CA2893087A1

CA2893087A1 - System and method for heating a well treatment fluid

Info

Publication number: CA2893087A1
Application number: CA2893087A
Authority: CA
Inventors: Marlin Romeo
Original assignee: Maralto Environmental Technologies Ltd
Current assignee: Zeet Inc
Priority date: 2014-05-28
Filing date: 2015-05-28
Publication date: 2015-11-28

Abstract

A system and method for heating a well treatment fluid, such as fracturing fluid or oil, using heat recovered from an engine exhaust gas emitted by an engine that drives a pump that pressurizes the treatment fluid. A manifold directs the engine exhaust gas from the engine either directly or indirectly into a heat exchanger. The manifold may direct the engine exhaust gas indirectly to the heat exchanger via a bum chamber of an incinerator, which combusts a fuel to generate a mixture of an incinerator exhaust gas and the engine exhaust gas. The heat exchanger transfers heat from the engine exhaust gas and, if present, the incinerator exhaust gas, to the well treatment fluid.

Description

SYSTEM AND METHOD FOR HEATING A WELL TREATMENT FLUID
Field of the Invention [0001] The present invention relates to treatment of oil and gas wells, and in particular, to a system and method for heating a well treatment fluid such as a fracturing fluid used in hydraulic fracturing operations or an oil used in hot oiling operations.
Background of the Invention

[0002] Hydraulic fracturing and hot oiling are two operations that are used to enhance production from an oil and gas well. Both of these operations involve injecting a heated well treatment fluid into the wellbore using an engine-driven pump.

[0003] Hydraulic fracturing involves injecting a fracturing fluid (a mixture of water, granular proppants, and optionally chemical additives) at high pressure and high flow rate into a low-permeability rock formation. The hydraulic pressure exerted by the fracturing fluid initiates and extends vertical cracks in the rock formation. The pressure is relieved to allow the fracturing fluid to flow back up the wellbore. The granular proppants remain trapped in the cracks, thereby keeping the cracks open and increasing the hydraulic conductivity of the rock formation. A burner unit coupled to a heat exchanger is used to the heat water used to make up the fracturing fluid. This prepares the water for mixing with the proppants and optional chemical additives, controls the viscosity of the fracturing fluid for optimal effectiveness, and, in some conditions, prevents freezing of the fracturing fluid. Typically, the fracturing fluid is heated so that it has a temperature of about 50 C when injected into the formation. A frac pump is used to inject the fracturing fluid into the rock formation. The frac pump is typically driven by a large-displacement, high output, diesel-powered engine. An exemplary engine of this kind has a displacement of 50 L (3000 in3) and a power rating of 1680 kW (2250 bhp),

[0004] Hot oiling involves injecting heated oil and cleansing additives into a wellbore to melt paraffin and asphaltene deposits that have stuck to the walls of wellbore tubulars at low temperature or pressure conditions. The melted deposits are pushed out of the well by the upward flow of oil. Hot oiling operations are typically performed using a hot oiling unit which includes a gas-fired burner, a heat exchanger coupled to the burner, and a pump, all of which are mounted on a truck trailer. Typically, the oil is heated to a temperature of about 100 C when injected into the wellbore. The pump is driven by an engine, typically diesel-powered, which is also used to power the truck.

[0005] The engines that drive the pumps used in hydraulic fracturing and hot oiling operations can emit substantial amounts of hot gaseous emissions (e.g., nitrogen oxides, hydrocarbons, and carbon dioxide) and solid particulate matter when operated for extended time periods. The conventional practice is to release the engine exhaust gases into the atmosphere. However, this practice wastes heat energy, contributes to environmental pollution, and presents potential health risks to nearby workers.
Summary of the Invention

[0006] The system and method of the present invention may be used to improve the energy efficiency of hydraulic fraeining operations or hot oiling operations, and control the atmospheric emissions associated with these operations.

[0007] In one aspect, the present invention provides a system for heating a well treatment fluid, using heat recovered from an engine exhaust gas emitted by at least one engine that drives a pump for pressurizing the well treatment fluid. The system comprises: a heat exchanger for transferring heat from the engine exhaust gas to the well treatment fluid; and a manifold adapted to direct the engine exhaust gas either directly or indirectly to the heat exchanger. In one embodiment, the system further comprises an incinerator for generating an incinerator exhaust gas and comprising a burn chamber, wherein the manifold directs the engine exhaust gas indirectly to the heat exchanger via the burn chamber of the incinerator.

[0008] In another aspect, the present invention provides a method for heating a well treatment fluid, using heat recovered from an engine exhaust gas emitted by at least one engine that drives a pump for pressurizing the well treatment fluid. The method comprises the simultaneous steps of: running the engine to drive the pump and emit the engine exhaust gas; directing the exhaust gas either directly or indirectly to a heat exchanger; and transferring heat from the collected engine exhaust gas to the well treatment fluid in the heat exchanger. In one embodiment, the exhaust gas is directed indirectly to the heat exchanger via a burn chamber of an incinerator, and the method comprises the further simultaneous steps of: combusting a fuel in the burn chamber of the incinerator to generate a mixture of an incinerator exhaust gas and the engine exhaust gas; and transferring heat from the mixture of the incinerator exhaust gas and to the well treatment fluid in the heat exchanger. In one embodiment, the engine exhaust gas is directed to or combined with an air intake for the incinerator.
Brief Description of the Drawings [00091 In the drawings, like elements are assigned like reference numerals.
The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of the present invention. Additionally, each of the embodiments depicted are but one of a number of possible arrangements utilizing the fundamental concepts of the present invention. The drawings are briefly described as follows:
[0010] Figure 1 is a drawing of a schematic representation of one embodiment of the system of the present invention used to heat a fracturing fluid, using heat recovered from the exhaust gas of an engine used to drive a frac pump.
[0011] Figure 2 is a drawing of a,schematic representation of another embodiment of the system of the present invention used to heat oil, using heat recovered from the exhaust gas of a truck engine used to drive a pump used in a hot oiling operation.
Detailed Description of Preferred Embodiments [0012] The invention relates to heating of a well treatment fluid for an oil and gas well.
When describing the present invention, all terms not defined herein have their common art-recognized meanings. To the extent that the following description is of a specific embodiment or a particular use of the invention, it is intended to be illustrative only, and not limiting of the claimed invention. It should be understood that alternatives, modifications and equivalents can be made or substituted without departing from the principle or scope of the claimed invention.
[0013] As used herein, the term "well treatment fluid" means any fluid that is injected into a well, and includes, without limitation, fluids used in hydraulic fracturing operations and hot oiling operations.
[0014] With reference to Figure 1, one embodiment of the system (10) of the present invention is now described. The system (10) is used to heat a fracturing fluid using heat recovered from a plurality of engines (100a ¨ 100d), each of which drives a frac pump (110a - 110d). In general, the system (10) comprises an incinerator (20), a manifold (40), and a heat exchanger (50).
[0015] Each engine (100) drives the associated frac pump (110) to inject the fracturing fluid under high pressure into the rock formation. The system (10) is not limited to use with a particular configuration or fuel source of the engine (100), provided that, when running, the engine (100) emits an engine exhaust gas through an engine exhaust opening. The engine (100) may be an internal combustion engine that combusts fuel in a combustion chamber to produce a high pressure and high temperature gas, which applies a driving force to an engine component such as a piston or turbine. In one embodiment, the engine (100) runs on diesel fuel. In other embodiments, the engine (100) runs on natural gas, gasoline, propane, or other combustible fuel. In embodiments, the engine (100) may be a reciprocating engine, a turbine engine or a rotary engine.
Engines (100) and frac pumps (110) suitable for use in hydraulic fracturing treatments are known to persons skilled in the art. The temperature of the engine exhaust gases may be on the order of about 900 C or more, but the system (10) of the present invention is not limited by any minimum temperature of the engine exhaust gas.
[0016] The incinerator (20) combusts a fuel to generate an incinerator exhaust gas, the heat of which is transferred to the fracturing fluid. Incinerators (20) suitable for heating fracturing fluid are known to persons skilled in the art. The system (10) is not limited to any particular configuration of incinerator (20), provided that the incinerator (20) has a burn chamber and generates an incinerator exhaust gas.

[0017] In one embodiment as shown in Figure 1, the incinerator (20) is a gas-fired cyclonic incinerator as described in U.S. Patent No. 8,443,740 to Romeo, the entire contents of which are incorporated herein, where permitted. The cyclonic incinerator (20) includes a cylindrical outer burn chamber (22) with an elongate forced air opening (24).
A forced air manifold (not shown) is disposed concentrically outside the outer burn chamber (22) to create a cyclonic air flow around the axis of the outer burn chamber (22).
An inner burn chamber (26) has one end (28) in communication with the outer burn chamber, and an opposite end that forms an exhaust gas opening (30). A gas inlet (32) is positioned to supply a gaseous fuel, such as propane, into the outer burn chamber (22).
The ignited gaseous fuel travels in the direction of the forced air through the outer burn chamber (22), and into the inner burn chamber (26). The combustion of the gaseous fuel produces an incinerator exhaust gas which exits through an exhaust gas opening (30).
[0018] The manifold (40) collects engine exhaust gas from the engine (100) and directs the engine exhaust gas into the heat exchanger (50) either directly, or indirectly, into the heat exchanger (50). In the embodiment shown in Figure 1, the engine (100) directs the engine exhaust gas indirectly to the heat exchanger (50), via the burn chamber of the incinerator (20), where it mixes with air that is to be combusted with the gaseous fuel. In one embodiment, the engine exhaust gas is directed to or combined with an air intake for the incinerator. In other embodiments (not shown), the manifold (40) may direct the engine exhaust gas into the heat exchanger (50) indirectly through components other than or in addition to the incinerator (20).
[0019] In the embodiment shown in Figure 1, the manifold (40) comprises a flow line.
A first end of the flow line has a plurality of branches (42a - 42d), each of which is connected to an engine exhaust opening of a different one of the engines (100a - 100d).
The second end (44) of the flow line terminates in the burn chamber of the incinerator (20). Preferably, the length of the manifold (40) is limited and the manifold is insulated to minimize loss of heat in the engine exhaust gas between the engine exhaust opening and the bum chamber of the incinerator (20). In embodiments, the manifold (40) may be either permanently or releasably coupled to the incinerator (20) and the exhaust gas opening of the engine (100). In embodiments, the manifold (40) may be adapted to sealingly engage the engine exhaust opening so as to direct substantially all of the engine exhaust gas to the burn chamber of the incinerator (20), or may direct only a portion of the engine exhaust gas to the burn chamber of the incinerator (20).
[0020] The heat exchanger (50) transfers heat from the engine exhaust gas to the fracturing fluid, Heat exchangers (50) suitable for heating fracturing fluid are known to persons skilled in the art. The system of the present invention is not limited to any particular configuration of heat exchanger (50).
[0021] In one embodiment as shown in Figure 1, the heat exchanger (50) is a heat exchanger as described in International Patent Application Publication no. WO
2014/063249 to Romeo, the entire contents of which are incorporated herein, where permitted. The heat exchanger (50) has a shell (52) internally divided into a first vessel (54) and an second vessel (56) by a pipe retaining plate (58) that sealingly retains a plurality of heat pipes (60). Each of the heat pipes (60) contains a heat transfer substance (e.g., water, alcohol, acetone, sodium or mercury), and has a first end located in the first vessel (54) and a second end located in the second vessel (56). The first vessel (54) has an inlet (62) coupled to the incinera4pr exhaust gas opening (30), and an outlet (64) that is coupled to an exhaust (66). A fan (68) situated between the outlet (64) and the exhaust (66) creates a suction to draw gas through the first vessel (54). The first vessel (54) is internally configured to direct gas through a porous dispersion plate (not shown) that distributes the gas amongst the first ends of the heat pipes (60). The second vessel (56) has an inlet (70) that may be coupled to a supply line to receive unheated fracturing fluid from a fracturing fluid source (not shown), and an outlet (72) that may be coupled to a supply line to discharge heated fracturing fluid to the frac pumps (100) as shown in Figure 1, or to a storage tank (not shown). The second vessel (56) has an internal baffle (not shown) that guides the fracturing fluid through a serpentine channel in the second vessel (56).
100221 The use and operation of the system (10) of the present invention is now described with reference to the embodiment shown Figure 1. The incinerator (20) and heat exchanger (50) are mounted on a mobile trailer (80), along with a pump (82), a generator (84) and a controller (86). The pump (82) is coupled to the inlet (70) of the second vessel (56) of the heat exchanger (50) to pump fracturing fluid through the second vessel (56). The generator (84) supplies power to the ignition source of the incinerator (20), the fan (68), the pump (82), and the controller (86). The controller (86) may be a programmable logic controller (PLC) and is operatively connected to the pump (82), generator (84), and the incinerator (20) to control these components, so as to achieve a desired flow rate and the temperature of the heated fracturing fluid produced by the system (10). The frac pumps (100) and their associated engines (110) may be mounted on a different trailer (not shown) or on a skid situated at the remote well location.

[0023] As necessary, each branch (42a ¨ 42d) of the manifold (40) is coupled to the engine exhaust gas outlet of a different one of the engines (100a - 100d). The gas inlet (32) of the incinerator (20) is coupled via a supply line to a gas fuel source (not shown), which may also be mounted to the trailer (80). The inlet (70) of the second vessel (56) of the heat exchanger (50) is coupled via a supply line to a source of unheated fracturing fluid (not shown), such as a reservoir, an above-ground storage tank or a tanker truck.
The outlet (72) of the second vessel (56) of the heat exchanger (50) is coupled via a supply line either to the inlet of the frac pumps (110), as shown in Figure 1, or to a storage tank.
[0024] Once set up in this manner, the engines (100) of the frac pumps (11) are run to inject the fracturing fluid into the fot;mation. The manifold (40) collects and directs these engine exhaust gases emitted by the running engines (100) into the burn chamber (22, 26) of the incinerator (20). In the bum chamber (22, 26), the engine exhaust gases mix with the relatively cooler ambient air that is drawn into the burn chamber (22, 26) for combustion with the gaseous fuel. At the same time, the incinerator (20) is ignited to combust a gas fuel supplied via the gas inlet (32) and possibly components of the engine exhaust gas, to produce an incinerator exhaust gas.
[0025] The fan (68) creates a suction that draws the mixture of incinerator exhaust gas and engine exhaust gas from the inner bum chamber (26), through the first vessel (54) of the heat exchanger (50), ultimately through exhaust (66). At the same time, the pump (82) pressurizes unheated fracturing fluid via the inlet (70) into the second vessel (56). As the mixture of incinerator exhaust gas and engine exhaust gas, and the fracturing fluid simultaneously stream through the first vessel (54) and second vessel (56), respectively,

9 the heat pipes (60) transfer heat from the mixture of incinerator exhaust gas and engine exhaust gas to the fracturing fluid. The outlet (72) of the second vessel (56) discharges the heated fracturing fluid to the inlet of the frac pumps (110) for immediate injection into the formation, as shown in Figure 1. Alternatively, in another embodiment (not shown), the outlet (72) may discharge the heated fracturing fluid to a storage tank (not shown) where it may be mixed with chemical additives or proppant materials, and subsequently injected into the formation using the frac pumps (110).
[0026] With reference to Figure 2, another embodiment of the system (10) of the present invention is now described. The system (10) and its operation are substantially similar to the embodiment of the system (10), except in the following respects. The inlet (70) of the second vessel (56) of the heat exchanger (50) is coupled via supply line to an oil storage tank (not shown) mounted on the trailer (80). The engine (100) that drives the pump (110) is the truck engine, which also powers a truck (not shown) used to tow the trailer (80). The pump (110) is mounted to the trailer (80) and is connected to a pump line for injecting hot oil into a wellbore during hot oiling operations. ' [0027] The recovery of engine exhaust gas has several potential benefits.
First, the resulting mixture of engine exhaust gas and incinerator exhaust gas at the exhaust gas opening (30) of the incinerator (20) should have a higher temperature than if the engine exhaust gas were not so recovered. The additional heat of the engine exhaust gas may be transferred to the well treatment fluid when the mixture of incinerator exhaust gas and engine exhaust gas is streamed through the heat exchanger (50). This reduces the amount of gas fuel that needs to be combusted by the incinerator (20) to produce a given flow rate and temperature of gas through the first vessel (54) of the heat exchanger (50).

Second, the engine exhaust gas warms the air drawn into the burn chamber of the incinerator (20). This decreases the lower flammability limit of the gaseous fuel combusted therein, thus allowing for the burning of leaner gaseous fuel mixtures in the incinerator (20). Third, collecting the engine exhaust gas facilitates control and treatment thereof, if so desired. As such, the system and method of the present invention may be used to improve the energy efficiency of hydraulic fracturing operations or hot oiling operations, and control the atmospheric emissions associated with these operations.
[0028] As will be apparent to those skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the scope of the invention claimed herein.

Claims

WHAT IS CLAIMED IS:

1. A system for heating a well treatment fluid, using heat recovered from an engine exhaust gas emitted by at least one engine that drives a pump for pressurizing the well treatment fluid, the system comprising:
(a) a heat exchanger for transferring heat from the engine exhaust gas to the well treatment fluid; and (b) a manifold adapted to direct the engine exhaust gas either directly or indirectly to the heat exchanger.

2. The system of claim 1 further comprising an incinerator for generating an incinerator exhaust gas and comprising a burn chamber, wherein the manifold directs the engine exhaust gas indirectly to the heat exchanger via the burn chamber of the incinerator.

3. The system of claim 2 wherein the incinerator further comprises a forced air manifold adapted to direct the engine exhaust gas in a cyclonic flow in the burn chamber.

4. The system of claim 1 for use with a plurality of engines, wherein the manifold is branched to direct exhaust gas generated by the plurality of engines.

5. The system of claim 1 wherein the heat exchanger is comprises a first vessel for the engine exhaust gas, a second vessel for the well treatment fluid, and a plurality of heat pipes for transferring heat between the first vessel and the second vessel.

6. The system of claim 1 wherein the treatment fluid is a fracturing fluid, and the pump is a frac pump for injecting the fracturing fluid into the well.

7. The system of claim 6 wherein the heat exchanger is coupled to the frac pump for discharging the heated fracturing fluid to the frac pump.

8. The system of claim 6 wherein the heat exchanger is coupled to a storage tank for discharging the heated fracturing fluid to the storage tank.

9. The system of claim 1 wherein the treatment fluid is an oil, and the at least one engine is an engine of a vehicle that drives the pump for injecting the oil into the well.

10. The system of claim 9 wherein the heat exchanger is coupled to the pump for discharging the heated oil to the pump.

11. A method for heating a well treatment fluid, using heat recovered from an engine exhaust gas emitted by at least one engine that drives a pump for pressurizing the well treatment fluid, the method comprising the simultaneous steps of:
(a) running the engine to emit the engine exhaust gas;
(b) directing the exhaust gas either directly or indirectly to a heat exchanger;
and (c) transferring heat from the engine exhaust gas to the well treatment fluid in the heat exchanger.

12. The method of claim 11 wherein the exhaust gas is directed indirectly to the heat exchanger via a burn chamber of an incinerator and the method comprises the further simultaneous steps of:
(a) combusting a fuel in the burn chamber of the incinerator to generate a mixture of an incinerator exhaust gas and the engine exhaust gas; and (b) transferring heat from the mixture of the incinerator exhaust gas and the engine exhaust gas to the well treatment fluid in the heat exchanger.

13. The method of claim 11 wherein the treatment fluid is a fracturing fluid, and method comprises the further step of using the pump to pressurize the heated fracturing fluid into the well.

14. The method of claim 11 wherein the treatment fluid is an oil, and the method comprises the further step of using the pump to pressurizing the heated oil into the well.