Westbay System Well Completion
The delivery system consists of two sizes of casing which were developed to fit two ranges of borehole sizes.
MP38 System has an inside diameter of roughly 38mm (1.5in) and is generally used in boreholes or casing whose inside diameter ranges from 76mm (3in) to 115mm (4.5in).
MP55 System has an inside diameter (ID) of 55mm (2.25in) and is generally used in boreholes or casing whose ID ranges from 98mm (3.9in) to 170mm (6.25in).
Both systems are designed for operation at maximum depths that range from 300m (1,000ft) to over 1,500m (5,000ft).
Both systems are available in plastic and in stainless steel. Steel systems are used in situations where tensile strengths, hydraulic pressures or temperatures are higher than would be suitable for the plastic systems.
Couplings joining the casing together consist of regular couplings and port couplings. Regular couplings simply join two pieces of casing together, while port couplings provide a controllable pathway for formation fluids on the outside of the coupling to reach the inside of the coupling.
The measurement port is the heart of the MP System. Measurement ports are used for the majority of the pressure measurement and fluid sampling operations. Each measurement port coupling has a small check valve that contains a spring that keeps the valve closed so that it will not open due to the application of an exterior fluid pressure. The measurement port is operated by means of a MOSDAX* probe that is lowered into the borehole, locates the measurement port and opens the port valve.
In contrast to the measurement port, a pumping port coupling has several relatively large openings. The total area of these openings is approximately equal to the cross-sectional area of the inside of the casing. A sliding sleeve valve controls the pumping port openings. Either mechanical or hydraulic operating tools operate pumping port valves.
Different levels (monitoring zones) in a borehole are separated by placing impervious layers of backfill around the outside of the casing between monitoring zones or by using water inflated packers.
Westbay has developed a series of modular hydraulically inflated packers that are mounted on plastic or stainless steel mandrels. Each packer has an individual inflation valve attached to the packer. After the packers have been positioned in the borehole, a packer inflation tool is lowered into the borehole and packers are inflated individually
Magnetic collars can be attached to the outside of the casing near components that will be visited frequently. The collars contain ceramic magnets. When a probe passes by a magnetic collar, a reed switch in the probe is triggered and a "beeping" noise is heard at the surface. This assists the probe operator in determining the location of the probe in the borehole.
A number of special components are available. These include:
- Y-connectors that permit twin–tubes to be installed in the upper part of the drillhole. This arrangement permits pumping to occur in one tube while sampling and pressure monitoring occur in the other.
- Telescopic casings that can extend or be compressed after installation. These protect the casing components should there be a tendency for the borehole to lengthen or shorten in the future.
- A borehole completion kit that permits de-stressing of the plastic casing during installations in deep boreholes.
Tools for Casing Installation and Recovery
Packer Inflation Tools: Each casing system (MP38 and MP55) has a specific tool to inflate packers. These tools have associated winches, hoses and control units for handling the packer inflation activities.
Pumping Port Operating Tools: The operation of pumping ports requires tools that will open and close the pumping port valve. A separate mechanical "open/close" tool is available for the plastic MP38 System. Hydraulic pumping ports for the steel MP38 System and the MP55 System are operated by a modified MOSDAX sampling probe or by a special tool.
Casing Recovery Tools: Casing recovery tools are available for those projects where it is necessary to demonstrate recovery capability before installation proceeds.