DEMONSTRATION OF A LOW COST
2-TOWER MICRO SCALE
N2 REJECTION SYSTEM TO
UPGRADE LOW-BTU GAS
FROM STRIPPER WELLS
a JOINT PROJECT by
THE KANSAS GEOLOGICAL SURVEY
(KUCR, University of Kansas)
&
AMERICAN ENERGIES CORPORATION
(Wichita, Kansas)
Low BTU Natural Gas – Resource Base
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Pipeline specifications – > 950 BTU/cu ft
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U.S. natural gas reserves – 204 Tcf (EIA, 2006)
Sub quality (low BTU) Gas & Reserves
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Less than 950 BTU/cu ft – considered as low-BTU
> 2% CO2, or > 4% N2 or inert gases
17.5 Tcf – Mid-Continent (Hugman, 1990)
9 Tcf – Rocky Mountain Region (Hugman, 1990)
33% of 1253 gas analyses in KS are low-BTU (Newell, 2007)
Low BTU due to presence of N2
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32 Tcf nationwide (17% of reserves) (Lokhandwala, 2006)
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Significant portion located in small or modest size fields
Great majority in Mid-Continent (Jenden, 1988)
Low-BTU Gas Reserves in KS
BTU/scf
< 750
750-849
850-949
Problem Statement
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Available N2 rejection technologies
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N2 rejection technologies under development
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Lean Oil Absorption & Membrane Separation
Most of the nation’s gas production – large fields
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Cryogenic – Large feed volumes (> 5 mmcfd) and expensive
Conventional (3 or 4 Tower) PSA/TSA – 0.5 to 20 mmcfd
Expensive to design and build – patented components/processes
Low BTU gas processed at centralized facilities – cryogenic/PSA
To meet long-term demand of natural gas in the US
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Small, isolated, low-BTU reserves have to be mobilized
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Currently SI or behind pipe – lacking micro-scale separation plants
REQUIRE LOW COST MICRO N2 REJECTION PLANT
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ECONOMIC at LOW VOLUME, LOW PRESSURE
Project Objectives
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Goals
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Design, build, optimize – 2-Tower Micro-Scale N2 rejection plant
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Using Pressure Swing Adsorption (PSA)
Patent free – off-shelf, non-proprietary components
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Economic at low feed volumes - < 200 mcfd (shallow/small fields)
Estimate well deliverability and decline – to size the plant
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Small field size affects production decline
User friendly techniques & commonly available software/freeware
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Conventional plants – use proprietary components and processes
Analyses – Wireline logs, 4-point test, and production decline
Disseminate LESSONS LEARNED to stripper well community
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Technology Transfer Workshops & Publications
Maps showing distribution of N2 rich low-BTU reserves in KS
2-Tower Micro-scale N2 Rejection Plant
Diam. 4 ft, Ht. 8 ft
Feed: 150 mcfd
Composition: 70%
CH4, 25% N2, 3%
HHC, 2% inert
Sales Stream: ~
100 mcfd, <4% N2,
~ 975 BTU/cu ft
Vent: ~ 5% CH4
Adsorbent – Activated Carbon made from coconut husks
Palletized Activated Carbon
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Made from coconut husks
Large surface area
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Adsorbs larger molecules
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N2, He, O2, H2, CO
Regenerate adsorbed CH4
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Activated Carbon from coconut Husk
CH4, H2S, CO2, H2O
Vents smaller molecules
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300 to 4000 m2/g
Pore size diameter – 10 to 25
Angstroms
Under vacuum
Proposed Technology vs. Conventional
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Conventional Commercial PSA Plants – patented parts/processes
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3 to 4 Towers – requires professional design (1/3rd cost mark-up)
Patented adsorption beds
Patented purge cycles – reduces pressure shock on beds
Surge towers – uniform composition of sales gas
Economic feed volumes – 500 mcfd to 20 mmcfd
Proposed Micro-scale Plant – non proprietary parts/processes
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2 Towers – Easy to design and build (<10 moving parts)
Use readily available palletized activated carbon for adsorption
Carry out pressure equalization by pause using vent gas
Discharge gas accumulator – uniform composition of sales gas
Economic feed volumes – 40 to 200 mcfd (<100 psi)
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Enhances bed life and reduces dust emission (compressor fowl up)
Additional Differences
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Micro plant – Modular & Scalable, Operate in remote locations
Conventional PSA Plants – 3 & 4 Towers
Surge Chambers
Each tower in different cycle:
1. Adsorption
2. Desorption
3. Pressure up slowly
4. Slowly going to vacuum
Cycle Time Optimization – Micro Plant
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Basic PSA Principle – TIME TESTED (IT WORKS)
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PSA used many different applications
CH4 can be adsorbed in a bed of activated carbon
Critical Question – How to optimize a micro-scale plant ?
Main Goal – Shortest cycle time for max CH4 recovery
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Selectively vary input parameters:
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Inflow rates
Cycle time
Adsorbent quality
Measure effect on
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CH4 recovery and breakthrough
Bed economics – degradation, compaction, & heaving
Operation costs
Elmdale Field, Chase County, KS
Other N2 Rejection Plants in KS
-Cryogenic plant (McCoy Pet)
-Feed volume – 5 mmscfd
-Hodgeman & Ness County
Other Features – Micro Plant
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Scalability
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Small, shallow, low BTU fields – production decline
Designed to handle varying feed - 40 mcfd to 200 mcfd
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Operating Economics
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Initial investment ~ $100,000 (Conventional PSA 3 to 4 times)
At $5/mcf, monthly income $4,500 to $11,250 (40 to 150 mcfd)
Building Material – Carbon steel
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Skid mounted units – attach/detach units to process high/low feed
Instruments & control panel – low cost cast iron (rated 125 psi)
Widespread availability & easy replacement
Patents – Proposed process and components not covered
Previous SWC funding – None to our knowledge
Anticipated Results – Micro Plant
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Significant Production Improvement
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U.S N2 rich low-BTU reserves – 32 Tcf (17%) (Lokhandwala, 2006)
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Proposed Micro Plant – Mobilize N2 rich low-BTU gas
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Could add 1 Tcf to U.S. reserves (Lokhandwala, 2006)
Within resource reach of stripper well operators
Reduction in Operating Costs
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Much of this “sub quality” gas – trapped in small, isolated fields
Optimized, plant runs unattended 95% of time – 2 operator visits/d
Monthly maintenance – compressor and bed level
Less than 10 moving parts (outside engine & compressor)
Minimal Environmental Impact
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Does not require electric power - compressor runs on feed gas
Compressor engine – Powers batteries to run unit
Solar panels – Power flare in vent gas line
Vent gas has no VOCs, heavy HC, H2S, CO2, and H2O
Small footprint - ~ 400 sq ft
Anticipated Results – Micro Plant (contd)
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Commercialization Viability
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Our micro plant – Simple, patent-free, off-shelf components
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Within resource reach of stripper well operators
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Technology Transfer Workshops – upon completion
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Build, design, operate on their own or with minimal outside help
No waiting period – for wide scale application
Easy to use techniques to determine well deliverability & decline
Step-by-step guide to scale & design a micro-plant – non-patented
Best practices regarding optimizing plant performance
Plant maintenance protocols
Application of 2-Tower Micro-Scale N2 Rejection Plant
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Small, isolated N2 rich low BTU fields/stripper wells in US
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Low feed volumes < 200 mcfd
If vent gas > 10% He – compress @ 3000 psi for He plants
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At current rates – value added by-product
NITROGEN AND HELIUM %
CENTRAL KANSAS GASES
10
Permian
Pennsylvanian
(Virgilian)
Pennsylvanian
(Missourian)
"subquality"
at BPU
1
"pipeline quality"
He %
0.1
2.5:1
5:1
N2:He
10:1
ratio
20:1
0.01
0.1
"low-BTU"
40:1
80:1
160:1
1
N2 %
10
100
How does our proposed project complement SWC’s goals?
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SWC seeks to identify new technologies
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Successful demonstration of our proposed project
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Significant production increase - domestic O&G stripper well/field
Significantly reduce operator costs
Improve environmental issues
Have broad applicability to large regions of the US
Mobilize an entire class of unproduced gas ~ 1Tcf N2-rich low-BTU
Unattended operation (95%), <10 moving parts, inexpensive spares
No emissions of CH4, H2S, CO2, HHC, & VOCs
$100,000 investment, attractive returns, technology transfer
OUR GOALS – Field Demonstration & Tech Transfer
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Demonstrate how stripper gas operators can build and operate a
low-cost N2 rejection plant using non-patented components
ACTIVATED-C BASED ADSORPTION WORKS – NEED TO
OPTIMIZE AT MICRO SCALES
Benefits to AEC & Stripper Well Operators
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AEC primarily owns and operates stripper wells in KS
Benefits to AEC
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Produce known low-BTU reserves behind pipe – Elmdale field
Phase II – bring online low volume, low BTU wells – SI presently
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Proposed 2-Tower Micro Scale Plant
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Within resource reach of stripper well operators such as AEC
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Technology and Financial
However, need to develop a learning curve
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Neighboring high BTU fields have depleted
No micro scale N2 rejection plant is currently operating in KS
Learn how to design, scale, build, operate, and optimize a micro plant
Request SWC support to try new patent-free technology
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Technology transfer workshops upon completion
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Convey transfer lessons learnt to stripper well community