METHOD AND APPARATUS FOR REPURPOSING WELL SITES FOR GEOTHERMAL ENERGY PRODUCTION

Abstract

A method and system for capturing geothermal energy. Injection and production well pairs in a geothermal zone are connected with a power generation apparatus between the production well of one well pair and the injection well of an adjacent well pair in a subterranean closed loop daisy chain configuration. Fluid circulated through the loop and the power generation apparatus recover subterranean heat energy. Specification is also disclosed in respect of application of the technology to repurpose an unused or suspended oilfield.

Claims

1. A geothermal method, comprising: drilling a first generally U shaped bore hole into an earth formation and a second generally U shaped bore hole in spaced relation therefrom each in a geothermal zone within said formation; providing a power generation apparatus; connecting said apparatus to an output of said first U shaped bore hole and an inlet of said second U shaped bore hole; circulating a fluid through each said bore hole; and recovering heat from said fluid.

2. The method as set forth in claim 1, wherein said earth formation is an oilfield.

3. The method a set forth in claim 1, further including the step of recovering heat from said output of said first U shaped bore hole with said apparatus prior to introduction into said inlet of said second U shaped bore hole.

4. The method as set forth in claim 1, further including the step of optionally bypassing said power generation apparatus.

5. The method as set forth in claim 1, further including the step of connecting a series of first and second U shaped bore holes and power generation apparatus in a looped configuration.

6. The method as set forth in claim 5, further including connecting discrete loops.

7. The method as set forth in claim 2, wherein preexisting adjacent oil wells in said oilfield having an injection well and a production well are retrofitted for connection with said apparatus within a geothermal zone for heat recovery.

8. The method as set forth in claim 7, further including the step of drilling additional U shaped wells for connection with said preexisting wells.

9. An energy production method comprising: providing a suspended oilfield having injection and production well pairs; connecting a power generation apparatus between the production well of one well pair and the injection well of an adjacent well pair in a subterranean loop; and circulating a fluid through said loop to recover subterranean heat energy.

10. The method as set forth in claim 9, further including connecting additional well pairs in a subterranean loop.

11. The method as set forth in claim 10, further including connecting loops in a subterranean connection.

12. The method as set forth in claim 9, further including bypassing said power generation apparatus.

13. A system for energy production, comprising: injection and production well pairs in a geothermal zone within a formation; a power generation apparatus connected between the production well of one well pair and the injection well of an adjacent well pair forming a closed loop; and fluid for circulation through said loop and said power generation apparatus to recover subterranean heat energy.

14. The system as set forth in claim 13, wherein said injection and production well pairs include a plurality of horizontal conduits.

15. The system as set forth in claim 14, wherein said horizontal conduits are arranged in an annular form.

16. The system as set forth in claim 15, wherein said conduits are in spaced relation.

17. The system as set forth in claim 13, wherein said power generation apparatus comprises an organic Rankine cycle.

18. The system as set forth in claim 13, wherein said power generation apparatus comprises a carbon carrier cycle.

19. The system as set forth in claim 13, wherein said power generation apparatus comprises a Kalina cycle.

20. The system as set forth in claim 13, wherein said formation is an oilfield.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 is a top view of daisy chained wells in a first embodiment;

[0038] FIG. 1A is an enlarged view of the multilateral arrangement of conduits employed in the arrangement;

[0039] FIG. 1B is a view similar to FIG. 1A illustrating the annular pattern of the conduits in the multilateral arrangement and the spaced relation between individual conduits.

[0040] FIG. 2 is an enlarged view of the power generation apparatus as disposed between the inlet of one well and the output of an adjacent well;

[0041] FIG. 3 is a top view of two daisy chained well loops integrated;

[0042] FIG. 4 is a top view of another embodiment of the present invention; and

[0043] FIG. 5 is a top view of yet another embodiment of the invention.

[0044] Similar numerals used in the Figures denote similar elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Referring now collectively to FIGS. 1, 1A and B shown is a schematic illustration of a daisy chain of wells, globally denoted by numeral 10. In this embodiment, each surface location, generally denoted by numeral 12, includes an injection well 14 connected to a lateral well conduit 16 and production well 18. In this manner, the continuous well structure subscribes to a generally U shaped structure, best referenced in FIG. 1B.

[0046] As illustrated in FIG. 1, each location 12 is discrete and linked to proximal locations in an elegant and advantageous manner. As an example, the distance between locations may be 3,500 meters. This will, of course, vary from one situation to another. Reference to FIG. 1B delineates linkage specification.

[0047] In FIG. 2, numeral 20 is representative of the power generation apparatus. Selections for the apparatus 20 will be discussed herein after, however for purposes of discussion, the apparatus 20 is responsible for converting steam into electrical energy. At each location 12, there is the injection well 14 and production well 18. As illustrated in FIG. 3, these are subterranean with the surface being denoted by numeral 22. The multilateral conduits 16 are similarly subterranean, but also within a geothermal zone 24 of formation 26.

[0048] For operation, FIG. 2 may also be referenced. A fluid with a suitable heat capacity is circulated in the injection well 14 of one location 12, processed through power generation apparatus 20 to recover the heat energy and subsequently passed as an output stream to be an inlet feed stream for a injection well 14 of a proximal location. The chain line 28 illustrates this relay or daisy chain sequencing. Since not all of the heat is recovered, the inlet feed stream for well 14 of a proximal location is preheated for injection into lateral conduit 16. The process then resets for repetition in the next location 12. For convenience of repair, analysis, etc. power generation apparatus includes a bypass loop 30 for bypassing the apparatus 20.

[0049] In respect of power generation apparatus 20, without being limiting, the apparatus may comprise an organic Rankine cycle, Kalina cycle or carbon carrier cycle.

[0050] In order to accommodate variable conditions such geological, environmental, thermal, etc. an array of conduits 16 may be employed as illustrated in FIGS. 1A and 1B. The arrays will be referenced as multilateral arrays 32 and are arranged in an annular pattern in spaced relation from proximal conduits 16. Other patterns may be employed depending on the specifics of the situation. Connection between the individual conduits 16 of an array 32 will simply integrated in a merger acting in a similar fashion to a single conduit 16. All or some of the locations 12 may be fabricated in this way, depending on the conditions of which examples have been referenced above. It is further contemplated that singular conduit arrangements may alternate with arrays 32. The arrays 32 increase the overall flow rate and power production. In situations where some locations 12 are closer together, a greater number of arrays 32 may be used to maintain heat recovery balance. The arrangement shown in FIG. 1 is exemplary of a 12,000 kW to 20,000 kW system.

[0051] Turning now to FIG. 3, shown is a further embodiment of the invention for example, a 8,000 kW to 12.00 kW system. In this example, individual loops may be joined at a centralized location, C, in order to centralize the power generation apparatus 20 (not shown) for increased power an efficiency.

[0052] FIGS. 4 and 5 illustrate smaller scale operations, 4,000 kW-6,000 kW (FIG. 4) and 2,000 kW-3,000 kW (FIG. 5).

[0053] One of the significant features of employing the daisy chain implementation is the lack of a requirement for a near surface return conduit. When required, as in conventional well loop arrangements, capital costs exceed 10%, there may be a need to negotiate rights of way and a 3-5 C heat loss and a pressure loss results causing equipment issues.

[0054] Geothermal loops have been proposed ostensibly in the prior art discussed supra, however, in mosaic, the prior art has not provided adequate guidance in terms of the surface to surface energy recovery, minimal geological invasiveness unified with consolidated recycling.

[0055] As noted in the prior art, the Halff reference, supra, broadly relates to loop systems, but does not appear to present an economically viable solution. This is evinced by the fact that there has been no implementation of the Halff technology, despite the nearly two decades that have elapsed since its disclosure. Following this, the Mickelson and McHargue, supra, were released, building on the concepts in this area. Neither of these technologies came to fruition and were abandoned. Clearly, this area of technology is complex and cumulative teachings, although many times instructive, singularly or in mosaic, do not direct to linked loops, preheated streams from waste heat, truncated horizontal conduit circuits or subterranean closed loop systems.

[0056] By contrast, the daisy chaining, since well loops are linked front to back, eliminates the need for a near surface return conduit. Further, the paired loops act as the return conduit for each other with the pair using waste heat as an input to create the preheated stream supra.

[0057] Other advantages include increased power production with no surface disruption (footprint) since everything is subsurface and reduced distance between locations 12. This commensurately reduces cost if shorter conduit 16 can be used owing to the increased temperature of the preheated feed stream design.