Structural Geometry and Evolution of BED 17 Field, Abu El Gharadig

Structural Geometry and Evolution of BED 17 Field, Abu El Gharadig Basin, Northern Western Desert of Egypt:
An Example of Restraining Stepovers in Strike-Slip Fault Systems*
Wael Salah Said1, M. Yousef2, H. Z. El-Mowafy3, and A. Abdel-Halim4
Search and Discovery Article #20266 (2014)
Posted August 25, 2014
*Adapted from oral presentation given at LIPE & AAPG European Region Northern Arabia Geoscience Conference & Exhibition in Lebanon on May 27-29, 2014
**AAPG © 2014 Serial rights given by author. For all other rights contact author directly.
1
Badr Petroleum Company ([email protected])
Ain Shams University
3
Al-Azhar University
4
Shell
2
Abstract
The Qattara Fault system in BED 17 Field area provides an exceptional opportunity to study the contractional structures at strike-slip
restraining stepovers associated with principal deformation zones (PDZs) using high resolution three-dimensional (3-D) seismic reflection data,
as well as the evolution of a pop-up structure developed coevally with a rejuvenation of the pre-existing Abu El Gharadig Basin northern
bounding fault. The Abu El Gharadig Basin is perhaps the largest basin in the northern Western Desert, is bordered to the north by the Qattara
Platform and to the south by the Sitra Platform. The Abu El Gharadig Basin has a stratigraphic sequence having a variety of lithologies and
facies with ages extending from the Paleozoic to Miocene. The BED 17 pop-up structure shows strong similarities in structural geometry with
the analog models discussed by previous study which provided guidelines for interpretation of seismic sections. In this case study the pop-up
structure is a small and narrow positive flower structure. The 3-D geometry of the pop-up structure is well-defined in Cretaceous sedimentary
rocks above restraining stepovers in an offset dextral strike-slip fault. Because of uplift, unconformity was formed due to partial erosion and
subsequent on-lapping within Khoman strata. The bounding faults to the pop-up structure are very steep with dips of ~75o in cross section view
and have a rhomboidal shape in map view. Within the Abu Roash sequence, the strongly uplifted region was interpreted across the center of the
pop-up structure and largely shows symmetrical doubly plunging anticline with a hinge line striking counter to the overall dextral shear
displacement of the main fault system.
The initiation of the pop-up structure was coeval with the Syrian Arc deformation at the climax of the convergence motion between the African
and Eurasian plates during the Late Cretaceous. Hence locally the inversion started in Santonian time and continued during the deposition of
the Khoman strata in pulses, as demonstrated by unconformities (on-lapping and truncation), and ended in Middle Paleocene.
Reference Cited
McClay, K., and M. Bonora, 2001, Analog models of restraining stepovers in strike-slip fault systems: AAPG Bulletin, v. 85/2, p. 233-260.
Structural geometry and evolution of
BED 17 Field
Abu El Gharadig Basin
North Western Desert of Egypt
“An example of Restraining stepovers in strike-slip fault systems ”
W. S. Said, M. Yousef, H. Z. El-Mowafy, A. Abdel-Halim
May 2014
Contents

An overview of the study area.

BED17 old structure model.

Strike-Slip Stepover structure styles.

BED17 new structural interpretation.

Outcrops Examples of Pop-Up Structures.

The impact of new model on hydrocarbon potential.
Abu El Gharadig Basin
Simplified tectonic map showing the main basins in the Northwestern Desert
Western Desert Stratigraphy & Tectonic Episodes
GENERALIZED STRATIGRAPHIC SEQUENCE OF
NORTHWESTERN DESERT
Regional Geo-Seismic Cross-Section
Qattara High
Abu El Gharadig Basin
Tertiary extension
Cretaceous Rifting
Jurassic Rifting
5 Km
Sitra
Platform
BED17 field overview
•
•
•
•
BED 17 field lies on the
downthrown side of the northern
main bounding fault of the Abu El
Gharadig
It was discovered in 1989 through
BED17-1.
Four wells have been drilled to
date.
The production mainly comes from
the upper Cretaceous ,Abu Roash C
sandstone oil-bearing reservoir.
Deeper reservoirs were found
water bearing in all wells .
Qattara High
BED17 old structure model
Qattara High
C.I: 100 m
BED 17 Development Lease
Old Abu Roash C Depth Map
Releasing stepover
Restraining stepover
(after McClay, 2001.)
BED17 New structural interpretation
PDZa
1 Km
Time slice (Semblance) display at the upper Cretaceous section (Abu Roash Fm. @1350 ms).
C.I: 1 m
Qattara High
100 m
BED 17 Development Lease
C.I: 200 m
Abu Roash-F Depth Map
Qattara High
Zone eroded
BED 17 Development Lease
C.I: 100 m
Abu Roash-C Depth Map
BED17 New structural interpretation
BED17 New structural interpretation
1
3
2
3
4
5
6
8
Unconformity
7
PDZa
9
Cretaceous Sequence
11
A
T
1.
1
Top Apollonia A
2.
2
Top Apollonia D
3.
3
Top Khoman A
4.4
Top Abu Roash A
5.
5
Top Abu Roash B
6.6
Top Abu Roash C
7.
7
Top Abu Roash F
8.
8
Top Alamein
9.9
Top Masajid
10.
10
11.
11
Top Palaeozoic
Basement
BED17 New structural interpretation
BED17 New structural interpretation
1
2
Unconformity
7
Cretaceous Sequence
3
8
4
5
6
9
1.
1
Top Apollonia A
2.
2
Top Apollonia D
3.
3
Top Abu Roash A
4.
4
Top Abu Roash B
5.
5
Top Abu Roash C
6.
6
Top Abu Roash F
7.
7
Top Alamein
8.
8
Top Masajid
9.
9
Top Palaeozoic
BED17 New structural interpretation
BED17 New structural interpretation
1
Paleocene time
2
Santonian time
Unconformity
7
3
4
5
8
6
9
Cretaceous
Sequence
1.
1
Top Apollonia A
2.
2
Top Apollonia D
3.
3
Top Abu Roash A
4.
4
Top Abu Roash B
5.
5
Top Abu Roash C
6.
6
Top Abu Roash F
7.
7
Top Alamein
8.
8
Top Masajid
9.
9
Top Palaeozoic
Echo Hills, Southeastern Nevada, USA
Owl Creek Mountains, Central Wyoming, USA
(after McClay, 2001.)
Qattara High
BED 17 Development Lease
C.I: 100 m
Abu Roash-C Depth Map

The northwestern desert was affected by Syrian arc deformation, which is
evident by the BED 17 field structural interpretation .

This model shows strong similarities in structural geometries to the analog
models from natural and experimental examples of pop-up structures.

BED 17 field is a good structural example of restraining stepovers in dextral
strike-slip fault systems.

The new field map provides a better understanding of the field and drilled
wells.

Impact: upside potential and new drill locations.

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