SEAM PHASE I GRAVITY

1
SEAM PHASE I GRAVITY

• Neda Bundalo

2
SEAM PHASE I GRAVITY MODEL
DENSITY MODEL- Cell size 40x40x20 m- Density
range 1.003 3.140 (2.64) g/cm3

SEAM Phase I model density cube
3
SEAM PHASE I GRAVITY MODEL
CALCULATED GRAVITY Gravity (vertical
component) Gz and six tensor components
(gradients) Txx, Txy, Txz, Tyy, Tyz, Tzz,-
GMSYS 3D (Geosoft) and 3MOD (LCT Fugro),-
free-air and Bouguer anomalies on two
calculation levels 0 m for marine and 150 m
for airborne data,- recommended data storage
formats Geosoft grid and ascii xyzg.

Vector (beige) and tensor (red) components of
gravity field after Murphy, 2004.
4
SEAM PHASE I GRAVITY MODEL
CALCULATED GRAVITY - with and without
background density - density of 2.2 g/cm3 used
as a background density (mean voxel density)
- density of 2.0 g/cm3 used for Bouguer
correction

SEAM Phase I model vertical density slice
5
SEAM PHASE I GRAVITY MODEL
Free-air anomalies at sea level background
density 2.2 g/cm3
Txy
Txx
Txz


Tyz
Tyy
Gz
Tzz
6
SEAM PHASE I GRAVITY MODEL
Free-air anomalies at 150 m level background
density 2.2 g/cm3
Txy
Txx
Txz


Tyz
Tyy
Gz
Tzz
7
SEAM PHASE I GRAVITY MODEL
Bouguer anomalies at sea level Bouguer correction
density 2.0 g/cm3 background density 2.2 g/cm3
Txy
Txx
Txz


Tyz
Tyy
Gz
Tzz
8
SEAM PHASE I GRAVITY MODEL
Bouguer anomalies at 150 m level Bouguer
correction density 2.0 g/cm3 background density
2.2 g/cm3
Txy
Txx
Txz


Tyz
Tyy
Gz
Tzz
9
SEAM PHASE I GRAVITY MODEL
Free-air anomalies at sea level, background
density 2.2 g/cm3

10
SEAM PHASE I GRAVITY MODEL
Free-air anomalies at 150 m level, background
density 2.2 g/cm3

11
SEAM PHASE I GRAVITY MODEL
Bouguer anomalies at sea level, Bouguer
correction density 2.0, background density 2.2
g/cm3

12
SEAM PHASE I GRAVITY MODEL
Bouguer anomalies at 150 m level, Bouguer
correction density 2.0, background density 2.2
g/cm3

13
SEAM PHASE I GRAVITY MODEL
RANGES OF GRAVITY ANOMALIES AND CORRESPONDING
GRADIENTS

14
SEAM PHASE I GRAVITY MODEL
NEXT STEP COMPARISON OF BASE OF SALT
INVERSIONS USING VERTICAL COMPONENT AND GRAVITY
GRADIENTS
CONTRIBUTORSDr. Neda Bundalo (Marathon Oil),
Dr. Richard Day (ConocoPhillips), John Bain (Bain
Geophysical Services, Inc.)THANKS TODr. Xiong
Li, Barry Wiggins, Pat Quist (Fugro Gravity and
Magnetics Services, Inc.), Dr. Stuart Hall
(Department of Geosciences, University of
Houston), Dr. Irina Filina (Hess)