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Applying Fluid Inclusions to Petroleum Exploration and Production*

By

D.L. Hall1, S.M. Sterner1, W. Shentwu1, and M.A. Bigge1

Search and Discovery Article #40042, (2002)

*Adapted from D.L. Hall’s presentation to the Tulsa Geological Society, March, 2002.

1Fluid Inclusion Technologies, Inc. (www.fittulsa.com) ([email protected]), 2217 N. Yellowood Ave., Broken Arrow, OK 74012 USA

Abstract

Mechanical crushing of core or cuttings samples, followed by bulk analysis of evolved organic and inorganic fluid inclusion volatiles by quadrupole mass spectrometry using a rapid, automated sampling system, allows for nearly continuous stratigraphic mapping of paleofluids in the subsurface. This technique is called Fluid Inclusion Stratigraphy (FIS). Application to over 6000 wells worldwide has established the utility of this technique in addressing elements of risk associated with petroleum exploration and production.

Key indicator compounds and compound ratios are used to document petroleum migration through specific stratigraphic intervals, evaluate product type and quality, and establish a time-integrated effectiveness for potential seals. Additionally, FIS has proven proficient in identifying zones that are near reservoired petroleum, even if that petroleum did not migrate directly through the analyzed section. In these cases, water-soluble hydrocarbons, particularly benzene, toluene and/or organic acids, occur in anomalous concentration and can often be shown to have migrated by diffusion through an aqueous phase away from known petroleum accumulations.

More recently, production applications have been developed, particularly in the general area of reservoir and resource characterization. Known applications include delimitation of pay zones, petroleum-water transition zones and fluid contacts for reserve estimation and EOR applications, as well as assessment of reservoir compartmentalization and connectivity. Application of this technology in real time on drilling wells has been used to influence drilling and testing decisions.

Integration of FIS with classical fluid inclusion methodologies provides additional and more specific data on petroleum fluid properties, salinity of associated aqueous pore fluids and timing constraints for petroleum migration and reservoir charging. These data can be used as input into basin models and to assess timing of petroleum charge as it relates to trap configuration and reservoir quality. Analysis by solvent-extraction or thermal-extraction GCMS of samples pre-screened and targeted by FIS as being petroleum-inclusion-rich effectively establishes links among petroleum-fluid-inclusion-bearing intervals and source rocks, thereby providing better control on migration pathways. Specific examples below illustrate how to use the above techniques to:

• Evaluate whether or not petroleum has moved through a dry hole with no shows that is adjacent to a prospect.

• Determine whether oil or gas should be anticipated in a given area.

• Assess the probability of encountering a deep, hydrocarbon-charged reservoir below a shallow boring.

• Pick perforation points in a problematic pay zone.

• Delineate a pay interval and fluid contact.

• Identify a failed seal.

• Infer a nearby oil field from a wet well with no shows.

• Explicitly evaluate bound-water salinity in the absence of a water analysis.

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uAbstract

uFigure captions (1-6)

uMain points

uFliud inclusions, their significance

uClassical approach

uFluid inclusion stratigraphy (FIS)

uFigure captions (7-24)

uE&P applications

tUpdip prospectivity

tLocal prospectivity

tDrilling success rate

tRegional evaluation

tIdentifying seals

tSeal effectiveness

tPay delineation

tDelineation statistics

tEOR application

uFigure captions (25-39)

uFollow-up analyses

tTools

tInformation

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigure captions (1-6)

uMain points

uFliud inclusions, their significance

uClassical approach

uFluid inclusion stratigraphy (FIS)

uFigure captions (7-24)

uE&P applications

tUpdip prospectivity

tLocal prospectivity

tDrilling success rate

tRegional evaluation

tIdentifying seals

tSeal effectiveness

tPay delineation

tDelineation statistics

tEOR application

uFigure captions (25-39)

uFollow-up analyses

tTools

tInformation

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigure captions (1-6)

uMain points

uFliud inclusions, their significance

uClassical approach

uFluid inclusion stratigraphy (FIS)

uFigure captions (7-24)

uE&P applications

tUpdip prospectivity

tLocal prospectivity

tDrilling success rate

tRegional evaluation

tIdentifying seals

tSeal effectiveness

tPay delineation

tDelineation statistics

tEOR application

uFigure captions (25-39)

uFollow-up analyses

tTools

tInformation

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigure captions (1-6)

uMain points

uFliud inclusions, their significance

uClassical approach

uFluid inclusion stratigraphy (FIS)

uFigure captions (7-24)

uE&P applications

tUpdip prospectivity

tLocal prospectivity

tDrilling success rate

tRegional evaluation

tIdentifying seals

tSeal effectiveness

tPay delineation

tDelineation statistics

tEOR application

uFigure captions (25-39)

uFollow-up analyses

tTools

tInformation

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigure captions (1-6)

uMain points

uFliud inclusions, their significance

uClassical approach

uFluid inclusion stratigraphy (FIS)

uFigure captions (7-24)

uE&P applications

tUpdip prospectivity

tLocal prospectivity

tDrilling success rate

tRegional evaluation

tIdentifying seals

tSeal effectiveness

tPay delineation

tDelineation statistics

tEOR application

uFigure captions (25-39)

uFollow-up analyses

tTools

tInformation

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigure captions (1-6)

uMain points

uFliud inclusions, their significance

uClassical approach

uFluid inclusion stratigraphy (FIS)

uFigure captions (7-24)

uE&P applications

tUpdip prospectivity

tLocal prospectivity

tDrilling success rate

tRegional evaluation

tIdentifying seals

tSeal effectiveness

tPay delineation

tDelineation statistics

tEOR application

uFigure captions (25-39)

uFollow-up analyses

tTools

tInformation

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigure captions (1-6)

uMain points

uFliud inclusions, their significance

uClassical approach

uFluid inclusion stratigraphy (FIS)

uFigure captions (7-24)

uE&P applications

tUpdip prospectivity

tLocal prospectivity

tDrilling success rate

tRegional evaluation

tIdentifying seals

tSeal effectiveness

tPay delineation

tDelineation statistics

tEOR application

uFigure captions (25-39)

uFollow-up analyses

tTools

tInformation

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigure captions (1-6)

uMain points

uFliud inclusions, their significance

uClassical approach

uFluid inclusion stratigraphy (FIS)

uFigure captions (7-24)

uE&P applications

tUpdip prospectivity

tLocal prospectivity

tDrilling success rate

tRegional evaluation

tIdentifying seals

tSeal effectiveness

tPay delineation

tDelineation statistics

tEOR application

uFigure captions (25-39)

uFollow-up analyses

tTools

tInformation

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uAbstract

uFigure captions (1-6)

uMain points

uFliud inclusions, their significance

uClassical approach

uFluid inclusion stratigraphy (FIS)

uFigure captions (7-24)

uE&P applications

tUpdip prospectivity

tLocal prospectivity

tDrilling success rate

tRegional evaluation

tIdentifying seals

tSeal effectiveness

tPay delineation

tDelineation statistics

tEOR application

uFigure captions (25-39)

uFollow-up analyses

tTools

tInformation

uSummary

uReferences

 

 

Figure Captions (1-6)

Figure 1. Fluid inclusions in sandstone in both grains and overgrowth.

 

 

 

Figure 2. Petroleum inclusion in quartz grain.

 

 

 

Figure 3. Petroleum inclusion in quartz, ultraviolet light.

 

 

 

Figure 4. Schematic of FIS technique—sample crushed in vacuum chamber with analysis by mass spectrometer to yield mass spectrum.

 

 

Figure 5. Automated FIS instrumentation.

 

 

 

Figure 6. FIS data. Depth plots of critical species and compound ratios integrated with electric logs indicate petroleum inclusion distribution seals and proximal pay.

Main Points

  • Fluid inclusion techniques are flexible tools applicable to fundamental E&P problems.

  • These techniques can increase our understanding of the petroleum system and help manage E&P risk by assessing the present and past distribution of petroleum, its sources and characteristics.

  • Fluid Inclusion Stratigraphy (FIS) can help high-grade present and future prospects.

Fluid Inclusions and Their Significance

Fluid inclusions are micron-scale, fluid-filled, isolated cavities in or between crystals in rock material (Figures 1, 2, and 3). They form during subsurface diagenetic processes in which mineral cement is added to intergranular pore space or microfractures. Fluid inclusions are representative of past or near-present-day pore fluids, and they track movement of aqueous and petroleum fluids.

Fluid inclusions may be the freshest samples of reservoir fluids we have. They remain even after pore fluids change (correspondingly with applications for fossil migration paths, flushed reservoirs and tilted oil-water contacts). Also, they record multiple charges, temperatures and pressures.

Classical Approach

  • Thin section based.

  • Assumes selection of the most relevant samples for analysis.

  • Best applications are for P-T-X (pressure, temperature, composition) assessment; petroleum compositions typically are crudely constrained or inferred by local production.

  • Difficult to apply to dry gas problems.

  • Regional evaluations are time-intensive.

Fluid Inclusion Stratigraphy (FIS) (Figures 4, 5, and 6)

  • Stratigraphic mapping of paleofluid chemistries through bulk mass spectrometric analysis of fluid inclusion volatile species (inorganics and organics to C13)

  • Rapid, automated analytical system allows cost-effective, regional evaluation of thousands of samples in a matter of days

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Figure Captions (7-24)

Figure 7. Updip prospectivity from wet well. Fluid Inclusion Stratigraphy (FIS) of downdip dry hole documents migration of liquids through reservoir section. FIS of subsequent oil discovery verifies off-structure signal.

Figure 8. Local prospectivity / deeper potential. Fluid Inclusion Stratigraphy (FIS) of rich gas condensate discovery indicates gas and liquids prospectivity of area.  FIS of dry hole from same basin shows little encouragement for liquids prospectivity.

Figure 9. FIS microseep over oil reservoir. FIS microseep in section where temperature is lower than 60oC and above sealing interval, which overlies main reservoir sand.

 

Figure 10. 3-D stochastic modeling of FIS data; Haltenbanken area, offshore Norway. From FIS, anomalous concentrations of methane, other light hydrocarbons, and sulfur compounds in the shallow subsurface probably reflect anaerobic alteration of vertically seeping gas-range compounds from depth by sulfate-reducing bacteria.

Figure 11. GOM FIS seep statistics show that 89% of producers show seepage and 76% of the deep dry holes have no seepage.

 

 

Figure 12. Gas vs. liquids prospectivity, at constant depth, in the Texas Gulf Coast and offshore.

 

 

Figure 13. Seal definition / characterization documented along transect by low methane abundance across regional seal, northern Oman.

 

 

Figure 14. Seal effectiveness shown by analyses of part of the Devonian section in a western Canada well, which, based on FIS, appears to indicate seal breach in the Lobstick and Ireton and evidence of a paleocolumn of gas in wet Leduc reservoir (Compartment 3).

Figure 15. Proximity-to-pay concept, illustrated by detectable benzene and toluene in formation waters.

 

 

Figure 16. Benzene in oil field brines at Buccaneer field, offshore southeast Texas, as proximity-to-pay indicator (from Burtell and Jones; 1996) BTEX=benzene, toluene, ethylbenzene, xylene.

 

Figure 17. Benzene in Alberta Nisku brines shows good correlation with proximity to production (from Burtell and Jones; 1996).

 

 

Figure 18. FIS infers nearby undrilled pay from dry well drilled on crest (on top of Kimmeridge Clay), by detection of anomalous levels of benzene in the lateral seal.

 

Figure 19. FIS “proximity” geometries. A. Downdip from a reservoir. B. Across a top seal. C. Across a fault seal. D. In a waste zone.

 

 

Figure 20. Pay and product definition, Devonian Leduc reef. FIS, along with log and core analyses, delineates gas reservoir and top seal.

 

 

Figure 21. Pay and product definition, Silurian Guelph reef. FIS, along with log and core analyses, delineates oil and gas legs.

 

 

Figure 22. Identifying bypassed pay by similar anomalies in C2, A/P (aromatics/paraffins), and H2S in interval above main pay.

 

 

Figure 23. Reservoir compartmentalization by delineation of barriers, based on FIS oil inclusion indicator, Sr-RSA (87Sr/86Sr from residual salt analyses), and fluid inclusion salinities.

 

 

Figure 24. EOR application, as shown by the delineation of the original oil-water contact by FIS attributes.

 

 

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E&P Applications of FIS

  • Mapping migration pathways.

  • Pay delineation / relative fluid saturation / oil-water and gas-water contacts.

  • Implying updip pay from wet wells.

  • Implying deeper prospectivity from shallow drilling.

  • Product type and quality issues (sour gas, biodegradation, oil vs. gas)

  • Reservoir connectivity

  • Seal identification and effectiveness.

  • Pressure compartments.

  • Identifying products evolved from mature source rocks.

  • Fault location.

  • Exposure surface delineation.

Inferring Updip Prospectivity from a Wet Well (Figure 7)

  • Well drilled off-structure with no shows; reservoir sand was wet.

  • Strong FIS liquid and gaseous petroleum indications were obtained on wet reservoir sand, suggesting that oil and gas migrated through target section.

  • Updip well discovered oil and gas in reservoir equivalent interval; API matched that measured in thin section on wet well.

Local Prospectivity / Deeper Potential from Shallow Drilling (Figures 8, 9, 10, and 11)

  • FIS data from rich gas-condensate discovery delineates top of pay and regional seal.

  • Shallow leakage of gas and liquids is encouraging for deeper potential.

  • FIS data from dry hole in same basin does not show evidence of shallow seep signature nor migration through reservoir section.

Predicted Drilling Success Rate (Figure 11)

  • 76% chance of deepening an existing shallow well with an FIS seep signal and encountering pay.

  • Only an 11% chance of deepening an existing shallow well without an FIS seep signal and encountering pay.

Regional Evaluation (Figure 12)

  • 20,000 samples from 180 wells evaluated with FIS in 6 weeks.

  • Defined areas of gas, condensate and oil prospectivity.

  • Suggested deeper potential in areas with shallow well control.

  • Basin-scale high-grading tool.

Identifying Seals (Figure 13)

  • FIS methane distribution for several wells along transect documents low abundance across regional seal.

  • Additional FIS data indicate that fluid on either side of seal has discrete chemistry, suggesting limited communication over geologic time.

  • Geochemical data suggest reservoirs produce petroleum from different source rocks.

Seal Effectiveness (Figure 14)

  • Wet Leduc reservoir.

  • FIS data provide evidence for paleocolumn of gas.

  • Data also suggest leakage of top seal as possible failure mode for prospect.

  • Reactivation of nearby fault is implicated.

Proximity to Pay and Inferring Nearby Undrilled Pay (Figures 15, 16, 17, 18, and 19)

  • Presence of benzene, toluene, and organic acids in formation waters.

  • Well through center of prospect encountered no reservoir; had no shows.

  • Cuttings document anomalous levels of benzene, toluene and organic acids in the reservoir equivalent section (the lateral seal).

  • Subsequent drilling discovered field.

  • Geochemical halo effect can be used to enlarge exploration target.

Pay Delineation and Bypassed Pay Application (Figures 20, 21, 22, and 23)

Shown in Figure 20 is an excellent top seal to gas reservoir. The gas column is delineated; chemistries track porosity. The present-day gas-water contact is defined; TSR products are identified; and moderately sour gas is indicated. The interpretations were verified with production tests.

Figure 21 shows the log suite, along with FIS results, for a well that was an oil discovery, where there was a shallow hole that was not logged. The shallow FIS anomaly is in regionally productive interval with porosity and staining, and the chemistry is analogous to deeper known pay zone.

 FIS Pay Delineation Statistics

  • 85% of pay zones have anomalous FIS response.

  • Distinction among migration, paleocharge and present-day charge can be made by looking at detailed FIS chemistry and support technologies.

EOR Application in a Mature Field (Figure 24)

  • Depth of original oil-water contact needed for waterflood planning.

  • Original contact was disturbed by production.

  • Wells were incrementally deepened over the history of field; log suites are minimal.

  • FIS data indicate the position of the OWC.

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Figure Captions (25-39)

Figure 25. Petrography and HRCL (high-resolution cathodoluminescence), as follow-up analyses.

 

 

 

Figure 26. Apparatus for fluid inclusion microthermometry.

 

 

 

Figure 27. Timing of biodegradation. (Left) Relatively early carbonate vein contains interpreted original and biodegraded oil. Degradation may have occurred during vein formation. (Right) Later vein is barren, hence may postdate both petroleum migration and biodegradation. Collection of fluid data on inclusions from these respective veins may help constrain timing of these events.

Figure 28. Example of CSIRO’s GOI (grains containing oil inclusions) technique for paleo-saturation determinations shows empirical threshold separating oil and water zones (see Liu and Eadington, 2000).

 

 

Figure 29. Homogenization behavior of petroleum inclusions shown diagrammatically to illustrate, respectively, bubble and dew points, along with critical phenomena.

 

Figure 30. Paired oil and brine analyses help constrain charge timing.

 

 

 

Figure 31. Effect of salinity on reserves estimate (from Larter and Aplin, 1996).

 

 

 

Figure 32. Fluid inclusion salinity variation in oil reservoir.

 

 

 

Figure 33. Oil inclusion, API gravity.

 

 

 

Figure 34. Crush GC (gas chromatography) data on fluid inclusions.

 

 

 

Figure 35. GCMS (gas chromatography - mass spectrometry) data from fluid inclusions.

 

 

 

Figure 36. GCMS data from biodegraded fluid inclusions.

 

 

 

Figure 37. Biogenic vs. thermogenic gas in fluid inclusions.

 

 

 

Figure 38. Prevailing migration model: Liuhua area, Offshore China (South China Sea), with updip migration along reservoir to well 11-1-1A.

 

 

Figure 39. Migration model with integration of FIS, GCMS and isotope data, Liuhua area, Pearl River Mouth Basin, China, indicating a two-stage migration history from two different source kitchens.

 

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Follow-Up Analyses: Tools and Information

Tools

  • Petrography (Figure 25)

  • Microthermometry (Figure 26)

  • API gravity determination (Figure 33)

  • Crush-gas chromatography (GC) (Figure 34)

  • Thermal-extraction or solvent-extraction gas chromatography - mass spectrometry (TE- or SE-GCMS)  (Figures 35 and 36)

  • Isotopic Analysis (Figure 37)

  • Confocal laser scanning microscopy (CLSM)

Information

Summary

  • Fluid inclusion techniques are robust, and applicable to many fundamental E&P questions.

  • Inclusion petroleum is unfractionated and unaltered by sampling or storage procedures. Applicable to oil-based muds.

  • FIS allows rapid, regional evaluation of migration, seals and proximity to pay.

  • Coupling FIS with petrophysical data improves reservoir evaluation.

  • Coupling FIS with classical geochemical methods improves analysis of petroleum system and reservoir continuity.

  • FIS and conventional fluid inclusion analyses constrain basin models.

References

Bernard, B. B., 1978, Light hydrocarbons in marine sediments: PhD thesis, Texas A&M University, College Station, Texas, 144 p.

Burtell and Jones, 1996, Benzene content of subsurface brines can indicate proximity of oil, gas: Oil & Gas Journal, June 3, 1996, p. 59-63.

Faber, E., and W.Stahl, 1984 Geochemical Surface Exploration for Hydrocarbons in North Sea: AAPG Bulletin , v. 68, p. 363 – 386.

Larter, S.R., and A.C. Aplin, 1996, Geochemical Application to Reservoir Assessment: AAPG Short Course Notes.

Liu, K., and P.J. Eadington, 2000, A new method for identifying oil migration pathways by combining analysis of well logs and direct oil indicators (Abstract): AAPG Bulletin, v. 84, no. 13 (annual meeting abstracts).

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