Progressing cavity pumps and centrifugal pumps help move oil and an oil/water mixture.
by Sean McCandless, Colfax Fluid Handling
March 28, 2013

OMV Austria Exploration & Production GmbH and its predecessors have been pumping crude oil in Vienna’s wine growing region for more than 50 years. Approximately 600 oil wells make up Austria’s Matzen oilfield. The company pumps an oil, gas and water mixture (approximately 90 percent water) through pipelines to a centralized, live oil collection station. At the station, the oil is separated from the water and natural gas. The oil is then pumped into the Auersthal tank farm for subsequent processing. Water is directed to the water treatment plant, and natural gas is sent to a compressor station in Auersthal.

Complete Renovation

Before the centralized station came online in 2005, 12 individual extraction stations were used. In 2005, in anticipation of pumping crude profitably for another 20 to 30 years, the company embarked on a comprehensive renovation of its entire infrastructure, including the network of pumps and 43.5 miles of piping. The system takes advantage of the discharge pressure of the oil wells to pump the oil, water and gas mixture through new pipelines to the centralized Matzen extraction station.

The earlier individual stations are now used only as measurement stations for the live oil. Preparation and separation of the live oil occurs only in the Matzen station. Thirty-one pumps from one manufacturer replaced the existing pumps from different manufacturers that were housed in the individual stations. The tank farm uses large progressing cavity screw pumps from this manufacturer to handle all qualities of crude oil. These pumps are equipped with frequency converters to control the rate at which the oil is moved through the approximately 15.5 miles of pipeline and into the Lobau reservoir (up to 528 gallons per minute [gpm], maximum of 560 psi). A progressing cavity pump moves slop oil (wastewater) out of the tank farm. Between 2005 and 2011, OMV invested €130 million to completely renovate the collection stations, the extraction station and the tank farm.

High Expectations for the Pumps

Progressing cavity pumps used for the production of crude oil must fulfill special requirements. First, they must be able to handle large crude oil viscosity differences. The pumps must cover a wide viscosity range with uniform and efficient performance. They are also needed to deliver high discharge pressure or high capacity, depending on the requirements.

Progressing cavity pumps are particularly well-suited for oil that contains gas or foreign objects. These pumps are relatively insensitive to oil that is contaminated with sand, rust or paraffin. They are even able to pump crude oil that contains gas or is mixed with salt water.

Their low net positive suction head values make them flexible in terms of installation. For example, they may be installed above the suction level. The progressing cavity pumps can handle long suction lines and completely drain tanks without compromising performance or efficiency. Low shearing forces minimize the mixing of pumped liquids. In the midstream process, separating oil and water components in the crude oil is straightforward and efficient.

Materials Optimized for Chloride Components

At the extraction station, six separators process the live oil and separate it into qualities—asphalt base (A quality) and paraffin base (P quality). Tanks for each quality and a reserve tank each hold 264, 172 gallons. Two water tanks hold 528,344 gallons. The total capacity of the system is approximately 245.6 million gallons.

The tanks for the A and P qualities and a reserve tank each hold 264,172 gallons. The two water tanks hold a total of 528,344 gallons. The A and P tanks are supported by progressing cavity screw pumps. The water tanks use centrifugal pumps.The tanks for the A and P qualities and a reserve tank each hold 264,172 gallons. The two water tanks hold a total of 528,344 gallons. The A and P tanks are supported by progressing cavity screw pumps. The water tanks use centrifugal pumps.

Water that is generated as a waste product is processed in the extraction station and treatment plant and then pumped back into the storage facilities. Six stainless steel centrifugal pumps act as circulation pumps, moving 176 gpm of the oil/water mixture at 28 to 42 psi at approximately 15 centistokes (A quality) and 200 to 300 centistokes (P quality).

The 10 loading centrifugal pumps for the two water tanks move 88 gpm at 63 psi. They are constructed of duplex stainless steel, making them corrosion-free despite the high level of chloride in the water. Salt content is between 0.125 and 0.309 pounds per gallon. For this reason, the mechanical seals on these formation water pumps are among the most critical components. A special metal bellows seal in the centrifugal pumps has proven to be effective in the extraction station. Two additional pumps are in service as surface-water pumps and condensate pumps. They pump salt water with natural gas condensate and are constructed in duplex stainless steel.

Screw pumps are used in the central Matzen extraction station to move the crude oil.Screw pumps are used in the central Matzen extraction station to move the crude oil.

Single Pump Source

In addition to the centrifugal pumps and progressing cavity pumps, three screw pumps are used at the site. These oil transfer pumps move up to 264 gpm of purified crude oil (in both qualities) to the Auersthal tank farm at 280 psi.

Centrifugal pumps are installed before these screw pumps, and they serve as booster pumps, moving up to 264 gpm at 39 psi. They move the crude oil from the tanks to the screw pumps, compensating for the loss of pressure in the screw pumps’ suction line. The centrifugal pumps are also used for pumping formation saltwater and reach a capacity of 2,420 gpm at 49 psi.

The formation water is then brought back into the storage facilities with three centrifugal pumps. The capacity of these wastewater transfer pumps is up to 3,520 gpm without resulting in significant wear.

Two stainless steel centrifugal pumps also move warm water for heating the system. All the pumps are from the same manufacturer.

A centrifugal pump that moves produced waterA centrifugal pump that moves produced water

Important factors in the pump manufacturer decision included the ability to obtain the entire set of pumps from a single supplier, the process design with straightforward maintenance and the spacer coupling. Together, these characteristics reduced expenses associated with maintenance and the storing of spare parts. These factors kept the total cost of ownership low.

OMV valued competent on-site service. They expected rapid reaction times and straightforward communication. These requirements eliminated most vendors outside Germany. The pump company provided all the pumps and installed them on a concrete foundation, aligned the couplings with a laser tool and commissioned the system in collaboration with OMV.

Continuous Operation

The pumps at the extraction station are equipped with pressure-resistant encapsulated motors. Frequency converters provide speed control. They fulfill the requirements of EX-Zone 1, “electrical and mechanical ATEX protection” (ATEX100a: II2G Zone 1 T4). Their power consumption, flow and pressure are all monitored continuously. Before installation, all 31 pumps passed a pressure and performance test in accordance with ISO 9906 Class 2.

Nearly all the pump/motor assemblies are redundant. This ensures that critical components in the extraction station work without interruption. If the transfer pumps for the formation water were to fail, the station would be able to absorb no more than four hours worth of material.

Price and Experience Were Critical

According to Peter Winkler, project manager for the extraction station, “The pump company was able to fulfill all the requirements with its chemical standard pumps at an attractive price/performance ratio. Over the years, we have also had good experiences with the quality of these pumps.”