POROSITY Many slides contain more detailed notes that may be
shown using the Notes Page View
Slide 2
Acknowledgments Dr. Walt Ayers, PETE 311, Fall 2001 NExT PERF
Short Course Notes, 1999 Note that many of the NExT slides appears
to have been obtained from other primary sources that are not
cited
Slide 3
Definition: Porosity is the fraction of a rock that is occupied
by voids (pores). Discussion Topics Origins and descriptions
Factors that effect porosity Methods of determination RESERVOIR
POROSITY
Slide 4
ROCK MATRIX AND PORE SPACE Rock matrix Pore space Note
different use of matrix by geologists and engineers
Slide 5
Porosity: The fraction of a rock that is occupied by pores
POROSITY DEFINITION Porosity is an intensive property describing
the fluid storage capacity of rock
Slide 6
ROCK MATRIX AND PORE SPACE Rock matrix Water Oil and/or
gas
Slide 7
OBJECTIVES To provide an understanding of The concepts of rock
matrix and porosity The difference between original (primary) and
induced (secondary) porosity The difference between total and
effective porosity Laboratory methods of porosity determination
Determination of porosity from well logs
Slide 8
CLASSIFICATION OF ROCKS SEDIMENTARY Rock-forming process Source
of material IGNEOUS METAMORPHIC Molten materials in deep crust and
upper mantle Crystallization (Solidification of melt) Weathering
and erosion of rocks exposed at surface Sedimentation, burial and
lithification Rocks under high temperatures and pressures in deep
crust Recrystallization due to heat, pressure, or chemically active
fluids
Slide 9
SEDIMENTARY ROCKS Clastics Carbonates Evaporites
Slide 10
CLASTIC AND CARBONATE ROCKS Clastic Rocks Consist Primarily of
Silicate Minerals Are Classified on the Basis of: - Grain Size -
Mineral Composition Carbonate Rocks Consist Primarily of Carbonate
Minerals (i.e. Minerals With a CO Anion Group) Limestone -
Predominately Calcite (Calcium Carbonate, CaCO 3 ) Dolomite -
Predominately Dolostone (Calcium Magnesium Carbonate, CaMg(CO 3 ) 2
) 3 -2
Slide 11
Relative Abundances Siltstone and shale (clastic) ~75%
Sandstone and conglomerate (clastic) ~11% Limestone and dolomite
~14% SEDIMENTARY ROCK TYPES,
Slide 12
Sand Grains Clay Matrix Chemical Cement Quartz Feldspar Rock
Fragments Quartz Calcite Hematite Illite Kaolinite Smectite Average
Sandstone Average Mudrock (Shale) Allochemical Grains Chemical
Cement Microcrystalline Matrix Calcite Fossils Pelloids Oolites
Intractlasts Calcite Average Sparry Limestone Average Micritic
Limestone Clastic Rocks Carbonate Rocks Comparison of Compositions
of Clastic and CarbonateRocks
Slide 13
Grain-Size Classification for Clastic Sediments
NameMillimetersMicrometers Boulder Cobble Pebble Granule Very
Coarse Sand Coarse Sand Medium Sand Fine Sand Very Fine Sand Coarse
Silt Medium Silt Fine Silt Very Fine Silt Clay 4,096 256 64 4 2 1
0.5 0.25 0.125 0.062 0.031 0.016 0.008 0.004 500 250 125 62 31 16 8
4 (modified from Blatt, 1982)
Slide 14
Average Detrital Mineral Composition of Shale and Sandstone
Mineral Composition ShaleSandstone Clay Minerals Quartz Feldspar
Rock Fragments Carbonate Organic Matter, Hematite, and Other
Minerals 60 (%) 30 4