Objective:
Identification of areas of micro-seismic activity in the process of PPT in the vicinity of two wells at the Yerunakovskoye field: А1 & А3.
Key features:
- Microseismic emission was recorded using an area monitoring system (Refer Figure 1)
- A seismic antenna (using 28 three-channel SCOUT seismic stations) installed on the surface in the epicentral region of the wells, where a plasma-pulsed treatment was performed
- Single-component GS-One seismic sensors were used as transmitters.
- The total number of observation points of a seismic antenna is 84.
- The interval between the points was 20-30 m.
Fig 1: Location of the observation system at the Yerunakovskoye field. The red color indicates the position of the seismic sensors, the yellow color indicates the position of the wellheads
Significance:
- Micro-seismic monitoring is the passive observation of very small scale seismic events which occur in the ground as a result of human activities
- Micro-seismic events are million times smaller than regular seismic events. Hence they are able to report the slightest disturbance in the formation
- Micro-seismic monitoring is performed while the PPT is taking place to provide us with real time monitoring of the extent and direction of the fracture propagation occurring due to implementation of PPT
Observations and Results:
Well A1:
Fig 2: Map of registered microseismic events during the monitoring of the PPT at the well A1 in the projection onto the surface
Fig 3: The energy density map of microseismic emission projected onto the surface
- The total number of events is 703, the emission energy is 3004 kJ, the maximum shear stress energy is 1950 kJ, the compression energy is 42.88 kJ, the separation energy is 35.83 kJ
- The highest energy density of microseismic events is observed under a seismic antenna, in the area of the bottom hole of the A1 well. The approximate linear dimensions of the microseismic activity area are about 1500 meters and 1250 meters.
Well A3:
Fig 4: The map of registered microseismic events during the monitoring of the PPT at the well A3 in the projection onto the surface
Fig 5: The energy density map of microseismic emission projected onto the surface
- The total number of events is 326, the energy of emission is 2215 kJ, the energy of maximum shear stress is 1446 kJ, the compression energy is 19.1 kJ, the separation energy is 18.16 kJ.
- The highest energy density of microseismic events is observed under a seismic antenna, in the area of the bottom hole of the A3 well. The approximate linear dimensions of the microseismic activity area are about 1350 meters and 1000 meters.
Conclusions:
- Data processing of micro-seismic monitoring allowed the localization of micro-seismic events.
- The coordinates, time of excitation and the mean velocities of propagation of seismic waves emitted from these sources were then determined, which in turn resulted in determining the energy parameters of micro-seismic events
- The highest energy density of micro-seismic events are observed under a seismic antenna, in the area of the bottom hole of the wells. The area of micro-seismic activity has an ellipsoid shape.
- The approximate linear dimensions of the micro-seismic activity area of well A1 are about 1500 meters in the North to South direction and 1250 meters in the West to East direction
- The approximate linear dimensions of the micro-seismic activity area of well A3 are about 1350 meters in the North to South direction and 1000 meters in the West to East direction
- These results enable us to observe the kinematic and dynamic characteristics of the area of micro-seismic activity in the system installation area, which may indicate an increase in permeability
This Case Study further reveal the optimal distance between the wells for drilling and implementation of PPT operations