CANADA-BRAZIL
COOPERATION
COOPERAÇÃO
BRASIL-CANADÁ
Northeastern Brazil
Groundwater Project
In March and April 2001, a helicopter-borne electromagnetic-magnetic-VLF survey was carried out in three pilot areas in northeast Brazil (see survey location map). The purpose was to test the usefulness of airborne electromagnetic methods to map water-bearing fractures in areas of crystalline bedrock to improve the success rate of drilling high yielding wells. The groundwater contained in fractures in the crystalline bedrock of NE-Brazil usually has a high salt content (up to 5000 mg/L) and was expected to respond as a conductor to an induced electromagnetic field.
Earlier, in June 2000, electromagnetic methods were tested in all three pilot areas using ground instrumentation (Geonics EM-34) in an attempt to predict how airborne EM would perform as a groundwater mapping tool in NE-Brazil and to establish survey parameters. The outcome of those tests left little doubt that frequency domain electromagnetic techniques offered great potential and that an airborne survey should give good results (see Ground Geophysics).
From this page, the reader can access several documents related to the Airborne Surveys including:
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The Preface - html in English - of the Technical Report submitted by the survey company (FUGRO Airborne Surveys Ltd) which includes a summary of survey specifications;
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The complete Technical Report - pdf (7.8mb) in Portuguese - by the survey company;
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A selection of results and maps from the 3 survey areas, Juá/CE, Samambaia/PE and Serrinha/RN;
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Comprehensive interpretation and ground follow-up reports by a CPRM team, headed by geophysicist Roberto Gusmão, in Ceará and Pernambuco (pdf in Portuguese).
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An article and an illustrated brochure on the possible role of airborne geophysics in an expanded groundwater management scheme for northeast Brazil.
Technology Transfer
The airborne geophysical survey provided an opportunity to transfer technology to CPRM technicians in the area of survey monitoring and quality control. A Canadian specialist was on hand for the training. Local school children and University of Ceará students also visited the field operations.
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FUGRO technicians describe geophysical equipment to a group of university and CPRM geophysicists on a visit to the Ceará survey area, situated near Juá in the municipality of Irauçuba, some 200 km west of Fortaleza, the state capital. |
FUGRO chief of operations, Albary Telles (with hat) describing the operation of the magnetic, VLF and GPS ground equipment at base station. GSC geophysicist Régis Dumont (left) was on hand to monitor field operations; CPRM chief hydrogeologist, Fernando Feitosa was also present (with camera). |
VLF base-station equipment |
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"Bird" containing delicate electromagnetic (EM) and magnetic equipment lifts slowly off the ground. All the equipment is contained in the cigar-shaped bottom part; the upper beam (with skirt) serves only to provide stability during flight. |
The EM equipment in the "bird" consists of transmitters and receivers operating at 5 frequencies ranging from 900 to 38,000 hertz. |
Helicopter with "bird" in tow, during routine surveying. The "bird" is maintained at an elevation of 30 metres above ground. |
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A group of geophysics students from the Federal University of Ceará (UFC) examine equipment inside the helicopter. |
UFC geophysics professor Mariano Castelo Branco (center) surrounded by students and local representatives. |
Data acquisition system inside the helicopter. |
last modified: 28 Sep 2004
click picture to enlarge
Helicopter
and "bird" lift slowly from base station situated about 4 km
north of the Juá, Ceará survey block. The "bird" holds
delicate electromagnetic (EM) and magnetic sensors consisting of
transmitters and receivers operating at 5 frequencies ranging from 900 to
38,000 hertz.