Our Corporate Motto “WE DON’T PASS GAS”

Our Corporate Motto “WE DON’T PASS GAS”
4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane Wells using Mudlogging Methods By William S. Donovan, PE Donovan Brothers Incorporated Automated Mudlogging Systems This presentation is titled: “Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods. I’d like to thank: COGA, RMAG and DGS the chair, Jennie Ridgley and you the audience. Thank you for allowing me to present a topic that I find very interesting. I’d like to acknowledge the Geologist working with me; Jack McDermott, Phil Jacob and Andy Herring who gathered the data presented. This presentation borrows heavily from papers presented by Mercer; Ewing and Williams; Diamond, DeVaney, Eakin and Graves; Amen; and DeLaune, Wright and Hanson and the text book “Petroleum Reservoir Engineering” by Amyx, Bass and Whiting. Sources are cited where appropriate. Mudlogging instrumentation has benefited from the computer and electronics revolution going on about us. This is a new era for mudlogging. With the increase interest in “unconventional resources” such as low resistivity, low porosity carbonates, tight gas, coal bed methane, gas hydrates, oil shale and shale reservoirs new interest in mudlogging is occurring. Our Corporate Motto “WE DON’T PASS GAS” © Automated Mudlogging Systems, 2006

© Automated Mudlogging Systems SM
4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Present an overview of presentation options A few definitions are in order before we start. It is important to understand the difference between the three gas measurements that are discussed. The first gas measurement is raw mudlogging readings (EMA or Units). The second gas measurement is gas at Standard Conditions, that is typically expressed in SCF. The third gas measurement is gas at reservoir temperature and pressure conditions rft3. Although EMA or Units are measured at Standard Conditions, SCF is reserved in this presentation for mudlogging readings that can be attributed to Bulk Volume Bulk Volume or Formation Volume or Reservoir Volume or Gross Rock Volume expressed in ft3 is the total volume of the formation including rock matrix, sorbed gas porosity and fluids therein. This volume would be the hole volume after drilling occurs. Depending on the information available mudlogging data can be presented as: Gas Units per Formation Volume (EMA/ bulk ft3) or (Units/ bulk ft3) Gas Units per Formation Volume and Mud Circulation Rate (EMA/(bulk ft3/gpm)) or (units/(bulk ft3/gpm)) Surface SCF of Gas per Formation Volume (SCF/bulk ft3), SCF/(acre x ft) or BCF/(section x ft) Formation Gas Volume per Formation Bulk Volume (gas rft3 / bulk ft3) or (gas Φ/ bulk volume) or Mudlogging Gas Fraction of Bulk Volume (BVmlg) SCF of gas per ton (SCF/T), if the density is know. Note only mudlogging data is needed for all but calculating gas content in SCF/T. The next two slides show how mudlogging data can be presented, if a few simple procedures are followed. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods This presentation can be generated using only mudlogging data in a LAS file format and a spreadsheet! The third column from the left, track 3, presents Gas Volume per Reservoir Volume in common and interchangeable units: SCF per Formation Volume (SCF/bulk ft3), SCF/(acre x ft) or BCF/(section x ft). The fourth column from the left, track 4, presents gas reserves in a cumulative fashion. We’ll revisit this slide and discuss it in more detail 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods If the Formation Gas Expansion Factor (Bg) is known the data in track 4 can be generated. This is Mudlogging Gas Bulk Volume (BVmlg) or Reservoir Gas Porosity. This presentation is analogous Bulk Volume Water. Mudlogging data used in conjunction with density data can calculate gas content in SCF/TON Again we’ll revisit these slides and discuss them in more detail. This is what can be done. Let’s start with some basic definitions. Later the technique used to generate this presentation will be presented. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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 Next to be defined and discussed is Equivalent Methane in Air and mudlogging gas Units. Mudlogging gas readings are a great source of confusion, hopefully this presentation will clarify the issue. Another topic discussed why mudlogging is an effective tool. Mudlogging is an effective tool because: 1) gas is measured at the surface 2) hydrocarbon gas is very insoluble in water and 3) hydrocarbon gas expands when the gas travels from the formation to the surface Carbide lagging and deterministic methods help to relate mudlog gas readings to formation gas volumes. The influence of 1) gas in the formation 2) hole size 3) drilling rate 4) gas expansion in the well bore 5) the gas trap and 6) other hard to quantify factors will be explored. Lastly, we’ll go back and discuss previous two slides in more detail 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

MUDLOGGING GAS MEASUREMENTS DEFINTION
4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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 Equivalent Methane in Air is becoming the accepted method of presenting mudlog total gas readings. The SPWLA defined this term and proposed methods to calibrate equipment in 1983. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

MUDLOGGING GAS MEASUREMENT DEFINITION
4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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. The Unit is the common representation of mudlogging total gas data. Unless more information is presented, it is not very useful. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

MUDLOGGING GAS MEASUREMENT DISCUSSION
4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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 It is very important to note that the raw gas readings are measured at the surface. In other word, gas is measured at or near Standard Temperature and Pressure. No gas properties are needed to convert reservoir gas volumes to standard conditions. Standard Conditions are the conditions under which gas is sold. The mudlogging unit is calibrated with methane gas. Methane is the most common constituent of natural gas usually comprising 90% or more of the volume. Most mudlogging unit sensors measure the number of carbon molecules, so the heavier hydrocarbons increase the number of Units measured. Chromatography can and is used in conjunction to total gas measurements. Minor calibration errors are introduced if the calibration gas is not at standard temperature; not at standard pressure; has moisture in the gas; and the sampling system is bypassed when calibrating. Gas trap efficiency, drilling rate, hole size, and many other factors influence gas readings at the mudlogging unit. These factors can and must be accounted for in order to measure gas in the formation. The concept of a unit has changed over time. In the early days, a unit was one, one hundredth of the lower explosive limit of gas either 5.00% or 5.40%. Some mudloggers adopted 0.02% EMA as a unit in California. Now that we’ve defined a Unit or EMA, we’ll discuss why mudlogging is effective 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

MUDLOGGING IS EFFECTIVE BECAUSE:
4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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 units measure gas at the shale shaker as it comes out the mud return line (flow line). The conditions are at or near standard conditions. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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 If one cubic foot of gas saturated water or one cubic foot of gas at 500, 1000, 5000 or 10,000 feet deep is brought to the surface then the amount of gas shown is liberated. Depth is used in this presentation rather than reservoir pressure for simplicity sake. The assumptions are a pressure gradient of psi/foot, a temperature gradient of 1 degree/100 feet and methane gas with standard pseudo critical properties. Gas is virtually insoluble in water at conditions found in reservoirs, as this slide demonstrates. Especially when compared against a cubic foot of gas at the same conditions. The source of this data is Amyx, Bass and Whiting, Petroleum Reservoir Engineering after Standing and Dodson. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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 Not only is gas insoluble in water, it is also insoluble in typical drilling mud. The most notable exception is oil base drilling mud. The source of this data is Methane Solubilities in Drilling Fluids, by W E DeVaney, B E Eakin and R H Graves. Other sources cite slightly different solubilities, but all sources agree that hydrocarbon gases are insoluble in water. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods MUDLOGGING IS EFFECTIVE BECAUSE: Gas is measured directly at the surface Gas is insoluble in water Gas expands as it travels to the surface This example shows the amount of gas volume at certain depths which expands to 1000 SCF at the surface. This is dramatic!!! The next slide is the same data on a logarithmic scale. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods MUDLOGGING IS EFFECTIVE BECAUSE: Gas is measured directly at the surface Gas is insoluble in water Gas expands as it travels to the surface 10 cubic feet of gas at 3000 feet becomes 1000 cubic feet of gas at the surface. That is a 100 fold change! 1/Bg =100 at 3000 feet. This is Boyles and Charles Law presented at depth using the standard hydrostatic and temperature gradient. Any volume from a cubic inch to a cubic yard behaves this way, even if it is measured in Quatlou’s. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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 The next slides present the amount of gas liberated and brought to the surface for coal, shale, oil and gas reservoirs. Typical and common values are present to give a feel for the magnitude of gas liberated. The previous slide only dealt with water, mud or gas, these slides present water and gas as a part of the Bulk Formation Volume. This is how much gas will be liberated if these formations are drilled. The red and blue bars on the left show gas and water values as they relate to formations. All slides have the same format, but different vertical scales. If a formation contains hydrocarbons, gas will be liberated in quantities detectable to mudlogging units. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Note the Coal is presented in SCF/T, but the gas liberated is shown in SCF. It was assumed the coal had a density of 1.35 gms/cc. Also note that fully gas saturated water in cleats and fracture of 10% bulk volume yield very little gas (0.0 or 0.2) depending on depth. A “free gas” volume of 10%, that is the cleats and fracture of 10% bulk volume are fully saturated with gas has about the same amount of gas as about a 75 SCF/T gas content. Remember shallower coals have less capacity to store free gas. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods The gas content numbers were supplied by Ann Priestman, the data was originally developed by GRI. Again, the gas content was converted to SCF at the surface using a 2.6 gms/cc density for shale. The oil shale gas content was estimate from mudlogging experience in Utah. The kerogen yields gas! 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods These are typical GORs for oil reservoirs. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Changing the depth doesn’t influence the surface gas volume (SCF). SCF is fixed by the GOR of the oil. However, typically deeper oil reservoir have more volatile oils (higher GOR). 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Generally coal beds contain more resources than conventional gas reservoirs at shallow depths. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Gas hydrates liberate the same amount of gas as a gas reservoir at 5000’ with 30% porosity and a 15% water saturation. 1) A cubic foot of tight gas sand with 10% porosity and a water saturation of 55%; 2) a cubic foot of coal with a gas content of 175 SCF/T and 3) a cubic foot of Ohio Shale with 90 SCF/T all liberate about the same SCF’s at the surface. All of the above reservoirs when drilled liberate gas that is circulated to the surface in detectable quantities. Mudlogging methods using some simple techniques can quantify the amount of gas in SCF liberated. The next slides explore the methodology. . 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Four methods can be used to relate mudlogging shows measured in EMA or Units to SCF gas volumes: Carbide lags or gas referencing™ (Amen) Deterministic modeling Normalizing using open hole logging Normalizing using core data All these methods can be used in concert. Carbide lag is my preferred method and is how the examples in this presentation were derived. Lagging and deterministic modeling will be discussed. Normalizing mudlogging data with geophysical logs and core data will not be discussed due to time constraints. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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 above process is explained in greater detail in publications at the website. Carbide lagging has been used since the advent of mudlogging. It is an established procedure. Calcium Carbide reacts with water to make acetylene. Before mudlogging a well, calibrated volumes of both methane and acetylene should be run through the sensors and the results should be plotted. Carbide lags must be run while the well is being drilled. Carbide lags can be run as often as needed, usually carbide lags are run before and after potentially productive zones With the above information, the formation gas shows can be converted to SCF liberated per minute. The drilling rate in minutes per foot and hole diameter can be used to calculate the Bulk Volume drilled per minute. If the density log is available the weight in tons per minute drilled can be calculated. The SCF per minute is divided by Bulk Volume in ft^3 of formation drilled per minute resulting in gas reserves in SCF per ft^3 of Formation Volume. Also, the SCF per minute is divided by the weight of the formation in Tons drilled per minute resulting gas content in SCF per TON 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods 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 Although carbide lagging is used, it is important to determine the factors which affect mudlogging shows. Deterministic modeling helps explain gas shows. Air drilling will not be discussed, but has very small shows when drilling and often large gas shows while circulation is regained after a connection or trip. Oil based mud will not be discussed, but are difficult to mudlog because the formation gas liberated is soluble in the mud’s oil. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods This is the basis of mudlogging. The more gas in the formation the larger the mudlogging show. However this is not the only factor. If all other factors are equal, doubling the gas in the formation doubles the gas show 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Hole, that is bit size, is a factor. A 9 7/8” bit should increase the gas readings by about 60% compared to a 7 7/8” bit. If all other factors are equal, doubling the hole diameter, quadruples the gas show 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Mercer was one of the first to realize the importance of drilling rate. Mudlogging works better in fast drilling because the gas shows tend to be large. If all other factors are equal, doubling the drilling rate, doubles the gas show 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods The mud pump rate is often overlooked in modeling. If all other factors are equal, doubling mud pump rate, decreased by one half the gas show 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Generally, the mudlogging gas show is larger for deeper hydrocarbon bearing formations. The depth-gas volume relationship is true for conventional gas reservoirs where the Gas Law predominates. The depth-gas volume relationship is also true once gas is in the drilling fluid. However unconventional reservoirs have other drive and storage mechanisms that don’t conform to the Gas Laws. That is why large unconventional resources can be found at relatively shallow depths. 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) 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods To quote Pogo “We have met the enemy and he is us”. Gas trap efficiency and stability is the largest cause of error in mudlogging. Other errors are measured in a few percent, trap errors are measure in multiples of the correct reading. Vast improvements in gas trap design have occurred in the last few years. Also the use of mud motors have caused drilling contractors to keep their mud pump output constant. This in turn keeps the mud level in the possum belly constant. The constant mud level in the possum belly results in stable gas trap efficiency. It is difficult, but not impossible, to account for the factors discussed when interrupting a gas show. However, surface gas loss, mud/gas interactions, drilling problems such as plugged jets, washed out pump liners, lost circulation and flowing wells make deterministic modeling difficult. Computers can help normalize mudlogging shows based on deterministic modeling. It is beyond the scope of this presentation to discuss gas traps in detail. Carbide lag “calibrates” the whole circulation system. That is why it is such a powerful tool. Carbide lags can be run often. This gives the mudlogger confidence that the system is stable and functioning. Gas trap efficiency and measurement stability is the largest cause of error in these calculations 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods This slide presents three formations in an abridged fashion. The upper most formation is a Powder River Basin Coal at 600’. The middle formation is a Shallow Niobrara formation at 750’ and the lowest formation is the Codell/Niobrara formation in the DJ Basin at 6700’. The minor vertical grid lines are at 2’ intervals, while major vertical grid lines are at 10’ intervals. Track 1, the left most track, displays the Drill Bit Diameter, API Gamma Ray, Mud Flow Rate and Penetration Rate. Notice the variation in the controllable factors: the hole diameter, in light blue, ranges from 4 3/4” to 8 1/2”; the gallons per minute of Mud Flow Rate, in green, ranges from 125 GPM to 410 GPM. Drilling Rate or Penetration Rate, in red, is scaled in minutes per foot with a range of 0 to 1 minutes per foot. API Gamma Ray, in dark blue, is scaled in API units with a range of 0 to 200 API units. The API Gamma Ray “wraps” in the Shallow Niobrara example to 250 API units. Track 2, the track second from the left, presents mudlog gas and density log density. Notice that the Total Gas curve, in red, is scaled in EMA and Units. The curve is the same it is just scaled in different units. Bulk Density, in dark blue, is scaled in grams per cubic centimeter with a range of 1.0 to 3.0 gm/cc. Tracks 1 and 2 will remain the same on the next slides. Tracks 3 and 4 will present different data. Track 3 presents Total Gas normalized for drilling rate and bit size, that is volume variations. The scale is in EMA or Units per Cubic Foot drilled (Unit/ft^3) Track 4 presents Total Gas normalized for drilling rate, bit size and mud flow rate. The scale is in EMA or Units per Cubic Foot drilled per barrel of mud flow (Unit/ft^3/BBL) If carbide lag data is not available this is the best normalization possible. Older mudlogs may benefit form this analysis. Notice the influence in Track 4 of mud flow rate. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Tracks 1 and 2 present the same data in the same format as the previous slide. Track 3 presents surface gas volumes at standard conditions (SCF) as a function of Bulk Formation Volume. If unconventional formations are considered reservoirs, then Bulk Formation Volume is Reservoir Volume. The difference between presentation in SCF per ft^3 of Bulk Volume, MCF per Acre Foot and BCF per Section is scaling. 1 SCF/ft^3 = BCF/Section ft and 1 SCF/ft^3 = MCF/acre foot 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods Track 3 presents gas content in the two most common formats: SCF/TON and cc/gram. No volume or ash corrections are needed as with core data. Density information is required to make these calculations. Track 4 presents Reservoir Gas Porosity or Bulk Volume Mudlogging Gas (BVmlg) in red. Knowledge of formation temperature, pressure and gas properties are required to make this calculation with Bg. A good approximation can be made by using typical values. It appears coal has a high gas porosity (BVmlg) in the Powder River Basin Coal 600’example. This is due to treating coal as a conventional “Gas Law” reservoir. Notice the DJ Basin Codell/Niobrara 6700’ example. The yellow is the density porosity from the density log. The Mudlog Gas Bulk Volume appears reasonable. 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

donovan@mudlogger.com www.mudlogger.com
4/1/2017 Evaluating Tight Gas, Shale Gas and Coal Bed Methane using Mudlogging Methods CONCLUSIONS Mudlogging is an effective evaluation tool If you have questions or comments contact me Bill Donovan (303) THE END 07/25/06 © Automated Mudlogging Systems SM © Automated Mudlogging Systems, 2006

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