Getting and Producing Liquid Natural Gas (LNG)
Figure 1: Hydraulic Fracturing4
Natural gas, along with oil, is found in deposits that form below the ground in geological formations that consist of shales, which are tight rock formations that can be a mile or more below the earth’s surface2. To obtain the gas deposits people must drill into the subsurface using a combination of hydraulic fracturing and horizontal drilling.
Before drilling can start scientists use imaging technologies to locate the gas reservoirs2. When the reservoir is located drilling of the well can begin, which takes about 6 to 8 weeks2. Once completed, hydraulic fracturing (Figure 1) is used to release the natural gas from the tight shale formation2. The natural gas is then brought to the surface where it then gets transported to a pipeline to be distributed for processing and use2.
Figure 2: LNG Process5
Natural gas processing consists of several stages (Figure 2). First, the gas needs to be treated to remove impurities such as carbon dioxide and organic sulfur compounds since too much CO2 can raise the temperature at which the gas will freeze3. Once these compounds have been removed, the gas must be dehydrated since the presence of water can cause the gas to freeze during the liquefaction process3. Mercury is then removed since it is corrosive and can damage the LNG heat exchangers used in the liquefaction process3.
After all of the contaminants are removed, the gas is cooled down by a variety of processes to a finished temperature of about -260 F (-160 C). The finished product is then stored at approximately atmospheric pressure and then eventually transported.
The conversion of natural gas to LNG is a process that reduces its volume by about 600 times1. This reduction in volume is beneficial since the resulting product can be easily transported via cargo ships in high abundance. Once delivered to its destination, the LNG is heated to its gaseous state so it can be distributed to homes and businesses1.
1. Center for Liquefied Natural Gas. (2015). Basics. Retrieved from About LNG.
2. Texas Natural Gas Now. (2015). How We Get It. Retrieved June 24, 2015
3. The University of Oklahoma. (n.d.). Refrigeration Cycles. Retrieved from The University of Oklahoma.
4. Figure 1 taken from Total E&P Denmark B.V. (n.d.). What is Hydraulic Fracturing (fracking)? Retrieved from Total E&P Denmark B.V.: http://en.skifergas.dk/technical-guide/what-is-hydraulic-fracturing.aspx
5. Figure 2 taken from Goldboro LNG. (2012-2015). What is LNG? Retrieved from Goldboro LNG: http://goldborolng.com/about-lng/what-is-lng/