Gravity Surveying
- Objectives of Gravity Surveying
- Investigation of large-scale structures and tectonics
- Hydrocarbon prospecting (oil & gas)
- Exploration and delineation of solid mineral deposits
- Engineering-geological investigations
- Geodynamic monitoring of mineral deposits
Advantages of Gravity Surveying:
- High precision: modern gravimeters deliver reliable gravity measurements
- Non-invasive: no drilling or soil disturbance, reducing environmental impact
- Cost-effective: balanced cost vs. quality of data
- Versatility: applicable on land, at sea, in the air, underground, and in boreholes
and Modern Solutions
Based on airborne geophysical and ground-based data, consolidated digital arrays were created, volumetric density and magnetometric models were calculated, zoning was performed, and comprehensive interpretation was conducted. Areas with potential for ore minerals were identified and recommended for exploration and appraisal work.
The results significantly expanded our understanding of the structural and tectonic structure of the suprasalt complex, as reflected in the gravity field. The gravity field was divided into localized anomalies associated with the salt roof topography (salt domes) and extensive positive first-order anomalies reflecting subsalt carbonate structures. Using gravity magnetometry data, the southern boundary of the Kungur salt deposits was refined, rudimentary salt massifs were localized, and positive structures were identified in the Devonian-Middle Carboniferous portion of the section, which are recommended for oil and gas potential studies.
Based on new data and archival materials, a consolidated digital anomaly model was created, informative transforms and a volumetric density model were calculated. Interpretation, taking into account seismic exploration, allowed us to identify zones of Kungur salt-bearing deposits, interdome troughs, salt-free zones ("salt-free windows"), and the proposed cornice contour. The obtained results confirm the high importance of gravity exploration in the complex of geological and geophysical works, especially at the stage preceding expensive seismic exploration.
The Tygasha South and Tygasha North sites are located within the Tygashasay ore district of the Kempirsay ultramafic massif (Aktobe Region). The purpose of the gravimetric survey is to create a detailed geophysical basis for deep geological mapping and optimal placement of chromite exploration boreholes. In 2023, a detailed ground survey was completed over a 40x20 m grid with a ±0.02 mGal resolution using CG-5 and CG-6 gravimeters and Trimble R7, R8s, and R9s satellite geodetic systems. Observation point catalogs and Bouguer gravity anomaly maps (ρ = 2.49 g/cm³, 0.2 mGal cross-section) were obtained. The interpretation is based on new data and materials from the previous stage: combined gravity and magnetic field models were generated, transformations were performed, 2D/3D modeling of density and magnetic characteristics, and interpretation schemes were developed.
In zones of positive anomalies, local maxima with parameters comparable to known chromite deposits in the southeast of the massif were identified. Their epicenters, combined with lower magnetic field values, are recommended for drilling testing. The results confirmed the high efficiency of combined gravity and magnetic surveys in chromite ore prospecting and exploration.
From 1999 to 2011, gravity surveys were conducted in the KSCF waters at individual structures and fields commissioned by subsoil users, including hard-to-reach areas: Kaidak Sor (1999), Terenozek-Prorva (1999), South Zaburunye and South Zhambai (2001), Katunsky (2001–2002), Aktoty-Kairan (2004), and Block A (2011). Surveys were conducted using CG-3, CG-3M, CG-5, and GT-2AM gravimeters using the tripod observation method; coordinates and elevations were determined using Trimble 4700 and Legacy satellite systems. Crews navigated open waters by boat, and in shallow waters and thickets by airboat, hovercraft, and VAZ-1922 Marsh amphibious all-terrain vehicles. The observation network was 2 x 0.5 km, with a resolution of 1 x 0.25 km. The use of modern equipment ensured high accuracy of gravity (±0.09 mGal and better), coordinates, and elevation data for survey points. Quality gravimetric maps, depth maps, and bottom relief maps were generated.
The data were used to develop a geological model of the KSKM, rationally plan subsequent seismic exploration work, and assess the oil and gas potential of the area. The resulting relief maps and studied working conditions improved the safety and efficiency of subsequent geological and geophysical surveys.
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