Technoeconomic evaluation of flared natural gas reduction and energy recovery using gas-to-wire scheme

摘要

Most mature oil reservoirs or fields tend to perform below expectations, owing tohigh level of associated gas production. This creates a sub-optimal performanceof the oil production surface facilities; increasing oil production specificoperating cost. In many scenarios oil companies flare/vent this gas. In additionto oil production constraints, associated gas flaring and venting consists anenvironmental disasters and economic waste. Significant steps are now beingdevised to utilise associated gas using different exploitation techniques. Most ofthe technologies requires large associated gas throughput.However, small-scale associated gas resources and non-associated natural gasreserves (commonly referred to as stranded gas or marginal field) remainslargely unexploited. Thus, the objective of this thesis is to evaluate techno-economic of gas turbine engines for onsite electric power generation called gas-to-wire (GTW) using the small-scaled associated gas resources. The range ofstranded flared associated gas and non-associated gas reserves considered isaround 10 billion to 1 trillion standard cubic feet undergoing production decline.The gas turbine engines considered for power plant in this study are based onsimple cycle or combustion turbines. Simple cycle choice of power-plant isconceived to meet certain flexibility in power plant capacity factor andavailability during production decline. In addition, it represents the basic powerplant module cable of being developed into other power plant types in future tomeet different local energy requirements.This study developed a novel gas-to-wire techno-economic and risk analysisframework, with capability for probabilistic uncertainty analysis using MonteCarlo simulation (MCS) method. It comprises an iterative calculation of theprobabilistic recoverable reserves with decline module and power plantthermodynamic performance module enabled by Turbomatch (an in-housecode) and Gas Turb® software coupled with economic risk modules with@Risk® commercial software. This algorithm is a useful tool for simulating theinteraction between disrupted gas production profiles induced by productiondecline and its effect on power plant techno-economic performance overassociated gas utilization economic life. Furthermore, a divestment and make-up fuel protocol is proposed for management of gas turbine engine units tomitigate economical underperformance of power plant regime experienced dueto production decline.The results show that utilization of associated gas for onsite power generation isa promising technology for converting waste to energy. Though, associated gascomposition can be significant to gas turbine performance but a typical Nigerianassociated gas considered is as good as a regular natural gas. The majority ofcapital investment risk is associated with production decline both natural andmanmade. Finally, the rate of capital investment returns decreases with smallerreserves.