GB2085296A - Gas controls - Google Patents

Abstract

The invention relates to a method of extinguishing ignited well "blow- outs". A cylindrical or conical curtain of nitrogen or other non-flammable gas is caused to surround the flame zone and in addition a multiplicity of jets of a fire extinguishant such as a halon may be directed into the flame itself. The nitrogen or other inert gas may be directed into the flame at cryogenic temperatures, and indeed may be in liquid form at the supply nozzles.

Description

SPECIFICATION Gas controls This invention relates to a method of and apparatus for controlling oil and gas well "blow-outs".

It has long been the experience of the oil and gas drilling industry that unforeseen events occur such as a sudden pressure pulse which may- result in equipment failure or safety precautions may not be adequately observed, with the result that high pressure oil and/or gas are released to the atmos phere under the very high pressures existing within the earth's structure. Such a "blow-out" is at least very costly and as can be readily appreciated is dangerous to the persons involved and not infre quently results in an ecological disaster.

If at the time of the "blow-out" or subsequently the oil/gas ignites, the magnitude of the disaster is substantially increased because of the possible need to extinguish the flames before any remedial steps can be taken to stopthe flow.

Methods have been developed for trackling a "blow-out" but these methods are both costly and uncertain in their effect. One such method is to drill a relief well as closely as safely possible to the blown-out well and thereby to stop the flow by pumping down heavy liquid such as drilling mud, water or cement. The cost of this method is clearly very high and progress is slow particularly bearing in mind the wastage, danger and possible ecological damage caused by the continuing "blow-out". It may be necessary to drill a mile or more along an inclined bath and to intercept the blown-out well, and it will be appreciated that this is a difficult operation.

In a second method, explosives are expertly used to "blow-out" the flame. This method is, however, particularly difficult to apply to off-shore rigs since rigs usually have ?multiple well-heads and an expert ly placed shaped explosive charge intended to "blow-out" an ignited well-head may result in damage to other well-heads. Both these known methods have severe disadvantages.

According to the present invention there is pro vided a method of extinguishing or at least controll ing an ignited hydrocarbon well "blow-out" includ ing the step of feeding into the flame and/or the ambient of the flame a quantity of inert gas, such as nitrogen, sufficient to extinguish the flame or to effect the required degree of control.

Further according to the present invention there is provided a method of extinguishing or at least controlling an ignited hydrocarbon well "blow-out" including the steps of developing an encircling curtain of nitrogen or other non-inflammable gas and injecting into the flame a fore extinguishant such as a Talon.

Still further according to the present invention there is provided apparatus for extinguishing or at least controlling an ignited hydrocarbon "blow-out" including a nozzle arrangement, capable of at least substantially surrounding the flame zone, and means for supplying an inert gas and/or a fire evfinng h:lnt ta the nozle arranaementto extinguish or to control the flame.

The method and apparatus in accordance with the invention will now be further described. In the event of an ignited "blow-out" of an oil or gas well, the flame is enveloped with an inert gas, preferably nitrogen, so that the flame is extinguished or at least brought under the required degree of control. It is necessary that the rate of nitrogen supply to the flame zone should be very large. In other words although the absolute quantity of nitrogen will be substantial, it is more important that the rate of delivery should be very high.

If the measures taken involve only control of the oxygen content of the ambient it will be necessary to provide a complete cyiindrical curtain of oxygendeficient gas, and to ensure that it has sufficient thickness and velocity to prevent penetration by normal air from outside the curtain.

The quantity of inert gas will be such that, if it is intended to form an oxygen-deficient gas mixture around the flame, that the resultant mixure will have an oxygen content less than 10%.

Nitrogen as the inert gas has the advantage of relatively low cost in comparison with other inert gases and the fact that it does not solidify at any temperature. The nitrogen may be supplied to the flame zone or to the flame itself as a liquid since this will have the added advantage that the inevitable low temperature will not only assist in the quenching process but will assist in cooling any hot metal structures which are liable to re-ignite the-flame after the initial supply of nitrogen. However, where low temperature liquid is used, care must be taken to ensure that it does not cause low temperature embrittlement of important parts of any metal structure. For this reason, the nitrogen supply will be maintained, at a closely controlled rate, until all hot metal parts have been adequately cooled.Repair work can be initiated in a nitrogen atmosphere thus substantially eliminating the risk of a spark causing re-ignition of the escaping hydrocarbon provided the workers are provided with breathirig masks. Under the latter conditions it will be sufficientto use nitrogen as a gas since the low temperatures inherent with liquid nitrogen may themselves give rise to dangers to the operators.

When a Halon is used it will be necessary to ensure that it does not solidify at a nozzle or other constriction, particularly if used in conjunction with liquid or low temperature nitrogen. A Halon has the advantage in offshore use that it reduces the quantity of nitrogen likely to be required which logistically can cause difficulties because of low temperatures storage requirements. The Halon does not require low temperature storage and thus can easily be kept at a standby storage instaliation.

Flames have the effect of entraining embient-air in an upwards direction and indeed with large fires it is well known that high velocity air currents are locally generated. The method in accordance with the invention can be used in such a way as to take advantage of this effect by arranging the angles of the nozzles of a supplying annular manifold so that they'are directed upwardly with a conical formation when the intention isto penetrate the flame.

While the invention envisages the possibility of using an inert gas, such as nitrogen, it is preferred to use liquid nitrogen since the quantities which can be delivered through pipes of convenient size is substantially higher, and moreover as noted above, the low temperature of the liquid nitrogen is advantageous in itself.

If designed for liquefied inert gas the nozzle manifold for delivery of the liquid to the flame and/or ambient and the supply pipe thereto will be made of a material capable of withstandng very low tempera- tures. In the case of offshore wells an emergency ship or barge carrying a large quantity of liquid nitrogen will be equipped with a grab-type boom carrying the required pipeworkto the nozzle manifold which can deliver the required inert gas quantities. Such pipeworkwill incorporate cryogenic swivel joints. Pipeworkwill also, where appropriate, be provided to carry a supply of Halon or other fire extinguishant, but low temperature precautions will not be required.

Emergency equipment can be mounted on existing ships or barges and any such vessel will also be equipped with high capacity pumps capable of delivering liquid nitrogen at the necessary very high rates which will result in rapid quenching of the flame and lowthermal transfer into the supply pipe and manifold. A tank for Halon will also be provided on any emergency vessel.

If the invention is applied to a land-based well, arrangements can be made for a supply of low temperature gas road tankers and appropriate piping.

Occasionally "blow-outs" do not ignite because the gas velocity is too high. If a "blow-out" has a somewhat lower velocity, the use of a high velocity inert gas curtain or direct injection into the flame can increase the "blow-out" velocity to above the critical velocity and consequently the flame may be extinguished merely by increasing its velocity, that is without the need to supply a sufficient gas quantity to starve the flame of oxygen.

As an alternative to nitrogen and certain Haloes, it is possible to use the substantially inert exhaust gases of an internal-combustion engine. A gas turbine is capable of supplying very large quantities of exhaust gases and by suitable choice of engine, the oxygen content can be kept very low. The use of gas turbine exhaust gases will normally require a cooling plant and although large volumes are readily available, it is correspondingly necessary to provide large volume ducting for delivery to the nozzle arrangement.

As a further alternative to nitrogen, carbon dioxide can be used either alone or in conjunction with a Halon or otherfire-extinguishant. While less costly it has the disadvantage of requiring special steps in its supply to ensure it does not solidify.

The method and apparatus herein proposed have the advantage that the safety equipment can be installed in an emergency at any drilling rig or indeed a production plateform at relatively low cost and far more rapidly than the drilling of a relief well.

Further, it will be understood that even if the gas or oil does not ignite initially any repair work can be carried out in an ambient of inert gas in safety for the repair crew as it will not be necessary to work, even initially, in a hydrocarbon atmosphere.

While the invention is primarily intended to extinguish an ignited "blow-out", it can also be used where an initial requirement is merely to control the form and hence the effect of the flame.

CLAIMS (filed 12/10/81) 1. A method of extinguishing or at least controll-' ing an ignited hydrocarbon well "biow-out", including the step of feeding into the flame and/or the ambient of the flame a quantity of inert gas sufficient to extinguish the flame orto effectthe required degree of control.

2. A method of extinguishing or at least controlling an ignited hydrocarbon well "blow-out" including the steps of developing an encircling curtain of nitrogen or other non-inflammable gas and injecting into the flame a fire extinguishant.

3. Apparatus for extinguishing or at least controlling an ignited hydrocarbon well 'blow-out" including a nozzle arrangement, capable of a least substantially surrounding the flame zone, and means for supplying an inert gas and/or a fire extinguishanttothe nozzle arrangements to extinguish or control the flame.

4. Apparatus according to claim 3, wherein the nozzle arrangement defines an annular curtain of nitrogen, whereby substantially to exclude entry of ambient air to the flame zone.

5. Apparatus according to claim 3 or claim 4, comprising means for supplying the nitrogen in liquid form.

6. A method of extinguishing or at least controll- ing an ignited hydrocarbon well substantially as herein described.

7. Apparatus according to any one of claims 3 to 5 substantially as hereinbefore described.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. While the invention envisages the possibility of using an inert gas, such as nitrogen, it is preferred to use liquid nitrogen since the quantities which can be delivered through pipes of convenient size is substantially higher, and moreover as noted above, the low temperature of the liquid nitrogen is advantageous in itself. If designed for liquefied inert gas the nozzle manifold for delivery of the liquid to the flame and/or ambient and the supply pipe thereto will be made of a material capable of withstandng very low tempera- tures. In the case of offshore wells an emergency ship or barge carrying a large quantity of liquid nitrogen will be equipped with a grab-type boom carrying the required pipeworkto the nozzle manifold which can deliver the required inert gas quantities. Such pipeworkwill incorporate cryogenic swivel joints. Pipeworkwill also, where appropriate, be provided to carry a supply of Halon or other fire extinguishant, but low temperature precautions will not be required. Emergency equipment can be mounted on existing ships or barges and any such vessel will also be equipped with high capacity pumps capable of delivering liquid nitrogen at the necessary very high rates which will result in rapid quenching of the flame and lowthermal transfer into the supply pipe and manifold. A tank for Halon will also be provided on any emergency vessel. If the invention is applied to a land-based well, arrangements can be made for a supply of low temperature gas road tankers and appropriate piping. Occasionally "blow-outs" do not ignite because the gas velocity is too high. If a "blow-out" has a somewhat lower velocity, the use of a high velocity inert gas curtain or direct injection into the flame can increase the "blow-out" velocity to above the critical velocity and consequently the flame may be extinguished merely by increasing its velocity, that is without the need to supply a sufficient gas quantity to starve the flame of oxygen. As an alternative to nitrogen and certain Haloes, it is possible to use the substantially inert exhaust gases of an internal-combustion engine. A gas turbine is capable of supplying very large quantities of exhaust gases and by suitable choice of engine, the oxygen content can be kept very low. The use of gas turbine exhaust gases will normally require a cooling plant and although large volumes are readily available, it is correspondingly necessary to provide large volume ducting for delivery to the nozzle arrangement. As a further alternative to nitrogen, carbon dioxide can be used either alone or in conjunction with a Halon or otherfire-extinguishant. While less costly it has the disadvantage of requiring special steps in its supply to ensure it does not solidify. The method and apparatus herein proposed have the advantage that the safety equipment can be installed in an emergency at any drilling rig or indeed a production plateform at relatively low cost and far more rapidly than the drilling of a relief well. Further, it will be understood that even if the gas or oil does not ignite initially any repair work can be carried out in an ambient of inert gas in safety for the repair crew as it will not be necessary to work, even initially, in a hydrocarbon atmosphere. While the invention is primarily intended to extinguish an ignited "blow-out", it can also be used where an initial requirement is merely to control the form and hence the effect of the flame. CLAIMS (filed 12/10/81)

1. A method of extinguishing or at least controll-' ing an ignited hydrocarbon well "biow-out", including the step of feeding into the flame and/or the ambient of the flame a quantity of inert gas sufficient to extinguish the flame orto effectthe required degree of control.

2. A method of extinguishing or at least controlling an ignited hydrocarbon well "blow-out" including the steps of developing an encircling curtain of nitrogen or other non-inflammable gas and injecting into the flame a fire extinguishant.

3. Apparatus for extinguishing or at least controlling an ignited hydrocarbon well 'blow-out" including a nozzle arrangement, capable of a least substantially surrounding the flame zone, and means for supplying an inert gas and/or a fire extinguishanttothe nozzle arrangements to extinguish or control the flame.

4. Apparatus according to claim 3, wherein the nozzle arrangement defines an annular curtain of nitrogen, whereby substantially to exclude entry of ambient air to the flame zone.

5. Apparatus according to claim 3 or claim 4, comprising means for supplying the nitrogen in liquid form.

6. A method of extinguishing or at least controll- ing an ignited hydrocarbon well substantially as herein described.

7. Apparatus according to any one of claims 3 to 5 substantially as hereinbefore described.