Device and method for surveying boreholes or orienting downhole assemblies

A heading transfer unit may be used to transfer a heading from a surface base to a MWD tool. The surface base may have a master north finder to determine a heading. The heading may be transferred to the heading transfer unit, which is in turn transferred to the MWD unit. The heading on the heading transfer unit is transferred to the MWD tool.

TECHNICAL FIELD/FIELD OF THE DISCLOSURE

The present disclosure relates to establishment of orientation of a downhole tool.

BACKGROUND OF THE DISCLOSURE

Current measurement while drilling (MWD) and gyroMWD techniques include a variety of sensors which are deployed into a borehole with a drilling assembly. These systems are designed to acquire headings on demand, and transmit these headings to surface via MWD telemetry (typically Mud Pulse or Electromagnetic). Standard MWD tools typically acquire headings using magnetic field sensors and acceleration sensors and, along with models of the Earth's magnetic and gravity fields, compute an instrument heading. Current gyroMWD techniques replace the magnetometers with a gyrocompass assembly, which uses a rate gyroscope to measure the direction of the Earth's rotation vector relative to the tool, and combine these with acceleration sensors (as in standard MWD tools) to compute an instrument heading. When using either method, the instrument must generally be kept still during the sampling period, to eliminate effects from movement and isolate acceleration due to gravity, and in the case of the gyroMWD method, to isolate Earth's rotation. Additionally, when using a standard MWD tool, the instrument can only be used when spaced sufficiently from external sources of magnetic interference (e.g. offset wellbores) to ensure that the modeled Earth's magnetic field is undisturbed.

SUMMARY

The present disclosure provides for a method. The method may include providing a master north finder. The master north finder may be positioned at the surface and coupled to a surface base. The method may include determining a heading with respect to true north and gravity with the master north finder. The method may include transferring the heading to a heading transfer unit. The heading transfer unit may include a non-transitory, tangible, computer readable memory media adapted to store the heading and a base alignment feature. The base alignment feature may be coupleable to the surface base. The method may include transferring the heading transfer unit to a MWD tool. The MWD tool may include a MWD interface having a MWD interface alignment feature, such that the base alignment feature engages the MWD interface alignment feature. The method may include transferring the heading from the heading transfer unit to the MWD tool.

The present disclosure also provides for a system. The system may include a surface base. The system may include a master north finder positioned at the surface and coupled to the surface base. The system may include a MWD tool including a MWD interface including a MWD interface alignment feature. The system may include a heading transfer unit. The heading transfer unit may include a non-transitory, tangible, computer readable memory media adapted to store a heading and a base alignment feature coupleable to the surface base and the MWD interface alignment feature.

DETAILED DESCRIPTION

With reference toFIG. 1, heading transfer unit13may be configured as a dart or other device deployable into a wellbore. In some embodiments, heading transfer unit13may include a pressure vessel. Heading transfer unit13may include a MEMS-based AHRS navigation unit. Heading transfer unit13may include non-transitory, tangible, computer readable memory media adapted to store one or more pieces of data such as a heading or inclination as discussed below. In some embodiments, heading transfer unit13may include a processor, such as a microprocessor, microcontroller, FPGA, ASIC, or otherwise. In some embodiments, heading transfer unit13may include one or more sensors including, for example and without limitation, one or more magnetometers, accelerometers, or gyro sensors. In some embodiments, heading transfer unit13may include a power supply including, for example and without limitation, a battery. In some embodiments, heading transfer unit13may include one or more defined orientation features including, for example and without limitation, one or more scribes, keyways, or other interfaces used to align heading transfer unit13with other tools.

Heading transfer unit13may include base alignment feature14. Base alignment feature14may, for example and without limitation, allow for positioning and alignment of heading transfer unit13on other tools as discussed below. Base alignment feature14may be a pin, scribe, keyway, hole, slot, groove, key seat, or other mechanical feature used to align heading transfer unit13with other tools. The other tools may contain a mating mechanical feature such as a pin, scribe, keyway, hole, slot, groove, or key seat. In some embodiments base alignment feature14may also contain electronics and sensors that enable heading transfer unit13to determine its orientation with respect to the mated tool. In some embodiments, base alignment feature14may allow for data transfer between heading transfer unit13and other tools as discussed below. In some embodiments, heading transfer unit13may communicate by central hub, over wireline, or via other electrical or wireless methods known in the art.

In some embodiments, heading transfer unit13may be used to transfer a known heading to downhole MWD tool20as shown inFIGS. 2-5positioned within drill string16within wellbore17from the surface. Drill string16may be a drill string, tool string, casing string, component thereof, or other downhole tool. In other embodiments, sensors in heading transfer unit13may be used by downhole MWD tool20. In some embodiments, MWD tool20may include a continuous gyro survey instrument. A continuous gyro survey instrument may include one or more gyroscope sensors and one or more accelerometer sensors, which may be continuously used to measure changes in azimuth relative to an initial azimuth, with the initial azimuth or heading obtained from heading transfer unit13. In some embodiments, MWD tool20may include MWD interface21. MWD interface21may include alignment feature22positioned to receive base alignment feature14when heading transfer unit13is engaged to MWD tool20. MWD interface21may provide an electromechanical interface for communication between MWD tool20and heading transfer unit13. MWD interface21may be positioned at a known alignment relative to MWD tool20. In some embodiments, alignment feature22of MWD interface21may provide for a known alignment between heading transfer unit13and MWD tool20. In some embodiments MWD interface alignment feature22may be a pin, scribe, keyway, hole, slot, groove, or key seat. In some embodiments MWD interface alignment feature22may also include electronics and sensors that enable MWD tool20to determine its orientation with respect to heading transfer unit13and its base alignment feature14. In some embodiments, MWD tool20may be capable of sending data to the surface by, for example and without limitation, electromagnetic signals or mud pulse telemetry.

In some embodiments, heading transfer unit13may be connected to surface base10. Surface base10may include master north finder11. Master north finder11may measure and report its heading with respect to true north and gravity independently. In some embodiments, master north finder11may measure and report its heading at least partially in response to a measurement made by heading transfer unit13. In some embodiments, master north finder11may measure, estimate, or obtain its heading with respect to true north and gravity by, for example and without limitation, inertial navigation or gyrocompassing, GPS, visual sighting, optics, or land surveying. Surface base10may include one or more electromechanical connections or antennae to allow communication between tools such as master north finder11and heading transfer unit13, charging of heading transfer unit13, or powering of master north finder11. In some embodiments the heading and inclination of master north finder11may be transferred to heading transfer unit13wirelessly.

In some embodiments, in operation, heading transfer unit13may be connected to surface base10. A north-finding exercise may be undertaken using master north finder11to establish the heading of master north finder11and, because master north finder11is mechanically connected to surface base10, the heading of surface base10. The heading may be transferred to heading transfer unit13through surface base10as heading transfer unit13is connected to surface base10at a known orientation. In some embodiments, while connected to surface base10, heading transfer unit13may be in a “slave” mode, wherein the heading from master north finder11is used as the heading reference of heading transfer unit13. In some embodiments, when in slave mode, the heading reference from the master north finder may be continuously transferred to heading transfer unit13.

Heading transfer unit13may then be switched or commanded into a “navigation” mode, wherein heading transfer unit13computes an updated heading reference based on the initial heading received from master north finder11and the motion sensed by the internal sensors of heading transfer unit13.

In some embodiments, heading transfer unit13may then be moved through drill string16or other casing to mechanically engage MWD tool20. As heading transfer unit13is moved, the internal sensors may measure and continuously track the heading of heading transfer unit13.

In some embodiments, as depicted inFIG. 2, heading transfer unit13may be transferred through drill string16by wireline or slickline19. In other embodiments, as depicted inFIG. 3, heading transfer unit13may be dropped or pumped through drill string16through fluid18within drill string16. In some embodiments, heading transfer unit13may contain fins or other mechanical features to control or constrain the physical movement that heading transfer unit13is subjected to as heading transfer unit13moves through drilling string16.

Once heading transfer unit13reaches MWD tool20, base alignment feature14may engage with alignment feature22of MWD interface21as depicted inFIG. 4. Heading transfer unit13may be at a known alignment relative to MWD tool20as discussed above. Heading transfer unit13may communicate the measured heading of heading transfer unit13to MWD tool20. In some embodiments, MWD tool20may update or calibrate internally-measured heading to that of heading transfer unit13, and may continue operations. In some embodiments, MWD tool20may communicate the heading to the surface using normal telemetry.

In some embodiments, heading transfer unit13may be retrieved from drill string16. In some embodiments, heading transfer unit13may remain connected to MWD tool20. In such an embodiment, the sensors of heading transfer unit13may be used by MWD tool20to, for example and without limitation, provide real-time axial rate data to MWD tool20. The real-time axial rate data may be used, for example and without limitation, to perform a modified zero-velocity drift check, potentially improving measurement capabilities of MWD tool20.

In some embodiments, while heading transfer unit13is connected to MWD tool20, a second heading transfer unit13′ may be transferred through drill string16above heading transfer unit13as depicted inFIG. 5. Heading transfer unit13may include upper alignment pin15. Upper alignment pin15may positioned to receive base alignment feature14′ of second heading transfer unit13′. Upper alignment pin15may provide an electromechanical interface for communication between heading transfer unit13and second heading transfer unit13′. Upper alignment pin15may be positioned at a known alignment relative to heading transfer unit13. In some embodiments, upper alignment pin15may provide for a known alignment between heading transfer unit13and second heading transfer unit13′.

Once second heading transfer unit13′ reaches heading transfer unit13, base alignment feature14′ may engage with upper alignment pin15of heading transfer unit13. Second heading transfer unit13′ may be at a known alignment relative to heading transfer unit13and MWD tool20as discussed above. Second heading transfer unit13′ may communicate the measured heading of second heading transfer unit13′ to MWD tool20through heading transfer unit13. In some embodiments, MWD tool20may update or calibrate internally-measured heading to that of second heading transfer unit13′, and may continue operations. Additional heading transfer units13, such as third heading transfer unit13″, may be further transferred through drill string16to engage with previous heading transfer units13, such as second heading transfer unit13′. Third heading transfer unit13″ may include base alignment feature14″ positioned to contact upper alignment pin15′ of second heading transfer unit13′.

In some embodiments, MWD tool20may include two or more sections that may be physically separated within the downhole tool in which MWD tool20is positioned. In some embodiments, for example and without limitation, MWD tool20may include main MWD tool26and auxiliary MWD tool24as shown inFIG. 6. In some embodiments, main MWD tool26and auxiliary MWD tool24may have a known relative orientation with respect to each other. In some embodiments, auxiliary MWD tool24may contain electronics and mechanical features that enable auxiliary MWD tool24to obtain the alignment from heading transfer unit13, then transfer that heading to main MWD tool26through a wired or wireless connection such as, for example and without limitation antennae25positioned on auxiliary MWD tool24and main MWD tool26.