Scientists develop sensor to detect interfaces in petroleum tanks

New system measures levels of different layers of materials in crude oil for half the cost of existing technologies.

By Elton Alisson

Agência FAPESP – The petroleum extracted from onshore and offshore wells is made up of various concentrations of gas, oil, water, and solids such as sand and other sediments. To enable the separation of these immiscible materials, the crude oil recovered from wells is stored in tanks at refineries to allow fractional decantation to occur. In this process, the materials contained in the oily liquid settle into strata, or superimposed layers.

The layered substances can then be selectively drained off. However, for this selective drainage procedure to be performed efficiently, the levels of the different layers must be accurately measured in order to locate their interfaces, particularly the water-oil interface.

The difficulty here, according to specialists in the field, is the high cost of these measurements using the technology currently available on the marketplace, which is based on nuclear instrumentation or guided wave radar.

“It can cost as much as R$300,000 [approximately US$112,500] to measure the oil level once, and refineries need to perform three measurements per day on average. What’s more, the level has to be measured in all stages of the petroleum value chain, from extraction and transportation to refining, storage and distribution,” Synbeeosis director Cláudio Dezidério told Agência FAPESP.

A manufacturer of products and systems for the control of industrial fluids established in São Carlos, São Paulo State, Synbeeosis has developed a capacitive sensor that promises to measure levels and interfaces continuously in real time and at half the cost of the existing systems for this purpose. The project to develop this particular device was supported by FAPESP’s Innovative Research in Small Business (PIPE).

Synbeeosis first tested the sensor in partnership with Cenpes, Petrobras’s Leopoldo Américo Miguez de Mello R&D Center in Rio de Janeiro.

“The results of the first stage of testing demonstrated the sensor’s technological and commercial feasibility,” said project coordinator Carlos Seleghim. “Nothing equivalent to the measuring technology that we have developed exists in Brazil today. The existing technologies are very expensive, and in some cases their large scale use isn’t feasible because of the cost.”

The sensor developed by the firm consists of a shaft containing a pipe made of non-metallic material, with electrodes fixed internally from one end to the other. The device functions as a capacitor and is actuated when it detects an electrical field at its surface that is generated by the electrical charge of a liquid or solid material that comes into contact with it.

The sensor’s electrical field (capacitance) increases when the electrodes touch water or oil. An electronic system built into the device detects variations in the sensor’s capacitance.

When the probe is vertically inserted into a petroleum storage and processing tank, the sensor acts as an “electronic ruler,” gauging the levels of stratified layers of immiscible materials in the crude oil by detecting capacitance changes between electrodes.

“The sensor measures the interface levels with great precision thanks to the high sensitivity of the capacitive instrument,” Seleghim said.

According to Seleghim, refineries use a system of valves installed at the bottom of each separation tank to drain off the water and leave only oil in the tank. He explained that this process of drawing off water from petroleum separation tanks is performed visually, and a considerable amount of oil is wasted for lack of a sensor that clearly indicates the levels of these substances in the tanks.

“The sensor we’ve developed can be used to measure precisely where the oil layer ends and the water layer begins in a petroleum tank, eliminating the risk of oil leakage while the water is being drawn off,” he said.

“Because the device is based on capacitive instrumentation, it’s highly cost-effective compared, for example, with a level gauge that uses nuclear technology, which costs as much as R$150,000, depending on its length,” he said.

Control system

The second stage of testing will take place at Petrobras’s Atalaia petroleum production and refining complex in Aracaju, the capital of Sergipe State. The sensor will be coupled to an online onshore oilfield remote monitoring and control system that was also developed by Synbeeosis, through another project supported by PIPE. The system, called Blueidea, is designed to control the production and quality of oil extracted from onshore wells and will be tested in an oilfield located at Canto dos Amaros in Rio Grande do Norte State.

“This oilfield has 14 onshore wells within a radius of 18 km,” Seleghim said. “The idea is to implement a rationalized system of remote management using wi-fi Internet access and instruments like the oil level sensor we’ve developed with support from FAPESP’s PIPE Program.”

The Rio Grande do Norte oilfield is operated by 18 workers, whose responsibilities involve actuating the valves of the oil pumps, among other tasks.

The system is designed to operate all oilfield devices, such as rod pumps, valves and pressure pumps; enhance the efficiency of the production process via rationalization; and minimize waste via leakage monitoring.

The data can be viewed in an integrated manner on computer consoles with synoptic control panels in the oil company’s operations center, located 40 km from the oilfield.

“The system is designed to rationalize operations and reduce losses from onshore oilfields, enabling the company to produce petroleum more cheaply and with higher productivity,” Seleghim said.

Call for proposals

On November 24, FAPESP issued a call for proposals for the PIPE Program’s First Analysis Cycle in 2015. The foundation has allocated up to R$15 million to fund selected proposals. The deadline for submission of projects via SAGe, FAPESP’s online project-management system, is February 2, 2015.

The research projects to which proposals may refer are expected to progress in two stages: (1) a demonstration of the technological feasibility of a product or process, lasting at most nine months and requiring up to R$200,000, and (2) development of the innovative product or process, lasting at most 24 months and requiring up to R$1 million.

When a project’s proponents have completed technological activities that demonstrate its feasibility, they can submit proposals for Stage 2.

Researchers are eligible if they are affiliated with a small firm (having up to 250 employees) that has a research and development unit in São Paulo State.

The complete manual for submission of proposals is available at www.fapesp.br/pipe.

FAPESP will send each proponent the reviewers’ technical opinions, which may be useful to enhance the proposal regardless of whether it is approved. In the event of non-approval, a proponent can rework the proposal to correct any identified flaws and submit a new application at the next call for proposals.

For more information on this CFP, visit www.fapesp.br/9095.