As hydrocarbon deposits become harder to find and the majority of the super giant oil fields continue to mature, the industry is being forced to consider increasingly challenging reservoir management issues which require intelligent completions and complex well designs to ensure their long term success.

One way forward has been the development of openhole intelligent completions whose advantages lie in the reduction in well construction cost, well slimming and improved productivity through maximum reservoir contact.

When completed open hole, the well drilled can be reduced to 61⁄8 in. while still accommodating the large 31⁄2-in. control valves - resulting in a major saving in the time taken to drill and complete the well. In a cased hole a 7-in. liner would need to be run to accommodate the 5.75-in. outside diameter of the 31⁄2-in. control valve.

The ability to complete a well open hole can also considerably reduce the time and cost by removing the need to cement and perforate, conduct multiple clean-up trips and side-track through the liner to drill the laterals off the motherbore.

Control line limits

However, the ability to monitor and control multiple laterals or zones is often impaired by the limits of the control lines and cables necessary for the functionality of these systems. In order to effectively isolate between multiple zones or laterals an isolation device must be deployed with the intelligent completion system, with monitoring and control lines passing through the device.

Mechanical packers can accommodate multiple control lines, but only by cutting the lines, feeding them through the packer, re-terminating and pressure testing the connections. This process can take from 2 to 6 hours per mechanical packer, depending on the number of control and monitoring lines.

A study carried out by a leading service company in 2000 revealed that 40% of system failures were attributable to cable connections. Each time a control line splice is added there is an increased risk of system failure and splicing operations rely heavily on the experience and training of the engineer.

Fiber optics

In the past 5 years, there has been a marked increase in the use of fiber optic systems in the industry for monitoring the temperature profiles of production and injection wells, single or multiple point pressure and temperature and flow metering.

There are currently two deployment methods for fiber optic monitoring systems. The first is the pump down system, where a control line u-tube is installed with the completion string. Here, the control line has a smooth internal bore and the fiber optic cable is pumped down the control line using water. The disadvantage with this process is that every connection can produce a point in the system where the fiber optic cable may be damaged.

The second method is a pre-packer fiber optic cable where splice connections must be made each time the cable has to penetrate through tubing hangers, packers or where it must be connected to a single point sensor. Every connection reduces the optical capacity of the system which can impair the measurements and impact on the long-term reliability of the monitoring system.

But, until recently it has not been possible to effectively monitor and control multilateral openhole wells due to the lack of an effective annular seal with cable and control line feed-through capability. Removing the need to terminate monitoring and control lines undoubtedly enhance the long-term reliability of the intelligent completion system.

The swell packer cable provides annular isolation for both openhole and cased-hole completions with the ability to install monitoring and control lines without the need for time consuming splicing operations. Swell packers are designed and manufactured with a pre-formed slot, the size of which is determined by the flat-pak or line size.

Installation

A specially designed installation tool is installed in the rotary table and as the packer passes through the tool and rotary table the cable slot is opened up and the cable is fed into the packer. The monitoring cables and control lines are held in place during the running of the completion by cross coupling cable protectors placed on the pup joints above and below each swell packer.

When the swell packer is installed at the correct setting depth and it comes into contact with hydrocarbons -- either from the reservoir, oil based mud or spotted fluids - the rubber element swells up to 200% of its original volume to form an annular seal either inside the casing or the open hole and at the same time seals around the flat-pak or individual control lines. The swell packer cable provides both an annular pressure seal and a pressure seal around the monitoring and control lines.

The ability to install permanent monitoring cables and control lines without the need to re-terminate has a dramatic impact on the reliability of intelligent completion systems by removing several potential failure points. Fiber optic monitoring systems also benefit from the use of splice-less cable feed through swell packer's by reducing the number of connections that may damaged the fiber optic cable during pump-round deployment and increasing the optical capability available when using the pre-packed fiber optic cable.

The first successful installation of cable feed-through swell packers was performed in the Caspian Region in April 2005. Two swell packers were installed in a cased hole as part of the lower sand face completion with a fiber optic data transfer system (DTS) and used for isolation between two producing zones.

Further installations with DTS are expected in the Caspian Region in 2005.

The first openhole smart well completion is planned for installation in the Middle East region by a national oil company. The swell packers will be installed in the openhole motherbore of a tri-lateral well to isolate between the control valves placed across each lateral. Three control valves will be installed with one single point pressure and temperature sensor per lateral with a maximum of five monitoring and control lines passing through the upper packers isolating the heel section. The main drivers for the operator are reduction of well construction costs through well slimming, reduced rig time, eliminating the need to cement and perforate and to simplify the completion process. The number of intelligent completions installed annually has dramatically increased with more than 60 installations expected in the Middle East region alone in 2006. Several of these installations are being considered as openhole intelligent completion candidates.

Swell packer-cables have the potential, therefore, to simplify and speed up the openhole approach and to add to the reliability of the whole monitoring and control operation of such wells.