We developed the motorhead assembly (MHA) in response to industry demands for compact, heavy-duty integrated bottomhole assembly (BHA) components. Combining the twin flapper check valve with the heavy-duty hydraulic disconnect and the dual circulation valve, the motorhead assembly is a compact, versatile, and robust upper BHA that offers the following components:
- Twin flapper check valve
- Heavy-duty hydraulic disconnect (HDHD)
- Dual circulation valve (rupture discs sold separately)
Twin flapper check valve
The MHA incorporates two flapper cartridge assemblies. Each flapper cartridge assembly incorporates a primary metal-to-metal seal, providing high-pressure sealing integrity and a secondary PTFE seal for low-pressure sealing. The flapper cartridge assemblies simply drop into the valve housing, providing a simple and easy redress of the MHA.
Heavy-duty hydraulic disconnect (HDHD)
The HDHD has been methodically designed to ensure assembly and disassembly of the tool is trouble free. The heavy-duty hydraulic disconnect allows the tool string to detach at a predetermined point by deploying a suitable drop/trip ball through the coiled tubing. The drop ball locates on a piston sleeve, creating sufficient backpressure to shear the pins and disconnect the tool. When this happens, the piston sleeve pushes the tool apart to ensure a clean disconnect, and circulation is immediately returned to the tool string, providing a surface indication of a positive disconnect. All piston sleeves and drop balls are returned to surface as well, leaving a standard GS internal fish neck for retrieval purposes.
The HDHD uses a heavy-duty single-piece threaded collet slip to hold the tool together. The collet slip endures higher tensile loading than collet finger-type release mechanisms and is far less susceptible to fatigue. The collet slip is backed up by a collet slip sleeve to provide maximum tensile strength to the disconnect during heavy jarring operations.
Only by dropping a ball and shearing the pins can the collet sleeve shift, allowing the collet and top sub to part. The piston sleeve is pressure balanced, so internal pressure does not affect the hydraulic configuration and shear values.
High torque capabilities are achieved through positive-torque drive teeth between the top sub and the main body of the tool. The heavy-duty hydraulic disconnect is therefore ideally suited for high-torque, heavy-duty coiled tubing drilling operations in which maximum performance and durability are essential.
Shear screws can be supplied in either brass or steel to give a comprehensive pressure range that will suit virtually any coiled tubing application. Shear screws are also integrally situated to eliminate the possibility of vibrating free during CT drilling operations.
The standard configuration consists of the maximum flow-through bore while maintaining maximum tensile strength in the tool. By interchanging the piston sleeve, the drop/trip ball size can be varied to suit the desired tool string requirements. This is a particularly useful feature when the hydraulic disconnect is situated below jars and intensifiers and ID restrictions are a considering factor. Running the heavy-duty hydraulic disconnect below jars and intensifiers ensures that if disconnection of the tool string is necessary, a greater proportion of the tool string is safely returned to surface.
Dual circulation valve
The dual circulation valve offers the traditional method of returning circulation of the tool string through use of a drop ball. In addition, the valve is capable of operating through internal overpressure within the tubing string.
- The MHA's compact design gives an overall length saving of approximately 30% over the use of conventional individual components.
- The high torque capability of the MHA provides the ideal motorhead for today's high-demand coiled tubing drilling applications.
- The choice of tubing connector is not dictated by the MHA, giving the operator the flexibility to choose. Most coiled tubing connectors can be used with the MHA.
- With a considerable reduction in the number of component parts, seals, and thread connections, the MHA is simple to assemble/disassemble and inexpensive to redress.
- The MHA is retrieved with a standard GS running tool.