BACKGROUND OF THE INVENTION [0002] The high pressures of natural gas wells offer a substantial quantity of kinetic energy. Efforts to harness this energy, however, have been generally ineffective due to the high operating pressures and the typically corrosive nature of the natural gas and other substances produced by the well, including sand, scale, liquid hydrocarbons, water, and other particulate matter. Gas expanders in particular have been proposed for converting the kinetic energy of natural gas wells into useful work, but have not proven capable of withstanding the harsh conditions for extended periods of time.

SUMMARY OF THE INVENTION [0003] The present inventor has succeeded at designing methods and systems for producing electric power and/or liquefied gas from the kinetic energy of pressurized natural gas emanating from natural gas wells, as well as from the kinetic energy of pressurized natural gas traveling in natural gas pipelines and pressurized water emanating from geopressure wells, using turbo-alternators. Additionally, the inventor has designed methods and systems for producing electric power from the geothermal heat of natural gas emanating from natural gas wells and/or the thermal energy of other fluids.

[0004] According to one aspect of the present invention, a method of producing electric power includes providing a turbo-alternator having a turbine, coupling the turbo- alternator to a natural gas well, and rotating the turbine with pressurized natural gas from the natural gas well to thereby produce electric power with the turbo-alternator.

[0005] Additional aspects and features of the invention will be in part apparent and in part pointed out below.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram of a turbo-alternator coupled to a natural gas well for producing electric power according to one embodiment of the present invention; [0007] Fig. 2 is a block diagram of a turbo-alternator coupled to a natural gas transmission pipeline for producing electric power according to another embodiment of the invention; [0008] Fig. 3 is a block diagram of a turbo-alternator coupled to a geopressure well for producing electric power according to another embodiment of the invention; [0009] Fig. 4 is a block diagram of a system for producing electric power from the thermal energy of a pressurized fluid according to another embodiment of the invention; [0010] Figs. 5A and 5B are block diagrams of exemplary systems for. producing liquefied gas according to another embodiment of the invention ; and [0011] Fig. 6 is a block diagram of a system for producing electric power from the kinetic and geothermal energy of a natural gas well according to another embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS [0012] A method of producing electric power according to one aspect of the present invention includes providing a turbo-alternator having a turbine, coupling the turbo- alternator to a natural gas well, and rotating the turbine with pressurized natural gas from the natural gas well to thereby produce electric power with the turbo-alternator. In this manner, electric power can be produced at modest cost from the kinetic energy of pressurized natural gas emanating from a natural gas well.

[0013] An exemplary system for practicing the above- described method is illustrated in Fig. 1 and indicated generally by reference character 100. As shown in Fig. 1, the system 100 includes a turbo-alternator 102 having a turbine 104. In this particular embodiment, the turbo- alternator 102 is coupled to a well casing 106 of a natural gas well 108 such that pressurized natural gas 110 emanating from the well 108 is routed to the turbine 104. The pressurized natural gas is allowed to expand in the turbine 104 so as to rotate the turbine 104 and thereby produce electric power 112 with the turbo-alternator 102. The expanded natural gas 114 can be provided to a natural gas transmission line 116, as shown in Fig. 1.

[0014] In many natural gas well applications, the turbine 104 must be capable of handling dual phase working fluids (e. g. , gas and water), extremely high gas pressures, as well as other harsh and corrosive conditions. Suitable turbines for use in such applications include a rotary vane turbine of the type disclosed in U. S. Provisional Application. No.

60/360, 421 filed March 1,2002, the entire disclosure of which is incorporated herein by reference, a Tesla turbine, and a jet turbine (i. e. , a turbine which utilizes jet propulsion for rotation, and which may or may not be bladeless). Exemplary jet turbines that can be used in the present invention are disclosed in applicant's U. S.

Provisional Application No. 60/397,445 filed July 22,2002, U. S. Provisional Application No. 60/400,870 filed August 5, 2002, U. S. Provisional Application No. 60/410,441 filed September 16,2002, and U. S. Provisional Application No.

[insert no. here] filed December 10,2002 [and entitled"Drum Jet Turbine with Counter-Rotating Ring Method of Manufacture"], the entire disclosures of which are incorporated herein by reference.

[0015] As used herein, natural gas wells are those which produce at least a 2 %"cut"by volume of natural gas, and are distinguishable from other types of wells (including geopressure and geothermal wells) which may sometimes produce lesser amounts of natural gas.

[0016] A method of producing electric power according to another aspect of the present invention includes providing a turbo-alternator having a turbine, coupling the turbo- alternator to a natural gas pipeline, and rotating the turbine with pressurized natural gas from the natural gas pipeline to thereby produce electric power with the turbo- alternator. In this manner, electric power can be produced at modest cost from the kinetic energy of pressurized natural gas traveling in a natural gas pipeline. Fig. 2 illustrates an exemplary system 200 for practicing this aspect of the invention.

[0017] As shown in Fig. 2, the system 200 includes a turbo-alternator 202 having a turbine 204. The turbo- alternator 202 is coupled to a natural gas pipeline 206 such that high pressure natural gas 208 traveling in the pipeline 206 is routed to the turbine 204. Similar to the natural gas well embodiment described above with reference to Fig. 1, the high pressure natural gas 208 is allowed to expand in the turbine 204 so as to rotate the turbine 204 and thereby produce electric power 210 with the turbo-alternator 202.

The expanded natural gas 212 (which has a reduced pressure as compared to the high pressure natural gas 208) can be provided to a natural gas distribution center 214, as shown in Fig. 2. Thus, in the particular embodiment shown in Fig.

2, the system 200 serves as a gate device for providing natural gas having a reduced pressure to the natural gas distribution center 214 while also producing electric power.

[0018] Suitable turbines for use in the embodiment of Fig. 2 (as well as the embodiments of Figs. 3-6) include those described above with reference to Fig. 1 and natural gas well applications, although other types of turbines may be employed in various applications of the invention.

[0019] A method of producing electric power according to yet another aspect of the present invention includes providing a turbo-alternator having a turbine, coupling the turbo-alternator to a geopressure well, and rotating the turbine with pressurized water from the geopressure well to thereby produce electric power with the turbo-alternator. As apparent to those skilled in the art, geopressure wells are those which predominantly produce high pressure water with little or no steam. As used herein, geopressure wells are those which produce high pressure water having a temperature below the boiling point of water at standard conditions (i. e. , 14.7 psi at 70° F), and are distinguishable from geothermal wells which predominantly produce high pressure steam and water having a temperature at or above the boiling point of water at standard conditions. Fig. 3 illustrates an exemplary system for practicing this aspect of the invention.

[0020] As shown in Fig. 3, the system 300 includes a turbo-alternator 302 having a turbine 304. In this particular embodiment, the turbo-alternator 302 is coupled to a well casing 306 of a geopressure well 308 such that pressurized water 310 emanating from the well 308 is routed to the turbine 304. This pressurized water drives rotation of the turbine 304 so as to rotate the turbine 304 and thereby produce electric power 312 with the turbo-alternator.

302. Upon exiting the turbine 304, the pressurized water can be routed to a lower pressure destination (e. g. , a reservoir), as shown generally in Fig. 3.

[0021] Suitable turbines for use in the embodiment of Fig. 3 include those described above with reference to natural gas well applications. Such turbines are generally preferred due to their ability to be driven by pressurized liquids, including water, which may be accompanied by various debris commonly produced by geopressure wells.

[0022] A method of producing electric power according to another aspect of the present invention includes providing a turbo-alternator having a turbine, transferring heat from a pressurized fluid to a fluid agent with at least some of the fluid agent vaporizing from a liquid state to a gas state in response to the transferred heat, and rotating the turbine using the vaporized fluid agent to thereby produce electric power using the turbo-alternator. In this manner, electric power is advantageously produced from the heat (e. g., geothermal heat) of a pressurized fluid. Fig. 4 illustrates an exemplary system 400 for practicing this aspect of the invention.

[0023] As shown in Fig. 4, the system 400 includes a turbo-alternator 402 having a turbine 404, a heat exchanger 406, and a fluid agent 408 circulating through the heat exchanger 406 and the turbine 404. A pressurized fluid 410 is delivered to the heat exchanger 406 via a fluid line 412.

The heat exchanger 406 removes heat from the pressurized fluid 410 by transferring such heat to the circulating fluid agent 408. At least some of the fluid agent 408 is vaporized in response to the transferred heat to produce a gas phase fluid agent 414. The gas phase fluid agent 414 is provided to the turbine 404 for driving rotation of the turbine to thereby produce electric power 416 with the turbo-alternator 402. Preferably, the gas phase fluid agent 414 is allowed to expand in the turbine 404, thereby causing at least some of the gas phase fluid agent 414 to condense to the liquid state to produce liquid phase fluid agent 418. The system 400 may further include a pump for circulating the fluid agent 408 as described above. The pump 420 may be driven by the electric power 416 produced from the turbo-alternator 402, or otherwise.

[0024] The fluid agent 408 shown in Fig. 4 (and Fig. 6) is preferably a low-boiling-point liquid, although other types of fluids can be employed without departing from the scope of the invention. Similarly, a wide variety of substances may be used as the pressurized fluid 410 including, for example, hot natural gas emanating from a natural gas well.

[0025] Additionally, the heat exchanger 406 shown in Fig.

4 can be a thermoelectric heat exchanger for producing additional electric power from the heat energy of the pressurized fluid 410, as further described below.

[0026] Optionally, the pressurized fluid 410 may be heated before entering the heat exchanger 406 using any suitable means. This will increase the amount of heat imparted to the gas phase fluid agent 414 which, in turn, can increase the electric power output of the turbo-alternator 402. Preheating the pressurized fluid 410 can also increase the amount of electric power produced by the heat exchanger if the heat exchanger is of the thermoelectric type. In some applications of the invention, the pressurized fluid can be preheated using a downhole choke as further explained below.

[0027] A method of producing liquefied gas according to another aspect of the invention includes providing a pressurized gas in a gaseous state, and expanding the pressurized gas in a turbine with at least some of the pressurized gas condensing to a liquid state in response to the expanding to thereby produce liquefied gas. In this manner, liquefied gas can be readily produced without the high cost of constructing and operating a cryogen plant.

Figs. 5A and 5B illustrate two exemplary systems 500,550 for practicing this aspect of the invention.

[0028] As shown in Fig. 5A, the system 500 includes a turbine 502 coupled to a gas line 504 such that pressurized gas 506 traveling in the gas line 504 is routed to the turbine 502. The pressurized gas is allowed to expand in the turbine, with at least some of the expanded gas condensing to a liquid state to produce liquefied gas 508. The system 500 may also include a conditioner 510, as shown in Fig. 5A, for removing various contaminants from the liquefied gas 508 <BR> <BR> (e. g. , nitrogen gas that is not liquefied) to produce conditioned liquefied gas 512.

[0029] In the alternative system 550 shown in Fig. 5B, the turbine 502 is part of a turbo-alternator 516 that produces electric power 518 in response to rotation of the turbine 502. In this manner, both electric power and liquefied gas can be produced from the pressurized gas 506 using the turbo-alternator 516. Additionally, the system 550 includes a control valve 520 for controlling a pressure drop in the pressurized gas 506 as it expands in the turbine 502.

The extent to which a pressurized gas will condense to a liquid state during expansion is a function of this pressure drop. Therefore, the control valve 520 can be used to control the amount of liquefied gas 508 produced by the system 550. The extent of liquefaction is also a function of the pressurized gas'temperature immediately prior to the expansion, with a lower initial temperature corresponding to increased liquefaction. For this reason, the system 550 includes a heat exchanger 522 for cooling the pressurized gas 506 before it is provided to the turbine 502 to thereby provide higher yields of liquefied gas 508. The heat exchanger 522 may be configured to reject heat to the environment, or to another fluid (such as a fluid agent like that shown in Fig. 4).

[0030] With further reference to Figs. 5A and 5B, the pressurized gas 506 may be pressurized natural gas. It should be understood, however, that a variety of other gases may be liquefied according to this aspect of the invention.

[0031] An exemplary system 600 incorporating several aspects of the present invention will now be described with reference to Fig. 6. As shown therein, the system 600 includes a first turbo-alternator 602 having a turbine 604 and a second turbo-alternator 606 having a turbine 608. The system 600 also includes a first heat exchanger 610, a second heat exchanger 612, and a pump 614 for circulating a fluid agent 616 between the first and second heat exchangers 610, 612. As shown in Fig. 6, the turbine 604 is coupled to a well casing 617 of a natural gas well 618 via the first heat exchanger 610. Thus, pressurized natural gas 620 emanating from the well 618 is routed through the first heat exchanger 610, which cools the natural gas before providing it to the turbine 614. The cooled natural gas 622 is then expanded in the turbine 614 to produce electric power 624 as well as liquefied natural gas 626.

[0032] The heat removed from the pressurized natural gas 620 by the heat exchanger 610 is transferred to the circulating fluid agent 616, which is vaporized in response to the transferred heat to yield gas phase fluid agent 628.

The gas phase fluid agent 628 is provided to the turbine 608 to drive rotation of the turbine and thereby produce additional electric power 624 with the second turbo- alternator 606.

[0033] The liquefied natural gas 626 is provided to a conditioner 630 to remove unwanted substances, such as nitrogen gas. The conditioner then provides cold and/or liquid natural gas to the second heat exchanger 612 where it is heated by the gas phase fluid agent 628. This causes the liquid natural gas to vaporize into pressurized natural gas 632 that can be provided to natural gas transmission lines, such as line 634. Additionally, the heat transfer from the gas phase fluid agent 628 to the liquid natural gas causes the fluid agent to condense back to liquid phase fluid agent 636. The pump 614 then pumps the liquid phase fluid agent back to the first heat exchanger 610 and the cycle repeats.

(0034] As indicated in Fig. 6, the heat exchangers 610, 612 are preferably thermoelectric heat exchangers having thermoelectric modules thermally coupled to the heat exchangers'hot and cold regions. In this manner, additional electric (DC) power 640 is advantageously produced from the thermal energy of the pressurized natural gas 620. Suitable thermoelectric heat exchangers are disclosed in U. S.

Application No. 09/873, 983 filed June 4,2001 and U. S.

Application No. 09/877,781 filed June 11,2001, the entire disclosures of which are incorporated herein by reference.

[0035] Additionally, the amount of electric power 640 produced by the thermoelectric heat exchangers can be increased by heating the pressurized natural gas 620 before providing the pressurized natural gas to the heat exchanger 610. One preferred method for heating the pressurized natural gas 620 is to expand the natural gas using a downhole choke 642, as shown in Fig. 6. Specifically, the choke 642 is positioned in the well casing 616 at a depth where the temperature of the pressurized natural gas 620 exceeds its inversion temperature. As a result, when the pressurized natural gas is expanded through the choke 642, the temperature of the gas will increase (rather than decrease as it would if its temperature was below the inversion temperature). In one preferred implementation, the downhole choke is positioned in the production zone of the natural gas well 618.

[0036] When introducing elements or features of the present invention and the exemplary embodiments, the articles "a","an","the"and"said"are intended to mean that there are one or more of such elements or features. The terms "comprising", "including"and"having"are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted.

[0037] As various changes could be made in the above embodiments without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.