HETEROGENEOUS GRAVITY DATA COMBINATION FOR

HETEROGENEOUS GRAVITY DATA COMBINATION
FOR GEOPHYSICAL EXPLORATION RESEARCH
Linking satellite gravity gradients to basin maturity;
Case study for basin and petroleum system analysis in the
Arabian Peninsula
J.A.C. Meekes, Rader Abdul Fattah, S. Colella (TNO), J. Bouman, M. Schmidt (DGFI)
J. Ebbing (NGU), R. Haagmans (ESA)
THE GOCE SATELLITE MISSION PROVIDES
GRAVITY MEASUREMENTS WITH
UNPRECEDENTED ACCURACY AND SPATIAL
RESOLUTION. THE GOCE DATA ARE USED TO
STUDY THE CRUSTAL AND LITHOSPHERIC
STRUCTURES IN THE NORTH-EAST ATLANTIC
MARGIN AND IN THE RUB’ AL-KHALI DESERT
(SAUDI ARABIA). THE OUTCOME IS USED TO
MODEL THE TECTONIC HEAT FLOW WHICH
CONTRIBUTES TO THE EVALUATION OF THE
MATURITY OF THE MAIN PETROLEUM SYSTEMS.
Introduction
GOCE was launched by the European Space Agency
(ESA) in 2009 to measure the gravity gradient with
high accuracy and spatial resolution. Two application
fields for GOCE data are considered in our ongoing
project:
- The well explored and understood North-East
Atlantic Margin. The sensitivity of satellite gravity
and gradients will be compared to a lithospheric
model established by integrating sources like
seismic, magnetic and terrestrial gravity data.
This analysis will provide a sensitivity matrix for
different types of gravity data, which can be used
for forward or inverse modeling.
- In the Rub' al-Khali desert the GOCE data will be
used to understand the structure of the crust and
the lithosphere on a regional scale which will
improve the estimation of maturity in the basin.
This multi-party project has started in 2011 and will
last for two years.
Application to the Arabian Peninsula
Methodology
GOCE gravity gradient data, in combination with other
data, will be used to better identify the structure and
composition of the crust and the lithosphere in the area.
Gravimetrical modelling of the basin will be performed in
order to identify basement inhomo-geneities and Moho
topography.
The improved
model of the crust
and the lithosphere
will allow us to
calculate the
history of the basal
heat flow in the
area. Based on
that, the maturity
of the main source
rock units will be
estimated (Fig. 2).
1. Gravity data combination and analysis
The GOCE gravity gradients in the gradiometer reference
frame will be used in forward and/or inverse modeling.
The original gravity gradients be used as much as
possible in the project, but it will also be combined with
other gravity data, e.g. from GRACE, Satellite Altimetry
or terrestrial gravity. Grids of gravity gradients will be
computed at various levels.
Within our project, the GOCE gravity gradient will first
be evaluated in the well explored and understood North
Atlantic Margin. The experience gathered here will be
used as input to the Rub’ Al-Khali study. This includes a
systematic analysis of the sensitivity to different
lithosphere depths for the gravity potential, the gravity
and the gravity gradient. The different accuracies of the
different GOCE gradiometers is included as well.
2. Input geological model
3. Heat flow modelling
The Arabian Peninsula is one of the key hydrocarbon
producing regions in the world. The main petroleum
systems in the region (the Paleozoic and Jurassic
systems) are well explored in the eastern part of the
Peninsula, but less understood further to the south
and in the Rub’ Al-Khali basin (Fig. 1).
The model includes the radiogenic heat of the basement due
to the effect of radiogenic elements in the crystalline basement.
Different structures in the basement with different radiogenic
element concentrations can result in variations in heat flow.
Fig 2: The workflow for using the GOCE gravity
data for basin maturity evaluation.
A geological model of the study area will be built. It is
used in the gravity inversion, heat flow and maturity
modeling. The geological model is based on public and
literature data. It includes the sedimentary succession as
well as the crust (Fig. 3).
Fig 1: Simplified map of the Arabian Plate and main geologic
and tectonic features. The study area (the Rub’ Al-Khali basin)
is shown in the red frame (modified after Pallastro, 2003).
Fig 3: Left panel: Depth top basement (modified after Konert et. Al, 2001)
repoduced by permission from GeoArabia.
Right panel: Geological cross section through Saudi Arabia (Pallastro, 2003).
We use a grid-based stochastic tool (PetroProb)
developed by TNO to model basal heat flow.
Calculated tectonic heat flow is derived from the
stretching of the crust and lithosphere. The tool
relies on the inversion of basin subsidence data to
calculate the tectonic subsidence in the area and
the tectonic heat flow (Fig. 4).
Fig 4: Schematic of the tectonic model of the lithosphere on which the basal
heat flow modeling tool (PetroProb) is based (modified after Van Wees
et al., 2008).
4. Maturity of petroleum systems
The maturity of the source rocks in the basin are estimated
based on the modeled heat flow. Regional maturity maps of
the Paleozoic and Mesozoic systems in the Rub Al-Khali basin
are produced. The crust and lithosphere models, derived from
GOCE gravity data, as well as the produced maturity maps will
be calibrated to known measurements in the area.
Summary
This study will demonstrate the added-value of the GOCE
gravity gradient data for hydrocarbon exploration in
underexplored basins such as the Rub’ Al-Khali area. The
resolution of GOCE gradient may help in mapping crustal
structures as well as the topography of the Moho. This will
have direct applications for heat flow modeling and thus
source rock maturity.
References
• Konert, G., A.M. Al-Afifi, Al-Hajri, Droste, H.D., 2001, GeoArabia, v. 6, no. 3,
p. 407-442.
• Pollastro. R.M., 2003, U.S. Geological Survey Bulletin 2202-H.
• Van Wees, J.D., Abdul Fattah, R., Bonte, D., Abbink, O., Cloetingh, S.,
2008, TNO report. PP. 65.