Porosity determination Introduction Porosity is the ratio of void space within a rock(or sediment) relative to bulk volume, reported either as a decimal fraction or as a percentage of total bulk volume. Sedimentary rocks that form petroleum reservoirs(e.g, Figure 1)typically have an average porosity value that will be between 5 and 40% Permeability is the ability of porous media to transmit fluid. At the most basic level, porosity determines the amount of fluid present within a reservoir, permeability governs what is recoverable. Because porosity and permeability represent important characteristics of a reservoir rock, the detection and evaluation of porosity and the inferred presence or absence of permeability are two important duties of the geologist. 159mD There are many ways of determining the porosity of a reservoir rock. Porosity can b Figure 1. Drill cuttings containing 14% intergranular visually estimated from drill cuttings or core fragments. porosity, click on the image to zoom in/out (image ourtesy of Calgary Rock and Materials Services In Determined for a given interval from petrophysical logs. and Hayden Geological Consultants). Measured by analyzing the injection behavior of a fluid or gas into rock cuttings or core fragments However, when values from different types of analysis are compared to one another, for the same sample or sample interval, discrepancies may occur. One potential discrepancy relates to the physical size of the sample and sample interval. Visual estimates of porosity and laboratory measured porosity values are typically conducted on small samples, derived from drill cuttings(Figure 2A)and/or selected core plug samples removed from drill core(Figure 2B) Drill cuttings represent a sampled of a drilled interval, the size of which is prescribed in the drilling prognosis or plan Typically sample intervals are 3 to 5 m(approx. 10 to 30 feet)in the upper part of an offshore exploration well (known as"topB hole ), decreasing to perhaps a I m(3 feet) sample interval as the drilling rate slows towards total depth(TD); for the sample in Figure 2A the interval is 3 m(approx. 10 feet). Because of the relative high cost of drill core, cored intervals are selected over zones of specific interest (i.e, potential reservoir) and therefore vary in length, but are typically 9m to 30m(27 to 90 feet). The drill core in Figure 2B is 5.7m(19 feet) Figure 2. Geological samples, showing drill uttings obtained over a sample interval of 3 m(approx. 10 feet), the yellow scale bar is 0.5 cm (A); drill core in which the measured length is 5.7 m (19 feet), the scale bar is subdivided into cm. The removal of a core plug leaves cylindrical holes in the drill core. he scale bar is in cm (drill core image courtesy of KM Bergman)
1 Porosity determination Introduction Porosity is the ratio of void space within a rock (or sediment) relative to bulk volume, reported either as a decimal fraction or as a percentage of total bulk volume. Sedimentary rocks that form petroleum reservoirs (e.g., Figure 1) typically have an average porosity value that will be between 5 and 40%. Permeability is the ability of porous media to transmit fluid. At the most basic level, porosity determines the amount of fluid present within a reservoir, permeability governs what is recoverable. Because porosity and permeability represent important characteristics of a reservoir rock, the detection and evaluation of porosity and the inferred presence or absence of permeability are two important duties of the geologist. There are many ways of determining the porosity of a reservoir rock. Porosity can be: • Visually estimated from drill cuttings or core fragments. • Determined for a given interval from petrophysical logs. • Measured by analyzing the injection behavior of a fluid or gas into rock cuttings or core fragments. However, when values from different types of analysis are compared to one another, for the same sample or sample interval, discrepancies may occur. One potential discrepancy relates to the physical size of the sample and sample interval. Visual estimates of porosity and laboratory measured porosity values are typically conducted on small samples, derived from drill cuttings (Figure 2A) and/or selected core plug samples removed from drill core (Figure 2B). Drill cuttings represent a sampled of a drilled interval, the size of which is prescribed in the drilling prognosis or plan. Typically sample intervals are 3 to 5 m (approx. 10 to 30 feet) in the upper part of an offshore exploration well (known as ‘top hole’), decreasing to perhaps a 1 m (3 feet) sample interval as the drilling rate slows towards total depth (TD); for the sample in Figure 2A the interval is 3 m (approx. 10 feet). Because of the relative high cost of drill core, cored intervals are selected over zones of specific interest (i.e., potential reservoir) and therefore vary in length, but are typically 9m to 30m (27 to 90 feet). The drill core in Figure 2B is 5.7 m (19 feet). B Figure 2. Geological samples, showing drill cuttings obtained over a sample interval of 3 m (approx. 10 feet), the yellow scale bar is 0.5 cm (A); drill core in which the measured length is 5.7 m (19 feet), the scale bar is subdivided into cm. The removal of a core plug leaves cylindrical holes in the drill core, the scale bar is in cm (drill core image courtesy of K.M Bergman). A Figure 1. Drill cuttings containing 14% intergranular porosity, click on the image to zoom in/out (image courtesy of Calgary Rock and Materials Services Inc. and Hayden Geological Consultants)
Therefore, drill cuttings typically represent the first, and sometimes only, geological samples from an exploration well. Furthermore, while it is possible to derive measurements of permeability on drill cuttings, generally more accurate, laboratory based, determinations are possible with drill core, which of course can be linked to a detailed geological description of the drill core and petrophysical logs The industry is heavily reliant on data derived from petrophysical logs via devices and methods of increasing sophistication. However, it is important to remember that the majority of porosity determinations from petrophysical logs are derived via the analysis of the mineral plus matrix density or the fluids within a given rock over an interval of depth. Petrophysical logs cannot directly measure void space! Figure 3 summarizes the relationship between various mineral and pore characteristics and various modes of analysis. Note that consists of isolated, unconnected pores and connected pores of ize. Also note that there is significant Total Porosity Neutron Log Total Porosity Density Log -+Humidity-dried Core-determined oi CLAY SURFACE AYERS INTERLAYERS SMALL LARGE ISOLATED BOUND ILLAR WATER WATER WATER I PORE VOLUM SHALE ABSOLUTE OR TOTAL POROSITY Figure 3. A simplified pore-system schematic that relates mineralogy, pore type, fluid type and state, and various means of determining porosity (after Cone Kersey, 1992) Figure 3 implies that both Neutron and Density log could report a higher percentage for porosity compared to the hydrocarbon pore volume, as could laboratory derived assessments of porosity. This is because when samples are prepared for either mercury, or gas porosimetry, samples are initially cleaned using reagents and/or solvents then subsequently dried, with the aim of removing all hydrocarbons. However, sample preparation may inadvertently reduce, or eliminate, the irreducible water content, which may generate an exaggerated porosity value(Figure 3). In contrast, petrophysical log analysis may also include clay-bound structural water; therefore care and caution must be exercised when evaluating data derived from all modes of analysis None of this is meant to imply that petrophysical log determinations and laboratory assessments of porosity are error prone and to be avoided, quite to contrary! They are widely used within the industry; petrophysical logs are discussed later in a 魔(○)( chapter devoted to petrophysical logging. However, every technique has limitations! In a similar way the visual assessment of porosity takes practice, skill and due diligence. The reporting ACCURACY PRECISION RACY and geologist must instill a high level of confidence by creating data that has high levels of both accuracy and precision; Figure 4 Figure 4. Accuracy and precision conveys the point Pore Type Carbonate rocks Because the porosity within a carbonate rock can be the product of diagenesis and/or the conditions of deposition (lucia, 1995), more pore types have been identified for carbonate than siliciclastic rocks (i.e. sandstone). A number of different types of porosity be ed e and in drill cuttings. However, the classification scheme of Choquet and ray(1970) initially subdivides porosity into three groups, known as Fabric Selective, Not Fabric Selective and Fabric Selective or Not Fabric Selective(Figure 4). Within the Fabric-selective group, the character of the grains or crystals(i.e the fabricof the rock defines pores types. In contrast, the Non-fabric selective porosity cross-cuts the rock fabric, and in Fabric selective or not pores may display a fabric control or not
2 Therefore, drill cuttings typically represent the first, and sometimes only, geological samples from an exploration well. Furthermore, while it is possible to derive measurements of permeability on drill cuttings, generally more accurate, laboratory based, determinations are possible with drill core, which of course can be linked to a detailed geological description of the drill core and petrophysical logs. The industry is heavily reliant on data derived from petrophysical logs via devices and methods of increasing sophistication. However, it is important to remember that the majority of porosity determinations from petrophysical logs are derived via the analysis of the mineral plus matrix density or the fluids within a given rock over an interval of depth. Petrophysical logs cannot directly measure void space! Figure 3 summarizes the relationship between various mineral and pore characteristics and various modes of analysis. Note that the absolute or total porosity (Figure 3) consists of isolated, unconnected pores and connected pores of varying size. Also note that there is significant difference between total porosity and the hydrocarbon pore volume. Figure 3 implies that both Neutron and Density log could report a higher percentage for porosity compared to the hydrocarbon pore volume, as could laboratory derived assessments of porosity. This is because when samples are prepared for either mercury, or gas porosimetry, samples are initially cleaned using reagents and/or solvents then subsequently dried, with the aim of removing all hydrocarbons. However, sample preparation may inadvertently reduce, or eliminate, the irreducible water content, which may generate an exaggerated porosity value (Figure 3). In contrast, petrophysical log analysis may also include clay-bound structural water; therefore care and caution must be exercised when evaluating data derived from all modes of analysis. None of this is meant to imply that petrophysical log determinations and laboratory assessments of porosity are error prone and to be avoided, quite to contrary! They are widely used within the industry; petrophysical logs are discussed later in a chapter devoted to petrophysical logging. However, every technique has limitations! In a similar way the visual assessment of porosity takes practice, skill and due diligence. The reporting geologist must instill a high level of confidence by creating data that has high levels of both accuracy and precision; Figure 4 conveys the point! Pore Type Carbonate rocks Because the porosity within a carbonate rock can be the product of diagenesis and/or the conditions of deposition (Lucia, 1995), more pore types have been identified for carbonate than siliciclastic rocks (i.e. sandstone). A number of different types of porosity may be recognized in core and in drill cuttings. However, the classification scheme of Choquett and Pray (1970) initially subdivides porosity into three groups, known as Fabric Selective, Not Fabric Selective and Fabric Selective or Not Fabric Selective (Figure 4). Within the Fabric-selective group, the character of the grains or crystals (i.e. the fabric) of the rock defines pores types. In contrast, the Non-fabric selective porosity cross-cuts the rock fabric, and in Fabric selective or not pores may display a fabric control or not! Figure 3. A simplified pore-system schematic that relates mineralogy, pore type, fluid type and state, and various means of determining porosity (after Cone & Kersey, 1992) Figure 4. Accuracy and precision
Fabric-selective porosity Intergranular /interparticle: primary porosity that exists or particle Fabric selective Not Fabric Selective Intraparticle: pores within the grains or particles. Intergranular Fracture Intercrystal: occurs between replacive crystals of dolomite Mouldic/Moldic: due to selective removal of fossil material D Intragranular Fenestral: small pores that typically form due to desiccation and yor gas generation Mouldic/Moldic Shelter: pores formed beneath larger particles Framework: created by the growth of frame-building organisms A--- Fenestral Cavern Not-fabric-selective porosity Fracture: due to tectonic deformation, slumping or solution 飞图 Framework Channel: created by dissolution, these are elongate pores with a Fabric or Not Fabric sel length to width ratio of 10: 1 Vug: pores with a diameter greater than 1/16mm, pinpoint porosity is often used to describe micro-vuggy porosity Cavern: diameter greater than Im. Difficult to detect in cuttings! Figure 4. A schematic of the three basic porosity-types Fabric-selective or Not-fabric-selective can be difficult to for carbonate rocks: fabric selective not fabric detect in drill cuttings(Swanson, 1981) selective and fabric selective or not fa brie selective and sub-types(after Choquette and Pray, 1970) Siliciclastic rocks Pittman(1979)recognizes four basic types of porosity in sandstone Dissolution rocks( Figure 4) which include Intergranular: Porosity that exists between grains Microporosity: Pore-throats are less than lum( Pittman, 1971) and difficult to detect with a 10x binocular microscope Dissolution: Porosity formed by the partial or complete dissolution of framework grains and /or the cement Figure 4. A schematic of the four basic pore-types for Fracture: Created by the natural fracturing of the rock fabric. siliciclastic rocks: intergranular, microporosity, Swanson(1981)also includes a Moldic porosity category for siliciclastic rocks, created by the leaching of soluble grains; also noting that this type of porosity can be difficult to detect Porosity type and drill cuttings/core Drill cuttings analysis and the visual determination of porosity from drill cuttings present unique challenges. Firstly, lithological characteristics, including porosity, are described for each recognizable lithology per sample interval Secondly, the geologist must examine several rock chips, per lithology, in order to get a good overview of distinguishing characteristics, especially porosity. Thirdly, you will not be able to use all terms devised by Pittman or Choquette and Pray, which were originally devised for thin section analysis; because of the level of magnification, some types of porosity are more readily recognizable than others. A listing of terms commonly used by well site geologists includes Intergranular, interparticle, intercrystalline*(porosity between grains/particles/crystals respectively) y*(voids greater than 1/16mm) Pin-point*(appear as though created by a pin prick)less than 1/16mm Fenestral(looks like tiny gas bubble) Fracture*(the result of tectonic deformation Moldic(mouldic)(due to the leaching of soluble grains "Earthy'(i.e low porosity) Terms denoted by ()are perhaps those most commonly used. Figure 5 and 6 are images of drill cuttings that contain ntergranular porosity. Figure 5 shows a coarse-grained basal sandstone, whereas Figure 6 shows a medium grained sandstone(A)and a very-fine grained sandstone (B and C). The predominant porosity type is intergranular and the
3 Figure 4. A schematic of the three basic porosity-types for carbonate rocks: fabric selective, not fabric selective and fabric selective or not fabric selective, and sub-types (after Choquette and Pray, 1970) Figure 4. A schematic of the four basic pore-types for siliciclastic rocks: intergranular, microporosity, dissolution and fracture (after Pittman, 1978) Fabric-selective porosity Intergranular / interparticle: primary porosity that exists between grains or particles. Intraparticle: pores within the grains or particles. Intercrystal: occurs between replacive crystals of dolomite. Mouldic/Moldic: due to selective removal of fossil material. Fenestral: small pores that typically form due to desiccation and /or gas generation. Shelter: pores formed beneath larger particles. Framework: created by the growth of frame-building organisms. Not-fabric-selective porosity Fracture: due to tectonic deformation, slumping or solution collapse. Channel: created by dissolution, these are elongate pores with a length to width ratio of 10:1. Vug: pores with a diameter greater than 1/16mm, pinpoint porosity is often used to describe micro-vuggy porosity. Cavern: diameter greater than 1m. Difficult to detect in cuttings! Fabric-selective or Not-fabric-selective can be difficult to detect in drill cuttings (Swanson, 1981). Siliciclastic rocks Pittman (1979) recognizes four basic types of porosity in sandstone rocks (Figure 4) which include: Intergranular: Porosity that exists between grains. Microporosity: Pore-throats are less than 1μm (Pittman, 1971) and difficult to detect with a 10x binocular microscope. Dissolution: Porosity formed by the partial or complete dissolution of framework grains and / or the cement. Fracture: Created by the natural fracturing of the rock fabric. Swanson (1981) also includes a Moldic porosity category for siliciclastic rocks, created by the leaching of soluble grains; also noting that this type of porosity can be difficult to detect in siliciclastics. Porosity type and drill cuttings/core Drill cuttings analysis and the visual determination of porosity from drill cuttings present unique challenges. Firstly, lithological characteristics, including porosity, are described for each recognizable lithology per sample interval. Secondly, the geologist must examine several rock chips, per lithology, in order to get a good overview of distinguishing characteristics, especially porosity. Thirdly, you will not be able to use all terms devised by Pittman or Choquette and Pray, which were originally devised for thin section analysis; because of the level of magnification, some types of porosity are more readily recognizable than others. A listing of terms commonly used by well site geologists includes: • Intergranular*, interparticle*, intercrystalline* (porosity between grains/particles/crystals respectively) • Vuggy* (voids greater than 1/16mm) • Pin-point* (appear as though created by a pin prick) less than 1/16mm • Fenestral* (looks like tiny gas bubble) • Fracture* (the result of tectonic deformation) • Moldic (mouldic) (due to the leaching of soluble grains) • ‘Earthy’ (i.e. low porosity) Terms denoted by (*) are perhaps those most commonly used. Figure 5 and 6 are images of drill cuttings that contain intergranular porosity. Figure 5 shows a coarse-grained basal sandstone, whereas Figure 6 shows a medium grained sandstone (A) and a very-fine grained sandstone (B and C). The predominant porosity type is intergranular and the amount
of porosity the same for all three examples. Note the increased degree of difficulty in identifying porosity with decreasing grain size! Lastly, porosity is easier to recognize in dry samples rather than wet! A B Fi micrograph in which the pores are coloured blue(A); drill cuttings under moderate high magnification [note scale bar for reference], large intergranular pores are visible at this magnification(B). The area outlined in yellow in B shown at higher magnification [note scale bar for reference], this magnification reveals a large number of intergranular pores some of which are indicated(see arrows)(C) (images courtesy of Calgary Rock and Materials Services Inc and Hayden Geological Consultants). A 3.5mD 1 mm 500um Figure 6. Different drill cuttings with similar measured porosity. Showing drill cuttings of a medium grained sandstone under moderate high magnification pores are visible at this magnification(see arrows)(A). Also showing drill-cuttings for a vf-grained sandstone under higher magnification [note scale bar for reference], at this magnifications pores are still somewhat difficult to detect (B), unless using a higher magnification(C); (images courtesy of Calgary Rock and Materials Services Inc and Hayden Porosity amount In addition to describing the physical appearance of pore type, the relative proportion or amount of porosity must be estimated also. A percentage chart (Figure 7) used in conjunction with samples of known proportion is a useful and good start; after that it is a matter of practice and diligence. As a general rule, do not over fabricate data. Fe unlikely that you will see pores in siltstone, unless you have access to a high qu or example, if you were to estimate the porosity type and amount using the example in Figure l, you should of 14%. A series of self-test examples follows
4 of porosity the same for all three examples. Note the increased degree of difficulty in identifying porosity with decreasing grain size! Lastly, porosity is easier to recognize in dry samples rather than wet! Porosity amount In addition to describing the physical appearance of pore type, the relative proportion or amount of porosity must be estimated also. A percentage chart (Figure 7) used in conjunction with samples of known proportion is a useful and good start; after that it is a matter of practice and diligence. As a general rule, do not over exaggerate volumes and never fabricate data. For example, you cannot see porosity in shale and it is unlikely that you will see pores in siltstone, unless you have access to a high quality, very high magnification microscope! For example, if you were to estimate the porosity type and amount using the example in Figure 1, you should recognize intergranular porosity and estimate an amount of 14%. A series of self-test examples follows. Figure 5. Images of a porous and permeable coarse-grained basal sandstone. Showing the drill cuttings as a thin section micrograph in which the pores are coloured blue (A); drill cuttings under moderate high magnification [note scale bar for reference], large intergranular pores are visible at this magnification (B). The area outlined in yellow in ‘B’ shown at higher magnification [note scale bar for reference], this magnification reveals a large number of intergranular pores some of which are indicated (see arrows) (C) (images courtesy of Calgary Rock and Materials Services Inc. and Hayden Geological Consultants). Figure 6. Different drill cuttings with similar measured porosity. Showing drill cuttings of a medium grained sandstone under moderate high magnification pores are visible at this magnification (see arrows) (A). Also showing drill-cuttings for a vf-grained sandstone under higher magnification [note scale bar for reference], at this magnifications pores are still somewhat difficult to detect (B), unless using a higher magnification (C); (images courtesy of Calgary Rock and Materials Services Inc. and Hayden G l i l C lt t )
Figure 7. Volume percentage chart(courtesy of AAPG) Self test: Siliciclastic rocks Examine the suite of samples given below. For each sample, attempt an estimation of the amount ( in %)and type of porosity. Each sample is represented by a thin-section micrograph and a micrograph of the drill cuttings. You should attempt to use the cuttings. The thin section micrographs are for assistance only. Answers are given after the references 500um Figure 8. Sample 1. Porosity type porosity amount mage courtesy of Calgary Rock and Materials Services Inc and Hayden Geological Consultants) 0 mm 1 mm Figure 9. Sample 2. Porosity type (image courtesy of Calgary Rock and Materials Services Inc and Hayden Geological Consultants) B 1 Figure 10. Sample 3. Porosity type porosity amount (image courtesy of Calgary Rock and Materials Services Inc and Hayden Geological Consultants)
5 Self test: Siliciclastic rocks Examine the suite of samples given below. For each sample, attempt an estimation of the amount (in %) and type of porosity. Each sample is represented by a thin-section micrograph and a micrograph of the drill cuttings. You should attempt to use the cuttings. The thin section micrographs are for assistance only. Answers are given after the references! Figure 7. Volume percentage chart (courtesy of AAPG) Figure 8. Sample 1. Porosity type = ___________________; porosity amount _______ %; (image courtesy of Calgary Rock and Materials Services Inc. and Hayden Geological Consultants) Figure 9. Sample 2. Porosity type = ___________________; porosity amount _______ %; (image courtesy of Calgary Rock and Materials Services Inc. and Hayden Geological Consultants) Figure 10. Sample 3. Porosity type = ___________________; porosity amount _______ %; (image courtesy of Calgary Rock and Materials Services Inc. and Hayden Geological Consultants)
Carbonate rocks Describe the amount (in %)and type of porosity for each sample using the nomenclature of Choquette and Pray ( 1970. XN.-crossed nicols(cross-polarized light), G P- gypsum plate( Quartz Red I plate) inserted. The red scale bar indicates a scale distance of 0.10 mm Figure ll. Sample 4 ⅹN. Figure 12. Sample5 XN holocene oolite, Great Salt Lake, Utah. Porosity in black(Scholle, 1978) Up. Eocene Ocala Fm, Florida. Porosity in black (Scholle, 1978) Porosity type porosity amoun Porosity type porosity amount Figure 13. Sample 6 X N. Figure 14. Sample 7. Holocene oolite, Great Salt Lake, Utah. Porosity in black ( Scholle, 1978) Up. Oligocene Suwanne Fm, Florida. Porosity in black. (Scholle, 1978) Porosity type Porosity type porosity amount geD Figure 15. Sample 8. G P. Figure 16. Sample 9. XN Up Oligocene Suwanne Fm, Florida. Porosity in purple. ( Scholle, 1978) Mid Ordovician Black River L.S. PA. Porosity in black. (Scholle, 1978) Porosity type= porosity amount Porosity type rosity amount
6 Carbonate rocks Describe the amount (in %) and type of porosity for each sample using the nomenclature of Choquette and Pray (1970. X.N.– crossed nicols (cross-polarized light), G.P.– gypsum plate (Quartz Red I plate) inserted. The red scale bar indicates a scale distance of 0.10 mm. Figure 11. Sample 4. X.N. Figure 12. Sample 5. X.N. Holocene oolite, Great Salt Lake, Utah. Porosity in black. (Scholle, 1978) Up. Eocene Ocala Fm., Florida. Porosity in black. (Scholle, 1978) Porosity type = ____________; porosity amount _____ %; Porosity type = ____________; porosity amount _____ %; Figure 13. Sample 6 X.N. Figure 14. Sample 7. X.N. Holocene oolite, Great Salt Lake, Utah. Porosity in black. (Scholle, 1978) Up. Oligocene Suwanne Fm., Florida. Porosity in black. (Scholle, 1978) Porosity type = ____________; porosity amount _____ %; Porosity type = ____________; porosity amount _____ %; Figure 15. Sample 8. G.P. Figure 16. Sample 9. X.N. Up. Oligocene Suwanne Fm., Florida. Porosity in purple. (Scholle, 1978) Mid. Ordovician Black River L.S. PA. Porosity in black. (Scholle, 1978) Porosity type = ____________; porosity amount _____ %; Porosity type = ____________; porosity amount _____ %;
References Cone, M.P. and Kersey, D.G. (1992), Porosity, in"The Development Geology Reference Manual,(Morton-Thompson, D and A M Woods Eds ) AAPG Methods in Exploration Series, No. 10, The American Association of Petroleum Geologists, Tulsa. Oklahoma, U.S.A., p204 to 209 Choquette, P.w. and Pray, L.C.(1970)Geological nomenclature and classification of porosity in sedimentary carbonates. AAPG 207-250 Lucia, F.J.(1995), Rock-fabric/petrophysical classification of carbonate pore space for reservoir characterisation, AAPG Bulletin, 79,p1275-1300 Pittman, E D, 1979, Porosity, diagenesis and productive capability of sandstone reservoirs: in, Aspects of Diagenesis (Scholle, P.A. and P. R. Schluger, Eds ) Society of Economic Paleontologists and Mineralogists Special Publication 26, p.p. 159-173 Swanson,RG, 1981, Sample Examination manual, AAPG Methods in exploration Series, AAPG, Tulsa, Oklahoma, Tucker, M. E. and Wright, PV.(1990)Carbonate Sedimentology, Blackwell Scientific Publications, Oxford, Londo Edinburgh, Boston, Melbourne 482p Acknowledgments I would like to thank the following for their kind permission to use images in this linked exercise The AAPG Calgary Rock and Materials Services Inc and Hayden Geological Consultants K M. Bergman Answers Figure 8. Sample 1. Porosity type= intergranular; porosity amount 14% Figure 9. Sample 2. Porosity type= intergranular; porosity amount 10% Figure 10. Sample 3. Porosity type= intergranular, porosity amount 8% 11 ple 4. Porosity type porosity amount-26% Figure 12. Sample 5. Porosity type= intergranular(interparticle); porosity amount% Figure 13. Sample 6. Porosity type vuggy (not fabric selective); porosity amount-32% Figure 14. Sample 7. Porosity type moldic; porosity amount-17% Figure 15. Sample 8. Porosity type= interparticle and intraparticle, porosity amount% Figure 16. Sample 9. Porosity type= fracture, porosity amount%
7 References Cone, M.P. and Kersey, D.G. (1992), Porosity, in ‘The Development Geology Reference Manual’, (Morton-Thompson, D and A. M Woods Eds.) AAPG Methods in Exploration Series, No. 10, The American Association of Petroleum Geologists, Tulsa, Oklahoma, U.S.A., p204 to 209 Choquette, P.W. and Pray, L.C. (1970) ‘Geological nomenclature and classification of porosity in sedimentary carbonates.’ AAPG Bulletin, v54, 207-250 Lucia, F.J. (1995), 'Rock-fabric/petrophysical classification of carbonate pore space for reservoir characterisation', AAPG Bulletin, v79, p1275-1300 Pittman, E.D., 1979, Porosity, diagenesis and productive capability of sandstone reservoirs: in, Aspects of Diagenesis (Scholle, P.A. and P.R. Schluger, Eds.), Society of Economic Paleontologists and Mineralogists Special Publication 26, p.p.159-173. Swanson, R.G., 1981, Sample Examination manual, AAPG Methods in exploration Series, AAPG, Tulsa, Oklahoma, 35p. Tucker, M.E. and Wright, P.V. (1990) ‘Carbonate Sedimentology’, Blackwell Scientific Publications, Oxford, London, Edinburgh, Boston, Melbourne 482p Acknowledgments I would like to thank the following for their kind permission to use images in this linked exercise. The AAPG Calgary Rock and Materials Services Inc. and Hayden Geological Consultants K.M. Bergman Answers Figure 8. Sample 1. Porosity type = intergranular; porosity amount 14% Figure 9. Sample 2. Porosity type = intergranular; porosity amount 10% Figure 10. Sample 3. Porosity type = intergranular; porosity amount 8% Figure 11. Sample 4. Porosity type = interparticle; porosity amount ~26% Figure 12. Sample 5. Porosity type = intergranular (interparticle); porosity amount ~18_ % Figure 13. Sample 6. Porosity type = vuggy (not fabric selective); porosity amount ~32% Figure 14. Sample 7. Porosity type = moldic; porosity amount ~17 % Figure 15. Sample 8. Porosity type = interparticle and intraparticle; porosity amount ~23 % Figure 16. Sample 9. Porosity type = fracture; porosity amount ~8 %
