Sensor transportation apparatus
A sensor transportation apparatus for conveying a sensor assembly through a wellbore comprises at least one engagement structure to connect the sensor transportation apparatus to the sensor assembly, at least one axle, a bearing connected to the axle, and a wheel connected to the bearing and provided with a shaft seal to prevent or reduce debris from the wellbore entering the bearing, and a lubrication delivery system to provide a lubricant to the bearing at a pressure which is greater than ambient wellbore pressure. The lubrication system comprises a bellows formation, and the apparatus comprises a housing to contain the lubricant, the housing in fluid communication with the bearing, the bellows formation sealingly mounted to the housing with at least a portion of the bellows received within the housing.
1. A sensor transportation apparatus for conveying a sensor assembly through a wellbore, the sensor transportation apparatus comprising:
at least one engagement structure to connect the sensor transportation apparatus to the sensor assembly,
at least one axle, at least one wheel, a bearing connected to the axle between the wheel and the engagement structure, a shaft seal to prevent or reduce debris from the wellbore entering the bearing, and
a lubrication delivery system to provide a lubricant to the bearing at a pressure which is greater than an ambient wellbore pressure, wherein the lubrication system comprises:
a spring bellows formation, and the apparatus comprising a housing to contain the lubricant, the housing in fluid communication with the bearing, the spring bellows formation sealingly mounted to the housing with at least a portion of the spring bellows formation received within the housing to provide a bias force so that the pressure in the lubricant is greater than the ambient wellbore pressure of a wellbore fluid surrounding the device;
a flexible member, an outer surface of the flexible member in communication with wellbore fluids surrounding the apparatus in use; and
a liquid contained in a sealed chamber defined, at least in part, by the interior of the spring bellows formation and an inner surface of the flexible member.
2. The apparatus as claimed in claim 1 , an exterior of the spring bellows formation is exposed to or facing the lubricant in use.
3. The apparatus as claimed in claim 1 , wherein the flexible member is a resilient diaphragm.
4. The apparatus as claimed in claim 1 , wherein the chamber has an invariable volume, such that deflection of the spring bellows formation causes deflection of the flexible member and vice-versa.
5. The apparatus as claimed in claim 1 , wherein the liquid comprises silicone oil.
6. The apparatus as claimed in claim 1 , wherein the lubricant is provided in a volume defined in part by the housing and an exterior of the spring bellows formation and the shaft seal.
7. The apparatus as claimed in claim 6 , wherein the bearing is contained in said volume, immersed in the lubricant.
8. The apparatus as claimed in claim 6 , wherein prior to use, the lubricant is forced into the volume, compressing the spring bellows formation.
9. The apparatus as claimed in claim 1 , wherein the spring bellows formation maintains a higher pressure in the lubricant than the liquid filling the interior of the spring bellows formation and hence the wellbore fluid.
10. The apparatus as claimed in claim 1 , wherein the spring bellows formation comprises a plurality of metal rings.
11. The apparatus as claimed in claim 10 , wherein the metal rings are stainless steel alloy rings.
12. The apparatus as claimed in claim 1 , wherein the bearing is between the wheel and the axle.