DEPLOYING MINERAL INSULATED CABLE DOWN-HOLE

Abstract

Methods, system and devices for deploying an MI cable heater down-hole into a hydrocarbon reservoir are provided, wherein one or more MI cables are housed inside a protective jacket, and connected to a pump-in device. The pump-in device allows the cable to be deployed by pumping fluid down-hole, and the pump-in device catches the fluid and pulls the cable down-hole, even in a horizontal well.

Claims

1. A method of deploying a mineral insulated (MI) cable heater down-hole, said comprising: a) providing an MI cable heater; b) attaching a pump-in device to a down-hole end of said MI cable heater; c) feeding said MI cable heater and pump-in device into a down-hole tubing; d) pumping an injection fluid into said down-hole tubing at a first pressure, said first pressure being sufficient to drive said pump-in device and attached MI cable heater down-hole; e) detecting when said MI cable heater is fully deployed; and f) ceasing said pumping step (d).

2. The method of claim 1, wherein said pump-in device is attached via a breakaway connector and said MI cable is retrieved by disconnecting the breakaway connector and winching said MI cable heater back up out of said down-hole tubing.

3. The method of claim 2, wherein said breakaway connector is activated by applying an electrical signal.

4. The method of claim 2, wherein said breakaway connector is activated by exceeding a breakway force.

5. The method of claim 1, wherein said pump-in device is a dissolvable pump-in device.

6. The method of claim 1, wherein said MI heater cable has one or more MI cables inside a single protective jacket.

7. A method of producing heavy oil, said comprising: a) providing an MI cable heater operably coupled to a pump-in device at a down-hole end of said MI cable heater; b) feeding said MI cable heater and pump-in device into an inside of a down-hole tubing in a well, said down hole tubing separate from a production tubing in said well; c) pumping an injection fluid into said down-hole tubing at a first pressure, said first pressure being sufficient to drive said pump-in device and attached MI cable heater down-hole into said reservoir; d) detecting when said MI cable heater is fully deployed; e) ceasing said pumping step d; f) heating heavy oil with said MI cable heater until it becomes mobilized; and g) producing said mobilized heavy oil via said production tubing.

8. The method of claim 7, wherein said pump-in device is attached via a breakaway connector and said MI cable is retrieved by disconnecting said breakaway connector and winching said MI cable heater out of said down-hole tubing.

9. The method of claim 8, wherein said breakaway connector is activated by applying an electrical signal.

10. The method of claim 8, wherein said breakaway connector is activated by exceeding a breakway force.

11. The method of claim 7, wherein said pump-in device is a dissolvable pump-in device.

12. The method of claim 7, wherein said pump-in device has a hollow cylindrical core into which said MI cable heater is fitted, and a plurality of angled vanes circumnavigating said core such that fluid pressure behind said pump-in device pushes said plurality of vanes against an interior wall of said down-hole tubing.

13. The method of claim 12, wherein said vanes comprise reinforced rubber.

14. The method of claim 12, wherein said vanes comprise rubber sheathed with polytetrafluoroethylene.

15. The method of claim 12, wherein said pump-in device comprise reinforced rubber.

16. The method of claim 12, wherein said pump-in device comprise rubber sheathed with polytetrafluoroethylene.

17. A down-hole heater, comprising a mineral insulated cable having three resistor elements, each resister element inside a mineral insulated jacket, all three resistor elements being contained inside a support jacket that is resistant to corrosion by crude petroleum, said down-hole heater having a down-hole end, and said down-hole end coupled to a pump-in-device.

18. The down-hole heater of claim 17, wherein said support jacket is braided metal.

19. The down-hole heater of claim 17, wherein said a second protective coating comprises polytetrafluoroethylene.

20. The down-hole heater of claim 15, wherein said support jacket is braided metal.

21. The down-hole heater of claim 15, wherein said pump-in device is attached via a breakaway connector.

22. The down-hole heater of claim 15, wherein said pump-in device is a dissolvable pump-in device.

23. A heated well system comprising a down-hole heater comprising a mineral insulated cable that is hung off or suspended in a wellhead such that it can be left in the well during production operations, but which allows the cable to be electrically connected to a surface control panel and transformer into order to power the device.

24. A heated well system comprising a down-hole heater comprising a MI cable deployed inside a dedicated tubing inside a production well or an injection well, said MI cable is hung off a wellhead and left in said well during production operations, said MI cable electrically connected to a surface control panel and transformer into order to power the MI said MI cable and connected at a down-hole end via a breakaway connector to a pump-in device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] FIG. 1A depicts an MI cable having two conductor cables.

[0072] FIG. 1B depicts an MI cable with various numbers of conducting cables.

[0073] FIG. 2. Schematic of MI cable deployment system.

[0074] FIG. 3A-B. Exemplary pump-in devices. A device can be designed specifically for this job (3A), or existing devices (3B) can be repurposed for use as pump-in devices. See also FIG. 5.

[0075] FIG. 4. Exemplary deployment of the system.

[0076] FIG. 5. Swab cups.

[0077] FIG. 6. MI heater cable.

[0078] FIG. 7A-E. MI heater cable layouts.

DETAILED DESCRIPTION

[0079] The disclosure provides a novel method of deploying an MI Cable heater down-hole that avoids the complex and expensive method using CT encapsulation, or difficult deployments to the outside of e.g., a stinger tube.

[0080] SPE-167347 (2013) by Parman, for example, teaches a heater that consists of a multi-stage, 3 cable MI heater in the pay zone, powered via ESP cable (see petrowiki.org/ESP_power_cable). The MI heater was constructed to provide highest power output (and heat) near the toe, somewhat less power in the middle section of the lateral, and less still near the heel. A “cold lead” section was also included to ensure that the ESP cable and connection components do not overheat. This three-cable system was deployed down-hole, attached to the outside of a stinger pipe in the horizontal section of pipe. Deployment details are not provided, but clearly deploying three cables down a significant length of horizontal pipe is not trivial. The invention herein described teaches how to avoid such difficult deployment issues.

[0081] FIG. 1A shows that basic structure of an MI cable, in this case a 2 wire cable with two copper wires inside a copper tubing, covered with MgO.sub.2 coating, and herein with an exterior sheath of jacket on Alloy 825. However, MI cable is available in a large number of sizes and configures, see e.g., FIG. 1B, and can have various exterior jackets according to the application needs. To make a heater from this cable, a closed circuit is created. Temperature may be controlled by a thermocouple or by changing the voltage delivered to the system. In one embodiment a closed loop cap is placed on the MI cable to close two of the insulated cables.

[0082] FIG. 2 shows one exemplary deployment method of the invention, wherein MI cable bundle 11 is provided on a reel 25. The details of the MI heater cable are not seen in this figure, but heaters are known in the art and exemplary layouts are shown in FIGS. 6-7. Instead, this figure demonstrates the overall deployment of such a cable down-hole. The MI cable 11 passes through pulley 13, down through flow tee or flow head 17, and injection fluid 27 feeds in through injection fluid line 29. Flow tee or flow head 17 has packing or other sealer on the top to seal off against the cable such that the fluid would be forced down-hole, yet cable entry is permitted. The cable 11 passes through cable-tubing 21 down hole to the point where it is needed, and the conveyance is by pump-in device or swab cup 23 at the end of the cable, which works by pushing the cable down hole under fluid pressure. The cup 23 essentially seals the fluid, driving the cable plus fluid down hole.

[0083] Weak line or a breakaway connector 31 is provided between the pump-in device 23 and the cable 11. Thus, on return, sufficient force (or an electrical signal) is provided to disconnect the cable, and the cable can be retracted with a winch (not shown), attached to pulley 13.

[0084] Pump-in device 23 is a conical plug, analogous to a wiper plug used in cementing operations or a swab cup for swabbing a well. A specific pump-in device can be provided per FIG. 3A. However, a special device is not necessary, as there are commercial devices available in a range of styles and sizes that can be used herein for this purposes. FIG. 3B shows swab cup styles that are already commercially available.

[0085] FIG. 3A shows a cup 31 having a central hole or tunnel 36 into which the cable can be frictionally fit, or screws can be provided to tighten the cable into the device. Sealing vanes 37 are angled such that they point towards the down-hole end, such that flow pushes the vane harder against the tubing, sealing off the wellbore fluid, thus building up pressure on the cable side of the cup (right in this figure), and pushing the cup with cable further down-hole. Additional vanes 38, herein arranged perpendicularly to the axis, can provide additional pressure points.

[0086] Any number of such pump-in devices can be fitted to the cable, thus providing a quick easy method of deployment of cables down-hole, however a single pump-in device may be preferred, since the breakaway connector is up-hole of these devices. Alternatively, a very flexible swab cup can be used that can be pulled backwards out of the hole can be used if the vanes are flexible enough to allow this. In such case, a plurality of pump-in devices may be better suited.

[0087] We initiated a project to install a down-hole mineral insulated (MI) heater into a test well. The objectives were to establish production without the need to inject diesel, previously required to achieve production on the North slope, in order to obtain a large volume uncontaminated sample of the 9.sup.0 API crude and to test the viability of using a down-hole heater to produce the reservoir in areas that are not applicable to Steam Assisted Gravity Drainage (SAGD) production due to limited net reservoir thickness.

[0088] The challenge faced in executing the project was to install a heater in the well without the use of a workover rig to deploy the coiled tubing. Only by using typical well servicing equipment available at the well and by tailoring the solution to the existing well would the cost of the experimental project render it viable. The solution required us to design, engineer, and fabricate a heater assembly and purpose-built well head-hanger assembly to accomplish the job.

[0089] Three MI heater leads plus braided support cable were installed into a spool of 1¾″ coiled tubing such that when run into the well to the toe of the lateral through an existing tubing string, only a short section would need to be cut before being hung off. The specialized hanger was installed onto the tree and allowed the coiled tubing to be hung off and provide for a pressure tight penetration to be made for the electrical connections. Although we envision deployment without coiled tubing, the extra tubing string was already deployed in our test well, and we took advantage of the existing layout. Importantly, the tubing did not need to be retracted and fitted with an MI Cable. Instead, the MI cable was sent down the already deployed tubing encapsulated in a string of coiled tubing

[0090] The MI cable used on the test well had three wires. The three-phase heater was used in order to impart sufficient heat down-hole in an Alaskan environment (watt density of 50-250 W/Ft, preferably >150 or >200 W/ft), but one or two lead heaters might also suffice in reservoirs with less viscous crude.

[0091] This method envisions encapsulating multiple wires into a single bundle with a common sheathing, but the three separate cables sufficed for proof of concept. It is noted, that multi-wire MI cables are available (e.g., from M.I. Cable Company or “MICC”) wherein the conductive leads are embedded in a highly dielectric magnesium oxide insulation surrounded by a metal sheath of Alloy 825. Wire can be e.g., a nickel-chrome iron with resistivity of 620 ohms-cmf at 68° F. (20° C.), or high conductivity copper ASTM B4 or B5, or solid nickel, or nickel iron, and the like.

[0092] Heater cable needs to be twice the pipe length, and thus each heater cable is factory fabricated for a specific length of a certain size pipe. It is important to install MI cable so that minimal bending occurs. Cable will work harden and break if repeatedly re-bent. It is also sometimes recommended that MI heater cable not be bent to an inside radius of less than five or six times the cable's diameter.

[0093] FIG. 4 shows the cable heater deployment. The heater is not in the production tubing 43, but through an adjacent tubing string. The MI cable 42 is deployed inside a dedicated tubing string 44, herein a string of coiled tubing. The CT termination spool 41 is modified to permit the power cable to exit the wellhead and allow fluid to be pumped into the tubing for pressure testing purposes. The MI cable is connected at the surface via connector 45 and surface cable 46 to a heater control panel 47 and transformer 48.

[0094] An installation as shown in FIG. 4 was accomplished using an MI cable encapsulated in 1¾″ coiled tubing deployed from a typical CT service unit, resulting in a virtually flawless deployment. The final electrical and instrumentation hookup and commissioning was done and the heater was powered up on a low heat setting. The heater was turned to its high setting a day later, and two days later, the well's progressive cavity electrical submersible pump (not shown) was started. The well immediately began surfacing fluids and established a rate of 70 BOPD with a 20-25% water cut. The temperature at the pump inlet increased from the static temperature of 65° F. to 195° F., which lowered the viscosity of the oil from its in situ value of 20,000 centipoise to 100 centipoise and allowed the well to produce.

[0095] The first objective of the project was accomplished when ten 55 gallon drums of uncontaminated North slope crude were collected and shipped to the lab for analysis. After sampling was complete, the pump speed was increased from 32 hertz to 50 hertz over a few months duration while the well rate increased from 70 BOPD to over 100 BOPD.

[0096] The well continues to produce at a water cut of 20% with little to no sand production. This is the most heavy oil ever produced from our North Slope acreage and the first time a down-hole heater has been utilized in an Alaskan oil field. This project has successfully demonstrated that heavy oil can be produced under primary production with down-hole heaters and has the potential to unlock up to one 100 MMBO of net resource from the oil sands. Further, the use of a pump-in device and releasable connecter allow much easier deployment and retrieval, contributing significantly to cost savings.

[0097] FIG. 6 shows a basic heater layout. The heater is comprised of three components: 1) A central conductor of an electrically resistive metal, 2) surrounded by a highly compressed mineral insulant (MgO), and 3) sheathed with a metal covering of copper or stainless steel. The metal sheathing provides a permanent ground to comply with NEC 427.23.

[0098] Copper sheathed cables are used for general environments where corrosion and high temperatures will not be present. The cables should not be used above a working temperature of 300° F. or where an exposure temperature of more than 400° F. is required. Nickel Chrome alloy cables, in contrast, are able to withstand 1250° F. energized and can maintain temperatures up to 800° F. The base sheath is unaffected by a wide range of aggressive alkalis and acids, thus making the cable ideal for projects in chemical plants, refineries, utilities, etc. Stainless steel sheathing is also available, e.g., from MCAAA.

[0099] Using single or three phase power supplies and carefully selecting the correct cable can make heating circuits for to 600 volts from most suppliers, and up to 4160 volts if MCAA cable is used. The higher voltage cable is preferred as more efficient per the following table, excerpted from SPE-170146-MS:

[0100] FIG. 7A-E shows various heater layouts commercially available from Thermon MIQ. These cable sets are available in four factory fabricated configurations: Type A, B, D or E. Other designs are available from other suppliers, e.g., Korea EHT (KR), Economy Engineering Corp. (IN), HotFoil EHS (NJ).

[0101] The standard assemblies consist of a predetermined length of heating cable joined to a standard 1.2 m or 2.1 m non-heating cold lead with 305 mm long thermoplastic insulated pigtails. The non-heating section of the unit is sealed and fitted with a high pressure, liquid-tight M20, M25 or M32 brass gland 3 for connection into the supply junction box. ESP cable is preferred for the cold lead uses described herein, and any suitable connectors can be used.

[0102] As described herein, the MI cable may be pumped in using a scab cup with fluid pressure for deployment. In one embodiment the plug is releasably attached to the cable such that when the MI cable has been deployed and reached its desired depth, the pressure is increased and the plug breaks away from the MI cable. In another embodiment a dissolvable plug is used such that once the MI cable has been deployed and reached its desired depth, the plug dissolves preventing the plug from interfering with subsequent production.

[0103] Alternatively, a down-hole tractor can be used, and this may be preferred for particularly long wells. A tractor can be placed to either push or pull a toolstring, but the toolstring is short in comparison to the cable connecting the tractor and toolstring to surface. Putting the motive force near the front of the conveyance string enables it to move tools and devices along extended horizontal sections. Even in locations where wellbore deviation exceeds 90°, the tractor pushes the toolstring uphill.

[0104] Such down-hole tractors are commercially available. e.g., from Schlumberger, Kodiak, Baker Hughes, Halliburton, Weatherford, NOV and other providers. For example, Schlumberger offers the MaxTRAC® down-hole tractor system, which is a reciprocating-grip down-hole tractor that delivers more than 40% efficiency. GE Energy also has a Modular Down-hole Tractor (MDT).

[0105] MI cable may be deployed in any situation where low temperature can interfere with production. In one embodiment, MI cable is deployed to maintain fluidity in a heavy oil reservoir. In another embodiment, MI cable may be deployed in a cold weather environment where cooling or freezing may be an issue. In yet another embodiment, MI cable may be deployed where hydrate inhibitors may not be sufficient to keep hydrates from forming. The ability to drive or push the MI cable inexpensively to any location within the well, will provide many new and unique opportunities to use MI cable.

[0106] The following references are incorporated by reference in their entirety for all purposes.

[0107] SPE-170146-MS: Sandberg et al., Advances in Electrical Heating Technology for Heavy Oil Production, available online at http://www.mcaaa.eu/resources/Advances-in-Electrical-Heating-Technology-for-Heavy-Oil-Production.pdf

[0108] SPE-167347 (2013) Parman D. et al., Use of Electric Down-hole Heaters to Improve Production and Recovery of Heavy, Viscous Oil in California and Venezuela.

[0109] U.S. Pat. No. 5,871,052: Apparatus and method for down-hole tool deployment with mud pumping techniques.

[0110] The present invention is exemplified with respect to MI cable heaters. However, this is exemplary only, and the invention can be broadly applied to any heater cable, or indeed any cable. Any examples herein are intended to be illustrative only, and not unduly limit the scope of the appended claims. Any detail herein provided is intended to be combinable with any other detail also mentioned here, whether in the same paragraph or not, and whether or not discussed as relates to the prior art or the invention, because providing separate paragraphs for each possible combination would be unduly lengthy and repetitive. DEPLOYING MINERAL INSULATED CABLE DOWN-HOLE