The deeper the ocean waters and the thicker the land mass under which gas and petroleum deposits are located, the greater the challenges to extract them. In order to extract these pre-salt products, which are deposits located beneath the salt layer, at depths between 3,500 and 5,500 meters below the ocean bed, drill pipes must extend more than 3,000 meters below the ocean floor. One of the critical points of the extraction is to have reliable methods of analysis and monitoring of pipes and systems that can withstand high pressures and significant temperature differences. To operate in this hostile environment, Petrobras, a pioneer in the development of fossil fuels in deep (300 to 1,500 meters) and ultra-deep waters (more than 1,500 meters), worked through its Research Center (Cenpes) to forge partnerships with institutions to develop the technologies for exploring the pre-salt layer. Two of these projects were conducted with the Pontifical Catholic University of Rio de Janeiro (PUC-Rio) and one with the National Nanotechnology Laboratory (LNNano), located in Campinas (SP).
One of the joint projects with PUC-Rio resulted in the development of equipment designed for internal inspection of pipes laid on the ocean floor or inserted beneath it. The equipment created for internal pipe inspection is a type of PIG, a device that is placed inside the pipes and is pushed forward by the fluid itself (oil or gas). It uses sensors to clean or inspect the interior walls of the pipe. “The pipes used in deep water have very thick walls and small diameters; they cross over long distances and may make sharp curves, in addition to being subject to high pressures and large temperature variations,” says Jean Pierre von der Weid, from the Inspection Technology Research Center (CPTI) of PUC-Rio. “For these reasons, and since this is a relatively small market, there are no commercial PIGs for this application.”
In order to meet the demand by Petrobras, the PUC-Rio group developed the PIG Palito, or Toothpick PIG, a cylindrical piece of equipment that features several shaft-shaped sensors. The system has an odometer that measures the exact location of the problem found by the sensors. The team prepared two prototypes of the Toothpick PIG capable of inspecting pipes with diameters ranging from 20 to 120 centimeters (cm). “We successfully tested one of them in the Santos Basin, in a 190 kilometer (km) long gas pipeline that runs between the Uruguá and Mexilhão fields,” says the researcher.
At the PUC-Rio Fiber Optic Sensors Lab (LFSO), the Flexible Riser Structural Integrity Monitoring (Moda) system was developed. According to project coordinator Arthur Braga, Petrobras is one of the largest operators of flexible pipelines in the world, with the majority of them operating in deep or ultra-deep waters off the Brazilian coast. “The first ones were installed at the end of the 1970s, and today the company has a network of more than a dozen kilometers, with more than a thousand risers,” he says. “Some of them are approaching the end of their useful lives, so the capability of early detection of the propagation or appearance of structural damage has become essential to guarantee and prolong the use of this equipment.”
Braga explains that the risers are made of alternating polymer and metallic layers. Between the latter are the traction reinforcements, made of steel wire, which support the pressures that result from the weight of the pipe itself, the oil and gas that are transported, and ocean movements. “With the passage of time, the wires get worn out and can break,” he explains. “That is why Petrobras now requires that flexible pipes operating in the pre-salt layer be equipped with real-time monitoring systems for the risers.” Among the components of Moda are sensors made of fiber optics, installed in the wires of the external traction layer, in the section of the riser between the platform and the water line. The system can be installed during the manufacture of the flexible pipe or in pipes that are in operation. “If one of them is ruptured, the fiber optic sensors detect these alterations and this information is sent to a computer in the control room.”
The project began in 2007, with financing of R$ 8.5 million from Petrobras. Between 2008 and 2013, several tests were conducted with the Moda system, both in the laboratory and in the field. Recently, the system was incorporated by the company into all of the pre-salt layer fields. This technology was licensed to the company Ouro Negro, a spin-off of the Fiber Optic Sensor Laboratory of PUC-Rio. “By the end of 2016, the number of Moda systems installed in the pipes of platforms operating in the pre-salt layer should reach something around 200 units, with around 13 thousand fiber optic sensors.”
In the case of the Toothpick PIG, the investment by Petrobras was approximately R$ 15 million, and the technology is also likely to be transferred to another company, which will produce the equipment on a commercial scale. The two technologies received the ANP Award, from the Brazilian National Agency of Petroleum, Natural Gas and Biofuels, in the category “Technological innovation developed in Brazil by a national science and technology institution in collaboration with a petroleum company” – the Moda in 2014 and the Toothpick PIG in 2016.
Analysis of the gas
In the project carried out with LNNano, a quantitative chemical analysis method was developed to determine the Monoethylene Glycol (MEG) content in samples from liquefied natural gas (LNG) processing. When transported from the underwater wells in both deep and ultra-deep waters to the offshore platforms or ships, solid substances called hydrates are created in the gas pipelines that can clog the pipes. MEG is added to the fuel to prevent the formation of these hydrates. The problem is that these substances are a contaminant that must be removed from the LNG. Through chemical processes, Petrobras is able to remove the MEG present in the LNG at its Gas Treatment Units (UTGs). However, the company needs to quickly and accurately know how efficient the process of MEG regeneration in the LNG is. “We created a method, which we call the Microemulsification-Based Method (MEC),” says project coordinator Renato Sousa Lima, a researcher at the Micro-manufacturing Laboratory of LNNano.
Lima explains that as it is separated from the gas, the MEG is dissolved in a liquid medium composed of water, sugars, acids and different metals. The test is done by adding oleic acid to this MEG-rich liquid, resulting in an insoluble water-oil mixture. Next, ethanol is added to this mixture while it is shaken. There are two types of results: cloudy or transparent. It is possible to know the amount of MEG and the efficiency of the system by observing the amount of ethanol that needed to be added to the mixture for it to become transparent. The MEC takes 5 to 10 minutes, while the technique used by Petrobras involves a series of chemical reagents and takes several hours. The project that led to the method developed by Lima received financing from FAPESP and from Petrobras, in the amount of R$ 1 million, and was the basis for a patent application and four scientific publications. This new technique has not yet become part of the Company’s operational routine. “We conducted three demonstrations for the company’s engineers and technicians,” says Lima. “We believe that the method will soon be adopted for routine use by Petrobras.”
Microemulsification in Analytical Chemistry for the development of point-of-care platforms: study of intervening parameters and automation in microfluidics (nº 2014/24126-6); Grant Mechanism Regular Research Grant; Principal Investigator Renato Sousa Lima (LNNano); Investment R$ 61,425.00.
DA CUNHA, J. G. et al. Microemulsification-based method: Analysis of monoethylene glycol in samples related to natural gas processing. Energy & Fuels. V. 29, p. 5649-54. 2015.