The zonal isolation barrier (ZIB) is a sleeve fitted to the outside of a completion base pipe that provides an inflatable permanent metal barrier to annular flow in either open-hole or within tubing/casing. The ZIB is inflated by HETS or by pressurizing the well if the liner has a sufficient pressure rating. The ZIB can be deployed and inflated immediately or as required, provides zonal isolation up to 10,000 psi during injection and fracturing, and up to 4,000 psi during production.

A hydraulically expandable tubular system (HETS) can deliver real improvements in well integrity and well design, offering a flexible set of design, construction, and repair tools for through tubing rotary drilling, deep, slim, extended reach, and horizontal wells. The system can be deployed on drillpipe and coiled tubing, and will soon be available for wirelines. The HETS product range is being continually expanded to meet individual client needs. With the use of external casing patches, liner hanger/casing packers, internal patches, and zonal isolation barriers (ZIB) a full range of innovative solutions can be accomplished.

External patch

An external patch (EP) system is the primary solution for many major North Sea operations. It avoids costly sidetracking, while offering a load-bearing, metal-to-metal, gas-tight seal that gives operators a simple solution to casing repair or stuck casing problems.

In the North Sea in August 2007, an operator installed a 95?8-in. external casing patch at the top of a well that had lost its integrity. The challenge for the operator was to cut and remove the upper section of the corroded casing, reconnect with an EP, and convert it to a 95?8-in. liner without loss of inside diameter.

The external patch was the preferred solution because of its qualification criteria and the simplicity of its engineering design, which provided a connection capable of carrying 300,000 lb in both tension and compression at operating production temperature.

To place the EP, a 95?8-in. casing was cut above the 133?8-in. shoe and recovered. The remaining 95?8-in. section was tied back into the 133?8-in. by running a conventional liner hanger and casing packer above a short string of new 95?8-in. casing, which was connected to the old 95?8-in. casing with the EP.

The 95?8-in. by 133?8-in. patch provided one of two integrity barriers around a gas-lift completion. Successful installation was confirmed by a pressure test from the surface. Re-instating the 95?8-in. casing allowed greater production than the alternative of reducing well diameter with a scab liner solution.

Liner hanger/casing packer

A liner hanger/casing packer is designed for both drilling with casing and conventional well construction methods. It provides high-integrity, gas-tight sealing. An uncomplicated “no-slips” design ensures safe deployment and long-term reliable service that works for close clearance casing systems and is an enabler for slim well construction.

A liner hanger/casing packer was used in the Norwegian sector of the North Sea in January 2007. The challenge was to casing directional drill a well to over 12,000 ft (3,660 m) and 70º deviation, and then convert the 73?4-in. casing string to a liner, with a completely gas tight 200-metric-ton load capacity liner hanger set at 5,000 ft (1,525 m).

The liner hanger was installed as part of the drillstring with the bit at approximately 7,000 ft (2,135 m) from where it drilled to the 73?4-in. shoe depth (12,000 ft). The 73?4-in. shoe was cemented and the tool was deployed on drill pipe and positioned across the 73?4-in. liner hanger before the system was activated. It generated 21,500 psi hydraulic pressure above hydrostatic to expand an 11 ft (3.4 m) long 73?4-in. liner hanger (15% in diameter) into the outer 103?4-in. casing.

Successful installation was confirmed by pressure test to 3,700 psi with mud (equivalent to 5,000 psi with water). The liner hanger met all operator requirements for the well design. Extensive onshore testing demonstrated that the 200-metric-ton rated hanger can withstand a bi-directional load of up to 360 metric tons. The liner hanger delivered the necessary performance even after being exposed to 20 days of in-hole drilling.

Another North Sea operator required a 75?8-in. by 95?8-in. liner hanger qualified to 5,000 psi gas in both burst and collapse, at 103ºF and 202ºF (40ºC and 95ºC), and load tested to 72 metric tons compression and 45 metric tons tension. The liner was to be deployed for possible use in a high-angle long-reach well positioned below a conventional hanger and seal assembly. It was essential to set the conventional hanger in wet cement to achieve a gas-tight seal. Foam cement was used because of the highly deviated trajectory of the well. Losses were experienced during cementing, and a cement bond log indicated that the top of the cement had not reached the conventional hanger, so it was no longer possible to set the hanger and achieve the required seal.

The contingency plan required an HETS expansion tool to be run and the system activated with low-pressure water pumped from surface. The down-hole hydraulic module controlled and intensified the pressure and achieved the desired expansion pressure of 21,950 psi above hydrostatic. The 75?8-in. liner was expanded into the 95?8-in. casing, creating a gas-tight connection.

The well was pressure tested to 5,000 psi from the surface, confirming successful installation of the liner hanger. The primary objective of a gas-tight seal was met despite failure of the conventional liner hanger and foam cement. The operator achieved improved well integrity, along with higher production rates than would have been possible using a scab-liner solution, which would have reduced the well diameter. Using the liner was a simple operation that required less rig time and delivered improved seal performance.

ZIB

ZIB is a sleeve fitted to the outside of a completion liner that provides an inflatable permanent metal barrier to annular flow in either an open hole or within tubing/casing.

The ZIB is inflated by an HETS or by pressurizing the well if the liner has a sufficient pressure rating. The ZIB, which provides zonal isolation up to 10,000 psi during injection and fracturing and up to 4,000 psi during production, can be deployed and inflated immediately or as required. It has a high expansion ratio and is not degraded by produced fluids. Because the ZIB can be expanded as soon as the completion is in the ground, maximum well productivity is provided as early as possible.

The testing phase of this technology concluded in 2008, and it is now qualified for major work in the North Sea. The challenge was to manufacture, test, and qualify 5-in., 51?2-in., and 65?8-in. ZIBs to provide zonal isolation during fracture operations with hydraulic fracture pressure peaking at 10,000 psi.

READ Well Services verified the fit-for-purpose design and qualified its ZIB in accordance with current industry standards and client test specifications. This included providing zonal isolation of up to 10,000 psi during injection and fracturing and 4000 psi during production. Fourteen 65?8-in. and 12 5-in. ZIBs were manufactured with nine of the 65?8-in. ZIBs being deployed and used successfully for the client’s first fracturing job. The company has recently manufactured an additional twelve 51?2-in. ZIBs and supplied them for customer for use.

Client testing of various zonal isolation barriers confirmed that ZIBs successfully withstood the required frac pressure, followed by exposure to hydrocarbons and water injection. A major benefit to the client is that the ZIB solution can be activated through expansion as required — immediately or after several years. In this case, the client requires expansion as soon as the completion is in the ground. This ensures that the well can be given the most suitable stimulation and provides maximum productivity as early as possible.