EP2666958A1

EP2666958A1 - Method of fraccing a well

Info

Publication number: EP2666958A1
Application number: EP13150380.7A
Authority: EP
Inventors: Arthur I. Shirley
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2012-05-23
Filing date: 2013-01-07
Publication date: 2013-11-27
Also published as: US20130312976A1; WO2013177114A1

Abstract

In order to overcome the problems that earlier methods have experienced, a method of fraccing or hydrofracturing or hydraulically fracturing a well is proposed, comprising
- injecting natural gas into the well, and
- recovering natural gas from the well.

Description

Technical field of the present invention

The present invention relates to a method for fraccing or hydrofracturing or hydraulically fracturing a well, in particular a production well, for example an oil well or a gas well, with natural gas.

Background of the present invention; prior art

In the production of natural gas from shale or other "tight-gas" formations, hydraulic fracturing (or "frac") is used to break up the rock around the well bore and reduce the resistance to gas flow. The frac technique generally requires injecting into the well large amounts of fluids that are

compressible, like nitrogen or carbon dioxide, or
incompressible, such as water or liquefied petroleum gas.

The fluids are pumped to high pressure to create large compressive forces around the well bore. These forces break the rock and create tiny fissures for gas flow. To aid in the penetration and stability of theses fissures, small amounts on the order of one to two percent by volume of hydrocarbons, mineral acids and "proppants" are added to the injected fluid.
Thousands of tons of fluid may be injected during each frac job and much of this fluid is returned to the surface when the flow is reversed (hereafter called "produced fluids") and natural gas is produced from the well.
If water is used as the fracturing fluid, the produced fluid water is typically brackish with small amounts of the other materials injected into the formation. Reuse of these waters is problematic because of their composition and consequently, the produced fluid water must be treated for environmental concerns and disposed of in surface waters.
Alternatively, the produced fluid water must be injected into deep saline aquifers. If gases or condensable hydrocarbons such as liquefied petroleum gas are used, their availability and disposal after use can also create difficulties for the producer.
US 2012/0012321 A1 discloses a method for producing natural gas from hydrocarbon hydrates while simultaneously storing carbon dioxide in geological formations. More particularly, a method for extracting methane from methane hydrates is revealed, comprising the following steps:

feeding supercritical carbon dioxide to the methane hydrate deposits;
allowing the carbon dioxide to take effect on the methane hydrate to release methane and store the carbon dioxide as carbon dioxide hydrate; and
removing the released methane.

This method known from US 2012/0012321 A1 can be realised in different variants. For example, hydrofracturing methods can be used to increase the permeability of the hydrate-containing sediment layers.

Disclosure of the present invention: object, solution, advantages

Starting from the disadvantages and shortcomings as described above and taking the prior art as discussed into account, an object of the present invention is to overcome the problems that earlier methods have experienced.
This object is accomplished by a method comprising the features of claim 1. Advantageous embodiments and expedient improvements of the present invention are disclosed in the dependent claims.
In one embodiment of the present invention, a well, in particular a production well, for example an oil well or a gas well, is fracced or hydrofractured or hydraulically fractured to recover natural gas present in the well after injecting natural gas into the well.
Before being injected into the well, the natural gas, in particular the liquefied natural gas (LNG), for example the methane gas,

can advantageously be vaporized, in particular rapidly vaporized, for example by means of at least one submersible combustion vaporizer, and/or
can expediently be mixed with at least one appropriate additive, in particular in order to form a foam or dense fluid to the degree necessary to suspend at least one proppant,

The natural gas, in particular the high pressure natural gas, is fed into the well, in particular injected into the well, for example at rates ranging from about 10.000 standard cubic feed (scf) per minute to about 100.000 scf per minute.
Once the well is pressurized and fracturing has begun, the flow of the high pressure natural gas can preferably be stopped and/or preferably be reversed. The natural gas produced and recovered from the well can be treated and made ready for use in other applications; in particular,

the natural gas which is recovered as both the compressed or pressurized natural gas and natural gas present in the well can be separated from at least one other produced fluid; and/or
the recovered natural gas can be fed directly to at least one pipeline where the recovered natural gas is sent to at least one storage facility or fed to at least one other industrial operation; and/or
the recovered natural gas can be combusted and the combustion products can be run through at least one heat exchanger, at least one expander and/or at least one turbine to produce electricity and/or steam.

Finally, the present invention relates to a method for using natural gas, in particular liquefied natural gas (LNG), for example methane gas, for stimulating a well, in particular a production well, for example an oil well or a gas well.
The present invention addresses the problems associated with the disposal of producing fluid by using liquefied natural gas (LNG) as a fluid source. The produced fluid will have roughly the same composition of natural gas and can be introduced into at least one pipeline without further processing.

Detailed description of the present invention; best way of embodying the present invention

The present invention provides for a method for fraccing or hydrofracturing or hydraulically fracturing a well, in particular an oil well or a gas well, to recover natural gas.
Natural gas, in particular liquefied natural gas (LNG), can be shipped to the well site in large quantities, such as about thousand tons.
The liquefied natural gas can be rapidly vaporized utilizing a high-speed vaporization technique such as by at least one submersible combustion vaporizer or other known technique.
The vaporized liquefied natural gas, which can, at least essentially, be methane gas, can be mixed with small amounts of additives to form a foam or dense fluid to the degree necessary to suspend at least one proppant.
The foam or dense fluid can then be compressed or pressurized, in particular by conventional techniques, to pressures between about 1.000 pounds per square inch (psi) [= about 6,9 Megapascal (MPa)] and about 10.000 psi [= about 69,0 MPa] for injection into the well, in particular at rates ranging from about 10.000 standard cubic feed (scf) [= about 283,2 cubic metres (m³)] per minute to about 100.000 scf [= about 2.832 m³] per minute.
Once the well has been fully pressurized and the fracturing process initiated, the flow of the pressurized natural gas can be stopped and/or can be reversed. The natural gas, in particular the methane gas, which is recovered as both the pressurized dense fluid and the gas present in the fractured well can be separated from other produced fluids.
The recovered natural gas, in particular the recovered methane gas, can be fed directly to at least one pipeline where the gas can be sent to at least one storage facility or fed to at least one other industrial operation.
Additionally or alternatively, the recovered natural gas can be combusted and the combustion products can be run through at least one heat exchanger, at least one expander and/or at least one turbine to produce electricity and/or steam.
The method of the present invention using natural gas from liquefied natural gas (LNG) has numerous advantages over water or inert gas as fracturing fluids:

Large amounts of water-based fracturing fluids, for example, can remain in the reservoir and reduce natural gas flow from the well.

The vaporized liquefied natural gas is essentially the same composition as the in-situ natural gas present in the well and when the flow is reversed, the produced fluids can be treated by the same equipment and in the same manner as the produced natural gas.
Further, no additional safety issues are created when the vaporized liquefied natural gas is fed into well.

Claims

A method of fraccing or hydrofracturing or hydraulically fracturing a well, comprising
- injecting natural gas into the well, and

- recovering natural gas from the well.
The method according to claim 1, wherein the well is a production well, in particular an oil well or a gas well.
The method according to claim 1 or 2, wherein the natural gas is liquefied natural gas (LNG).
The method according to at least one of claims 1 to 3, wherein the natural gas is, at least essentially, methane gas.
The method according to at least one of claims 1 to 4, comprising the additional step of compressing or pressurizing the natural gas before the step of injecting it into the well.
The method according to claim 5, wherein the natural gas is compressed or pressurized to pressures between about 1.000 pounds per square inch (psi) and about 10.000 psi for injection into the well.
The method according to at least one of claims 1 to 6, comprising the additional step of vaporizing, in particular rapidly vaporizing, the natural gas before the step of injecting it into the well, in particular before the step of compressing or pressurizing the natural gas.
The method according to claim 7, wherein the natural gas is vaporized by at least one submersible combustion vaporizer.
The method according to at least one of claims 1 to 8, comprising the additional step of mixing the natural gas with at least one amount of at least one additive before the step of injecting the natural gas into the well, in particular comprising the additional step of mixing the vaporized natural gas with at least one small amount of at least one additive before the step of compressing or pressurizing the natural gas.
The method according to at least one of claims 1 to 9, wherein the natural gas is injected into the well at rates ranging from about 10.000 standard cubic feed (scf) per minute to about 100.000 scf per minute.
The method according to at least one of claims 1 to 10, comprising the additional step of stopping and/or reversing the flow of the compressed or pressurized natural gas before the step of recovering natural gas from the well.
The method according to at least one of claims 1 to 11, wherein the natural gas which is recovered as both the compressed or pressurized natural gas and natural gas present in the well is separated from at least one other produced fluid.
The method according to at least one of claims 1 to 12, wherein the recovered natural gas is fed directly to at least one pipeline where the recovered natural gas is sent to at least one storage facility or fed to at least one other industrial operation.
The method according to at least one of claims 1 to 13, wherein the recovered natural gas is combusted and the combustion products are run through at least one heat exchanger, at least one expander and/or at least one turbine to produce electricity and/or steam.
Use of the method according to at least one of claims 1 to 14 for stimulating a well, in particular a production well, for example an oil well or a gas well, with natural gas, in particular with liquefied natural gas (LNG), for example with methane gas.