The undetected gas leak, also referred to as fugitive gas emissions, are produced from natural gas infrastructure during operational activities. If not monitored, this undetected gas leakage can lead to undesirable economic loss of natural gas from installed infrastructures and are often accompanied by toxic air pollutants that typically pose safety and public health concerns. The efficient quantification of gas leaks from natural gas infrastructure value chain is still largely inadequate. Several studies have repeatedly opined that the actual rate of leaks from natural gas infrastructure is often higher than the documented estimates. The latter is largely dependent on assumptions that rely on inadequate data. This study reviewed most of the existing methods implemented to detect and quantify gas leaks in natural gas infrastructure by assessing the techniques based on the amount of leak detected compared to the amount of gas produced from such facilities. The study illustrates both the problem of methane leakage and the opportunities for instantaneous reduction from natural gas transmission facilities. Furthermore, this review provides a detailed account of the various analytical models and instrumentation-based research performed to identify and quantify gas leak detection. The study opined that the uncertainties associated with efficient quantification of natural gas leak rates demonstrate the need for innovative approaches or processes to identify and quantify leak rates from natural gas infrastructure.

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The use of separated flow models to specify the vertical lift performance of an oil well is usually somewhat complex- due to the many equations and correlations involved in the determination of the required variables. Consequently, coding these models in the computer presents an extent of difficulty. In this study however, with the view of developing a computer model (DOBB) to perform nodal analysis for oil wells, an efficient algorithm was established to facilitate the determination of the operating pressure and liquid flow rate of oil wells (which is the point of intersection between the VLP and IPR curve). More so, Hagedorn Brown model was incorporated into the computer model to account for liquid hold ups and various flow regimes (excluding bubble flow regime) in the tubing string. The computer model developed in this study is equipped with the ability to determine fanning friction factor of the tubing string provided that the roughness of the pipe is known.  Also, when the developed computer model was tested with some ranges of data points, nodal analysis plots were obtained from the different data points. Nonetheless, DOBB (a production engineering toolkit developed in this study) was proven to be efficient on the part of performing nodal analysis for oil wells.