Passive Seismic Tomography: A New Era for Hydrocarbon Exploration

Mesozoic sediments are the main objective for hydrocarbon exploration in the eastern part of Akimeugah Basin, Papua. However, little information is currently available on paleogeography and subsurface distribution of the Mesozoic rock unit. This study analyzed Mesozoic rock unit from outcrops at Wamena and surrounding area to wells data in the eastern part of Akimeugah Basin, Papua. Outcrop and well correlation was made to interpret paleogeography of Mesozoic unit. This study was using existin 2D seismic and passive seismic tomography data to determine the distribution of Mesozoic rock unit in the subsurface and its hydrocarbon potential. The Mesozoic rock unit in the eastern part of Akimeugah Basin is divided into four formations based on their lithological characteristic. Respectively from old to young, Kopai, Woniwogi, Piniya and Ekmai Formation. The depositional environment of Mesozoic rock unit in the southern part of the study area is shore/tidal to shelf and basin fl oor in the northern part. Three Mesozoic potential plays in the studied area are divided into 1) Central Range Mountains thrust-fold belt play, 2) Akimeugah low land thrust-fold belt play and 3) Tanah Merah pinch-out play. The results presented in this paper are expected to be a guide for further hydrocarbon exploration in the study area. Mesozoic sediments are the main objective for hydrocarbon exploration in the eastern part of Akimeugah Basin, Papua. However, little information is currently available on paleogeography and subsurface distribution of the Mesozoic rock unit. This study analyzed Mesozoic rock unit from outcropsat Wamena and surrounding area to wells data in the eastern part of Akimeugah Basin, Papua. Outcrop and well correlation was made to interpret paleogeography of Mesozoic unit. This study was using existing 2D seismic and passive seismic tomography data to determine the distribution of Mesozoic rock unit in the subsurface and its hydrocarbon potential. The Mesozoic rock unit in the eastern part of Akimeugah Basin is divided into four formations based on their lithological characteristic. Respectively from old to young, Kopai, Woniwogi, Piniya and Ekmai Formation. The depositional environment of Mesozoic rock unit in the southern part of the study area is shore/tidal to shelf and basin fl oor in the northern part. Three Mesozoic potential plays in the studied area are divided into 1) Central Range Mountains thrust-fold belt

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Passive seismic tomography using recorded microseismicity: Application to mining-induced seismicity

Geophysics ◽

10.1190/geo2018-0076.1 ◽

2019 ◽

Vol 84 (1) ◽

pp. B41-B57 ◽

Cited By ~ 4

Author(s):

Himanshu Barthwal ◽

Mirko van der Baan

Keyword(s):

Seismic Tomography ◽

Velocity Model ◽

P Wave ◽

Double Difference ◽

Lateral Velocity ◽

Study Region ◽

Arrival Times ◽

3D Velocity Model ◽

Passive Seismic ◽

Dip Angle

Microseismicity is recorded during an underground mine development by a network of seven boreholes. After an initial preprocessing, 488 events are identified with a minimum of 12 P-wave arrival-time picks per event. We have developed a three-step approach for P-wave passive seismic tomography: (1) a probabilistic grid search algorithm for locating the events, (2) joint inversion for a 1D velocity model and event locations using absolute arrival times, and (3) double-difference tomography using reliable differential arrival times obtained from waveform crosscorrelation. The originally diffusive microseismic-event cloud tightens after tomography between depths of 0.45 and 0.5 km toward the center of the tunnel network. The geometry of the event clusters suggests occurrence on a planar geologic fault. The best-fitting plane has a strike of 164.7° north and dip angle of 55.0° toward the west. The study region has known faults striking in the north-northwest–south-southeast direction with a dip angle of 60°, but the relocated event clusters do not fall along any mapped fault. Based on the cluster geometry and the waveform similarity, we hypothesize that the microseismic events occur due to slips along an unmapped fault facilitated by the mining activity. The 3D velocity model we obtained from double-difference tomography indicates lateral velocity contrasts between depths of 0.4 and 0.5 km. We interpret the lateral velocity contrasts in terms of the altered rock types due to ore deposition. The known geotechnical zones in the mine indicate a good correlation with the inverted velocities. Thus, we conclude that passive seismic tomography using microseismic data could provide information beyond the excavation damaged zones and can act as an effective tool to complement geotechnical evaluations.

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