Downhole temperature sensing of the fluid flow in and around a drill string tool

A method of determining downhole fluid temperature at a drill string in a borehole, the method comprising:

• coupling a resistance temperature sensor to an internal surface of a thermal conductor with thermally conductive epoxy;
• inserting the thermal conductor into a cylindrical cavity of a cylindrical thermal insulator;
• installing a plurality of seals between an outer cylindrical surface of the thermal conductor and an inner cylindrical surface of the thermal insulator and between an outer cylindrical surface of the thermal insulator and an inner surface of a cavity in the drill string;
• installing a first retaining ring in a groove formed in the inner surface of the thermal insulator;
• and
• installing a second retaining ring in a groove formed in the inner surface of the cavity in the drill string.

A temperature sensing device for determining downhole fluid temperature at a drill string in a borehole, the device comprising:

• a thermal insulator to be received and secured in a cavity in the drill string;
• a thermal conductor to be received and secured in the thermal insulator;
• a temperature sensor to be received and secured in the thermal conductor and disposed adjacent a first opening in the cavity;
• and
• a thermally insulating plug to be received in a second opening in the cavity and to be secured in the cavity to retain the thermal insulator and the thermal conductor;
• wherein the thermal insulator provides a first thermal barrier between the thermal conductor and the drill string and the thermally insulating plug provides a second thermal barrier between the thermal conductor and the drill string.

A temperature sensing device for determining downhole fluid temperature at a drill string in a borehole, the device comprising:

• a thermal insulator to be received and secured in a cavity in the drill string;
• a thermal conductor to be received and secured in the thermal insulator;
• a temperature sensor to be received and secured in the thermal conductor and disposed adjacent a first opening in the cavity;
• and
• an inner cavity portion disposed radially inward of the thermal insulator and the thermal conductor;
• wherein the thermal insulator provides a first thermal barrier between the thermal conductor and the drill string and the inner cavity portion provides a second thermal barrier between the thermal conductor and the drill string.

A temperature sensing device for determining downhole fluid temperature at a drill string in a borehole, the device comprising:

• a housing having a cylindrical cavity;
• a resistance temperature sensor coupled with thermally conductive epoxy to an internal surface of the cavity;
• and
• a plurality of stabilizers configured to secure the housing within the drill string.