scholarly journals Cost-Effective Seismic Exploration: 2D Reflection Imaging at the Kylylahti Massive Sulfide Deposit, Finland

Minerals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 263 ◽  
Author(s):  
Suvi Heinonen ◽  
Michal Malinowski ◽  
Felix Hloušek ◽  
Gardar Gislason ◽  
Stefan Buske ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Imaging Techniques ◽  
Mineral Exploration ◽  
Massive Sulfide ◽  
Seismic Profile ◽  
Seismic Exploration ◽  
Sulfide Deposit ◽  
Depth Imaging ◽  
Seismic Reflection Profiles

We show that by using an advanced pre-stack depth imaging algorithm it is possible to retrieve meaningful and robust seismic images with sparse shot points, using only 3–4 source points per kilometer along a seismic profile. Our results encourage the use of 2D seismic reflection profiling as a reconnaissance tool for mineral exploration in areas with limited access for active seismic surveys. We used the seismic data acquired within the COGITO-MIN project comprising two approximately 6 km long seismic reflection profiles at the polymetallic Kylylahti massive sulfide mine site in eastern Finland. The 2D seismic data acquisition utilized both Vibroseis and dynamite sources with 20 m spacing and wireless receivers spaced every 10 m. For both source types, the recorded data show clear first breaks over all offsets and reflectors in the raw shot gathers. The Kylylahti area is characterized by folded and faulted, steeply dipping geological contacts and structures. We discuss post-stack and pre-stack data processing and compare time and depth imaging techniques in this geologically complex Precambrian hardrock area. The seismic reflection profiles show prominent reflectors at 4.5–8 km depth utilizing different migration routines. In the shallow subsurface, steep reflectors are imaged, and within and underneath the known Kylylahti ultramafic body reflectivity is prominent but discontinuous.

Seismic reflection imaging over a massive sulfide deposit at the Matagami mining camp, Québec

Geophysics ◽  
1999 ◽  
Vol 64 (1) ◽  
pp. 24-32 ◽  
Author(s):  
Andrew J. Calvert ◽  
Yexu Li
Keyword(s):  
Seismic Reflection ◽  
Massive Sulfide ◽  
Seismic Profile ◽  
Seismic Survey ◽  
Normal Faults ◽  
Sulfide Deposit ◽  
Seismic Reflection Profile ◽  
Massive Sulfide Deposit ◽  
Volcanic Stratigraphy ◽  
Seismic Reflections

A 2-D seismic reflection profile was shot across the southern flank of the Matagami mining camp, almost directly above the recently discovered Bell Allard massive sulfide deposit, now estimated at more than 6 million metric tons. All orebodies found in the southern part of the mining camp, including Bell Allard, are located at the contact between the primarily basaltic Wabassee Group and the underlying rhyolitic Watson Lake Group. Seismic reflections were recorded from the basalt‐rhyolite contacts of the lower Wabassee Group, as well as from gabbro sills that intrude much of the volcanic stratigraphy. A strong reflection from the top of the Bell Allard orebody was also detected, but the reflection does not extend over the full width of the deposit as defined by drilling, appearing to correlate with the lower pyrite‐rich zone. Faulting, which can be interpreted from discontinuities in the observed reflections, probably controlled the formation of the Bell Allard deposit. If the interpreted gabbro sills are accepted as isotime markers, then faulting of the deeper sill complex defines a series of half grabens within the rhyolitic Watson Lake Group. The Bell Allard deposit is found at the intersection of one of these apparently low‐angle normal faults with the top of the Watson Lake Group, indicating that sulfide mineralization may have been associated with fluid flow along the fault, which likely penetrates to the underlying mafic intrusion. Although the precise geometry of subsurface faulting cannot be estimated from a single 2-D seismic profile, these results indicate that a full 3-D seismic survey should allow the mapping of many of the subsurface fault systems and the verification of hypotheses of fault‐controlled deposit formation.

Reflectivity randomness revisited

Geophysics ◽  
1999 ◽  
Vol 64 (5) ◽  
pp. 1630-1636 ◽  
Author(s):  
Ayon K. Dey ◽  
Larry R. Lines
Keyword(s):  
Seismic Data ◽  
Real Data ◽  
Seismic Profile ◽  
Synthetic Seismograms ◽  
Seismic Exploration ◽  
Well Log ◽  
Simple Test ◽  
Vertical Seismic Profile ◽  
Seismic Reflectivity

In seismic exploration, statistical wavelet estimation and deconvolution are standard tools. Both of these processes assume randomness in the seismic reflectivity sequence. The validity of this assumption is examined by using well‐log synthetic seismograms and by using a procedure for evaluating the resulting deconvolutions. With real data, we compare our wavelet estimations with the in‐situ recording of the wavelet from a vertical seismic profile (VSP). As a result of our examination of the randomness assumption, we present a fairly simple test that can be used to evaluate the validity of a randomness assumption. From our test of seismic data in Alberta, we conclude that the assumption of reflectivity randomness is less of a problem in deconvolution than other assumptions such as phase and stationarity.

Seismic reflection profiling of the Pyhäsalmi VHMS-deposit: A complementary approach to the deep base metal exploration in Finland

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. WC15-WC23 ◽  
Author(s):  
Suvi Heinonen ◽  
Marcello Imaña ◽  
David B. Snyder ◽  
Ilmo T. Kukkonen ◽  
Pekka J. Heikkinen
Keyword(s):  
Contact Zone ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Massive Sulfide ◽  
Drill Hole ◽  
High Grade ◽  
Seismic Reflection Profiling ◽  
Vhms Deposit

In the Pyhäsalmi case study, the seismic data is used in direct targeting of shallowly dipping mineralized zones in a massive sulfide ore system that was deformed in complex fold interference structures under high-grade metamorphic conditions. The Pyhäsalmi volcanic-hosted massive sulfide (VHMS) deposit ([Formula: see text]) is located in a Proterozoic volcanic belt in central Finland. Acoustic impedance of Pyhäsalmi ore ([Formula: see text]) is distinct from the host rocks ([Formula: see text]), enabling its detection with seismic reflection methods. Drill-hole logging further indicates that the seismic imaging of a contact zone between mafic and felsic volcanic rocks possibly hosting additional mineralizations is plausible. Six seismic profiles showed discontinuous reflectors and complicated reflectivity patterns due to the complex geology. The most prominent reflective package at 1–2 km depth was produced by shallowly dipping contacts between interlayered felsic and mafic volcanic rocks. The topmost of these bright reflections coincides with high-grade zinc mineralization. Large acoustic impedances associated with the sulfide minerals locally enhanced the reflectivity of this topmost contact zone which could be mapped over a wide area using the seismic data. Seismic data enables extrapolation of the geologic model to where no drill-hole data exists; thus, seismic reflection profiling is an important method for defining new areas of interest for deep exploration.

Seismic reflection profiles across the "Mine Series" in the Noranda camp of the Abitibi belt, eastern Canada

1995 ◽  
Vol 32 (2) ◽  
pp. 167-176 ◽  
Author(s):  
Pierre Verpaelst ◽  
A. Shirley Péloquin ◽  
Erick Adam ◽  
Arthur E. Barnes ◽  
John N. Ludden ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Reflection ◽  
Mineral Exploration ◽  
Drill Hole ◽  
Seismic Survey ◽  
Volcanic Complex ◽  
Eastern Canada ◽  
Crustal Layer ◽  
High Resolution Data ◽  
Seismic Reflection Profiles

The Abitibi–Grenville Lithoprobe project completed a regional (line 21) and a high-resolution (line 21-1) seismic survey in the Noranda Central Volcanic Complex of the Blake River Group, Abitibi, Quebec. Line 21 provides a regional framework in which the Archean crust is divided into three layers, two of which are discussed here: the uppermost layer, which corresponds to the Blake River Group, is the least reflective, and lies above 4 s (12 km), and the mid-crustal layer, which is composed of a complex pattern of generally east-northeast-dipping reflectors and lies between 4 and 8 s. Within the regional data, the Mine Series of the Central Volcanic Complex is imaged as a semitransparent series of reflectors overlying a highly reflective east-facing structure interpreted as the subvolcanic Flavrian pluton. The high-resolution data (line 21-1) were collected in the vicinity of the Ansil mine. The seismic images in this region can be controlled by surface geology and extensive drill-hole data, and the project was designed to test the applicability of seismic reflection profiling in providing structural and stratigraphic information for use in mineral exploration: shallow-dipping reflectors correlate well with lithological variations or contacts in the volcanic sequence; strong subhorizontal reflectors correspond to diorite and gabbro dykes and sills; several abrupt lateral changes in the reflectivity coincide with known intrusive contacts such as the Lac Dufault pluton.

scholarly journals Subsalt Depth Imaging Using 3-D VSP Technique in the Ras El Ush Field, Gulf of Suez, Egypt

GeoArabia ◽  
1999 ◽  
Vol 4 (3) ◽  
pp. 363-378
Author(s):  
Mohammed A. Badri ◽  
Taha M. Taha ◽  
Robert W. Wiley
Keyword(s):  
Seismic Data ◽  
Seismic Profile ◽  
Poor Quality ◽  
Gulf Of Suez ◽  
Geological Model ◽  
Vertical Seismic Profile ◽  
Depth Imaging ◽  
Vsp Data ◽  
Basement High ◽  
Definition Of

ABSTRACT In 1995 oil was discovered in the pre-Miocene Matulla and Nubia Sandstones in the Ras El Ush field, Gulf of Suez, Egypt. The discovery was based on an aeromagnetic anomaly from a basement high. After drilling several delineation wells, based on a geological model, it became evident that the field is very complex as it is broken into tilted and rotated compartmental blocks by two perpendicular fault systems. Also the 2-D seismic data were of poor quality beneath the thick Miocene South Gharib Evaporite. Since part of the field lies below shallow-water, 3-D seismic was considered to be too costly. When a delineation well did not encounter the reservoir, due to an unanticipated fault, a 2-D walkaway Vertical Seismic Profile (VSP) was acquired. It clearly revealed the presence of a cross fault. The success of the 2-D VSP in imaging the fault led to the acquisition of the first Middle East 3-D VSP survey in the following well. A downhole, tri-axial, five geophone array tool was used to acquire the 3-D VSP. The 3-D volume of the final migrated VSP data provided the means for the reliable mapping of horizons beneath the South Gharib Evaporite. These maps improved the definition of the field and helped detect previously unrecognized prospective blocks. Four further successful delineation wells confirmed the 3-D VSP interpretation.

scholarly journals Acquisition and Processing of Wider Bandwidth Seismic Data in Crystalline Crust: Progress with the Metal Earth Project

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 145 ◽  
Author(s):  
Mostafa Naghizadeh ◽  
David Snyder ◽  
Saeid Cheraghi ◽  
Steven Foster ◽  
Samo Cilensek ◽  
...  
Keyword(s):  
Seismic Data ◽  
Early Stage ◽  
Mineral Exploration ◽  
Regional Scale ◽  
Waveform Inversion ◽  
Active Sensors ◽  
Full Waveform ◽  
Time Migration ◽  
Petroleum Sector ◽  
Seismic Reflection Profiles

The Metal Earth project acquired 927 km of deep seismic reflection profiles from August to November of 2017. Seismic data acquired in this early stage of the Metal Earth project benefited greatly from recent advances in the petroleum sector as well as those in mineral exploration. Vibroseis acquisition with receivers having a 5 Hz response (10 dB down) generated records from a sweep signal starting at 2 Hz, sweeping up to 150 Hz or 200 Hz. Not only does this broadband signal enhance reflections from the deepest to the shallowest crust, but it also helps the use of full waveform inversion (e.g., to mitigate cycle-skipping) and related techniques. Metal Earth regional-scale transects using over 5000 active sensors target mineralizing fluid pathways throughout the crust, whereas higher spatial-resolution reflection and full-waveform surveys target structures at mine camp scales. Because Metal Earth was proposed to map and compare entire Archean ore and geologically similar non-ore systems, regional sections cover the entire crust to the Moho in the Abitibi and Wabigoon greenstone belts of the Superior craton in central Canada. Where the new sections overlap with previous Lithoprobe surveys, a clear improvement in reflector detection and definition is observed. Improvements are here attributed to the increased bandwidth of the signal, better estimates of refraction and reflection velocities used in processing, and especially the pre-stack time migration of the data.

Case Study: Improving the quality of the seismic reflection image for a Fujian mineral exploration data set with offset-domain common-image gathers

Geophysics ◽  
2021 ◽  
pp. 1-45
Author(s):  
Guofeng Liu ◽  
Xiaohong Meng ◽  
Johanes Gedo Sea
Keyword(s):  
Wave Equation ◽  
Image Quality ◽  
Seismic Data ◽  
Seismic Reflection ◽  
Mineral Exploration ◽  
Velocity Model ◽  
Image Point ◽  
Single Shot ◽  
Data Set ◽  
Depth Migration

Seismic reflection is a proven and effective method commonly used during the exploration of deep mineral deposits in Fujian, China. In seismic data processing, rugged depth migration based on wave-equation migration can play a key role in handling surface fluctuations and complex underground structures. Because wave-equation migration in the shot domain cannot output offset-domain common-image gathers in a straightforward way, the use of traditional tools for updating the velocity model and improving image quality can be quite challenging. To overcome this problem, we employed the attribute migration method. This worked by sorting the migrated stack results for every single-shot gather into the offset gathers. The value of the offset that corresponded to each image point was obtained from the ratio of the original migration results to the offset-modulated shot-data migration results. A Gaussian function was proposed to map every image point to a certain range of offsets. This helped improve the signal-to-noise ratio, which was especially important in handing low quality seismic data obtained during mineral exploration. Residual velocity analysis was applied to these gathers to update the velocity model and improve image quality. The offset-domain common-image gathers were also used directly for real mineral exploration seismic data with rugged depth migration. After several iterations of migration and updating the velocity, the proposed procedure achieved an image quality better than the one obtained with the initial velocity model. The results can help with the interpretation of thrust faults and deep deposit exploration.

Potential pitfalls of crooked‐line seismic reflection surveys

Geophysics ◽  
1996 ◽  
Vol 61 (1) ◽  
pp. 277-281 ◽  
Author(s):  
Jianjun Wu
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Mineral Exploration ◽  
Crystalline Rock ◽  
Complex Nature ◽  
Data Sets ◽  
Implicit Assumption ◽  
Coherent Noise ◽  
Straight Line ◽  
Processing Techniques

During the last few years, the Geological Survey of Canada has pioneered the application of seismic reflection profiling to mineral exploration, in close collaboration with Canadian mining companies and with the Lithoprobe project (e.g., Spencer et al., 1993; Milkereit et al., 1994). Because of the rugged terrain in crystalline rock environments (Dahle et al., 1985; Spencer et al., 1993), vibroseis seismic surveys are frequently conducted along existing roads, resulting in extremely crooked survey profiles. Crooked profiling geometry, coupled with the complex nature of the geological targets, pose special challenges for seismic data processing and interpretation. Many common‐midpoint seismic processing techniques are based on an implicit assumption of a straight‐line survey and are most effective with uniform fold and even offset distribution within common‐midpoint (CMP) gathers. However, with crooked‐line acquisition the CMP gathers are characterized by variable fold and uneven offset distribution. Based on experience with several seismic data sets from mining camps, I have identified two potential pitfalls that stem from acquisition along crooked profiles: (1) seismic transparent zones; and (2) coherent noise. To address these problems, I have critically re‐examined the basic aspects of the CMP processing techniques and have developed robust strategies for dealing with crooked profiles. In this paper, I present a field data example to demonstrate the artifacts and also discuss solutions to eliminate them. Although developed for seismic prospecting in mining camps, the methods presented here are applicable to seismic data acquired in any environment.

scholarly journals 2D seismic exploration of the Ancona landslide (Adriatic Coast, Italy)

Geophysics ◽  
2009 ◽  
Vol 74 (5) ◽  
pp. B139-B151 ◽  
Author(s):  
Eusebio Stucchi ◽  
Alfredo Mazzotti
Keyword(s):  
Seismic Reflection ◽  
Seismic Exploration ◽  
Data Sets ◽  
Air Gun ◽  
Combined Use ◽  
Landslide Body ◽  
Adriatic Coast ◽  
Seismic Reflection Profiles ◽  
Detachment Surface ◽  
Ancona Landslide

We have used on- and offshore seismic reflection profiles to determine the extension of a historic landslide at depth and toward the sea. The subsurface landslide structure was delineated by using four separate data sets produced by the combined use of geophone and hydrophone spreads, and of explosive and air-gun sources which also illuminated, through an undershooting configuration, the subsurface below the coastal road and railway. Many noise problems related to the source and environment were overcome and alleviated with several signal-processing routines. The resulting stack and depth-migrated sections reveal the deep geometry of the main landslide body and indicate the emergence location, at the landslide foot, of a deep, potential detachment surface, which previous investigations failed to evidence.

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