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