Cryogenic Sour Gas Process Attractive for Acid Gas

Cryogenic Sour Gas Process Attractive for Acid Gas Injection Applications P. Scott Northrop Exxon. Mobil Upstream Research Rene F. Bialek Imperial Oil Resources 03/11/04

Cryogenic Sour Gas Process • The following items will be discussed: – Controlled-Freeze Zone (CFZ™) process overview and background – Earlier pilot plant results – CFZ™- why now? – New case study – Experimental program 03/11/04

CFZ™ Overview/Background • Problem: CO 2 Freezing in Cryogenic Separations – Solid CO 2 plugs standard distillation equipment – CO 2 is present in many natural gas streams • Solution: – Instead of trying to avoid CO 2 freezing, induce it in a specially-designed part of the distillation column • CFZ™ was originally conceived for methane/CO 2 separation, but it has general application to cases where a solid phase forms in a distillation column 03/11/04

CFZ™ Process Schematic CH 4 Vapor (N 2, He) From Pump Spray nozzles Liquid level Feed Gas Liquid CO 2, H 2 S 03/11/04 (C 2+, Trace sulfur compounds)

Clear Lake Pilot Plant Test Parameters • Feed rates: 200 -600 kscfd • Feed CO 2: 15 -65% • Overhead CO 2: 700 -2500 ppm • Bottoms CH 4: 0. 5 -2% Demonstrated • Concept and operability of unit • Multiweek operation at 600 psig • Performance predicted by tools • Two start-up procedures • Spray temperature key • Reflux to spray line helped Problem - Inadequate insulation • Limited test to high pressure • Limited tests that could be run 03/11/04

CH 4, N 2 Why Now? CFZ™ is easily integrated with acid gas injection (AGI)! CFZ PI Dry Gas • H 2 S/Sulfur: - Eliminates Claus/TGT units, sulfur blocks Saturated sulfur markets Slow development of alternative uses • CO 2: - Canadian producers may have Kyoto limits - Enhanced oil recovery possible 03/11/04 H 2 S, CO 2

Case Studies: General Remarks CAPEX and OPEX savings can be in the 10 -20% range over commercial technologies At moderate to high CO 2 concentrations, CFZ is competitive Major benefits: Fewer processing steps Reduction in acid gas injection costs Total contaminant removal Economic issues: Higher refrigeration loads than solvents Means of CO 2/C 2+ separation required in some cases 03/11/04

Case Study - Gwillim • Several processing options evaluated • Gas composition & reinjection requirement are good fit for CFZ™ • Basis: 100 MCF/D Feed, . Pipeline spec. (4 ppm H 2 S) 03/11/04

Gwillim Resource Overview Est’d. CH 4 Resource: Approx. 1 TCF Initial Reservoir Pressure Reservoir Temp Average Well Depth: 4500 psig 203 F 11, 000 ft Wells drilled to date 4 Gas Composition (mol %) Methane H 2 S CO 2 C 2 & C 3 C 4+ N 2 Elemental sulfur 58. 3 24. 5 16. 8 0. 00 0. 3 Trace Reservoirs with similar acid gas content are being produced by other operators in the area 03/11/04

Gwillim: Existing Infrastructure • Duke Pine plant • Duke Kweon acid gas stripper plant Pine • Burlington sweet plant (Noel) Kwoen Gwillim 03/11/04 Noel • High pressure sour gas gathering system to Pine & Kweon • No sweet fuel line • 240 KV power line nearby Challenges: • Insufficient existing plant capacity for entire development • Processing fees

Detailed Sweetening Process Screening Relative Comparison Completed by an independent consultant 100 MCF/D, 40% Acid gas & 950 psig plant inlet Selexol CFZ™ Capital Investment 1. 3 1. 0 Annual Operating Cost 1. 19 1. 0 Plant Horsepower 1. 41 1. 0 Gas sales 0. 93 1. 0 03/11/04

Preliminary Conceptual CFZ™ Processing Plant Cross Exchanger CFZ Tower Reboiler Raw Gas Chiller Aerial Cooler Expander (Optional) Reflux/Sales Comp. Sales Gas Dehy. Spray Pump Liquid Acid Gas to disposal <1% CH 4 03/11/04 CFZ Tower

Impact of H 2 S Increasing H 2 S After Fig. 16 -32 of GPSA Databook 03/11/04 • Shrink freezing zone - Liquid H 2 S dissolves solid CO 2 • Relative volatility - 4 ppm H 2 S spec achievable, drives reflux/tray req. • Other solids - Elemental sulfur, other contaminants may freeze ahead of column • Metallurgical requirements - Since liquefied acid gas is dry, no special materials needed

Experimental Program • Cold depletion experiments – Collected wellhead sample, cooled to -80°C, expelled gas – Identified presence of elemental sulfur • CO 2 adhesion in the presence of H 2 S – “Cold finger” experiments in progress • H 2 O solubility in liquid acid gas at low T – Experiments planned • CO 2, H 2 S K-values at infinite dilution in liquid methane – verify numerical models, simulation results at top of column 03/11/04

Summary CFZ™ best fits include: • Lean gases where hydrocarbon liquids recovery is not needed • Total acid gas and mercaptan removal, e. g, pre-LNG • Acid gas injection (acid components are already liquefied) CFZ 03/11/04 AGI

Back-up Slides 03/11/04

CO 2/CH 4 Phase Behavior T vs. x, y for CO 2/CH 4 at 600 psia 03/11/04

CO 2/CH 4 Phase Behavior T vs. x, y for CO 2/CH 4 at 800 psia 03/11/04