CORROSION AGENTS IN OIL AND GAS PIPELINES

CORROSION AGENTS IN OIL AND GAS PIPELINES
Pipelines play a very critical role in the transportation of oil and gas process because, crude oil and other petroleum resources moves through pipelines for atleast part of the route. After the crude oil is separated from natural gas, pipelines transport the oil to another carrier or directly to a refinery. Pipelines are indispensable in safe, reliable and efficient transportation of oil and gas. One of the key problems of the carrier pipeline systems in the oil and gas industry is the exposure of the pipes to corrosion failures caused by the interaction of pipe material and aggressive environments. According to statistics about 90% of all pipeline emergencies are due to corrosive processes. Protectives in use (means of electrochemical protection (ECP means), corrosion prevention chemicals (corrosion inhibitors), insulation materials etc) are mostly turned out to be inefficient. In this respect the acute problem of searching for alternative ways of upgrading the oil and gas pipeline systems in the industry is crucial, especially when transporting aggressive environments. The application of pipes made of high strength and corrosion resistant composite and fibre patterns (CFP) is considered to be an evidently advanced and upto date trend. The petroleum industry is gradually building increased acceptance of fibreglass reinforced plastic (FRP) materials, while some companies make extensive use of FRP pipe for onshore and offshore hydrocarbon gathering and transmission lines. A few companies have used FRP down hole tubing products. In offshore there is limited use of FRP products in secondary structure such as cable trays, walkways, railing and grating. Recent developments in the North Sea area have resulted in projected increased usage of GRP pipe for various  types of low pressure water service offshore.
With ever-increasing challenges in developing deep-water offshore structures for petroleum exploration and production, composite materials technology is expected to play a more important role in meeting the stringent requirements of cost effective operations and enabling the capability of petroleum technology and its supporting industries.
Composite materials offer substantial weight reduction, superior corrosion resistance, long fatigue life, outstanding vibration damping and energy absorption, and also unlimited potentials of innovative material and structural tailoring to meet desired performance requirements. Along with low maintenance, low total life cycle costs, ease of fabrication  and installation are some of the advantages of using fibre reinforced polymer pipes for onshore and offshore applications. Composite materials are structurally ideal and suitable for immediate and future deep water challenges. Coatings can be developed to reduce the rate  at which fire exposure can affect GRP pipe.
Current protective coating technology for oil and gas pipelines is recognised to have both technical and economical disadvantages. Many factors such as climate, temperature, physical state of fluid being transported, physical location,  properties of the substrate travelling through the pipeline, product flammability and rate of flow contribute to the complexity of  designing efficient pipeline coating formulations.  In addition, the position of the pipeline must be taken into consideration, if the pipeline is laid underwater, the coating must be formulated to provide long term terminal and external durability.
Unprotected FRP pipe made with epoxy resin systems will be consumed when exposed to fire but it is self extinguishing  when the flame is removed. Under continuous fire exposure and with water flowing through the pipe, it tends to degrade to a given level and then maintains that performance level. The movement of fluid inside the pipe remains cool (i.e FRP is a low conductor of heat) and gives an extinguishing effects.
The use of phenolic resin as the polymer matrix in fire is being investigated as a fire resistant non-mettalic pipe. The features provided by phenolic resins include low toxicity, flame spread and smoke developed indices. A recent technological breakthrough in this area will allow the use of this previously difficult material for fire resistant piping.
Corrosion is fast becoming one of the most critical threats in pipelines and pipeline systems. Uncontrolled corrosion will result in loss of pressure containment. Corrosion can also affect flow efficiency through increased friction on the pipe wall and the resulting debris can damage the pipeline and associated equipment, as well restrict flow and reduce capacity.
Corrosion Agents in Oil and Gas include:
Carbon dioxide – CO2
Hydrogen sulphide – H2S
Oxygen –O2
Chlorides – Cl
Water- H2O
Causes of Corrosion in the Oil and Gas Industries
CO2 corrosion: general metal loss due to the presence of co2 in the process field
H2S corrosion: localized metal cracking and corrosion due to presence of h2s in the process fluid.
Chlorides and bicarbonates- cracking in the metal due to the presence of stress and chlorides in the process fluid
Corrosion due to oxygen – oxidation and metal loss due to the contact of metal with oxygen in the process fluid.
Microbiologically induced corrosion- bacteria that induces corrosion particularly within h2s
Erosion abrasion) corrosion- corrosion due to the fluid flow and velocity within the pipe environments.
The objective of this research is to clarify the principles of development corrosion-resistant leak tight and strong GRP pipes for the natural gas and oil industry.