Pipeline & Gas Journal
October issue 1999:

Statoil Application

Asgard B And Kårstø To Use Aeroderivative Gas Turbines

Statoil has long relied on GE Industrial AeroDerivative Gas Turbines’(GE-IAD)LM aeroderivative gas turbines for compressor drive and power generation applications. Therefore it was no surprise that Norway’s state-owned oil/gas company—through a frame agreement with Dresser-Rand—would select seven LM2500+ aeroderivative gas turbines for its power needs at the Asgard B floating production system and the Kårstø gas treatment plant.
Six of the seven gas turbines will be equipped with GE-IAD’s Dry Low Emissions (DLE)

combustion systems and all will be packaged by Dresser-Rand AS, Kongsberg, Norway. GE-IAD’s DLE system has an environmentally friendly design to meet and exceed the stringent emissions requirements in Norway and throughout the globe.

Asgard Field
The Asgard field lies on the Halten Bank in the Norwegian Sea, about 200 kilometers from mid-Norway and 50 kilometers south of Statoil’s Heidrun field. Oil production began in early 1999 and gas will start flowing in the second half of 2000. The field makes it possible to expand Norway’s gas exports to continental Europe.

The Asgard Field is one of Norway’s largest in terms of reserves, investment and technological challenges. The field includes a ship to produce the oil, a semi-submersible gas production facility and the world’s most extensive use of subsea systems—58 wells for production and injection for 17 seabed templates. The field’s location in the North Sea also presents numerous challenges such as the harsh climate and subsea floor terrain.
Halliburton’s Kellogg Brown & Root Energy Services (formerly Brown & Root Energy Services) is the contractor for marine operations and subsea floor pipeline installation for the Asgard field.

Asgard B/Kårstø
The Kårstø gas treatment plant is located onshore in Kårstø near Stavanger, Norway. The first gas arrived at the Kårstø complex in July 1985 from Statoil’s Statpipe trunkline. After treatment, lean gas is piped on to continental Europe while natural gas liquids (NGLs) are shipped out in carriers. Kårstø also receives condensate from the Sleipner area for stabilization and storage before export by ship. This part of the complex began operation in October 1993, and it ranks as Europe’s largest processor and export of NGLs and condensate.

Two GE LM2500+ gas turbines will be used for gas compression at the Kårstø treatment plant. Gas from the Asgard field will be piped through the Asgard transport line to the Kårstø plant. Each LM2500+ train will be connected to a heat recovery unit for steam production. These two units will drive Dresser-Rand DATUM efficient centrifugal compressors.

Three GE LM2500+ gas turbines will be used for the compressor drive on Statoil’s Asgard B semi-submersible production facility to be situated in the Norwegian sector of the North Sea. Each gas turbine will be connected to a heat recovery system. Two additional LM2500+ gas turbines will provide power generation for the Asgard B floating production system.

In June 1999, two GE LM6000 aeroderivative gas turbines, also sold and packaged by Dresser-Rand, began operating on the Asgard A floating production, storage and off-loading vessel (FPSO). Two GE LM2500+ gas turbines also drive DATUM compressors on the same FPSO. Statoil expects to see increased efficiencies of 2 percent to 5 percent above the 83 percent industry standard by using DATUM compressors.

The Gas Turbines LM2500+
In 1994, GE-IAD introduced the LM2500+ that is derived from its popular LM2500 gas turbine. GE-IAD’s conservative design and development philosophy was to use existing and proven technology as a basis for the LM2500+.
In addition, reliability, availability and the apparent need for a product to fill a gap in the 29-megawatt/40,000-shaft horsepower (shp) power range were driving factors behind the introduction of the LM2500+.

By increasing the compressor airflow 20 percent, with a minimal increase in combustor firing temperature, the extra power and 40 percent thermal efficiency of the LM2500+ were achieved (see Table 1 for LM2500+ specifications).
As of July 1999, there were 65 industrial LM2500+ gas turbines slated for service throughout the world; those units already operating have logged nearly 65,000 fired hours.

For applications in the 3000-3600 rpm output shaft speed regime, the LM2500+ uses an uprated version of the LM2500 six-stage power turbine. The seven LM2500+s for the Asgard B and Kårstø projects use this six-stage power turbine. This version is suitable for 50 and 60 hertz power generation applications.

LM6000
The introduction of this gas turbine in 1990 marked a significant advance in aeroderivative gas turbine technology. The LM6000 shares 90 percent commonality with GE’s CF6-80C2 aircraft engine.

The LM6000 low-pressure rotor consists of a five-stage low-pressure compressor (LPC) and a five-stage low-pressure turbine (LPT) connected by means of a mid-shaft, which extends through the center of the engine. The high-pressure rotor consists of a 14-stage high-pressure compressor and a direct-coupled, two-stage high-pressure turbine.

The LM6000 is designed to operate at an output shaft speed of 3600 rpm for electrical power generation. A reduction gearbox reduces shaft speed from 3600 rpm to 3000 rpm in 50-hertz applications.

The gas turbine is equipped with three systems that control airflow to achieve the desired performance characteristics. Variable inlet guide vanes in front of the LPC modulate airflow entering the engine. Variable bleed valves between the low- and high-pressure compressors allow some airflow to be bled off at low power conditions. Six stages of variable stator vanes on the high-pressure compressor stage maintain high efficiency over the power range.

The first LM6000 began commercial operation in late 1992. Since that time, more than 200 LM6000s have been selected for a variety of power generation applications throughout the globe.

In 1995, just three years after the first LM6000 began commercial service, GE-IAD announced the uprated LM6000PC (standard combustion system) and LM6000PD (DLE combustion system) models.

Statoil and LMs
Statoil has the largest industrial fleet of LMs in the world. Including the Asgard A, B and Kårstø projects, Statoil will have 68 LMs in or slated for service at various processing facilities, offshore platforms and pipeline stations.

With GE-IAD’s DLE combustion systems in place, the LM2500+ and LM6000 gas turbines for Statoil’s Asgard A, B and Kårstø projects can achieve maximum values of 25 ppm NOx and 25 ppm CO or less.

(GE-IAD is part of GE Power Systems, and is headquartered in Evendale, OH. GE-IAD is the world’s largest designer, developer and manufacturer of aeroderivative gas turbines for a variety of power generation and gas compression applications). P&GJ