Published on November 6, 2007
Installing Vapor Recovery Units to Reduce Methane Losses: Installing Vapor Recovery Units to Reduce Methane Losses Lessons Learned from Natural Gas STAR Processors Technology Transfer Workshop Pioneer Natural Resources, Inc., Gas Processors Association and EPA’s Natural Gas STAR Program September 23, 2004 Vapor Recovery Units: Agenda: Vapor Recovery Units: Agenda Methane Losses Methane Recovery Is Recovery Profitable? Industry Experience Discussion Questions Sources of Methane Losses: Sources of Methane Losses Estimate 373 MMcf/yr methane lost from atmospheric condensate storage tanks in gathering stations EPA/GTI study estimates the methane emissions from storage tanks in the processing sector to be 311 MMcf/yr EF from Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990 - 2002, AF from EIA financial reporting system (FRS) Types of Methane Losses: Types of Methane Losses Flash losses - occur when condensate in pipeline systems enters tanks at atmospheric pressure Working losses - occur when condensate levels in tanks change Standing losses - occur with daily and seasonal temperature and barometric pressure variations Methane Recovery: Methane Recovery Vapor recovery units capture up to 95% of hydrocarbon vapors vented from tanks Recovered vapors have higher Btu content than pipeline quality gas Recovered vapors are more valuable than natural gas and have multiple uses Re-injected into pipeline to recover NGLs Used as on-site fuel Types of Vapor Recovery Units: Types of Vapor Recovery Units Conventional vapor recovery units (VRU) Use rotary compressor to extract vapors out of atmospheric pressure storage tanks Require electrical power or engine Venturi ejector vapor recovery units (EVRUTM) Use Venturi jet ejector in place of rotary compressor Do not contain any moving parts Require source of high pressure gas and intermediate pressure system Conventional Vapor Recovery Unit: Conventional Vapor Recovery Unit Venturi Jet Ejector*: Venturi Jet Ejector* High-Pressure Motive Gas (~850 psig) Flow Safety Valve Pressure Indicator Temp Indicator PI TI TI PI (-0.05 to 0 psig) Low-Pressure Vent Gas from Tanks (0.10 to 0.30 psig) PI TI Discharge Gas (~40 psia) EVRUTM Suction Pressure *Patented by COMM Engineering Vapor Recovery with Ejector: Vapor Recovery with Ejector Note: Production application example. Example Facility for EVRUTM: Example Facility for EVRUTM Oil production: 5,000 Bbl/d, 30 Deg API Gas production: 5,000 Mcf/d, 1060 Btu/cf Separator: 50 psig, 100oF Storage tanks: 4 - 1500 Bbls @1.5oz relief Gas compressor: Wauk7042GSI/3stgAriel Suction pressure: 40 psig Discharge pressure: 1000 psig Measured tank vent: 300 Mcf/d @ 1,850 Btu/cf Emissions Before EVRUTMCO2 Equivalents: Emissions Before EVRUTM CO2 Equivalents Engine exhaust: 3,950 Tons/yr @ 790 Hp load Tank vents: 14,543 Tons/yr Total CO2 equivalents: 18,493 Tons/yr Fuel consumption @ 9000 Btu/Hp-hr = 171 MMBtu/d Gas sales: 5,129 MMBtu/d Gas value: $25,645/d @ $5/MMBtu Emissions After EVRUTMCO2 Equivalents: Emissions After EVRUTM CO2 Equivalents Motive gas required: 900 Mcf/d Engine exhaust: 4,897 Tons/yr @ 980 Hp load Tank vents: 0 Tons/yr Fuel consumption @ 9000 Btu/Hp-hr: 190 MMBtu/d Total CO2 equivalents: 4,897 Tons/yr Reduction: 13,596 Tons/yr (73.5%) Total CO2 equivalents: 4,897 Tons/yr Reduction: 13,596 Tons/yr (73.5%) Gas sales: 5,643 MMBtu/d Gas value: $28,215/d @ $5/MMBtu Income increase: $2,570/d = $77,100/mo EVRU cost installed: $75,000 Installed cost per recovered unit of gas: $0.68/Mcf/yr Payout: <1 month Vapor Recovery Unit Decision Process: Vapor Recovery Unit Decision Process IDENTIFY possible locations for VRUs QUANTIFY the volume of losses DETERMINE the value of recoverable losses DETERMINE the cost of a VRU project EVALUATE VRU project economics Criteria for Vapor Recovery Unit Locations: Criteria for Vapor Recovery Unit Locations Steady source and sufficient quantity of losses Condensate tanks at gathering/ boosting stations Pig trap liquids tanks Outlet for recovered gas Access to pipeline or on-site fuel Tank batteries not subject to air regulations Quantify Volume of Losses: Quantify Volume of Losses Estimate losses from chart based on oil characteristics, pressure and temperature at each location (± 50%) Estimate emissions using the E&P Tank Model (± 20%) Measure losses using ultrasonic meter (± 5%) Measure losses using recording manometer and orifice well tester (± 100%) Estimated Volume of Tank Vapors: Estimated Volume of Tank Vapors Source: Natural Gas Star, Lessons Learned – Installing Vapor Recovery Units on Crude Oil Storage Tanks Quantify Volume of Losses: Quantify Volume of Losses E&P Tank Model Computer software developed by API and GRI Estimates flash, working and standing losses Calculates losses using specific operating conditions for each tank Provides composition of hydrocarbon losses What is the Recovered Gas Worth?: What is the Recovered Gas Worth? Value depends on Btu content of gas Value depends on how gas is used On-site fuel - valued in terms of fuel that is replaced Natural gas pipeline - measured by the higher price for rich (higher Btu) gas Gas processing plant - measured by value of NGLs and methane, which can be separated Value of Recovered Gas: Value of Recovered Gas Gross revenue per year = (Q x P x 365) + NGL Q = Rate of vapor recovery (Mcfd) P = Price of recovered natural gas NGL = Value of natural gas liquids Cost of a VRU: Cost of a VRU Major cost items: Capital equipment costs Installation costs Operating costs Cost of a Conventional VRU: Cost of a Conventional VRU Value of Recovered NGLs: Value of Recovered NGLs Is Recovery Profitable?: Is Recovery Profitable? Economics for various sized conventional VRUs Trade Offs: Trade Offs Slide25: Technology Comparison Mechanical VRU advantages Gas recovery Readily available Mechanical VRU disadvantages Maintenance costs Operation costs Lube oil contamination ~ 70% runtime Sizing/turndown EVRU advantages Gas recovery Readily available Simple technology 100% runtime Low maintenance/ operation /install costs Sizing/turndown (100%) Minimal space required (mount in pipe rack) EVRU disadvantages Need HP Motive Gas Recompression of motive gas Lessons Learned: Lessons Learned Vapor recovery can yield generous returns when there are market outlets for recovered gas Recovered high Btu gas or liquids have extra value VRU technology can be highly cost-effective EVRUTM technology has extra O&M savings, higher operating factor Potential for reduced compliance costs can be considered when evaluating economics of VRU/EVRUTM Lessons Learned (cont’d): Lessons Learned (cont’d) VRU should be sized for maximum volume expected from storage tanks (rule-of-thumb is to double daily average volume) Rotary vane or screw type compressors recommended for VRUs where there is no source of high-pressure gas and/or no intermediate pressure system EVRUsTM recommended where there is gas compressor with excess capacity Case Study – Pioneer: Case Study – Pioneer Pioneer Natural Resources USA, Inc. recycled vapors from 3 phase separators to the plant inlet Methane emissions reduction = 3796 Mcf Estimated cost incurred = $5,000 Total value of gas saved = $11,388 Vapor Recovery Units: Vapor Recovery Units Profitable technology to reduce gas losses Can help reduce regulatory requirements and costs Additional value of NGLs further improves cost-effectiveness Exemplifies profitable conservation Discussion Questions: Discussion Questions To what extent are you implementing this BMP? How can this BMP be improved upon or altered for use in your operation(s)? What is stopping you from implementing this technology (technological, economic, lack of information, focus, manpower, etc.)?