1. INTRODUCTION
Petroleum consists of many components of which natural gas NG is one of the components. In Nigeria, estimated natural gas reserve capacity is 187 trillion cubic feet and United States Geological Survey USGS study estimates the gas reserves potentiality in Nigeria could be as high as 600 trillion cubic feet. And Nigeria is the seventh largest producer of natural gas in the world [1]. Natural gas has been proved to be the cleanest burning fossil fuel and more economical world-wide. This is because, when combusted it emits less emission particles and pollutants to the atmospheres. Therefore, it is accepted as being of immense energy sources for domestic and industrial purposes. During its processing a lot of gas is being vaporized and displaced from storage vessels or containers .The minimization of vaporization and displacement losses from storage vessels become very imperative for investigations [2]. Natural gas is being processed into liquefied natural gas (LNG) because it is more economical to transport it in this form to prospective buyers. Since pipeline transportation is not feasible for long distances natural gas is liquefied stored in containers for ship loading. Another alternative to liquefied natural gas is liquefied petroleum gas produced by refining petroleum during the refining of crude oil or separating gas streams obtained from reservoirs. The LPG includes C3 and C4 -fractions and can be transported as pure C3 , pure C4 or a mixed LPG i.e a blend of C3 plus C4 at specified ratio to meet standard specifications i.e 70 percent C3 and 30 percent C4. Liquefied petroleum gas can evaporate at normal temperatures and pressures. It is