Our geophysicists work closely with geologists to narrow down the potential sweet spots for detailed exploration and drilling. For doing so, we provide the following disciplines for our clients:

Gravity

Magnetic

Magnetotelluric (MT)

Electromagnetic (EM)

Seismic
APG’s Integrated Workflow for Petroleum Prospect Generation
Gravity
Gravity data acquisition
Gravity data processing
Gravity data interpretation
Gravity inversion
In gravity surveys we measure gravitational acceleration (g). Gravitational acceleration varies with elevation, latitude, topography, tides, instrument drift, and subsurface density. We make a number of corrections to produce a gravity anomaly that only reflects density variations.
Salt domes, sedimentary basins, mine shafts = gravity low
Metalliferous ore bodies, anticlines = gravity high
A modern gravimeter
APG removes all the following factors to enhance gravity variations solely due to density contrast of the target:

Latitude correction

Free air correction

Bouguer correction

Terrain correction

Drift correction

Tidal correction

Isostasy correction

Eötvös correction
Salt dome gravity anomaly
Indian Ocean (Sea Floor Gravity): The sea floor topography
is relatively flat, but gravity imaging highlights the fracture zones as the sediments infilling these fractures are lower in density than the oceanic crust.
Magnetic

Magnetic data acquisition

Magnetic data processing

Magnetic data interpretation
Fluxgate magnetometer
Magnetic observations are routinely collected using any one of three different field operational strategies.

Airborne

Shipborne

Ground Based
Airborne magnetic operation
Magnetic data processing

Reduction of data to a uniform grid by 1D interpolation

Preprocessing

Continuation (Upward and downward)

Derivatives

Extraction of vertical component


Summation of several profiles to attenuate background noise

Filtering and setting threshold to locate anomalous areas

Analyzing the profiles for the locations and orientations of anomalies

Interpolating profiles normal to strike ad centered on anomalies for more detail analysis

Comparing profiles with curves developed from models
Reduction to pole
magnetic inversion
Total magnetic intensity field
Magnetotelluric (MT)
MT is a passive method that employs measurements of naturally occurring electrical currents, or telluric currents, generated by magnetic induction of electrical currents in the ionosphere. Telluric currents flow with circular patterns in earth and change with geographical longitude and season.
Telluric currents have relatively low frequencies (2020000 Hz), so MT can be used to determine electrical properties of materials at relatively great depths (down to and including the mantle) inside the Earth.
In this technique, a time variation in electrical potential is measured at a base station and at survey stations. Differences in the recorded signal are used to estimate subsurface distribution of electrical resistivity.
MT is of great importance in petroleum exploration and has been used to map salt domes and anticlines.
MT inversion: Salt body with max depth of 5.5 km is imaged.
Electromagnetic (EM)
EM methods come in a wide variety of different configurations:

Surface

Borehole

Surfacetoborehole

Crossborehole
The electromagnetic fields may be of natural origin (magneto telluric MT) or generated by artificial sources. They are quasistatic (DC resistivity) or timedependent. The latter are processed either in the time domain (transient electromagnetic TEM) or in the frequency domain (controlledsource electromagnetic CSEM). A virtual experiment serves for identifying the appropriate EM method and a suitable experimental design for resolving the desired target.
Crosswell EM
Marine CSEM receivers
Acquiring CSEM data
CSEM signal
Multichannel transient EM (MTEM) : the source puts in a measured timevarying current. The receiver measures a timevarying voltage, which is the convolution of the current input with the impulse response of the earth, plus noise. We deconvolve the received voltage for the measured input to get the earth impulse response.
MTEM impulse response of 1D model on land: This function contains all the information about the subsurface resistivity. The response starts with a deltafunction at t = 0, whose strength depends on the surface resistivity. This is the ‘air wave’. The air wave precedes the earth impulse response.
EM real time processing
EM defines extent of potential hydrocarbon charge
Integrated seismic and EM data imaging
Waterflooding into a black oil reservoir (top), marine CSEM finite element modeling (middle), and 4D CSEM modeling indicating the potential of EM data to monitor water flooding (bottom)
Seismic
We provide the following services to our clients:

Supervision/consultancy of seismic projects

Targetoriented seismic survey design and modeling

Seismic data acquisition

Offshore & land

Dynamite & vibrator


Seismic data processing

PSTM, PSDM, and FWI

Isotropic & Anisotropic

PostMigration Reprocessing (PMR)

Timelapse data matching

Conventional and multicomponent (3C)

VSP processing (zerooffset, offset, walkaway)


Seismic data interpretation

Quantitative interpretation (QI)

Petrophyscial evaluation using well logs and core data

Seismic petrophysics and rock physics modeling

Amplitude vs. Offset (AVO)

Seismic inversion (post & prestack; deterministic and stochastic )

Anisotropy analysis and AVOZ for fracture detection

Facies classification (lithology, porosity, fluid)

4D (timelapse) feasibility study, modeling, inversion

Seismic reservoir history matching

Multicomponent feasibility study, modeling, and inversion

Seismic geomechanics

Pore pressure and fracture gradient (PPFG)

Reservoir depletion

Wellbore stability

Well placement


Unconventional resource play

Application of machine learning in seismic analysis

Seismic stratigraphy to detect lateral variations of stratigraphic traps

Optimum fault detection using modern algorithms

Acquiring seismic data on land and offshore
Full elastic seismic modeling in complex geology
Seismic survey design and modeling (ray tracing)
Priority inhouse 1D seismic modeling
Seismic data processing
4D seismic data conditioning (alignment, filtering, frequency boosting, noise attenuation)
Seismic gather conditioning for quantitative interpretation (QI)
Seismic AVO analysis for facies classification
Wedge modeling
Seismic well tie and wavelet extraction
Stochastic coupled seismic and wavelet inversion
Differential Effective Medium (DEM) theory: Rock physics modeling
Rock physics modeling using ultrasonic core for a dualporosity carbonate
Rock physics and associated seismic modeling
PDF of seismicderived vuggy porosity verified by well logs and thin section