 desired volume of inert gas under pressure
8
9 OPERATION
During normal well operations, the purge valve 32 is closed, keeping
11 the pressurized inert gas in the storage vessel 30. In the event of an
emergency at
12 the well site involving a flammable gas or liquid release, purge valve 32
is actuated
13 to open. Flow of inert gas is immediately begun into the flare line 12 and
pilot line
14 20 through the purge line 22 and past the check valves 24, 26. The flow of
inert
cool gases from the purge line 22 through the flare line 12 and then into the
flare
16 stack 14 cools the flare stack 14 down and ensures that no oxygen can enter
the
17 flare stack 14 as it is cooled down.
18 What results is a quick, within a few seconds, purging of flare stack 14
19 and pilot line 20 with inert gas from the storage vessel 30.
Advantageously, the
ignition source 16 is also cut off from its fuel gas by the entry of inert gas
into the
21 pilot line 20, and is thereby extinguished and cooled. The rapid cool down
of both
22 the flare stack 14 and burner 18 precludes the availability of either as a
further
23 source of ignition to escaping gas from the well. More advantageously,
because the
4

CA 02465735 2004-04-29
1 vented gases are still able to flow from the well, through the flare Line
12, into the
2 flare stack 14, the well pressure can be relieved while having eliminated
the danger
3 of igniting escaped flammable vapors from the well and causing a fire.
4
SECOND EMBODIMENT
6 Figure 2 illustrates a second, slightly different embodiment, wherein
7 the ignition source 16 is an electronic igniter 50 maintained constantly in
the on
8 position through use of switch or control labeled A. Accordingly there is no
pilot line
9 nor does the purge line 22 connect to the ignition source. The purge valve
32 is
controlled by switch B. When switch B is actuated, it accomplishes the
following
11 tasks: the purge valve 32 is opened and the ignition source 16 is cut off.
12 Accordingly, in the event of an emergency at the well site switch B is
13 actuated which overrides the ignition source 16, closing it off while at
the same time
14 opening the purge valve 32. Switch B can be manually activated or it can be
tied
into a flammable gas detector which will set off switch B automatically as
well as
16 sound an audible alarm.
17
18 THIRD EMBODIMENT
19 Figure 4 illustrates a third embodiment of the flare stack safety system
10, wherein a plurality of flare stacks 14a, 14b are shown, each connected to
the
21 purge line 22 of the flare stack safety system 10.
22
23
5

CA 02465735 2004-04-29
1 METHOD
2 In one embodiment a method of operation of a flare stack safety
3 system comprises:
4 purging at least one flare stack with a non-combustible inert gas;
cutting off at least one ignition source; and
6 allowing waste gases to continue to exit out at least one flare stack.
6

Representative Drawing