NORWAY IN SOUTHEAST ASIA: Microwave technique improves accuracy of water cut measurements

Roxar's IRPM technology takes informtion from a variety of sources and uses it to optimize well performance.

Roxar, the Norwegian supplier of res-ervoir management technology, has made a concerted attempt to pen-etrate the market for water-cut and multiphase meters in the Asia Pacific region over the past couple of years, significantly reinforcing its offices in Perth, Kuala Lumpur and Beijing.

Sandy Esslemont, Roxar's Eecutive Vice-President for the region, explained that high water cuts were a characteristic of wells in the region. Also, many operators had expressed disappointment with the quality of service generally being provided by meter suppliers. "Roxar identified a need for someone to bring in accurate, reliable meters and to back this up with first-class technical support," he said.

The last 12 months have vindicated Roxar's decision to invest in the region and in this market sector. The company has supplied three multiphase meters to Chevron's Niugini development, two to CNOOC's Wen Field development in the South China Sea, a multiphase and a water-cut meter to the Daqing Oilfield Development in China, a water-cut meter to Maxus in Indo-nesia and one multiphase meter to Petronas in Malaysia. But the biggest order has been with Caltex Pacific Indonesia for 39 of the firm's FullCut water-cut meters for the onshore Duri Field in Sumatra.

Esslemont described how Caltex had experienced problems previously with water-cut meters and approached Roxar for a single meter on which to carry out an extensive test program. This was successful, leading to the near-$1 million order. About half of the meters have so far been installed - all 39 should be operational by the end of the year. The company is currently undergoing a similar qualification process with Shell Brunei.

Roxar's FullCut meters are capable of measuring the amount of water in a hydrocarbon stream over the full range 0-100%. The analyser's electronics are mounted in an explosion-proof enclosure, linked to a full-bore spool-piece containing the sensing device. Currently available in 2-in. and 3-in. versions, the meters can cope with pressures up to 30 bar. Key features of the design include:

• Low pressure drop
• Automatic compensation for temperature and salinity
• Ease of calibration
• Low sensitivity to gas entrainment
• High temperature capability
• Capacity to deal with mixtures containing oil and water having the same density.

The meters record the amount of water in the mixture by measurement of the dielectric properties of the liquid and comparison with the dielectrics of the pure components. Patented microwave technology, based on the resonant cavity method, is applied to achieve measurements with unusually high accuracy and resolution. This basic technique, which is applied widely in the laboratory, has hitherto not been adopted on-line since it could not handle flowing streams - the resonant cavity is normally formed in a closed metal box.

Roxar has overcome this using a straight spool piece with two microwave sensors: one transmitter and one receiver. The pipe is used as a cylindrical wave-guide, within which the transmitted electromagnetic waves propagate freely, permeating the entire cross-section rather than just the region surrounding the transmitter. The waves are confined within the measurement section by metal plates which make-up the resonant cavity.

Monitoring/control

The region also recently saw the first application of Roxar's new Promac downhole internal control valve, which is capable of monitoring and also controlling fluid flow form various zones in the reservoir. Texaco placed an order recently for a test installation of the system in a Caltex-operated onshore well in Sumatra.

Promac is a development of the company's well-proven permanent downhole monitoring system (PDMS). Since there are no electronics actually downhole, the tool is simple, robust and highly reliable. Under remote control from the surface, the tool is capable of static and dynamic reservoir monitoring and inflow regulation in various zones in the well. A typical device uses a single electrical conductor to communicate with three quartz pressure and temperature gauges. One takes measurements inside the tool, a second records in the annulus and a third measures hydraulic pressure at the control valve.

The tool was developed with the help of DEMO-2000 funding from the Norwegian Government. This July, Roxar was granted further funding from the same source to develop and test its integrated reservoir and production management (IRPM) system, which was short-listed for an Innovation Award at the recent ONS conference in Stavanger.

IRPM combines Roxar's metering and downhole monitoring and control technology with advanced reservoir modeling and production control software to provide users with a real-time, remote control capability. The company claims that the system, which is intended to be tailored to each individual application, combines monitoring and metering data directly in a way not previously possible. It says reservoir exploitation will "resemble a process industry plant" where operators will continuously measure reservoir production characteristics and then act on the data to optimize well output in real-time.

The first prototype system is being installed on Statoil's Huldra gas condensate field in the Norwegian North Sea, production from which is expected to start in fall 2001. In combination with Roxar multiphase meters and downhole monitoring equipment, the system will be integrated with a range of third-party packages. Control will be from a center located near Bergen.