Ocensa's Pumps Key To Meeting Production Goals

Ocensa's El Porvenir pumping station.

Ocensa's Miraflores pumping station. [11,410 bytes]

Installation of 11 engine-driven centrifugal pump packages is being completed on Oleoducto Central S.A.'s (Ocensa) Central Llanos pipeline between Cusiana and Vasconia and Cove?as, Colombia.

The pump packages were supplied by Caterpillar Inc.

When combined with 12 existing pump packages commissioned in 1994 as part of the first phase of the project, the 23 packages supplied by Caterpillar will deliver nearly 94,000 hp to meet production goals.

The pump packages, according to Caterpillar, play a key role in Ocensa's ability to transport oil cost-effectively from the Cusiana-Cupiagua oil fields by:

Providing the horsepower match needed to allow each pump to operate continuously at or near capacity for maximum flow per pump station
Performing efficiently by burning crude-oil fuel
Operating at nearly 100% availability.

Phase 1 packages

Phase 1 of the pipeline upgrade project, managed by British Petroleum Exploration Colombia, began in 1992. The project involved upgrading the capacity of the existing pipeline between La Belleza and Vasconia with a goal of increasing production from 100,000 b/d to a nominal 180,000 b/d by the fall of 1994.

Increased production also dictated the need for additional engine-driven pump capacity at pumping stations located at El Porvenir, Miraflores, and Caucasia.

To meet Phase 1 production goals and provide sufficient pump package redundancy, engine pump packages with the capability to deliver a combined 48,960 hp were needed, says Caterpillar.

British Petroleum dictated that the pump packages incorporate programmable logic controller (PLC) based systems for optimal control and monitoring of pump package parameters, including vibration. String testing of the first completed package was also necessary because of the critical nature of the application and the remote location of the pipeline.

Remoteness, as well as obstacles involved in the 310-mile trek from the coast to the project, also called for pump-package designs that minimized complications in transit.

Low equipment-owning and operating costs were equally key to the success of Phase 1.

After thorough analyses, British Petroleum specified 12 pump packages featuring multistage centrifugal pumps operating at 4,000 rpm and driven by Cat 3612 engines, rated at 4,080 bhp at a continuous speed of 987 rpm each.

Based on flow and pressure requirements, British Petroleum determined four pump packages would initially be installed at El Porvenir, 1,115 m above sea level; five at Miraflores, elevation 1,773 m; and three at Caucasia, elevation 120 m.

In 1993, assembly and testing of the pump packages began at the Caterpillar Large Engine Center. A string test of the first unit was conducted to ensure system components (including the engine, speed increaser, pump and custom-designed PLC-based control and monitoring system) met performance requirements.

In 1994, all 12 pump packages were delivered, installed, and commissioned. Each engine pump package was split for transportation into two packages with the engine shipped separately from the pump, gear box, and base.

On site, individual control panels of the packages' PLC-based system at each station were integrated with Ecopetrol's (Empresa Colombiana de Petr?leos) central control room to meet the unique control requirements. Nominal pipeline production reached 180,000 b/d by fall 1994, with peak production as high as 300,000 b/d.

Phase 2 power needs

The goal of Phase 2 has been to increase production to 556,000 b/d by the end of 1997.

Meeting the goal called for additional engine-driven pump packages with a combined capability to deliver 44,880 hp total, says Caterpillar. An additional 28,560 hp was needed at the El Porvenir and Miraflores main line stations.

At the same time, 16,320 hp were needed for a new re-booster station at El Porvenir. The re-booster station is used to pump oil out of storage tanks and into the main pipeline.

The tanks alternately store oil originating from Cuisiana and oil supplied by other shippers. The re-booster station operates approximately 6 hr out of 48 hr, dictating the need for the main pipeline feeding oil from Cuisiana to be shut down.

Conversely, oil from Cuisiana is routed directly to the El Porvenir main line station when the re-booster station is off line.

Total horsepower needed at the re-booster station for Phase 2 was 16,320 hp. At the El Porvenir and Miraflores main line stations, a total 28,560 of additional hp was needed.

Additional pump packages were not needed on the existing line routed through the Caucasia pumping station.

Pump-package design

Selection of the pump packages used for Phase 2 was based in part on the performance of the Phase 1 units and the need to retain the Phase 1 package designs, which minimized the need to inventory additional parts, as well as the need to service dissimilar units.

After the bid process, British Petroleum specified 11 multistage pump packages powered by Cat 3612 engines rated at 4,080 bhp at 950 rpm.

To balance flow, four packages were added to the existing units at the El Porvenir main line station and three additional units at Miraflores. Both main line stations at El Porvenir and Miraflores feature two separate pump houses, each of which houses four pump packages.

As such, one of the original five engines on the existing units at Miraflores was relocated from one pump house to the other and coupled to a new speed increaser and pump.

Meanwhile, four pump packages were installed at the El Porvenir re-booster station. Assembly and testing of the Phase 2 units began at the Caterpillar Large Engine Center, Lafayette, Ind., in early 1996, with string tests conducted on the first two main line units and first re-booster package for a total of three.

Shipment of the packages began in April 1996, commissioning is taking place this month, and the units will be on line by October 1997.

Full oil flow is targeted for December this year. At that time, six of the eight pump packages at each main line station at El Porvenir and Miraflores will serve as primary units, operating at capacity continuously to maintain nominal production of 556,000 b/d.

The remaining two units at each station provide the backup capacity needed when primary pump packages are shut down for maintenance. All four units at the El Porvenir re-booster station operate at capacity.

Performance analysis

To date, all the engines on the Phase 1 pump packages have accumulated more than 100,000 hr with availability of 98%, including routine maintenance.

After 10,000 hr of continuous service, Caterpillar says critical engine components were evaluated to determine the projected service life and establish optimum maintenance intervals.

Components analyzed included unit injectors, cylinder heads, turbochargers, connecting rods, pistons, and main and rod bearings. Overall, the components were found to be in good condition for the number of hours and the type of fuel consumed, according to the company.

Oil consumption of the engines ranged from 0.003 to 0.004 lb/bhp-hr. Local product support of the units is provided by General de Equipos de Colombia S.A., the local Caterpillar dealer who also assisted with pump package installation and commissioning.

Startup of the 11 Phase 2 engine pump packages is scheduled for September 1997. Based on the performance of the initial 12 units installed and string testing, Caterpillar expects positive results.

The pump packages include:

Sulzer-Bingham multistage centrifugal pumps are used at the main line stations at El Porvenir and Miraflores, as well as the El Porvenir rebooster station. A Lufkin speed increaser features a 4:1 ratio, giving the pump an operating speed of 4,000 rpm.
Flexible couplings absorb torsional stress and allow thermal growth. A Geislinger coupling connects the engine output to the gearbox and a Kop-Flex coupling is used between the gearbox and pump. Ingersoll-Dresser pumps are used on the units at Caucasia.
A portion of crude oil is routed through Alfa Laval fuel treatment equipment and an additional treatment system designed by Caterpillar for fueling the engines, which are configured to run specifically on crude oil with a significantly high wax content.
Engine jacket water is cooled by a remote-mounted Amercool radiator with two 15-kw electric fans. The same radiator is also used for cooling of the engine-mounted oil cooler and charge air cooler designed by Caterpillar.
Engine exhaust is routed through a dual-inlet Beaird Maxim MSA-2, industrial grade, spark-arresting silencer.
A PLC-based, local control and monitoring system specifically engineered for pumping applications was designed and manufactured by Caterpillar.

The system, which incorporates a 28-channel vibration monitoring system supplied by Bently Nevada, communicates to a central control station via a redundant serial link.