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![Gas Specific Gravity
It provides a possible indicator of the type of hydrocarbon in the reservoir!
Constants: Gas SG
C1 = .55
C2 = .75
C3 = 1.53
C4+= 2
SG = ([ C1/TG ] *.55 ) + ([ C2/TG ] * .75) + ([ C3/TG ] * 1.53) + ([ C4/TG ] * 2)
Nomenclature
SG = Specific Gravity
TG = Total Gas
C1-4 = Component Gas Value](https://image.slidesharecdn.com/944ad8da-b763-4cca-a9b5-a9818fa30057-150218131229-conversion-gate02/75/Advanced-Techniques-14-2048.jpg)
Advanced Techniques
- 1. PALADIN GEOLOGICAL SERVICES 1 AdvancedTechniques to Increase Returns for Horizontal Wells and Reservoirs Tom Arnold, Director of Training @ Paladin Geological Service GEOGAP Training Service Co-Founder & Director
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- 3. 3 What is NOTnew! Logging 1985 Photographing Samples Infrared Total Gas Infrared Chromatograph Full Sensor EDR & Logging System
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- 5. Equipment used inmud logging today.. NOTHING NEW HERE! • Desktop PC • Bloodhound IR Gas Analyzer • Agitator • WITS • Pason EDR • Totco RigSense • Rig Watch • Microscope and sample trays
- 6. 6 MUDLOGGING ADVANCES Gas DetectionHas Changed…
- 7. 7 FTIR GAS DETECTION FourierTransform Infrared C1-C5 under a second because …no column
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- 9. 9 2.5-13 micron range SystemHardware Mounted at the shaker w/wireless data transfer Optical Bench and onboard computer
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- 11. 11 Increased Accuracy Assures better‘SweetSpot’ placement and Formation Evaluation
- 12. 12 What can belearned from this new DATA? …increased analysis of formation evaluation?
- 13. Average Specific Gravityof Typical Hydrocarbons Gas .56 - .66 Condensate Gas .6 - .8 Volatile Oil .77+ Heavy Oil 1 Air=1 What is the importance of Specific Gravity? Specific gravity is unit- less and is the density of the gas divided by the density of air at 68 deg F. @ 1 atmosphere. Gas Specific Gravity Knowing the Specific Gravity of a gas sample can tell you what type of hydrocarbon created it!
- 14. Gas Specific Gravity Itprovides a possible indicator of the type of hydrocarbon in the reservoir! Constants: Gas SG C1 = .55 C2 = .75 C3 = 1.53 C4+= 2 SG = ([ C1/TG ] *.55 ) + ([ C2/TG ] * .75) + ([ C3/TG ] * 1.53) + ([ C4/TG ] * 2) Nomenclature SG = Specific Gravity TG = Total Gas C1-4 = Component Gas Value
- 15. Gas Specific GravityExamples Example 1 TG = 68 C1 = (60 units / 68) * .55 = .642 C2 = (8 units / 68) * .75 = .086 SG = .728 Dry Gas •Example 2 TG = 680 C1 = (500 units / 680) * .55 = .404 C2 = (150 units / 680) * .75 = .165 C3 = (25 units / 680 ) * 1.53 = .056 C4 = (5 units / 680 ) * 2 = .015 SG = .640 Gas Condensate Example 3 TG = 1200 C1 = (650 units / 1200) * .55 = .298 C2 = (200 units / 1200) * .75 = .125 C3 = (175 units / 1200) * 1.53 = .223 C4 = (100 units / 1200 ) * 2 = .167 C5 = (75 units / 1200 ) * 2 = .125 SG = .938 Oil
- 16. Based on thespecific gravity of each of the component gases in the total gas sample, the gas specific gravity gives a direct indicator of the type of hydrocarbon that produced it. Specific Gravity in Cross-Section Well A
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- 19. Data from MolecularRatios GWR – Gas Wetness Ratio LHR – Light to Heavy Ratio OCR - Oil Character Ratio
- 20. Benefit in HorizontalDrilling
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- 22. Evaluation of Hydrocarbon Fluorescencefor Fluid Type A simple visual examination of the fluorescence of hydrocarbon can yield a general idea as to the nature of the oil.
- 23. Evaluation of Hydrocarbon Fluorescencefor Fluid Type By measuring the frequency at which a hydrocarbon sample produces light under fluorescence, the type of oil can be readily determined. Thus quantifying the visual inspection discussed previously.
- 24. Quantitative Fluorescence Testing(QFT) At the rig UV-fluorescence technique for detecting and analyzing extractable whole oil from drill cuttings. Users can obtain both oil quantity and API gravity from emission measurements at two wavelengths. HC Fluorescence – Oil / Gas Shows
- 25. Advantages • Provides repeatableresults with greatly improved sensitivity over visual methods, especially for light oils and condensates. •Provides immediately useful weight percent oil (Wt % Oil) instead of relative (subjective) visual or descriptive values of fluorescence. • Provides API gravity estimates that help characterize in-situ hydrocarbons. • Provides a direct estimate of oil in the formation. HC Fluorescence – Oil / Gas Shows
- 26. 26 Geochemistry at theWell Site
- 27. Advanced Geochemistry inSurface Logging • Prediction Of Producible Oil Via Real-time Onsite Rock Eval • Hollow Fiber Micro-extraction To Measure Oil Content (C5+) • Stage-wise Degassing For Rock Porosity And Permeability • Real-time Onsite Isotope Analysis (GC-IR2)
- 28. Field Requirement inShale Oil/Gas Systems GLWD with in-situ, on-site advanced geochemistry! • There is a significant amount of samples available from the drilling wells. Normally, these samples will be shipped to laboratory for advanced chemical and isotopic analysis. • However, by the time of analysis, a prominent amount of light HCs are gone forever. • In addition, drilling cannot wait for laboratory analysis, which usually requires turning-around time up to months. 28
- 29. How to identify“Sweet Spot” and Keep In It? Conventional Surface Logging?? • Field S1/TOC—oil show • S1 from cuttings (“remaining” oil) • Direct idea of liquid HCs (Closer to “produced” liquid HCs) • Isojar Headspace Gas (“produced” gases) To Identify and stay in the “Sweet spot” 29
- 30. Deliverables: Extractable oilon Log DescriptionsLithology high liquid HCs; Extractable OilMud Log 30
- 31. Real Time, HighDensity Data DescriptionsLithology High Perm by Mud vs. headspace gas Permeability indicatorMud Log 31
- 32. Deliverables: Gas qualityon log DescriptionsLithology Gas QualityMud Log Wetter Gas 32
- 33. (1) Oil show (2) Oil Extractable (3)Gas wetness (4) Isotopes of C1,C2 and C3 (5) Permeability 33
- 34. (1) Sources ofgases • Biogenic vs. Thermogenic (biological or heat created) • Shale vs. Coalbed • Primary vs. Secondary 34 Specific Advantages of Geochemistry
- 35. (2) Thermal Maturity •In general, gas Isotopes increase with maturation. • As thermal indicator, gas isotopes can tell if the reservoir is at the right window for oil, condensate and gas generation. 35
- 36. “Sweet Spot” canbe predicted by: • Secondary Cracking Source (oil-related) • High Nano porosity and permeability • Isotope Reversal (3) “Sweet Spot” prediction 36
- 37. (4) Primary vs.Secondary • Gas isotopes help differentiate the sources of gases (primary vs. secondary). • Oil-related gas wells are usually of high production rates.-50 -40 -30 -20 -10 -55 -45 -35 -25 delta13C3(permil) delta 13C2 (per mil) Red: High Production Well Blue: Low Production Well Gas from secondary cracking of oil or condensate Gas from Kerogen (adapted from JIP Report , 2013) 37
- 38. (5) Production DeclinePrediction Two inputs: Gas production rates Real time C1 isotopes for minimum of 6 months (Gao et al., in prep, GCA) 38
- 39. 39 Geosteering …keeping the wellborewithin the target bed.
- 40. When Everything WorksRight…. When the gamma data is good and matches the offset, life is good. The bad news is that it is often not the case. Lay-over correlation The wellbore remains near the center- line of the target zone.
- 41. When Faulting Occurs…It Gets Interesting! start end major change resultWithout the aid of software, determining the throw of the fault would require careful analysis of the drill cuttings. Even then, the exact displacement would be in question. But with good software the value is known to the foot.
- 42. Eroded Top: MississippiFormation The wellbore entered the top of the Mississippi as it emerged from the unconformity, showing a normal transition between shale and carbonate. Then after drilling several hours, the wellbore entered the eroded surface indicating shale once more. Know your geologic setting and never loose sight of the BIG PICTURE! Otherwise this could have been miss-interpreted as a fault.
- 43. Mississippian Carbonate Signature Whatappears to be noisy gamma, may indicate fractures and micro-faults within the formation. ..many are present but a few are pointed out.
- 44. Delaware Basin Turbidities Gammaindicated significant shift in lithology. Drill cutting confirmed the same, showing extensive clastic detritus.
- 45. The Smaller thePay Zone, the more Critical the Fault fault compression fold 4’ fault begins fault ends With small pay zones, a fault of only a few feet can make a big difference. Couple that with increased dip angles and folding, makes interpretation while drilling a nightmare. Without good software to keep the wellbore in zone and either knowledge of the area or experience to assist, the productivity of the well can come into doubt.
- 46. Even without geologicchanges, other factors effect the wellbore; directional drillers, drill motors, anisotropy, other equipment, etc… These situations lead to porpoising of the wellbore or drilling out the pay zone . This can mean having difficulty during completion. Other Factors porpoising
- 47. Often times allwe have is the general shape between the LWD and offset gamma to work with. Since carbonates have such a low gamma signature, how is correlation possible? Geosteering in a Carbonate offset LWD Other times we have nothing more than an educated guess. The ‘educated ‘ part comes from experience.
- 48. Bakken The Final Product AccurateGeosteering requires being able to see the ‘Big Picture’. That means the ability to look beyond the LWD data. When correlations come into question, consider the lithology and gas data from the logger. Account for other information from LWD sensors like resistivity, azimuthal gamma ray, neutron density and others if available. When you add in experience, this is the point where both science and art merge. The assimilation and analysis of ALL DATA available provides the most accurate correlations and are necessary to assure the successful completion of a horizontal well. Successful Horizontal!
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