Fracture Spacing in Miss. Madison LsFracture Spacing in Miss. Madison Ls

Log CharacterizationLog Characterization

• Acoustic & electrical imaging logs and their interpretative workstations are becoming the subsurface standard for data acquisition, rapidly replacing core.

• Dipole sonic logs are attempting to quantify fracture occurrence and fracture porosity.

Quantitative Fracture AnalysisQuantitative Fracture Analysis

0 N

90 E

180 S

270 W

360 N

BOREHOLE• Planar features are

expressed by ellipses on borehole walls which are expressed as sine waves

• Steepness of ellipses reflect the dip magnitude and orientation

• Apparent strike and dip relate to amplitudes and inflections in sine waves

For straight hole:

•Dip magnitude is proportional to amplitude of sine wave

•Dip azimuth is located at minimum of sine waveTD: 53 / 270 W

David Spain (1998)

FaultsFaultson on

FMIFMI

TD: 62/304TD: 62/304

Normal faultNormal fault

Striking:Striking:N25E-S25WN25E-S25W

Down to WNWDown to WNW

Courtesy of Steve Hansen, Schlumberger

FractureTrace

False-Color STAR ImageFalse-Color STAR Image

RED: Acoustic amplitude

GREEN: Microtopography

BLUE: Resistivity

Oil well in granite.

Depths in meters below arbitrary datum.

Green fracture is filled withsomewhat hard, resistive,slightly erodible material.

Open fractures are black

Courtesy A. Lacazette

Different fracture types are different colors Different fracture types are different colors in multivariate images.in multivariate images.

Examples Amplitude Microtopography Resistivity

Open Dark Dark Dark

Vein Bright Bright Bright

Fault gouge

Soft

Hard

Moderate

Bright

Variable

Depends on

drilling erosion

Permeable:

Dark

Impermeable:

Bright

Courtesy A. Lacazette

Production Logging TechniquesProduction Logging Techniques

• Spinner flowmeters• Temperature logs• Noise Logs

Perfs

Flowrate

FractureWidth

Fracture Density and Porosity

Lithology

(Courtesy of Dave Spain)

Fracture Zone IdentificationFracture Zone Identification

Seismic attributes– Single– Multiple

Study AreaStudy Areawith 3-dwith 3-dSeismicSeismic

CoverageCoverage

Lake Maracaibo,Lake Maracaibo,VenezuelaVenezuela

Amplitude MapAmplitude MapTop SocuyTop Socuy

Lake Maravaibo,Lake Maravaibo,VenezuelaVenezuela

Note Fault Traces

3-D Seismic data coherency :3-D Seismic data coherency :delineating faults and fractures

(Courtesy of Robert Humphreys)

TWT horizon Structure mapSeismic coherency extractedalong horizon

Courtesy of S. Agar