STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable.

BACKGROUND

This disclosure relates to the field of wellbore heating apparatus and methods. More specifically, the disclosure relates to apparatus and methods for enabling wellbore instruments and/or deployment cables to remain in wells for longer times without heat damage.

There is sometimes a need to deploy a heating tool or system to heat a wellbore tubular, heat the near wellbore area externally of the heating tool or system or the produced fluids flowing past said heating device. Heating may be required, for example, to heat the formation adjacent to the wellbore tubular to establish a barrier by heat-related events taking place as a result of the heating process, for reducing viscosity of wellbore fluids, and maintaining liquid state for certain types of hydrocarbons susceptible to solidification, among other reasons. Heating is also beneficial with respect to the production of methane hydrate from underground and seabed sources, as heating will improve flow and prevent hydrates from solidifying in the flow system to the surface, i.e., a wellbore production casing, liner or tubing.

Such a heating tool or system may be deployed into the wellbore by an electrical cable extended from the surface, where heat is generated, e.g. when a resistance heater is activated by passing electrical current along the cable. The temperature obtained by a resistance heater may be very high. Such a high temperature may be a challenge for the deployment cable and other delicate parts of the tool or system and may result in an increased cost of the cable and other components. A way to reduce the effective operating temperature of the cable and other components when exposed to a wellbore heater may be beneficial.

SUMMARY

One aspect of the present disclosure is a method for thermally insulating a power cable or other temperature sensitive equipment from a wellbore tool comprising a heater. The wellbore tool is deployed at an end of the power cable in a well. A flow restrictor is deployed in an annular space between the heater and a wellbore tubular. The heater is axially spaced apart from the power cable such that the heater is disposed on one side of the flow restrictor and a connection to the power cable is disposed on another side of the flow restrictor. A thermal insulator is introduced into the annular space on the one side of the flow restrictor and the heater is operated.

Some embodiments further comprise moving fluid in the wellbore from the one side of the thermal insulator, through a part of the wellbore tool passing through the thermal insulator and the flow restrictor to the wellbore tubular on the other side of the flow restrictor.

In some embodiments, the moving fluid comprises moving the fluid through a bypass conduit having one port on one side of the thermal insulator and another port on the other side of the flow restrictor.

In some embodiments, the deploying of a flow restrictor comprises inflating a packer.

Some embodiments further comprise continuing pumping a fluid after the packer is inflated to operate a pressure relief valve, thereby causing the fluid to flow into the annular space below the packer.

In some embodiments, the deploying of a flow restrictor comprises expanding an iris-type shutter.

In some embodiments, the introducing of a thermal insulator comprises pumping gas from the surface through a port disposed below the flow restrictor.

In some embodiments, the introducing of a thermal insulator comprises pumping gel from the surface through a port disposed below the flow restrictor.

A wellbore heating system according to another aspect of this disclosure includes a wellbore tool comprising a heater coupled to one end of a spacer, the spacer comprising thermally insulating material therein. A radially expandable flow restrictor is disposed on the spacer. An electrical cable is connected to another end of the spacer. The flow restrictor is expandable to close an annular space between the spacer and a wellbore tubular. The electrical cable comprises a conduit therewith having an outlet disposed on a side of the flow restrictor opposite to a side on which the electrical cable is connected. The spacer comprises a bypass conduit having a port on each side of the flow restrictor.

In some embodiments, the flow restrictor comprises an inflatable packer.

Some embodiments further comprise a pressure relieve valve disposed in the conduit, and the conduit comprises an outlet within the inflatable packer on a surface side of the pressure relief valve.

Other aspects and possible advantages will be apparent from the description and claims that follow.

