Fracture Properties NeededFracture Properties Needed

Fracture porosity & permeabilityare both a function of

Fracture Width (e) &

Fracture Spacing (D)

Fracture PorosityFracture Porosity

Fracture Porosity MagnitudeFracture Porosity Magnitude

Fracture Porosity is Difficult to Calculate

and Even More Difficult to

Interpret

While Fracture Porosity is While Fracture Porosity is Small in MagnitudeSmall in Magnitude

• It is very effective porosity

• A possible large volume per well due to large drainage area and reservoir thickness

• An assumed high recovery factor

Fracture System Volume as a FunctionFracture System Volume as a Functionof Fracture Porosity & Drainageof Fracture Porosity & Drainage

Nelson (1985)

Fracture Fracture PorosityPorosity & Scale& Scale

2 ft

Nelson (1985)

Depth & Depletion CorrectionsAre Much More Severe

in Fracture Porosity

Than in Matrix Porosity

Fracture & Matrix PorosityFracture & Matrix PorosityCompressibilityCompressibility

Tr Ss from Daw & Others (1974)

Fracture & Matrix PermeabilityFracture & Matrix PermeabilityCompressibilityCompressibility

Fracture Porosity CalculatorFracture Porosity Calculator

Nelson (1985)

Fracture Porosity DeterminationsFracture Porosity Determinations

Average Porosity From Whole-Core Analysis (Arithmetic Average) Silurian Tuscarora Quartzite, Amoco #1 Texas-Gulf (Assumes < 0.5% = 0.0%) All Core = 0.9% Best Zone = 1.4% Unfractured Rock = 0.6% All Core f = 0.4% Best Zone f = 0.9% Highest f = 2.9%

Fracture Porosity from Core AnalysisFracture Porosity from Core Analysis

Fracture Porosity vs. Fracture Porosity vs. Fracture PermeabilityFracture Permeability

Nelson (1985)

Fracture Fracture Porosity/Porosity/

PermeabilityPermeabilityRelationshipRelationship

K. North SeaChalk

Valhall Field

Nelson (1985)

Fracture Porosity from OutcropFracture Porosity from OutcropFracture IntensitiesFracture Intensities

Assumes Fracture Width for Ls at 10,000 ft from Lab Measurements

Nelson

(1985)

Sometimes FracturePorosity & Matrix

Porosity are Related

Calcite Filled Vessicle Trains Calcite Filled Vessicle Trains Surrounding Fractures in Tert. BasaltSurrounding Fractures in Tert. Basalt

West Rozel, Great Salt Lake, Utah

Matrix Saturation Around FracturesMatrix Saturation Around Fracturesin Tert. Basaltin Tert. Basalt

West Rozel, Great Salt Lake, UtahCalcite fill in Outcrop

Calcite Along Vessicle Trains AlongCalcite Along Vessicle Trains AlongFractures in BasaltFractures in Basalt

West Rozel, Great Salt Lake, Utah