Mapping reservoirs based on resistivity and induced polarization derived from continuous 3D magnetotelluric profiling: Case study from Qaidam basin, China

Zhanxiang He,¹ Zuzhi Hu,¹ Weifeng Luo,¹ and Caifu Wang^1
1China National Petroleum Corporation, GME department BGP, Zhuozhou, China.

In Sanfu, Qaidam basin, China, traditional geophysical methods have failed to find subtle hydrocarbon reservoirs. In an attempt to predict anddelineate gas reservoirs, we used a type of magnetotelluric (MT) profiling called 3D continuous electromagnetic profiling (CEMP). Electric logs indicate that gas-bearing formations have high resistivity relative to nongas-bearing formations.

Modeling and analysis of the response of a triaxial, frequency-domain electromagnetic induction sensor to a buried linear conductor

Sean P. McKenna¹ and Jason R. McKenna^2
1Northrop Grumman Information Systems, Andover, Massachusetts, U.S.A.
²U. S. Army Engineer Research and Development Center, Vicksburg, Mississippi, U.S.A.l

This paper presents analytical modeling results for a triaxial frequency-domain electromagnetic-induction (EMI) sensor over a homogeneous earth containing a long linear conductor. Although the conductor studied is intended to represent an underground wire or pipe, it can represent any subsurface, linear geologic structure that can channel current.

Comprehensive approaches to 3D inversion of magnetic data affected by remanent magnetization

Yaoguo Li,¹ Sarah E. Shearer,²

¹Colorado School of Mines, Center for Gravity, Electrical, and Magnetic Studies (CGEM), Department of Geophysics, Golden, Colorado, U.S.A.
²Formerly Colorado School of Mines, Center for Gravity, Electrical, and Magnetic Studies (CGEM), Department of Geophysics, Golden, Colorado, U.S.A. Presently Ultra Petroleum Corp., Denver, Colorado, U.S.A. E-mail:

Three-dimensional (3D) inversion of magnetic data to recover a distribution of magnetic susceptibility has been successfully used for mineral exploration during the last decade. However, the unknown direction of magnetization has limited the use of this technique when significant remanence is present. We have developed a comprehensive methodology for solving this problem by examining two classes of approaches and have formulated a suite of methods of practical utility.

Leveling HEM and aeromagnetic data using differential polynomial fitting

Majid Beiki,¹ Mehrdad Bastani,¹ and Laust B. Pedersen^1
1Uppsala University, Department of Earth Sciences, Geophysics, Uppsala, Sweden.

We introduce a new technique to level aerogeophysical data. Our approach is applicable to flight-line data without any need for tie-linemeasurements. The technique is based on polynomial fitting of datapoints in 1D and 2D sliding windows. A polynomial is fitted to data points in a 2D circular window that contains at least three flight lines.

Extraction of structure-based geoelectric models by hybrid genetic algorithms

Irfan Akça¹ and Ahmet Tuğrul Basokur^1
1Ankara University, Faculty of Engineering, Department of Geophysical Engineering, Tandogan Kampusu, Ankara, Turkey.

A major difficulty in electrical resistivity imaging is the identification ofthe lithologic units, especially in the sedimentary environments. The geologic interpretation generally is realized by visual inspection of the final resistivity section. Although sharp boundary inversion techniques based on a local linearization could allow the delineation of interfaces between geologic units, these techniques will succeed only if an initial model already close to the best solution is available.

One of the known volcanogenic massive sulphide (VMS) districts is  Snow Lake which is located in central Manitoba. The VMS mineralization is associated with juvenile rocks of the Flin Flon greenstone belt. The belt is one of the most prolific VMS belts and the largest Paleoproterozoic VMS district in the world. There are several recent examples of geophysical supporting of the exploration programs on the region.

At the end of last year Rockcliff Resources Inc. announced that Geotech Ltd. of Aurora, Ontario has commenced a 3,000 line kilometre airborne survey on the Company’s Snow Lake VMS Project. The ZTEM survey focused on Rockcliff’s Squall and Tramping Properties. Both properties are located approximately 6 km north and south of HudBay’s recently discovered (2007), buried Lalor Deposit where recent deep drilling intersected a new gold/copper zone grading 34.5 m of 5.33% copper and 13.35 g/t gold. The survey also covered Rockcliff’s five near surface copper-rich deposits and additional areas with VMS potential. The survey has the capability of locating conductive bodies down to depths of over a kilometer.

The purpose of the survey was to integrate Rockcliff’s existing VTEM database (13,000 line km) on the project with Geotech’s state of the art ZTEM geophysical technology. The combined surveys allows for complete geophysical coverage and locate conductors buried from near surface to depths in excess of a kilometre. All conductors identified in the survey prioritized based on their conductivity, resistivity and proximity to juvenile arc rocks.

The survey utilized Geotech’s ZTEM or Z-Axis Tipper Electromagnetic system, an innovative airborne EM system which uses the natural or passive audio frequency fields of the Earth as the source of transmitted energy.

Now Rockcliff Resources Inc. announces the drilling program. A minimum of 5,000 metres (m) of drilling are planned in approximately 30 holes. Drilling is planned on the Rail, Reed, Freebeth, Tramping and Squall properties. The targets include extensions of a known copper-gold rich horizon (Rail), additional testing of DPEM & BHPEM anomalies (Reed), an untested borehole anomaly (Freebeth) and untested, buried ZTEM targets (Tramping and Squall). Drilling at the Reed property will focus on a series of deep, off-hole anomalies indicative of multiple, stacked, highly conductive lenses with conductivities typical of massive sulphide mineralization. Four off-hole anomalies at vertical depths of 500 m, 750 m, 880 m and 930 m will be tested.

VMS Ventures Inc. has completed  its diamond drill testing of phase one targets, at the Tower Zone, on  its 100% held Reed 5188 and Reed 5196 claims.  The program consisted of three holes and the extension of a previous hole for a total of 1809 metres.   Diamond drill hole (TZ-08-01) was extended to assess a Borehole Pulse Electromagnetic (BHPEM) anomaly. All drill holes intersected sulphide mineralization explaining the Surface Pulse Electromagnetic (DPEM) and coincident Versatile Time-Domain Electromagnetic (VTEM) anomalies. The Super Zone has been defined on the basis of “AdTau” (see image 2), which is a calculated measurement derived from the analysis and interpretation of VTEM data. AdTau is a direct indication of rock conductivity. The metal-rich mineralization that comprises VMS-type deposits typically produces strong conductivity responses. The 550 hectare Reed Lake Super Zone is interpreted to be highly prospective for this style of deposit. The Company is building its Super Zone exploration plans based on the hypothesis that it may host a VMS camp of several deposits.

Deep-EM and Magnetic Survey Results Map

Troymet Exploration Corp.  announces the commencement of its winter program on the McClarty Lake project located near Snow Lake, Manitoba. The property lies ~45 km south of HudBay Minerals’ Chisel Lake and Lalor Lake volcanic massive sulphide (VMS) deposits.

The establishment of a 10.6 km grid on Troymet’s 100% owned MAC 3 claim is expected to be completed this week, followed by a fixed large loop surface pulse electromagnetic (PEM) survey under contract to Crone Geophysics of Mississauga, Ontario. The grid is centred over the Mac EM conductor that was identified by the Company’s 2008 deep penetrating VTEM helicopter-borne survey and is on trend with the Discovery zone.

The Mac conductor is a high priority target that offers the potential for immediate and significant new VMS discoveries on 100% owned Troymet ground. A 2010 winter diamond drilling program (~1,500 metres) is planned to follow up on results of the PEM survey.

Salares Lithium Inc.  reports the status of the first phase exploration program on its ‘Salares 7′ project in Region III, Chile. The Project encompasses 960 square km of which 394 square km are prospective for sub-surface lithium and potassium in seven salares (brine lakes).

Exploration. The first phase of the exploration programme is a 54-line kilometre Transient Electromagnetic (“TEM“) geophysical survey on the Salar de La Isla and Salar de Las Parinas. This phase is on-going with completion anticipated for early February, 2010. The TEM geophysics program will continue onto the other five salares once the survey at the Salar de La Isla and Salar de Las Parinas is completed.

The data generated by the TEM survey will define the size and extent of the brine pools within the basins and enable the individual basin profiles to be constructed. This information will be utilized in planning the sampling / drilling program expected to begin in February, 2010.

The TEM geophysics program is being carried out by Geodatos SAIC of Santiago, Chile, a well known Chilean geophysics company with broad international experience. Pertinent to the Company’s needs is that Geodatos has conducted surveys at the lithium rich Salar de Atacama, located approximately 200 kilometres north of the Project.

About TEM. TEM uses electromagnetic impulse excitation to investigate the subsurface. It is a variation of the electromagnetic method in which electric and magnetic fields are induced by transient pulses of electrical current in coils or antennas instead of by continuous current. TEM surveys have become the most popular surface EM technique used in exploration for minerals and groundwater and for environmental mapping.

CanAlaska Uranium Ltd. has commenced exploration on its Cree East uranium project in the Athabasca Basin, Saskatchewan, Canada.



Previous geophysical modelling and initial drill tests have outlined four zones of uranium mineralization and hydrothermally-altered rocks associated with major basement offsets along a 4 km mineralizing trend. Drill-hole spacing in the target areas from previous drilling in 2008 and early 2009 is from between 100 to 200 metres. Most of the 2010 targets are located between existing holes, or are short step-outs from existing holes. The new drilling will attempt to cross-cut the fault and alteration modelled by the existing holes, geology and geophysics.

Additional targets on the Cree East project have been defined following intensive airborne and ground geophysical work over summer 2009.

CanAlaska carried out VTEM airborne surveys across the property area in 2005 and determined priority targets. In 2006, detailed collection of over 2,000 surface rock samples and over 400 lake sediment samples by CanAlaska’s field crews defined three large areas of dravite and clay alteration on surface, and localized boulder samples containing anomalous uranium. Before April 30, 2007, initial ground geophysical data from the first lines of IP-Resistivity surveys, provided the CanAlaska with evidence of strong alteration in the sandstone horizons overlying these basement conductors. Additional IP-Resistivity and Audio Magneto Telluric geophysical surveys were used to further define these targets this year. Drill programs started on the project in late February 2008 and large zones of alteration were intercepted. Extreme clay alteration and unconsolidated sands prohibited the CanAlaska from completing the majority of the drill holes.

During the summer of 2008, CanAlaska undertook a multi-faceted $1.6M exploration programme at its consisting of IP/Resistivity surveying on land and high-resolution single channel seismic data collection on Cree and McIntyre Lakes, lake sediment sampling on Cree Lake, and a 5- hole diamond drilling programme. All of the drill holes reached their target depth in basement.

In summer 2009 detailed geophysical surveys, and infill VTEM surveys were used to prioritize target areas for 2010 drilling.

The 4th International Conference & Exhibition: “New Discoveries through Integration of Geoscience” is going to be 5 – 8 April 2010 in S.Petersburg, Russia.

Some of the geophysical presentations:

- 3D-TEM survey in the petroleum exploration problem solving on the Siberian platform – G. Trigubovich (SNIIGGiMS), A. Efimov (SNIIGGiMS);

- Electrical resistivity tomography: A source focusing approach. – A.E. Kaminsky (KGE Astra) & K.V. Titov (KGE Astra);

- Marine CSEM technology performance – Limitations or opportunities? – A. Stefatos (Rocksource), J. Hesthammer (Rocksource) & M. Boulaenko (Rocksource);

- Intergrated Resistivity Imaging of Suswa geothermal field, Kenya – D. Saitet (Jomo Kenyatta University);

- Asymptotic Anomalies of Uniform Thin Polygonal Sheets – H. Holstein (Aberystwyth University) & C. Anastasiades (Aberystwyth University);

- Potential of forward and contact problems of magnetometry in finding kimberlite objects – V.A. Kochnev (Institute of Computational Modeling SB RAS) ;

- Magnetic field statistical characteristics and their relation to the geological structure of quartz- gold deposits. – L. Y. Erofeev* (Tomsk Polytechnic University)

- New seismic technologies for tight gas exploration and development – A. Araman* (Colorado School of Mines) & P. Mazumdar (Colorado School of Mines);

- Use of CSEM in exploration in open acreage. A case study from the 20th Licensing Round, Norway – Susanne Sperrevik* (Rocksource ASA);

- Geophysical Benefits of an Improved Seismic Vibrator – M.A. Hall (ION Geophysical Corporation);

- New approaches to interpretation of geophysical and well data in forecasting hydrocarbon accumulations in oil-gas basins – A.I. Kushmar (VNIGRI);

- Application Electric Method HRES-IP to Explore Prospects North of West Siberia – K.V. Tertyshnikov (Geoneftegaz);

- Application High-resolving Electrical Prospecting on the Pfcific Shelf of China – A.G. Nebrat (SOLITON);

- Combine use of airborne geophysical methods to constrain geology – J. Deparis (BRGM);

- Use of DC and FDEM methods to image the Quaternary aquifer and saltwater at Lüdingworth, Cuxhaven area, Germany – Mohamed Attwa* (LIAG institute, Hannover);

- Exploration of a copper gold porphyry deposit with a complex of geophysical and geochemical methods - Andrey V. Tarasov (Elgeo Ltd.);

- New perspectives of electromagnetic isoparametric soundings applied to oil and gas deposits – L.V. Smetanina (Trofimuk institute of petroleum geology).

Instrumentation GDD Inc. (Quebec) announces its newest breakthrough in the field of geophysics with the Sample Core IP Tester, model Time Domain Low Voltage.
Made after the GDD IP Receiver, model GRx8-32, this new geophysical instrument is perfect for determining a core sample resistive properties. Tests done with the SCIP will determine the chargeability and resistivity of the diamond drill core or field. Knowing what are the physical properties of your sulfites, will help you plan the appropriate geophysical survey. Rugged, compact, inexpensive and easy to operate, the SCIP is built like a 1 dipole GDD IP Receiver.

In May 2010 the CSPG, CSEG and CWLS will join with GAC, MAC, IAH-CNC, CCPG and CFES to bring GeoCanada, a once-in-a-decade event, to Calgary. This valuable earth science Convention will boast an expanded technical program, extended Exhibit Floor and plenty of networking opportunities for the more than 4,500 expected attendees.

Geophysics related Sessions:

Advances in Seismic Acquisition

This session may include any topic to do with onshore seismic acquisition (offshore is a separate session) including, but not limited to; land access, environmental aspects, line clearance and reclamation, geomatics, community relations, sources, receivers and case histories.

Seismic Interpretation and Case Studies

Innovative Groundwater Exploration and Discovery Methods

Groundwater exploration and discovery methods have seen many advances in the past decade, particularly in the application of downhole, airborne, and space-based remote sensing methods as well as computer modelling and scientific visualization. But sound geological mapping, rigorous field observations and aquifer testing are still required to turn conceptual ideas into wells. This session invites papers highlighting innovative geological, geochemical and geophysical methods to explore for groundwater or to map aquifers.

Geophysical Exploration 1: Gravity, Magnetics, MTEM, Remote Sensing

Potential Fields, EM, MT, Remote Sensing Papers are invited which describe the application of gravity, magnetics, electro-magnetics, magneto-tellurics and remote sensing to mining and petroleum exploration and exploitation. The topics will be broken down into land, marine, airborne and satellite techniques.

Geophysical Exploration 2: Lidar, Sonar, Hi-Res Seismic

Signal Processing and Algorithms

Signal processing is at the very heart of seismic analysis. This session welcomes theoretical submissions discussing new or existing algorithms, but also presentations featuring applications of these algorithms in the seismic process. It is hoped that the final programme will feature a combination of the theoretical and the practical.

Subsurface Imaging and Structure

How do we unlock the secrets of the Earth? Knowledge of the Earth’s structure, whether the near subsurface or the core, is essential to geoscientists. This “subsurface imaging and structure” session will present the latest techniques employed to further our knowledge of the structure and geological history of our planet.

Delta Mining & Exploration Corporation announces that a geophysical work program will begin this week on the Delcer Buttes gold/copper property in Elko County.

The property consists of 31 unpatented hard-rock mining claims (680 acres) and lies to the east of the Carlin trend which contains numerous mines producing close to 3 million ounces gold per year in total and south of Long Canyon, Fronteer Development’s new Nevada gold discovery.

Gradient Geophysics, Inc. will conduct high-resolution magnetometer and high-powered induced polarization (“IP”) surveys to identify potential copper/gold skarn mineralization and possible sediment hosted mineralization which may lie beneath extensive covered areas.

Gradient intends to undertake approximately 50 line kilometers of magnetometer and 15 line km of IP surveys. Results of the geophysical exploration work are expected by the end of April. Gradient will provide Delta Corp. with a detailed interpretive map of the magnetometer results and an advanced computer model of the IP results to assist the company in the evaluation of the potential size of the mineralization at the Delcer Buttes property.

Gradient Geophysics has been on the forefront of geophysical data surveying and interpretation for mineral exploration for many years. Responsible for over 600 projects throughout the Americas, Gradient has worked extensively in the mining sector, conducting large-scale geophysical programs for major mining companies such as Rio Tinto, BHP, Newmont and Barrick and for many junior exploration companies. Gradient focuses on high-resolution magnetometer and high-powered IP data collection using robust computer modeling methods for advanced interpretation of mineral deposits.

GEOSOFT continues to produce video lessons for their users and leaners.

Some of the video materials are specially for geophysicists: Geophysics: What’s new in 7.1;  Scripting in Oasis montaj; Math Expressions..

And the live Webinar “Integrating Gravity and Magnetic Data into your Geophysical Portfolio” is going to be.