Computerized Analysis of Flowing
Conditions for Use of Chemical Sticks in
Natural Gas Wells
John Rhoads
Ranette Halverson
Nelson L. Passos
Department of Physics
Department of Computer Science
Midwestern State University
Outline
• Oil field applications
• Chemical sticks
• Required field computation
• Results
• Summary
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OIL FIELD
COMPUTER APPLICATIONS
•STRUCTURAL DESIGN (OFFSHORE PLATFORMS)
•RESERVOIR SIMULATION
•SEISMIC ANALYSIS
•FUTURE PRODUCTION FRECASTS
•FINANCIAL MANAGEMENT
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OIL FIELD
COMPUTER APPLICATIONS
USUAL REQUIREMENTS:
•SUPERCOMPUTERS
•PARALLEL SOFTWARE
•HIGH COSTS
•REMOTE DATA PROCESSING
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OIL FIELD
COMPUTER APPLICATIONS
SMALL SOFTWARE TOOLS:
•directional/horizontal drilling
•water and CO2 flood prediction
•tubing and casing design routines
•tubular inventory
•analysis of geological features
• risk analysis
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THE CHEMICAL STICK PROBLEM
WELL-KNOWN PROBLEMS:
• Internal corrosion of tubular products
• Corrosion results cessation of production
• Liquid chemical treatments cannot be dumped
down tubing in a flowing gas well
• Liquid treatment requires shut down of
production operations
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THE CHEMICAL STICK PROBLEM
PROCEDURE:
• Delivery of chemicals to the bottom of hole is made by
dropping a solid chemical stick inside the tubing
• Stick designed to fall to the bottom of the hole, become
static, slowly dissolving over time to release active
corrosion control ingredients
• Question? whether or not a given size
chemical stick will fall in a gas stream
flowing inside a tube
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FIELD COMPUTATION
INPUT:
• Flow rate from the well
• Wellhead pressure
• Chemical stick falls under the influence of gravity
REQUIRED:
• Impulse of gas stream incident on and normal to the
cross sectional area of the bottom of the chemical stick.
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FIELD COMPUTATION
CALCULATIONS:
• Assumptions were required due to lack of information
on frictional data (dragging forces), bottom hole
pressure, heat exchange (gas and environment), etc.
REQUIRED ANSWER:
• Will the stick fall to the bottom?
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SOLUTION
StickDrop Algorithm
Estimate flowing bottom hole pressure
Estimated bottom hole temperature
Calculate the gas density at the bottom hole
Compute the mass flow rate MFR (lbs/second)
Calculate the velocity in feet per second
Compute force per second impact on end of stick:
Calculate the mass
Calculate the buoyancy
If weight is greater than the impulse force,
the stick will drop.
END
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IMPLEMENTATION
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IMPLEMENTATION
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EXPERIMENTAL DATA
Tubing dimensions
Tubing
1.90"
2.375"
2.875"
Area (square inches)
2.138
3.272
4.680
Chemical stick dimensions
Stick
Area
Length
Weight
(lbs)
1.00"
1.25"
1.625"
0.785
1.227
2.074
15
15
18
0.55
0.75
1.50
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EXPERIMENTAL DATA
1.90"
1.00"
90° F
Chemical Stick
Bottom hole temperature
A 2.138 sq in
Tubing
Flow rate = 5,000 Mcfd
(million cubic feet/day)
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EXPERIMENTAL DATA
Chemical stick not heavy enough
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~ Summary ~
• Computer applications availability
• Field operation requirements
• Computerized solution for the chemical
stick drop
• Benefits of a field solution
Questions??
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