WO1998040603A2

WO1998040603A2 - Apparatus and methods for generating energy utilizing downhole processed fuel

Info

Publication number: WO1998040603A2
Application number: PCT/US1998/005094
Authority: WO
Inventors: Michael H. Johnson; Paulo S. Tubel; Christopher L. Gann
Original assignee: Baker Hughes Incorporated
Priority date: 1997-03-12
Filing date: 1998-03-12
Publication date: 1998-09-17
Also published as: AU6466898A; WO1998040603A3

Abstract

The present invention provides methods and systems for generating energy at the well sites. Hydrocarbons are processed downhole to produce fuel for use in the generation of energy. The desired energy at the well site is processed downhole or at the surface. The generated energy includes heat energy, electric power, mechanical and hydraulic power. Useful byproducts such as heat is utilized to enhance production. Harmful or undesired byproducts are disposed of by re-injecting it into one or more lateral wellbore drilled for such purpose. Such waste is suitably treated prior to its disposal. Fuel cells are preferably used to generate heat energy and electrical power. Heat generated by the fuel cell is utilized to enhance production of formation fluids and to improve fluid processing.

Description

TITLE: APPARATUS AND METHODS FOR GENERATING ENERGY

UTILIZING DOWNHOLE PROCESSED FUEL

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to generating energy at a well site for use

at the surface or downhole to perform one or more useful functions. More

particularly, this invention relates to processing hydrocarbons downhole to

obtain a fuel and utilizing such fuel to generate energy, such as electric power and/or heat energy, at the well site and utilizing the generated energy to

perform a desired function or operation, preferably at the well site. This invention also relates to utilizing fuel cells as a source of producing energy at

the well site and utilizing such energy for a variety of purposes. This invention also relates to utilizing energy present due to the differential pressure between

spaced apart two or more subsurface zones to operate a device disposed in the wellbore, including pumping equipment to lift the hydrocarbons to the surface

and separation equipment, such as a centrifuge, for separating components of

the formation fluids. 2. Background of the Art

To obtain hydrocarbons such as oil and gas, boreholes or wellbores are drilled from one or more surface locations into hydrocarbon-bearing

subterranean geological strata or earth formations (also referred to in the oil and

gas industry as "pay zones" or "reservoirs") . Some reservoirs contain

predominantly crude oil (or "oil") while the others may contain mostly natural gas ("gas") or gas condensate. Typically, the fluid produced from a wellbore

(generally referred to as the "formation fluid") is a mixture of oil, gas, water and solids. The formation fluid is usually processed at the surface to separate the

various components. Often, in remote locations, the oil is transported from the well site to a processing facility while gas is flared or burned-off , re-injected into

earth formations or transported to a market. Flaring gas is common in remote areas and in underdeveloped countries because they generally do not have

market for such gas. Flaring gas is hazardous, may have environmental

implications and is waste of a natural resource. It would be highly desirable to

utilize gas that would otherwise be wasted to generate electric power at the well site, which can be utilized at the well site or transported via conventional

methods to a market. This invention provides methods of utilizing gas and oil to produce electric power within the wellbore and at the well site.

Processing formation fluids at the surface produces waste or by- products, such as solids, sulphur oxides, nitrous oxides and asphaltenes, which

pollute the environment. It is, thus, desirable to process (even partially) the

formation fluids downhole and safely dispose of any undesirable by-products in subsurface formations located several thousand meters below the earth's

surface. The present invention provides methods for processing formation fluids downhole and utilizing the processed fluids to generate energy (such as

heat energy, electric power, mechanical power or hydraulic power) at the well

site (downhole or at the surface).

Also in remote locations, gas fields are frequently not developed or gas

wells are capped. This is primarily due to the unavailability of gas markets.

The methods of the present invention may be utilized to generate energy within

gas wells or at the surface. The generated energy may then be utilized to perform useful operations in the wellbore, such as operating devices or heating

formation fluids to enhance production and/or at the surface. The electric power may also be transported to an infrastructure or grids by conventional

methods, which are easier and less expensive to install than gas pipelines or

providing facilities and equipment such as roads and vehicles to transport fluids.

The fluids flowing from the formations into a wellbore have kinetic

energy, which is typically not utilized to perform any useful operation

downhole. Additionally, in low pressure or low production wells, devices, such as an electric submersible pump (ESP), or an artificial stimulation method, such as the injection of steam to enhance recovery of formation fluids. The present

invention provides methods and apparatus for utilizing the kinetic energy of the

formation fluids and or the injected fluids to perform a useful operation

downhole, such as operating pumping equipment or fluid separation equipment within the wellbore.

SUMMARY OF THE INVENTION

In general, the present invention provides methods and systems for generating energy at the well sites. Hydrocarbons are processed downhole to produce fuel for use in the generation of energy. The desired energy at the well

site is processed downhole or at the surface. The generated energy includes heat energy, electric power, mechanical and hydraulic power. Useful byproducts such as heat is utilized to enhance production. Harmful or undesired byproducts are disposed of by re-injecting it into one or more lateral

wellbore drilled for such purpose. Such waste is suitably treated prior to its

disposal. Fuel cells are preferably used to generate heat energy and electric

power. Heat generated by the fuel cell is utilized to enhance reservoir productivity, fluid flow to the surface and to improve fluid processing at the

well site. In one method, the formation fluid containing hydrocarbons is recovered from a producing zone and passed to one or more fluid processing units

downhole. The formation fluid is processed to remove solids, water and other non-hydrocarbon gases. The heat energy produced as the byproduct of the

fluid processing is preferably used to enhance production of hydrocarbons by injecting the heat into the earth formation via one or more wellbores. The undesired waste produced is preferably disposed of by re-injecting it into one

or more lateral wellbores drilled for such purpose to minimize the impact on the

environment. Such waste may be suitably treated prior to its disposal.

The gas may be separated from liquid hydrocarbon downhole and utilized as a fuel for producing energy at the surface. Examples of energy generation

equipment includes gas-fired turbines and associated generators, gas-fired

engines and associated generators and fuel cells.

Alternatively, the processed hydrocarbons may be utilized to generate the

desired form of energy downhole. For downhole energy generation, the energy

generation equipment, preferably a fuel cell, is disposed in the wellbore. The

downhole-processed hydrocarbons are utilized to operate the energy generation equipment. Oxidant gas required by the energy generation equipment may be

supplied from a chemical source disposed in the wellbore or from the surface in a suitable form, such as compressed air, compressed oxygen, etc. The undesired discharge or waste from the downhole energy unit is re-injected into^{^} a selected formation, preferably via a lateral wellbore drilled for such purpose. The discharge from the processing equipment and the energy generation equipment may be suitably treated to reduce or eliminate the harmful effects of

such waste prior to discharging it into the selected formation, such as by chemically treating the waste. Heat energy produced may be used to improve

the processing of the fluids and/or to enhance hydrocarbon production from the reservoirs.

In one aspect of the present invention a fuel cell is used to generate

electric power and to generate heat downhole utilizing, at least in part, the downhole processed fuel. The electric power is utilized to operate one or more devices downhole or for use at the surface. The heat generated by the fuel cell

is utilized to perform a useful function, including heating the formation fluid

prior to processing it and heating the formation fluid to enhance hydrocarbon production. In another aspect of this invention, a fuel cell at the surface

utilizes, at least partially, the downhole processed fuel and the heat generated by the fuel cell is re-injected into the wellbore or formation producing the

formation fluids. In another aspect of this invention, the fuel cell provides the

energy to a fluid processing unit deployed to process the wellbore fluid at the

well site. In yet another aspect of this invention, a fuel cell downhole generates heat energy that is distributed into the formation and/or a production wellbore to enhance the fluid flow through the production wellbore and to improve the fluid flow from the formation to the production wellbore.

In another aspect of the invention, fluid energy created by differential

pressure between two zones is utilized to generate mechanical energy, which is then utilized downhole to perform a useful function, such as operating a

device. The fluid flow from one zone enters a wellbore where it operates a

device such as a turbine. The turbine is then used to operate a device

downhole, such as pumping equipment to pump hydrocarbons to the surface, separation equipment to separate constituents of the formation fluid or another

suitable device.

Examples of the more important features of the invention have been summarized rather broadly in order that the detailed description thereof that

follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims

appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS For detailed understanding of the present invention, reference should be made to the following detailed description of the preferred embodiment, taken

in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein:

Figure 1 shows a schematic illustration of a wellbore with a fluid processing equipment for producing a fuel downhole and an energy generation equipment in the wellbore or at the surface for generating energy that utilizes

the downhole processed fuel as the fuel source.

Figure 2 shows a schematic illustration of a wellbore with fluid processing equipment for producing fuel downhole and a fuel cell in the

wellbore for generating energy.

Figure 3 shows a schematic illustration of a wellbore with a fuel cell at

the surface that is supplied with fuel from a source at the surface or with

downhole processed fuel and wherein the heat generated by the fuel cell is injected into the wellbore.

Figure 4 shows a schematic illustration of a well site wherein fluid

processor processes formation fluid produced by a wellbore and a fuel cell

provides energy to the fluid processor. Figure 5 shows a schematic illustration of a wellbore wherein a heatr source heats the formation fluid prior to the processing of the formation fluid

downhole.

Figure 6 shows a schematic illustration of a wellbore system wherein the heat generated by the fuel cell is used to heat the formation fluid to reduce its

viscosity and to enhance fluid flow from the formation into a production

wellbore.

Figure 7 shows a schematic illustration of multi-lateral wellbores wherein

electric power is generated within a main wellbore by utilizing a suitable fuel

obtained by processing formation fluids within the main wellbore or one of its

laterals.

Figure 8 is a general flow diagram according to the present invention which may be utilized for processing formation fluids within a wellbore to

produce a fuel acceptable for use in electrical power generation equipment.

Figure 9 (Prior Art) shows a schematic illustration of a fuel cell.

Figure 10 is a schematic diagram showing the use of pressure differential

created downhole to operate a device in the wellbore. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In one aspect, the present invention provides methods and systems for at least partially processing hydrocarbons downhole to provide fuels which may

be utilized for generating energy at the well site (in the wellbore or at the

surface). In another aspect, the invention provides methods for utilizing energy

that is present due to differential pressure of fluids between zones to perform a useful operation downhole.

Figure 1 shows a schematic illustration of a wellbore system 10-1 at a

well site wherein a fluid processing equipment 20 in a wellbore 12 produces a

fuel 22 downhole that is utilized to generate energy at the well site 10. A

suitable fluid processing unit or equipment 20 is located at a desired location in the wellbore 12 by any known method in the art. The formation fluid 21 flows from the earth formation 16 into the wellbore 12 due to the pressure

differential between the formation 16 and the wellbore 12. A packer 18 may

be utilized to prevent the formation fluid 21 flow into the wellbore 12 below the

formation fluid processor 20. In one aspect of this invention, at least a portion

of the formation fluid 21 is processed by the fluid processing equipment 20. One output of the fluid processor 20 is a refined or partially refined fuel which

can be utilized in energy generation equipment, such as 24 to generate energy

26. Other outputs or byproducts of the energy generation equipment 24 typically include hot waste gases and/or liquid or solid waste byproducts,

generally shown herein by numeral 27. The fluid processor also generates

similar byproducts, which are referred to by numeral 23. in one aspect of the invention, the heat generated is injected into the wellbore or the formation to enhance flow of the formation fluid into the wellbore and the undesired waste byproducts or effluent are discharged into a separate wellbore or formation as

described below. In the wellbore system of Figure 1 , the formation fluid is

processed at least partially downhole by a fluid processor 20. The processed

fluid may be utilized to generate the desired form of energy by the energy generation equipment 24 in the wellbore 12 or 24a located at the surface 14.

Still referring to Figure 1 , any fluid processing method and equipment

known in the art may be utilized to produce the fuel 22 and to generate the energy 26. The fuel produced may be natural gas or a liquid hydrocarbon. The

energy generation equipment may include a fuel cell that generates electric power as the energy 26 and heat as one of the byproducts 27. A turbine may

be used to generate mechanical or hydraulic power which may be used to

perform any useful operation in the wellbore 12 or at the surface 14, including

generating electric power. Certain exemplary wellbore systems utilizing fuel cells as energy generation equipment are described below, it should be noted,

however, that this invention is not limited to such equipment or the specific

configurations. Any other equipment or method may be utilized for the intended purposes described herein. Exemplary manners of utilizing the generated energy and certain byproducts and the disposal of the undesired

waste byproducts are also described below.

Figure 2 shows a schematic illustration of a wellbore system 10-2 wherein a fuel cell 30 in the wellbore 12b generates electric power 31 and heat

energy 33. The desired fuel 32 to the fuel cell 30 may be provided from a

downhole fuel processor 20a or from a fuel source 20b at the surface 14.

Oxidant gas to the fuel cell 30 may be provided from a surface source 32, preferably in the form of compressed air, compressed oxygen or in any other

suitable form or from a chemical reaction source in the wellbore (not shown) .

The electrical energy 31 , in one aspect, is utilized downhole to operate

downhole devices and to supply electric power to various sensors normally

disposed in the wellbores for monitoring the condition of the wellbore, formation and downhole devices. The electrical power may also be transported to any existing infrastructure. The hot gas 33 is preferably re-injected into a

formation to enhance the fluid flow through one or more sections of the wellbore system 10-2.

Figure 3 shows a schematic illustration of a wellbore system 10-3

wherein a fuel cell 40 at the well site surface 14 generates electric power 41

and heat energy 43. The desired fuel 42 to the fuel cell 40 may be provided from a downhole fuel processor 44a or from a fuel source 44b at the surface^{^} 14. Oxidant gas to the fuel cell 30 may be provided from a surface source (not

shown) in the form of compressed air, compressed oxygen or in any other

form. The electric energy 41 is utilized at the surface and/or to operate downhole devices and to supply electric power to various sensors normally disposed in the wellbores for monitoring the condition of the wellbore,

formation and downhole devices. The hot gas 43 is preferably compressed by

a suitable device 44, such as by a pump or compressor, and re-injected into the

wellbore 12c which is producing the formation fluid 21 or into a lateral wellbore 13c. Re-injection of the hot compressed gas 43 reduces the viscosity (which improves reservoir productivity) of the formation fluid 21 and/or increases the

pressure in the formation 16 which enhances the flow of the formation fluid 21

into the wellbore 12c.

Figure 4 shows a schematic illustration of a wellbore system 10-4 wherein a fuel cell 50 at the well site surface 14 generates energy 51 that can

preferably be utilized by a formation fluid processor 52 located at the surface

14. The fuel 53 to the fuel cell may be provided from a surface source (not

shown) or from a downhole fluid processor 54. The fluid processor 54 processes the formation fluid 21 produced by the wellbore 12d and utilizes the

energy produced by the fuel cell 50. The fluid processor 52 or 54 may include

a super critical partial oxidation process that hydrogenates the oil to produce upgraded oil. Such a processor is especially useful for heavy oil applications: A method of utilizing the super critical partial oxidation process downhole is

described below in reference to Figure 6. In one aspect, the heat generated by

the fuel cell 50 is applied to the formation fluid 21 prior to processing it by the

fluid processor 54. The fluid processor 54 preferably produces a upgraded hydrocarbon that is transported to desired locations.

Figure 5 shows a schematic illustration of a wellbore system 10-5

wherein a fluid processor 60 in the wellbore 12e processes the formation fluid

21 to produce a fuel 61. A heat source 62 in the wellbore 12e, such as a fuel

cell, heats the formation fluid 21 prior to it being processed by the fluid processor 60. The heating of the formation fluid prior to the processing,

especially the heavy crude, is known to improve the efficiency of the fluid

processing equipments, such as fluid processor 60. The configuration of Figure

5 provides one embodiment for heating the formation fluid prior to processing such fluid downhole. A heat jacket 64 powered by the fuel source 62 or by

batteries (not shown) or powered from the surface may also be utilized to heat

the formation fluid 21 prior to processing by the fluid processor 60.

Figure 6 shows a schematic illustration of a wellbore system 10-6 wherein heat 72 generated by a fuel cell (heat generator) downhole is utilized

to enhance production of formation fluid 74 from earth formation 80. Figure 6 shows a main wellbore 80 formed from a well site surface 14 and a lateral wellbore 82 formed from the main wellbore 80. In the exemplary configuration

of Figure 6, the formation fluid 74 flows from the reservoir 80 and into the lateral wellbore 82. The formation fluid then flows into the main wellbore 80

from where it is pumped to the surface by a pump 85 such as an electric submersible pump (ESP). The fuel cell 70 generates heat which may be

dispersed or distributed into the wellbore 82 via conduction paths or tubings disposed longitudinally along the wellbore 82.

The heat 72 generated by the fuel cell 70 disperses along the wellbore

82 (as shown by arrows 87) and into the reservoir 75 (as shown by arrows 88) thereby heating the formation fluid 74 before it enters and along the wellbore 82. Heating of crude oil reduces its viscosity thereby improving the reservoir

productivity. This is especially useful in heavy oil bearing formations. The low

viscosity fluid also is easier to transport to the surface whether it is done by an artificial device such as the ESP 85 or by natural pressure differential between

the formation 75 and the surface 14. Distributing the heat along the wellbore 82 allows heating a large area of the formation 75. The electric power

generated by the fuel cell may be used to operate the ESP 85 and other

downhole devices.

The heat generated during the processes and by the various devices described herein and injected into the wellbores or formations also reduces the adverse affects of paraffins and waxes in the wellbores. Increasing the

temperature of the formation fluid also prevents flocculation of asphaltenes. Heat generated by the fuel cells according to the present invention can be at

very high temperatures. In one aspect this heat is injected into the wellbore to

set chemicals in the wellbores. In addition, the heat generated downhole is

utilized to produce steam downhole by supplying water from the surface via suitable lines (not shown) or by utilizing water present in the formation. Steam

injected into the formations is known to improves reservoir productivity. As

described above, heat generated by the methods of the present invention also

is used to break emulsions to improve hydrocarbon production and/or to enhance the efficiency of the fluid processing equipment at the well site.

Still referring to Figure 6, a super critical partial oxidation reactor 70a

may be used in place of or in addition to the fuel cell 70. Such reactors are known and are thus not described in detail herein. Water and oxygen for the reactor are provided from the surface. Oil from the formation 75, water and

oxygen (supplied from the surface) react exothermically in the reactor and

produces carbon monoxide, carbon dioxide and extensive amounts of heat

energy. This heats the mixture to super critical conditions. Carbon monoxide

passes through a shift conversion and produces H₂, which hydrogenate the oil to produce upgraded oil. The products are quenched and separated, preferably in the main wellbore.

Figures 7-9 show schematic illustrations of an exemplary systems for

processing formation fluids downhole, generating electric power within the

wellbore or at the surface utilizing the downhole processed fluids and methods for the disposal and use of byproducts generated by the processing of the fluids downhole and by the power generation equipment.

Figure 7 shows a multi-lateral wellbore system 100 having a main

wellbore 1 10 and a desired number of lateral or branch wellbores, such as

wellbores 1 12, 1 14 and 1 16. In Figure 7, the lateral wellbore 1 12 is shown as a producing wellbore, i.e., a wellbore for recovering hydrocarbons from a hydrocarbon bearing formation, also referred to as the "pay zone" or "reservoir" . Lateral wellbores 1 14 and 1 16 are formed for re-injecting waste

or byproducts into selected formations. The production wellbore 1 10 is completed according to known methods in the art. It typically would contain

one or more perforated zones having perforations, such as perforations 1 12a. Formation fluids 111 from the production wellbore enter the wellbore 110 at a

juncture 1 13. The wellbore 1 10 is isolated at a zone 1 15 by isolation devices,

such as packers 1 18a and 1 18b in a manner that enables the formation fluid 1 1

to flow from the production wellbore 1 12 into the zone 1 15. A fluid processing unit or a series of processing units, generally denoted herein by numeral 120, are placed in the zone 1 15. The processing unit processes or treats the

formation fluid 1 1 1 to provide fuel 125 and waste or byproducts, generally denoted herein by numeral 123. The waste 123 from the formation fluid 1 1 1 is re-injected or disposed into a formation via the lateral wellbore 114, which

may be specially drilled for such purpose. The waste 123 passes into the formation surrounding the lateral wellbore 1 14 via perforations 1 14a.

In the exemplary embodiment of Figure 7, the fuel 125 is utilized as the

fuel for operating an electrical power generation unit 130 disposed in the

wellbore 1 10. The power generation system includes the power generation unit

130, an oxygen source 160, a control unit 140 for controlling the operation of

the power generation unit 130 and a system for disposing waste 131 from the

power generation unit 130. In the embodiment of Figure 7, the power generation unit 130 is preferably disposed uphole of the fluid processing unit

120 for ease of transporting the fuel 125 from the processing unit 120 to the power generation unit 130. A passageway 135 is provided to carry the power

unit waste 131 to the lateral wellbore 1 16 for disposition. The power unit 130, the conduit or tubing 124 and a liner 128 are disposed in the wellbore 1 10 by anchors 126a, 126b and anchors 127a and 127b.

The power generation unit 130 may be any desired type of unit, including a turbine and an associated generator, a gas-fired engine and an associated generator, or a suitable fuel cell. The use of such power generation equipment

is known and is, thus, not described herein in detail. The general mode of operation for a fuel cell, however, is described in reference to Figure 9. A fuel cell is preferred as it can operate at relatively high temperatures and tends to

generate lesser amounts of harmful by-products, such as nitrogen oxides, sulfur oxides and carbon oxides compared to gas-fired turbines. However, to reduce

the effect of high downhole temperature, the power generation unit 130 may be located substantially uphole of the production formations, but deep enough to safely dispose of the waste from the power generation unit 130. Alternatively, the power generation unit may be disposed at relatively shallow

depth and the branch wellbore 1 16 may be formed at a relatively great depth,

which would keep the power unit near the surface but allow injecting the waste at great depths, alleviating any negative impact on the environment.

During operations, the fuel 125 passes from the processing unit 120 to the power generation unit 130 via the conduit 124. The fuel 125 and the

oxygen fire the power generation unit and produce electrical power, which is carried to the surface by conductors 150. The control unit 140 controls the

operation of the power generation unit 130 including controlling fuel and air

supply to the power generation unit 130. The waste 131 from the power

generation unit 130 discharges into the passageway 135 and is carried into the

wellbore 1 16. A pump 170 may be disposed in the passageway 135 or in the wellbore 1 16 to facilitate discharging of the waste 131 into the wellbore 1 16.

The waste 131 may include nitrogen oxides, sulfur oxides, carbon oxides and

water depending upon the type of the power generation unit utilized. Such

waste may be treated or processed by mechanical and/or chemical methods prior to re-injecting the waste 131 into the formation surrounding the wellbore 1 16.

The fluid processing unit 120 may produce hot waste in the form of hot

gases 123a, which may be discharged or injected into a lateral wellbore such as 1 14a to enhance the production of hydrocarbons 1 12a. The power

generation unit 130 (whether a turbine or a fuel cell) produces heat as a major

byproduct, generally in the form of hot gases. This heat is preferably injected

into the formation at a suitable place, preferably a lateral wellbore such as 1 14a to enhance the production of the hydrocarbons 1 12a as described above.

In the embodiment of Figure 7, the power generation unit is disposed

within the wellbore. However, processed gas may be transported to the surface and utilized to generate electric power at the surface. In this manner,

the formation fluids are processed downhole to a desired extent and the useful hydrocarbons are transported to the surface. The waste generated by

processing the formation fluids is re-injected in the manner described earlier,

thereby reducing the negative impact on the environment. The power generated by the methods described here may be utilized for operating any number of devices, including electrical submersible pumps, if deployed for

pumping hydrocarbons to the surface, processing equipment, separators and

any other device. These methods enable producing electric power with

relatively little impact on the environment compared to the conventional methods where hydrocarbons are processed at the surface to obtain dry gas,

which is then transported to a market. The power generated at the well site

may be utilized at the surface or within the wellbore to operate any number of

devices including electrical submersible pumps, completion device (sliding

sleeve, downhole sensors, and other electrically operated devices), and separation units.

In gas fields, where a large number of gas wells may be drilled, electric power generated at several such well sites may be combined and transported to a market by conventional methods. Such a grid system is especially useful in regions where gas fields are not developed, or where gas wells are not drilled

or where gas is flared.

The type of formation fluid processing used depends upon the nature of the formation fluid 1 1 1 and the power generation device 130 used. Figure 8

shows a flow chart showing a typical processing method 200 that may be

utilized for the purposes of this invention. The formation fluids shown in box 210 are passed to a liquid separator 212 to separate gas, water and natural gas liquids (NGL's) . The water is discharged as waste. The gas from the separator

212 passes to a sweeting gas process 214, wherein the received gas is

processed to remove by-products 216 , such as sulphur oxides to produce

sweet gas 220. The sweet gas 220 may then move to an expansion process 224 to remove remaining natural gas liquids 226 and to generate or extract

energy 228, which energy may be utilized to operate the liquid separator 212 and in sweeting gas process or to perform another useful operation. The gas

230 obtained from the above-described process is then utilized to generate

electrical power downhole or transported to the surface. In some cases it may be necessary to remove asphaltenes from the formation fluid. Additionally, chemical and biological masses may be utilized to process the formation fluids.

Any other suitable method may be utilized to process formation fluids downhole

for the purposes and concepts of the present invention.

For simplicity and ease of understanding, the invention has been described by way of an example of a multi-lateral wellbore construction of

Figure 7. The specific wellbore construction, the type and manner of formation

fluid processing and the location and type of power generation unit will depend

upon the specific field conditions. United States Patent Application Serial No. 08/641 ,562, filed on May 1 , 1 996, which is a continuation-in-part of the United States Patent Application Serial No. 08/469,968, filed June 6, 1 995, which is a continuation-in-part of Serial No. 08/41 1 ,377, filed on March 27, 1 995, each assigned to the assignee of this application, disclose various methods of forming multi-lateral wellbores, storing various materials and devices downhole and various methods of treating fluids downhole. Each of these applications is

incorporated herein by reference as if fully set forth herein.

Figure 9 shows the operation of a fuel cell 310. Fuel, such as gas 312 and an oxidant gas 314, such as compressed air or oxygen, are provided to the

fuel cell in a controlled manner. A control unit 320 controls the operation of

the fuel cell 320 including the fuel 312 and oxidant gas supply 314. The power

generated is carried by conductors 318 to the consumers while the waste 330 generated by the fuel cell, such as nitrous oxide and water, is preferably re- injected into the earth formations.

Figure 10 shows a wellbore 400 wherein energy present due to differential pressure between different zones is utilized to perform a useful operation. The wellbore 400 intersects a producing formation 410. Hydrocarbons 415 from the formation 410 flow into the wellbore 400 at a zone

414 via perforation 412. The zone 414 is isolated from the formations above

and below the perforations 412 by seals 416a and 416b, such as packers. The

hydrocarbons 415 flow into a flow tube 430, from where they are brought to the surface. The device 420 or another device is used to prevent the flow of the hydrocarbons 415 downhole of the device 420.

Two spaced zones 440 and 450 downhole of the device 420 are isolated form each other by seals 432a and 432b. Perforations 442 are formed in the

zone 440 to allow the fluid communication between the zone 440 and the wellbore 400. Similarly, perforations 452 are formed in the zone 450 to allow

fluid communication between the zone 450 and the wellbore 400. A power converter 446, such as a turbine, is disposed in the wellbore 400 across from the perforations 442. This arrangement allows fluids to flow between the

zones 440 and 450 via the power converter. All other paths of fluid

communication between the zones 440 and 450 through the wellbore 400 are sealed. Use of this method may be limited to stimulation where zone 440 has

abnormally high fluid pressure relative to the zone 450. Alternatively, if the fluid pressure in the formation 450 is abnormally high relative to the fluid

pressure in the formation 440, then the formation fluid 454 from the zone 450

may be allowed to flow from the zone 450 to the lower pressure zone 440

through the power converter 446. The flow of fluid 454 operates the power unit, which then provides power to the device 420 as described above. Thus,

the system shown in Figure 10 enables using the energy present due to

differential pressure between subsurface zones or formations to perform a

useful operation downhole. It will be obvious that any number of configurations

can be adopted to achieve the results herein described. While the foregoing disclosure is directed to the preferred embodiments

of the invention, various modifications will be apparent to those skilled in the

art. It is intended that all variations within the scope and spirit of the appended claims be embraced by the foregoing disclosure.

Claims

WHAT IS CLAIMED IS:

1 . A method of generating energy at a well site utilizing downhole produced fuel, comprising:

(a) producing formation fluid containing a hydrocarbon from an earth formation through a wellbore;

(b) processing at least partially said formation fluid in the wellbore to

produce a hydrocarbon-based fuel ("Fuel") for use in energy generation equipment to produce energy; and (c) generating the energy with the energy generation equipment

utilizing the Fuel.

2. The method of claim 1 wherein the energy generated is one of (a) heat energy, (b) electrical power, (c) combination of heat energy and the electrical

power, (d) mechanical power, or (d) hydraulic power.

3. The method of claim 1 wherein the energy generation equipment is

selected from a group consisting (a) a fuel cell (b) a turbine and (c) an engine-

powered system.

4. The method of claim 2, wherein the energy is generated (a) at least

partially in the wellbore, or (b) at the surface.

5. The method of claim 3 further comprising providing an oxidant to the energy generation equipment from a source thereof located at one of (a) in the

wellbore, or (b) at the surface.

6. The method of claim 4 wherein the source of the oxidant is selected from a group consisting of (a) a chemical source (b) a source of compressed fluid

containing oxygen.

7. The method of claim 1 further utilizing the generated energy to perform an operation selected from a group consisting of (a) altering a physical property

of the formation fluid, (b) operating a device, (c) preheating a fluid prior to processing said fluid, and (d) processing the formation fluid to obtain a refined

hydrocarbon.

8. The method of claim 1 wherein the generated energy is electrical power and further comprises utilizing the electrical power to operate a device selected

from a group consisting of (a) an electrical submersible pumps, (b) a sliding

sleeve, (c) a flow control valve, (d) a completion device, (e) a separation

equipment, (f) sensors, ((g) pumps, (h) heaters, and (i) robots.

9. The method of claim 1 wherein the Fuel is one of (a) natural gas or (b)

a liquid hydrocarbon.

10. The method of claim 1 wherein the processing of the formation fluid to produce the Fuel comprises removing liquid hydrocarbons from the formation

fluid to produce gas as the Fuel.

1 1 . The method of claim 1 further comprising disposing of any by-products produced by the energy generation into a selected formation.

1 2. A method of generating heat energy at a well site and injecting said heat

energy downhole, comprising: (a) locating a fuel cell at a desired location at the well site, said fuel cell being adapted to generate heat as an end product; (b) providing a desired fuel from a source thereof to the fuel cell to

cause it to generate the heat; and (c) injecting at least a portion of the heat generated by the fuel cell int

an earth formation.

1 3. The method of claim 1 2, wherein the fuel cell is located at suitable

location selected from a group consisting of (a) a surface location and (b) a

downhole location.

14. A method of processing at a well site a formation fluid produced from a

wellbore; said method comprising: (a) producing a formation fluid through a wellbore formed in an earth formation;

(b) processing the formation fluid with a fluid processor at the well

site to produce a refined fluid; and

(c) generating energy with a fuel cell disposed at the well site and utilizing the generated energy to operate at least partially the fluid

processor to produce the refined fluid.

1 5. The method of claim 14 further comprising providing the fuel cell at location selected from a group consisting of (a) a surface location and (b) a

downhole location.

16. The method of claim 14 further comprising locating the fluid processor

at a location selected from a group consisting of (a) a surface location , and (b)

a location in the wellbore.

17. A method of processing a formation fluid at a well site; said method

comprising: (a) producing a formation fluid through a wellbore formed in an earth formation; (b) processing the formation fluid with a fluid processor located at

least partially in the wellbore; and (c) heating the formation fluid prior to processing the formation fluid with the fluid processor to enhance the processing of the fluid.

1 8. A method of producing a fuel for generating energy at a well site,

comprising: (a) recovering formation fluid from containing a hydrocarbon from an earth formation by flowing said formation fluid into a wellbore; (b) processing said formation fluid to produce a hydrocarbon-based

fuel that can be utilized in an energy generation equipment to produce energy; and (c) re-injecting at least some of the by-products produced by the processing of the formation fluid and the energy generation

equipment into a formation.

1 9. The method of claim 18, further comprising treating the by-products downhole prior to re-injecting the by-products in to the formation.

20. The method of claim 1 9, wherein the treating of the by-products

comprises chemically treating the by-products.

21 . A method of enhancing production through a wellbore comprising: (a) producing oil from an earth formation through a wellbore formed in said earth formation; (b) providing a super critical partial oxidation reactor in the wellbore adapted to hydrogenate the oil when mixed with water and oxygen under wellbore conditions;

(c) providing oxygen and water to the reactor, thereby hydrogenating the oil; (d) separating the hydrogenated oil from other constituents and flowing said separated oil to the surface.

22. A method of utilizing energy present downhole due to a pressure differential between zones of a wellbore to perform a useful operation,

comprising: (a) isolating a first and a second zone within the wellbore, said first

zone being at a higher pressure than the second zone;

(b) causing a formation fluid to flow from the first zone into the second zone via the wellbore; (c) providing a power generator operable by the flow of the formation

fluid from the first zone to the second zone;

(d) operating the power generator by the flow of the formation fluid

through the power generator to generate the power; and (e) utilizing the power generated by the power generated to operate

a device downhole.

23. The method of claim 22 wherein the device is selected from a group consisting of (a) a pump, (b) a separator, and (c) completion device.

24. The method of claim 23, wherein the power generator is selected from

a group consisting of (a) a turbine, (b) an electric power generator, and (c) an

hydraulic power generator.