Extracting the Shales


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What is fracking? What is retorting? How can it be done? Why should India go for extracting the shales?
This is a brief introduction to all the answers you might be wanting regarding shale gas and shale oil......
After all this is a research in progress in which India has a huge potential!

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  • The gas bearing shale rocks are the source rocks through which oil and gas is squeezed out into the reservoir rocks which are the conventional source of oil and gas. But much amount of gas is still present inside these shale rocks, through which we extract out the gas by fracking.Oil shale generally contains enough oil that it will burn without any additional processing, and it is known as "the rock that burns.
  • Shales are normally source rocks, whereas the sandstones are reservoir rocks. The reservoir rocks being much more permeable than source rocks, it is easier to extract oil from reservoir rocks.
  • Shell's current plan involves use of ground-freezing technology to establish an underground barrier called a "freeze wall" around the perimeter of the extraction zone. The freeze wall is created by pumping refrigerated fluid (brine at -10 degree C) through a series of wells drilled around the extraction zone. The freeze wall prevents groundwater from entering the extraction zone, and keeps hydrocarbons and other products generated by the in-situ retorting from leaving the project perimeter.
  • You might be wondering, why I explained you, Retorting in detail, while just introduced you to fracking?Because, What we have, is about 15 billion tonnes of oil in oil shales.
  • Extracting the Shales

    2. 2. The Great U.S. Success story Indian Energy Scenario • It imports about 75% oil that it consumes. • During 2011-12 country imported 171.73 MMT crude oil. Crude oil production during 2011-12 at 38.09 million metric tons. • • • • • The International Energy Agency (IEA) has predicted that the U.S.A. would become the world’s largest oil producer by 2020. And a BIG CONTRIBUTING FACTOR IS SHALE OIL and the SHALE GAS. Shale gas accounted for 39% of total natural gas production in 2012. With 25.7 cubic feet per day, it makes U.S.A. the largest producer of shale gas. Canada obtains 15% of natural gas from shale oil. China holds the world’s largest potentially recoverable reserves of shale gas with estimated reserves of 1,115 trillion cubic feet versus 665 trillion cubic feet for the US.
    3. 3. SHALES Oil Shale Gas bearing Shale Rock Black organic shales are the source rock for most of the oil and gas reservoir. Much of the Shale Gas is obtained from these rocks. Gas is obtained from these rocks by fracking/(fracturing + cracking). The term oil shale generally refers to any sedimentary rock that contains kerogen . Over long periods of time, heat and pressure transformed the materials into oil shale in a process similar to the process that forms oil; however, the heat and pressure were not as great. Oil from the Oil Shales is obtained by Retorting.
    4. 4. FRACKING • Natural Gas produced from shale is called unconventional gas, while that produced from sandstones and lime stones is called conventional gas. In both the cases, methane is produced. • Method of extracting the gas directly from the source rocks is by pressurized hitting of water to split the rocks open which is called Fracking. • Fractures are created in the source rocks allowing the passage of gas. Once the fractures are created, small particles of sand are pumped into them to keep the fractures open. • Fracking involves no explosives.
    5. 5. What is Kerogen and what it is not!! • It is the complex carbonaceous (organic) material that occurs in sedimentary rocks, carbonaceous shales, and oil shales. • It is for most part insoluble in the common organic solvents. • And contradictory to popular opinion, there is a distinct possibility that it may not be a precursor to petroleum but one of the by-products of the petroleum generation and maturation processes. • It is composed of two parts:1. 80-95 wt% non-porous, impermeable mineral matrix 2. 5-20 wt% organic material
    6. 6. Retorting the Solid Oil Shales • Explosives are positioned at suitable places inside the reservoir, which are exploded. • Large oil shales are converted into smaller rock fragments (or rubble) • This is called a rubblized bed. • Rubblized shale is heated at a large temperature, thermally decomposing the kerogen. Two ways in which mining and processing of oil shale can be done:1. Underground mining using the roomand-pillar method or surface retorting  It involves mining of ores  It is a well known technology  Large environmental effect like: Popcorn effect  Large open mines  Emissions 2.     In Situ Retorting Underground conversion Research in progress Lower environmental effect Not commercially proven
    7. 7. Surface Retorting Hot Recycled Solids: Alberta Taciuk Processor It delivers heat to the oil shale by recycling hot solid particles—typically oil shale ash. It employs rotating kiln or fluidized bed retorts, fed by fine oil shale. The recycled particles are heated at 800 °C and then mixed with the raw oil shale to cause the shale to decompose at about 500 °C. Oil vapor and shale oil gas are separated from the solids and cooled to condense and collect the oil. These are also called Ex-situ technologies. There are five such methods:1. Internal Combustion Mined shale is fed from the top of the chamber, hot gases from the bottom, resulting in retorting. 2. Hot Recycled Solids 3. Conduction through Wall Direct heat transfer through hot gases doesn’t take place, but heat is transferred via conduction through walls. 4. Reactive Fluids Extraction through reactive fluids is being tested currently. 5. Plasma gasification Oil shale is bombarded by ions to produce oil and gas. Water is not used in this method.
    8. 8. IN SITU COMBUSTION •In vertical in situ retorts, a flame front moves downwards through a rubblized bed to liberate shale oil, off gases and condensed water. •There are two types of in situ retorts : 1. True In situ retorts • Burning a portion of oil shale underground, to produce the heat needed for retorting the remaining oil shale • It is difficult to maintain and control the underground combustion process 2. Modified In situ Retorts • A volume beneath the retort zone is mined and sent for surface retort which in turn improves the access to air for carrying out combustion and supporting the flame front.
    9. 9. THERMALLY CONDUCTIVE IN SITU CONVERSION •The process involves heating underground oil shale, using electric heaters placed in deep vertical holes drilled through a section of oil shale. •The volume of oil shale is heated over a period of two to three years, until it reaches 650–700 °F, at which point oil is released from the shale. •The released product is gathered in collection wells positioned within the heated zone. •An underground barrier surrounding the extraction zone ‘freeze wall’ is created by pumping refrigerated fluid (brine at -10 0C). •Freeze wall prevents ground water from entering the extraction zone, and prevents the hydrocarbon from leaving its perimeter.
    10. 10. COSTS The following costs must be taken into consideration:•Drilling Cost In a ten acre plot, there are 250 heater wells and 80 producer wells. Total cost is $ 26.4 million ($80,000 per well) •Refrigeration Costs Q = 5*10^6 KW. Purchase cost : $12.5 million Operating Cost: $3.2 million/day •Pumping Costs Now 80 centrifugal pumps are used to remove ground water trapped in the freeze wall at a rate of1.6 million gallons/hr for a period of 2 weeks. Cost of Pump: $83,000/pump $120,000 /day needed for electricity •Heating Cost $80,000 per heater Electricity cost: $80,000/day
    11. 11. Environmental Pollution LAND USE AND SOLID WASTE MANAGEMENT WATER POLLUTION Disposal of spent shale is a menace as it causes water pollution. A good oil shale yields only 20-30 gallons of oil per ton of rock, with 85 to 90% of the weight of the original rock appears as spent shale. When water falls on the spend shale, some material is leached out, which will in turn pollute surface water as well as ground water. AIR POLLUTION  Oil shale-fired power plants causes emissions of gaseous products like nitrogen oxides, sulfur dioxide and hydrogen chloride, and the airborne particulate matter (fly ash). Due to kerogen, the emission of CO2 increases, giving rise to global warming. Surface mining and in situ processing requires extensive land use. Mining, processing and waste disposal require land should be far away from high density population areas. It will harm the biodiversity. Sub-surface mining might cause caving-in of the mined out are.
    12. 12. India : Shale Scenario • India has huge shale gas deposits in Vindhyan, Gondwana, Cambay, Rajasthan • On the other hand, it is estimated that greater than 15 billion tons of oil is present in oil shales. • Oil Shales are found in north east India, Assam and neighboring areas of Arunachal Pradesh. Thank You