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MORE THAN 40 YEARS OF EXPERIENCE IN AIRBORNE GEOPHYSICAL SURVEYS

WITHIN RUSSIA AND WORLWIDE

Airborne gravity survey

Airborne gravity data, currently, is in a great demand for evaluation ofoil and gas perspectives of project areas. The airborne gravity survey is a mandatory part of the initial exploration stage. This innovative method is especially helpful in territories with a strong probability of major oil and gas field discoveries, but available geological-geophysical information is insufficient for managerial or investment decisions.

Aerogeophysica inc. (AGP) has employed different airborne gravimetric systems for wide range of exploration tasks since 2001.

 

Volume of airborne gravity surveys produced by Aerogeophysica between 2005 and 2015

Volume of airborne gravity surveys produced by Aerogeophysica between 2005 and 2015

Features

The main block of the system, mounted on a gyro-stabilized platform, is a gravimetric sensor with reference mass in the form of a flat coil, installed in the gap of the differential magnetic system.The magnetic system consists of four temperature-compensated magnets.

A required element of the system is a high-resolution airborne magnetometer with its sensor installed in towed-bird or stinger configurations.

The GPS Navstar-Glonass satellite constellation is used for aircraft positioning, providing positioning accuracy to the first centimeters.

GT-2 installed in survey aircraft (AN-30)
GT-2 installed in survey
aircraft (AN-30)

AN-30 in Magadan
AN-30 in Magadan

Currently, for airborne gravity surveys, Aerogeophysica Inc. (AGP) operates gravimeters GT-2A, designed by Russian company Gravimetric Technologies, intensively employed by west survey companies.

AGP developed a survey technique for fixed-wing and helicopter installation with accuracy 0.4 mGal and 0.2 mGal respectively.These parameters meet the requirements for a gravity survey up to a scale of 1:50,000 or finer.

line spacing speed accuracy performance aircraft
1000 m 300 km/h 0,4 mGal 20000 km2/month АN-30 (26)
500 m 300 km/h 0,4 mGal 20000 km2/month АN-30 (26)
250 m 180-200 km/h 0,2 mGal 8000 km2/month MI-8

Survey tasks:

  1. Detection of territories (structures), promising for hydrocarbons localization; structural-tectonic mapping of the upper section of the basement; structural-tectonic mapping of the regions; mapping of the disjunctive zones, including possible thrust dislocations and fracture zones; substantial-petrophysical mapping of the buried basement; mapping of the most contrasting formations within sedimentary cover; primarily salt-bearing sections and intrusions; mapping of the paleochannels; research into possibility of identifying the direct indicators of the hydrocarbons accumulations.
  2. Optimization of planning and execution of expensive seismic and drilling operations.
  3. Enhancing the investment attractiveness of the project territories.

Survey equipment

Four-channels cesium magnetometer Aeromaster-100 is a base module of the most surveys systems, employed by Aerogeophysica. Aeromastre-100, beside the measurements of magnetic field intensity, combined the functions of system integrator and synchronizer, collecting the data from radio-altimeter, 3-components flue-gate meter, barometer, temperature sensor, GPS receiver.

Aeromastre-100 measures intensity of magnetic field, receiving as frequency signals from cesium sensors (CS-3 or analog), with measurement rate up to 1000 per second and resolution 0,001 nT.

Airborne gravimeter GT-2A.This gravimeter system designed by Russian company GravimetricTechnologies, and dedicated for onboard measurements of gravity field. The main module of the system is a gravimetric sensor, mounted on a three-axis gyro-stabilized platform. Reference mass has a form of a flat coil and installed in the gap of the differential magnetic system, consisting of four temperature-compensated magnets.

Currently, this gravimetric system is a best in the world, and intensively employed by leading west survey companies.

Technical features

Airborne gravimeter GT-1A

This system was developed by GravimetricTechnologies Ltd., and is dedicated for airborne gravity surveys from fixed-wing aircraft (helicopter).

  • Measurement range – 976 Gal - 984 Gal.
  • Measurement mean-square error with aircraft (helicopter) at rest – less than 0.1-10-5 m/s2.
  • Time constant of the sensor – 0.01 sec.
  • Dynamic measurement range – 400 Gal.
  • Measurement rate – 16 Hz.
  • Vibro-accelerations tolerance on frequencies – 5-100 Hz -100 Gal.
  • Operating temperature range – from + 5°C to + 35 °C.
  • Range of geographic latitudes – 75° S - 75° N.
  • Warm-up time – 48 hours.
  • Power consumption – 150 W.
  • Main block dimensions – 600 x 600 x 750 mm.
  • Net weight – less 140 kg.

Data acquisition system and positioning

This system collects and synchronizes data from gravimeter and magnetometer channels, and satellite navigation data from GPS-GLONASS systems. As well, it provides flight steering and survey line tracking with a special indicator installed on the pilot's cockpit panel.

Using this program in combination with a GPS signals it provides positioning accuracy meeting the requirements for a geophysical survey up to a scale of 1:5000.

 

Ground equipment

The use of base magnetometer stations and base GPS stations is provided for differential correction of navigational solutions.

Samples of the surveys

Airborne gravity survey maps: a) Fay reduction; b) Bouguer reduction, o = 2.67 g/сm3

Airborne gravity survey maps: a) Fay reduction; b) Bouguer reduction, o = 2.67 g/сm3

Root-mean-square error under the helicopter survey is 0,2 mGal.

 

Interpretation scheme with elements of hydrocarbon forecasting

Interpretation scheme with elements of hydrocarbon forecasting

Model of effective density distribution, based on residua gravity field using the method of  approximative interpretation tomography.  Depth interval 0 - 5000 m

Model of effective density distribution, based
on residua gravity field using the method of
approximative interpretation tomography.
Depth interval 0 - 5000 m

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Airborne gravity survey Tuesday, 21 November 2017