Micro-Seismic Interpretation of Hydraulic Fracture Treatments. Hans de Pater Pinnacle Technologies Delft

Transcription

1 Micro-Seismic Interpretation of Hydraulic Fracture Treatments Hans de Pater Pinnacle Technologies Delft

2 Outline Micro Seismic Technology in the Oil industry Velocity Structure Examples Fault interaction Natural fractures Conclusions

3 Principle of Microseismic Fracture Mapping Micro earthquakes induced by hydraulic fracture» Changes in stress and pore pressure» Slippages along planes of weakness Distance And Elevation From Arrival Times Direction From P-wave Particle Motion Microseisms: Small Amplitude, High Frequency Monitor Distance = Typical Interwell Spacing Mapped About 70 Fracs in 2001 Hydraulic Fracture Microseismic Event Fiber-optic Wireline to Logging Truck for Data Handling and Processing Multi-Level, 3 Component Tool String

4 Microseism Origins Microseisms Originate in an Envelope Surrounding the Fracture

5 Mapping Distance and Elevation Slippage Emits Both P & S Waves (Compressional & Shear) Velocities Are Different P Wave > S Wave Detected At Tri-Axial Receiver P SHEAR SLIPPAGE S(t 1 ) P(t 1 ) S Y X S(t 2 ) RECEIVER P(t 2 )

6 Only Use Horizontal Components (X & Y) to Determine Azimuth Hodogram Window Z P Arrival Vertical Direction Is Skewed by Layering Elevation Is Found from Triangulation Y First Cycle of P Wave Is Most Accurate Later Arrivals Induce Noise (Reflections & Refractions) X Copyright GRI 2000

7 Microseism Azimuth The Direction to a Microseismic Source Is Found by Determining the Particle Motion of the P Wave. t x y Amplitude Data The Simplest Representation Is a Hodogram, which is a Crossplot of the Amplitudes. Waveform Time x y Y Amplitude Example Hodogram Angle from x Axis X Amplitude

8 Velocity-structure example for centered array 1175 V p = V s = V s 3500 m/sec 2,000 m/sec Depth (m) V p V s = 4500 m/sec = 3,000 m/sec 1275 V p V s = 3500 m/sec = 2,000 m/sec Distance (m) 1175 Correct Location Depth (m) (ft) Low Velocity 1275 Regression Grid Search Receivers RMS Velocity High Velocity Distance (m) (ft)

9 Example data set from perforation with trigger pulse on zero level Timing Data P P Arrival S Arrival S Receiver Depths (m) Timing Pulse 25 msec

10 Monitor Well Receivers Treatment Well Perforations 465 ft Separation York Sandstone

11 Velocity comparison for Bossier test Depth (ft) York Velocity (ft/sec)

12 1000 Microseismic locations using 3-layer velocity structure from dipole sonic log Microseismic locations using 3- layer velocity structure from perforation timing Treatment Well 800 South-North (ft) South-North (ft) Treatment Well 0 Monitor Well West-East (ft) Treatment Well Monitor Well West-East (ft) Treatment Well Depth (ft) Top of York Depth (ft) Top of York Bottom of York Bottom of York Distance Along Fracture (ft) Distance Along Fracture (ft)

13 Fracture treatment in the Bonner sand Breakdown Mini-frac Slick Water Acid X-Link Proppant Flush ) psi Closure Grad Closure Grad Pressure ( psi/ft psi/ft Pressure (psi) ISIP Grad 0.94 psi/ft ) ppg ( Proppant Conc (ppg) Time 0

14 APC Anderson #2 Bonner Stimulation, Microseismic Data Side View BM Moore Depth (ft) Fault communicating the Bonner and Moore/BM Bonner York MS toolstring Distance Along Fracture (ft)

15 Large Waterfracs with Extremely Long and Complicated Fracture Growth South-North (ft) Observation Well West-East (ft) Plan View of Microseismic Map

16 Conclusions Improved perforation-timing system aids in extracting appropriate horizontal compressional and shear wave velocities. This provides a more accurate and more realistic velocity interpretation than using dipole-sonic logs alone. Perforation-timing velocities are often considerably different than those obtained from dipole-sonic logs. The perforation-timing measurements have been found to yield more consistent microseismic locations. The determination of an accurate velocity structure is particularly important when the array is situated above the zone where microseisms are induced. Complex fracture growth has long been considered a disadvantage, but new stimulation designs in tight reservoirs can benefit from fracture complexity.