Westbay Systems - Well Completion

At the heart of every Westbay System

Casing

The delivery system (sometimes referred to as a borehole completion system) consists of two sizes of casing, which were developed to fit two ranges of borehole sizes:

• The MP38 System has an inside diameter of roughly 38 mm (1.5 in) and is generally used in boreholes or casing whose inside diameter ranges from 76 mm (3 in) to 125 mm (5 in).
• The MP55 System has an inside diameter (ID) of 55 mm (2.25 in) and is generally used in boreholes or casing whose ID ranges from 98 mm (3.9 in) to 170 mm (6.25 in).

Both systems can be used with alternate packers and completion methods for larger borehole sizes. The delivery systems are designed for operation at maximum depths that range from 300 m (1,000 ft) to over 1,000 m (3,300 ft). Installations to depths of 1,000 m are relatively routine for experienced Water Services personnel.

The MP38 System is available in plastic, while the MP55 System is available in plastic and in stainless steel:

• Plastic systems are typically PVC, with some other plastics and some stainless steel components used. The unique sealed nature of Westbay System during installation control of the buoyancy and differential pressures acting on the casing assembly. In this manner, plastic components can be installed to depths of 1,000 m (3,300 ft) or more, provided temperatures do not exceed about 40° C.
• Steel systems are used in situations where tensile loads, hydraulic pressures (in particular differential pressures), or temperatures are higher than would be suitable for the plastic systems. Steel rather than plastic might also be used in situations where the casing will be subjected to unusual abrasion and wear. The stainless steel is typically 316L or better.

Regular couplings

The casing systems have been designed with interchangeable modular components. Couplings joining the casing together consist of regular couplings and port couplings:

• Regular couplings simply join two pieces of casing together.
• Port couplings (measurement ports or pumping ports) provide a controllable means to access the fluid outside the casing at the depth of the port.

Measurement ports

The measurement port is the heart of Westbay System. Measurement ports are used for the majority of the pressure measurement and fluid sampling operations. Measurement ports can also be used for hydraulic testing in low-permeability environments.

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 Westbay probe that, when lowered into the well, locates the measurement port and opens the port valve. Some MP55 measurement ports contain two valves. These dual-port measurement ports are designed for use with probes containing in-situ sensors or other advanced testing devices.

Pumping ports

In contrast to the measurement port, a pumping port has several relatively large openings, allowing more rapid movement of larger volumes of fluid than is possible with the measurement port. 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. Pumping ports remain closed until opened. They are used for purging following installation, for taking large volume samples and for permeability testing in moderate to high-permeability units.

Packers

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.

We have developed a series of modular hydraulically-inflated packers that are mounted on plastic or stainless steel mandrels. Each packer incorporates an individual inflation valve.

After the packers have been positioned in the borehole, a packer inflation tool is lowered into the MP casing and the packers are inflated individually. No permanent packer inflation hoses are left in the borehole. During the inflation process, the inflation pressure and volume of water are recorded for each packer. The packers remain inflated for the life of the monitoring well. If servicing or decommissioning of the well requires removal of the casing system, some types of packers contain a valve that allows the packer to be deflated, while other packers are deflated by perforating the mandrel.

Magnetic collars

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.

Specialized components

A number of special components are available. These include:

• Y-connectors permit twin casings to be installed in the upper part of a borehole. This arrangement permits pumping to occur through one casing while sampling, pressure monitoring, or pumping port operation occur in the other.
• Telescopic casings 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.