Evaluating Tight Gas, Shale Gas and Coal Bed Methane Wells using Mudlogging Methods By William S. Donovan, PE Donovan Brothers Incorporated Automated Mudlogging

Evaluating Tight Gas, Shale Gas and Coal Bed Methane

Wells using Mudlogging Methods

Evaluating Tight Gas, Shale Gas and Coal Bed Methane

Wells using Mudlogging Methods

ByWilliam S. Donovan, PE

Donovan Brothers IncorporatedAutomated Mudlogging Systems

Our Corporate Motto

“WE DON’T PASS GAS”Our Corporate Motto

“WE DON’T PASS GAS”

07/25/0607/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems SM Slide 2 of 33Slide 2 of 33

Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods


• Present an overview of presentation options• Present an overview of presentation options










• Present an overview of presentation options

• Define mudlogging gas measurements

• Explain why mudlogging is an effective tool

• Relate mudlogging shows to formation gas

• Discuss presentation options in detail

• Present an overview of presentation options

• Define mudlogging gas measurements

• Explain why mudlogging is an effective tool

• Relate mudlogging shows to formation gas

• Discuss presentation options in detail




MUDLOGGING GAS MEASUREMENTS DEFINTION

EQUIVALENT METHANE IN AIR (% EMA) is a measure of methane in air at the measurement point expressed as a percent of methane in the sample or expressed differently 10,000 parts per million methane by volume. Other hydrocarbon gases are presented as if they were methane

MUDLOGGING GAS MEASUREMENTS DEFINTION

EQUIVALENT METHANE IN AIR (% EMA) is a measure of methane in air at the measurement point expressed as a percent of methane in the sample or expressed differently 10,000 parts per million methane by volume. Other hydrocarbon gases are presented as if they were methane




MUDLOGGING GAS MEASUREMENT DEFINITION

A UNIT is a measure of hydrocarbon gases in air at the measurement point expressed as a fraction of sample’s total volume; typically, but not always, it is 0.01% of the total volume or expressed differently 100 parts per million gas by volume. Typically methane is the calibrating gas.

MUDLOGGING GAS MEASUREMENT DEFINITION

A UNIT is a measure of hydrocarbon gases in air at the measurement point expressed as a fraction of sample’s total volume; typically, but not always, it is 0.01% of the total volume or expressed differently 100 parts per million gas by volume. Typically methane is the calibrating gas.




MUDLOGGING GAS MEASUREMENT DISCUSSION

•Measured at the mudlogging unit

•Measured as methane

•Subject to calibration errors

•Not a direct measure of formation gas

•The definition of a “UNIT” has changed

MUDLOGGING GAS MEASUREMENT DISCUSSION

•Measured at the mudlogging unit

•Measured as methane

•Subject to calibration errors

•Not a direct measure of formation gas

•The definition of a “UNIT” has changed




MUDLOGGING IS EFFECTIVE BECAUSE:•Gas is measured directly at the surface•Gas is insoluble in water•Gas expands as it travels to the surface




MUDLOGGING IS EFFECTIVE BECAUSE:•Gas is measured directly at the surface•Gas is insoluble in water and drilling mud•Gas expands as it travels to the surface




MUDLOGGING IS EFFECTIVE BECAUSE:•Gas is measured directly at the surface•Gas is insoluble in water and drilling mud•Gas expands as it travels to the surface












The next six slide present the amount of gas liberated and brought to the surface for coal, shale, oil and gas reservoirs.

The red and blue colored bars to the left show gas (red) and water (blue) values relative to the reservoirs.

All slides have the same format, but different vertical scales

Again the conclusion reached is that both conventional and unconventional hydrocarbon reservoirs liberate gas in quantities significantly higher than reservoirs containing water






















Four methods can be used to relate mudlogging shows measured in EMA or Units to SCF gas volumes:

1. Carbide lags or gas referencing™ (Amen)2. Deterministic modeling3. Normalizing using open hole logging4. Normalizing using core dataAll these methods can be used in concert.

Carbide lag is my preferred method and is how the examples in this presentation were derived.

Four methods can be used to relate mudlogging shows measured in EMA or Units to SCF gas volumes:

1. Carbide lags or gas referencing™ (Amen)2. Deterministic modeling3. Normalizing using open hole logging4. Normalizing using core dataAll these methods can be used in concert.

Carbide lag is my preferred method and is how the examples in this presentation were derived.




• Carbide lagging is an established mudlogging tool• Calcium Carbide reacts with water to make acetylene

gas CaC2 + H20 = C2H2 +CaO • The relationship between acetylene and methane is

established for the mudlogging unit before logging• A measured amount of Carbide (acetylene) is put in the

drill string during connections and pumped to the surface• The peak gas value, the lag time, the gas reading before

the peak and other data is recorded by the mudlogger• Using the above data a gas show in EMA or units can be

converted to SCF of gas liberated while drilling• SCF/bulk volume (ft3) can be calculated if hole volume is

calculated. If density is known SCF/T can be calculated




• The deterministic model gives insight into the mudlogging process

• Factors affecting mudlog gas shows will be presented starting from the formation being drilled to the mudlogging unit

• These factors are: 1) gas in the formation; 2) hole size; 3) drilling rate; 4) mud pump rate; 5) gas expansion and 6) gas trap efficiency

• Some factors such as flushing, flow line losses, gas trap instability and drilling mud interactions cannot be quantified by deterministic modeling

• The deterministic model gives insight into the mudlogging process

• Factors affecting mudlog gas shows will be presented starting from the formation being drilled to the mudlogging unit

• These factors are: 1) gas in the formation; 2) hole size; 3) drilling rate; 4) mud pump rate; 5) gas expansion and 6) gas trap efficiency

• Some factors such as flushing, flow line losses, gas trap instability and drilling mud interactions cannot be quantified by deterministic modeling




If all other factors are equal, doubling the gas in the formation doubles the gas show

If all other factors are equal, doubling the gas in the formation doubles the gas show




If all other factors are equal, doubling the hole diameter, quadruples the gas show

If all other factors are equal, doubling the hole diameter, quadruples the gas show




If all other factors are equal, doubling the drilling rate, doubles the gas show

If all other factors are equal, doubling the drilling rate, doubles the gas show




If all other factors are equal, doubling mud pump rate, decreased by one half the gas show

If all other factors are equal, doubling mud pump rate, decreased by one half the gas show




If all other factors are equal, doubling the depth of the formation doubles the gas show with some limitations

The formula displayed is the basis for calculating Bulk Volume Mudlog Gas (BVmlg)

If all other factors are equal, doubling the depth of the formation doubles the gas show with some limitations

The formula displayed is the basis for calculating Bulk Volume Mudlog Gas (BVmlg)




Gas trap efficiency and measurement stability is the largest cause of error in these calculations

Gas trap efficiency and measurement stability is the largest cause of error in these calculations













CONCLUSIONS

Mudlogging is an effective evaluation tool

If you have questions or comments contact me

Bill Donovan

(303) 794-7470

CONCLUSIONS

Mudlogging is an effective evaluation tool

If you have questions or comments contact me

Bill Donovan

(303) 794-7470

[email protected] www.mudlogger.com

mailto:[email protected]

Documents

Evaluating Tight Gas, Shale Gas and Coal Bed Methane Wells using Mudlogging Methods By William S. Donovan, PE Donovan Brothers Incorporated Automated Mudlogging