Orinoco Projects Choose Dilution To Move Production

Warren R. True
Pipeline/Gas Processing Editor

Orinoco Gathering System (Fig. 1 [127,889 bytes])
Petrozuata's 36-in. pipeline, shown being installed near Jose, will carry diluted crude oil for upgrading (Fig. 2; photograph from Pdvsa, Caracas) [33,799 bytes].
Two subsea pipelines will carry upgraded Petrozuata crude 6.9 km to an SPM for tanker loading (Fig. 3; photograph from Conoco, Houston [32,595 bytes]).
Cerro Negro Pipe ([77,214 bytes])

Transporting Orinoco Belt bitumen and heavy oil economically and efficiently is critical for project viability.

Vast amounts of research funds and time have been spent studying various transportation schemes, not only for Orinoco projects but also for heavy-oil prospects elsewhere in the world.

(An article exclusive to OGJ next week will review major technologies for heavy-oil and bitumen transportation.)

One answer in Venezuela has been to turn the heavy oil into another product, Orimulsion, and place it on the world's coal markets. Until only a few weeks ago, in fact, the only significant pipeline out of the region was the 26 and 36-in. Orimulsion system from the Cerro Negro region (Fig. 1) installed and formerly operated by Lagoven S.A. Another, 42-in. Corpoven S.A. line has carried heavy but mostly non-Orinoco production; more on this line presently.

Currently, however, operators have moved to transportation schemes that employ diluting heavy oils, either with lighter crude oils or condensates, or with naphtha.

The most recent project to begin production and transportation from Orinoco, Petrozuata, at the end of August began moving a heavy crude blended with a lighter one northward through a new line to Jose on the Caribbean Sea coast. From there, the blended crude oil will be exported for further processing.

Following is a review of the transportation schemes from the Orinoco and current plans for future ones.

Dilution

Blending bitumen or heavy oil with a less-viscous condensate, natural gasoline, or naphtha reduces the heavy oil's viscosity and thereby reduces the pressure gradient in the heavy-oil pipeline, according to Gustavo Núñez, planning for manager for Pdvsa-Intevep.

An exponential relationship exists between the resulting mixture viscosity and the volume fraction of the diluent: small percentages of diluent can have a marked effect on the viscosity of the mixture, he says. The smallest viscosity that can be achieved by diluting the oil is the viscosity of the diluent.

Pressure drops can be calculated by conventional methods, assuming isothermal, single-phase flow of an homogeneous mixture with a viscosity value corresponding to the percentage of diluent in the mixture.

Condensate is an optimal diluent. But if unavailable, other schemes are possible, such as manufactured diluent, light crude, or diluent recycling. Diluents with characteristics similar to condensate can be manufactured from any light crude from fractions normally used to produce gasolines, jet fuels, and middle distillates.

Many light crudes (35-45° API) can also be used directly as diluents, he says, although more is usually required to do the same job as condensate.

Recycling can be achieved by recovering the diluent from the mixture downstream and reinjecting it upstream-as in the case of all the projects under way or planned in the Orinoco Belt.

The main difficulties with this scheme are the need to incorporate facilities to remove the diluent at the end of the pipe and the construction of a return pipe. These add both cost and operational complexity to the diluent option, says N#?ez.

Zuata field

Injection of diluted Zuata bitumen into a new double-line system began in late August from Petrozuata partners' project approximately 125 miles south of Jose.

This system employs two pipelines: a 36-in. line to move diluted crude oil to Jose (Fig. 2); and a 20-in. line eventually to return separated naphtha diluent to the Zuata field. At Jose, a crude-oil upgrader, under construction (see accompanying article), will strip naphtha from the stream and manufacture the resulting crude oil into a synthetic crude for export.

At start-up and currently, however, Petrozuata has been blending 30° API gravity Mesa crude oil with the 9° Zuata crude oil in a 2:1 (Zuata/Mesa) mixture that moves north to Jose and is being marketed as such until the crude-oil upgrader is operating.

Upon start-up of the upgrader in 2000, a light (47° API gravity) naphtha will move south from Jose and be blended in the field with the extra-heavy Zuata crude oil in a mixture for transportation that will have a gravity of approximately 17° API.

The naphtha diluent, according to earlier announced plans, will make up approximately 18-20% of the blend. The diluted-crude-oil line has a capacity of 510,000 b/d; the diluent line, 125,000 b/d.

Two Venezuelan companies in a $44.6 million contract supplied the 36-in. pipe: Industria Mecanica Orion S.A. and Soldadura y Tuber!as de Oriente C.A. Brazil's Confab obtained the $16.6 million contract for the 20-in. diluent-return pipe. Coating was by Atlantida Internacional C.S., a Venezuelan company.

Synthetic Zuata crude oil from the Jose upgrader will move from tank storage to tanker loading at an SPM via two 6.9-km, 24 and 36-in. subsea lines installed earlier this year (Fig. 3).

Among planned projects, the Sincor partners will tap into Petrozuata's new system, also to move their 8.5° API bitumen to upgrading in Jose. Majority partner Total said earlier this year that production will begin in November 2000, blending 40,000 b/d of Zuata crude with 20,000 b/d of Mesa crude.

Eventually, Sincor production will use the same 47° API naphtha diluent as Petrozuata, returned from the Jose upgrader and blended with the crude oil to produce a 17° API transportation mixture. Ultimate transportation capacity will be 220,000 b/d of heavy crude oil, of which 70,000 b/d will be diluent.

Cerro Negro

East of the Zuata field is Cerro Negro, which until August had been the source of the only major production from Orinico Belt.

In 1993, Bitor began moving Orimulsion from near Morichal to Jose for export. At the time, Bitor was an affiliate of state oil company Petr?leos de Venezuela S.A. (Pdvsa); it remains an affiliate of Pdvsa but is now called Pdvsa-Bitor in the division Petr?leo y Gas. Now, the state company operates the line for Pdvsa-Bitor.

A 36-in. line carries Orimulsion 148 km to the Oficina tank farm (PTO; Fig. 1). The mixture then moves 107 km through a 26-in. line to KM 52, and thence 49 km through a 36-in. line to Jose. An intermediate pumping station is located on the initial 36-in. segment.

The pipeline can carry 200,000 b/d of Orimulsion but is currently moving only about 100,000 b/d because of reduced Cerro Negro bitumen production. OGJ calculations indicate that average Orimulsion production last year was 73,400 b/d. According to Pdvsa, Bitor in 1997 exported 3.8 million metric tons of Orimulsion.

Activity is under way, however, to produce from another part of the Cerro Negro field-using dilution.

Between PTO and Jose will run a 175-km, 42-in. leg in a diluted-crude-oil transportation scheme for Cerro Negro bitumen (8.5° API) to another upgrader. According to Cerro Negro partner Mobil, 120 km of the line was built by former Pdvsa-subsidiary Corpoven.

Cerro Negro partners will complete the north section of the line to Jose and install a 140-km, 30-in. southern line to move the diluted crude oil to PTO. A separate 315-km, 20-in. diluent-return line from Jose to Cerro Negro will complete the system. Table 1 presents a breakout of the pipe supplied for the project along with the coaters.

As in the Petrozuata scheme, initial bitumen production will be mixed with a lighter oil, this time Nigerian Oso condensate (47° API), to produce a crude-oil blend that will be marketed from Jose until Cerro Negro partners' upgrader there is complete in 2001.

Mobil declined to provide technical specifications of the pipeline system.

Upon initial start-up in October 1999, says Mobil, the Cerro Negro system will transport 80,000 b/d of diluted crude oil and return 20,000 b/d of diluent. Oso condensate for diluent will begin flowing from Jose in August 1999.

Flow capacities will increase by mid-2001 when the Jose upgrader is complete: diluted crude at 155,000 b/d, diluent 35,000 b/d.

Mobil has no plans for intermediate, booster pumping between initial pumping at Cerro Negro for the diluted crude and at Jose for the diluent. Pipeline control will likely be from Jose.

Planned capital expense for the entire Cerro Negro project, Mobil says, including field, pipelines, and upgrader is $1.9 billion. The company declined to break out costs of constructing the pipelines.

Hamaca

Also planning to use the diluent-mixture transportation scheme are the Ameriven partners in a system to move Hamaca crude oil north.

They plan a single 30-in. line from production in Hamaca Block H to carry diluted crude oil 65 km initially to the PTO, then 165 km to Jose, according to Hamaca partner ARCO, paralleling the 42-in. line to be used by Cerro Negro partners.

A 20-in. (150-km) and 16-in. (55 km) line will return diluent to the production area for further use in transporting the heavy crude oil.

Both Hamaca lines will be coated with a mill-applied fusion bonded epoxy with no internal coating, says ARCO. Additional corrosion protection will be supplied by an impressed current cathodic-protection system.

Also, as in the Petrozuata project, initial production will be by blending two crude oils: 36,000 b/d of 8.6° API crude oil with 30° API Mesa crude to achieve 16° API before shipping. Scheduled start-up is second quarter 2000 with full production of 165,000 b/d by mid-2003.

Beginning in 2003, the bitumen will be blended with approximately 50,000 b/d of naphtha to make 215,000 b/d of diluted crude oil shipped through the 30-in. line to Jose.

Current Hamaca partnership plans do not call for booster stations in either direction along the 225-km route. The line will be controlled from the producing area in Block H.

Basic engineering on the line was completed Oct. 1, says ARCO, which declined to release a cost estimate on the project.