CO_2 ENHANCED OIL RECOVERY-SUPPLY OPTIONS,TREATMENT FACILITIES AND EFFECT ON EXISTING DOWNSTREAM PROCESSING

摘要

CO_2 Enhanced Oil Recovery(EOR)projects are receiving increased attention with crude oil prices close to 30/Bbl.Oil producers in the United States,the Middle East and Asia are looking at enhanced oil recovery for aging oil fields,or for under-producing areas of otherwise productive oil fields.Some of these projects are considering flue gas recovery as a source of CO_2.This paper reviews the various aspects of a complete CO_2 EOR project including CO_2 capture,compression and transmission,CO_2 injection wells,produced CO_2-rich gas treating options,and corrosion control.Most of the CO_2 EOR projects in the world are using naturally occurring CO_2 resources as the supply of injectant CO_2.Other sources of CO_2 include industrial sources,such as gasification plants and ammonia plants,and recovery from flue gas.Commercial processes for recovery of CO_2 from flue gas use a typical amine solvent configuration to recover CO_2 from coal,oil or gas fired boilers,gas turbines or fired industrial heaters.The cost reported in the literature for CO_2 recovery from flue gas,compression to 2000 Psig,and dehydration varies widely from a low of 1.00 per thousand standard cubic feet(MSCF)to almost 3.00/MSCF.Critical factors that affect this cost are the CO_2 concentration in the flue gas,extent of integration of the facility,number and location of flue gas sources,and the cost of fuel or steam.The flow rate and CO_2 concentration of associated gas from the oil production will change substantially over the life of a CO_2 EOR project.The CO_2 concentration can vary from zero to over 80 volume percent.This has major implications on the downstream processing system.The options for downstream CO_2 recovery are:(1)no recovery,(2)recycle of all associated gas,(3)membrane system,(4)simple fractionation,(5)multi-tower fractionation.The selection of the most appropriate process for a given application depends on the capacity of the existing processing facility,the materials of construction required for the higher CO_2 content,and the value of natural gas and natural gas liquids(NGL's).Corrosion in a CO_2 EOR project is a serious concern due to the presence of CO_2 at high partial pressure under water-wet conditions.A comparison of the relative economics was made for a sample project to increase oil production from 10,000 Bbl/day to 37,000 Bbl/day,using 200 MMSCFD miscible injectant.The total cost of incremental oil production is 29/Bbl for a project with a 400 MM grass roots flue gas CO_2 capture plant and 1.00/MSCF of CO_2 operating cost.Using purchased CO_2 at 1.90/MSCF,and by recovering and re-injecting CO_2,the cost of incremental oil production can be reduced to 25/Bbl.The viability of CO_2 EOR projects is highly influenced by the cost of the CO_2 supply,the distance the CO_2 must be pipelined,the cost of additional oilfield production facilities,and the extent of modification needed for the oil and gas processing facilities,as well as the world price of oil.