Chitosan: A multi utility chemical

Gone are the days when an oil well was drilled with drilling fluid composed of simple ingredients like Bentonite, viscosifier and fluid loss agents, dispersant and fluid loss controlling agent and water. In those days, only vertical wells were drilled and it took months for a well to be drilled and start producing hydrocarbons. Subsequently many repair jobs had to be done for undoing the damage done to permeability of the producing formations which hampered the optimum flow of liquids from the well. These incurred large amounts of money.

As the demand for hydrocarbons knows no limits, technologies have been developed to reach at the places in the reservoir where earlier it was not possible to reach. Technologies have made the horizontal penetration of the producing formations to expose large area to production. These are called drain-holes. Thrust is also nowadays on exploiting oil shales, coal bed methane and the latest hot cake is the methane trapped as hydrates in the frozen water.

To match these technologies, drilling fluids chemistry has undergone a revolutionary change. The drilling fluids of the old days are now passé. Nowadays drilling fluids use polymers of organic types. Also for various repair jobs many exotic chemicals are being tried. Interestingly many of these chemicals are consumed by humans in one form or the other. Examples are Carboxy Methyl Cellulose (CMC) which is used in ice creams, Linseed oils, Chitosan which is used as a sliming diet.  One of the technologies to coax the oil sitting tightly in the reservoirs is called secondary recovery in which the in-place unproductive oil is pushed out by water injection, conformance control in which the more permeable zones are temporarily plugged with polymers so that oil trapped in the tighter zones comes out. Similarly to enhance the production stimulation with acids is done. Acid is diverted to the zones of interest by plugging off the zones of no interest with polymers.

One such chemical which is used to make the thick gel to divert the acids is called Chitosan. It is derived from Chitin which is obtained from the shells of prawns. Many groups of amide are reduced selectively to amine groups to tailor made the required chemical.

Chitosan1

This chemical has the beauty of yielding a very thick gel in water in acidic conditions and loses all the viscosity when the mixture is made alkaline.

I read another wonderful use of this chemical. It is being used to make the bandages for the wounded personnel in the battleground. Most of deaths occur due to excessive bleeding. Chitosan has the quality to clotting the blood very fast. Secondly it is a strong antibacterial agent. This is also very much desired to ward off the infections in the unhygienic conditions prevailing in the battleground.

These bandages were used in Iraq for the first time. I wonder how many uses a chemical can have. In the sixth episode of “Brave New World” hosted by the great mathematician Stephan Hawking, the use of this chemical to clot the blood immediately was shown. The name of the episode was “Hyper Connections“.

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