The original objective of solid expandable technology (SET) was to increase the number of casing points in deepwater wells. Now SET applications have gotten much broader in combination with other technologies.

Sidetracking with expandables
As with conventional tubulars, it is necessary to dress off the window in preparation for installing an expandable liner. Standard operating procedures also include running a caliper log and dummy drift prior to the expandable in order to verify the hole has been opened to the proper gauge.

A Middle East operator identified two wells for application of expandable casing through a

Figure 1. Solid expandable tubulars can be combined with intelligent well completion systems. (All figures courtesy of Enventure)
milled window. The wells had watered out in the main bore and required a sidetrack to access an additional drainage area in the same reservoir. A 51¼2-in. by 7 in. solid expandable openhole liner system was deployed through a newly created window in the existing 7-in., 26 lb/ft casing. An expandable openhole liner made drilling of a 61¼8-in. drain hole possible using a bicenter bit.

After abandoning the original well bore below the 7 in. liner, procedures called for installing a conventional whipstock and milling a window. The window was properly cleaned for the expandable liner by working the mills across the window exit until no torque or drag was encountered. The sidetracked hole was then drilled using a 6-in. by 7-in. bicenter bit. To save rig time, the expandable was run without a caliper log or dummy drift. The expandable liner system (consisting of 32 joints) was run in the hole with no indication of the string taking weight at the whipstock face. Approximately 200 ft (61 m) below the window, the string took weight and the expandable liner had to be retrieved to surface. A caliper log confirmed that the hole section was not open to 7 in. as required. A separate run with an under-reamer achieved the required hole diameter and the liner was successfully rerun to bottom. Once on bottom, expansion was initiated as expected and expansion rate remained consistent until the expansion assembly exited the top of the liner. The liner was pressure-tested to 2,000 psi for 30 minutes before the shoe was drilled out and the openhole section drilled to total depth (TD).

The successful application of an expandable openhole liner through a window resulted in the operator reaching the target zone with a hole size that maximized production and provided significant cost savings compared to a sidetrack program higher in the well bore.

Expandable casing
Expandable tubulars provide the hole size required to drill additional laterals as well as complete the well with intelligent tools too large for conventional casing. This unique combination of multilaterals, intelligent completions and expandable casing enables re-entry into the lateral.

An advantage of combining intelligent well technology with solid expandable tubulars is that
Figure 2. The combination of solid expandable tubular technology with other new technologies is making ultradeepwater, small plays and redevelopment of existing fields more economically accessible.
additional reservoir rock exposed from the multilateral well bores can be controlled as with a single well bore. This type of completion also facilitates remedial drilling operations as they become necessary. In a multi-well development project, this technology may reduce overall well count and project capital expenditures. Larger reservoirs that can produce at high rates and have higher recoverable volumes are prime targets for this combination of technologies.

Completions in a limestone reservoir
A well in a field located in a desert where the terrain is composed of flat salt areas and mountainous sand dunes up to 600 ft (183 m) high was worked over by converting an existing 1-km horizontal well into a trilateral, fork-type multilateral. Total reservoir exposure from the three legs exceeded 18,000 ft (5,490 m). The original main bore was under-reamed from 6 1/8 in. to 7 1/2 in. from the 7-in. shoe for 1,209 ft (368.7 m). The 5 1/2-in. by 7-in. expandable liner was then made up and run in the hole on a 2 7/8-in., PH-6 inner string.

Once on depth, the hole was circulated with water to ensure adequate hole cleaning.
The liner was then hydraulically expanded. The liner was pressure tested to 1,500 psi for 30 minutes followed by running and setting a cement retainer at 6,697 ft (2,042 m). A 51¼2-in. outside diamter whipstock was run inside the expandable liner and set on top of the cement retainer after being oriented 54° left. A window was milled in the expandable casing from 6,678 ft to 6,690 ft (2,036 m to 2,040 m). A 51¼2-in. directional drilling assembly was run in the well to drill the lateral off of the whipstock for a total of 4,625 ft (1,410 m) before reaching total depth. The whipstock was then retrieved in preparation for drilling the second lateral.

A retrievable plug was run and set at 6,430 ft (1,961 m) and a whipstock was run on top of the plug and oriented 55° right before setting. Again, a 51¼2-in. assembly was used to drill the second lateral, which achieved 7,340 ft (2,238 m). The whipstock and plug were retrieved and a concave mill drilled out the float shoe in the expandable liner.

The final step in the workover operation involved installing the intelligent completion system. This included three retrievable, hydraulic-set packers, three control valves and the required encapsulated hydraulic control lines. After completing workover operations, the well had more than 18,000 ft (5,490 m) drilled in the reservoir — more than 11,000 ft (3,355 m) from the two laterals drilled through the window exits in the expandable liner. The resulting increase in production enabled the operator to recover all workover costs in approximately 10 days.

Expandables and compact rigs
Combining expandable technology with the compact rig has significantly reduced deepwater exploratory and development drilling costs. This approach incorporates solid expandable tubulars as part of a system that includes the compact rig with its smaller blowout preventer (BOP) and riser. The process of “slenderizing” the well results in lower overall cost because operators are able to use smaller, more compact rigs in deepwater environments previously requiring Generation 5 rigs.

The majority of wells are drilled with large rigs using an 183¼4-in. subsea BOP stack and 21-in. marine riser. Designing solid expandable tubulars into the well plan allows for a smaller well bore at surface while still retaining an adequate hole size at TD. A slender well design allows existing lower class rigs (second- and third-generation semisubmersibles) to drill wells with a smaller BOP and riser. These rigs become more cost-effective to operations with pre-installed moorings to extend the water depth envelope of existing rigs.

Hydraulic workover units
A major operator in Africa faced the challenge of isolating four different pay zones (H2S producers) and a leaking multistage cement tool using a hydraulic workover (HWO) unit, the only available rig at the time. The objective was to convert the well from a shallow, sour Azile reservoir completion into a deep, sweet Madiela reservoir producer.

The operator installed ~1,400 ft (~427 m) of 7 5/8-in. by 9 5/8-in. expandable cased-hole liner with an HWO unit to isolate the sour oil zone. After expanding the first anchor hanger and conducting an overpull test of 50,000 lb, a combination of hydraulic pressure and mechanical overpull was used to expand the rest of the liner. After expansion, the expandable cased-hole liner was pressure tested to 2,000 psi, confirming successful isolation of the Azile perforations and the leaking DV tool. The successful installation eliminated waiting a year for an available backup drilling rig. US $1.5 million was saved by using the HWO, and time to payout was greatly reduced.

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