Case Study of Pilot Application and Efficiency Analysis of Waste Heat Recovery from Gas Engine Generator Jacket Cooling Water to Heat Waxy Multiphase Fluid at Offshore Platform

Abstract

The oil and gas industry is in continuous look out of innovative means to improve the efficiency of its energy-intensive oil- and gas-processing operations through improved energy use and waste-heat recovery. This paper details about an integrated pilot application of two waste-heat-recovery units designed and implemented in an Offshore platform off Caspian Sea. Actual results are compared with simulation / design results. A thermodynamic analysis of a gas generator engine waste-heat-recovery cycle is carried out. The offshore platform has a water injection plant supporting water flooding project for reservoir pressure maintenance. The Sea Water Lift and Main Injection Pumps are powered by multiple Gas Engine Generators of @ 1000 kW power rating. The exhaust gas from each of these gas engine contains approximately 10 million Btu/hr recoverable heat. Also the heat energy from the jacket cooling water used for engine cooling is used for heating the waxy crude oil and natural gas. A Shell & Tube Heat exchanger is used for recovering the heat energy. By utilizing the heat energy of flue gas and jacket cooling water the energy efficiency of gas engine can be doubled from 35% to 75 %. Two such Gas Generators with Heat Recovery system has been introduced which collectively creates an energy saving of approximately 1500 KW daily for crude oil heating. Approximately 8000 bbl oil with 100 scf/bbl gas oil ratio was able to heat to get a temperature differential of 25-35 degree C. The cooling water temperature was dropped to 60 degree C. With rising fuel costs, energy conservation has taken on added significance. Installation of waste heat recovery units (WHRU's) on gas turbines is one method used in the past to reduce gas plant fuel consumption. More recently, waste heat recovery on multiple reciprocating compressor engines also has been identified as having energy conservation potential. This paper reviews the development and implementation of a WHRU potential. This enhance hydrocarbon recovery, and reduce utility cost in a plant. In an era when energy conservation and fuel shortages are not uncommon, mechanical systems designed to improve the thermal efficiency of fuel-consuming equipment have become a necessity. This paper presents an energy efficient process and mechanical design along with footprint saving.