gravstat™ a oex technology registered in the u. s. patent and trademark office and offered through...
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GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™A method of determining seismic statics
from gravity data.
An OEX TechnologyRegistered in the U.S. Patent and Trademark Office offered through
Lockhart Geophysical.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
What is the goal of GravStat™?
To determine seismic statics through the interpretation of high spatial frequency gravity anomalies caused by lateral changes in near surface geology.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ Model
d (ft)
D (ft)
²g (mgal)
static t (ms)
Psw—Vsw
Pw—Vw
Psw > Pw
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Datum Velocity & Bouguer Density
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Pb = 1.7 g/ccPb = 2.6 g/cc
Nettleton Density Profile
Pb = 2.2 g/cc
Pw = 2.2 g/cc; Vw = 8370 ft/sec Vw = 2550 m/sec
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Bouguer Density Analysis in Sandunes
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Density and Velocity are relatedby Gardner's Equation:
P = 0.23 V1
4
V (feet/sec)P (g/cc)
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ Model
d (ft)
D (ft)
²g (mgal)
static t (ms)
Psw—Vsw
Pw—Vw
Psw > Pw
Weathering Layer4000 ft/sec1219 m/sec
Sub Weathering Layer8000 ft/sec2438 m/sec
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
ms/mGal Nomogram
28 ms/mGal
17 ms/mGal6000
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Bouguer Density Analysis in Sandunes
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ Statics in Sandunes
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
The GravStat™ Method
• Acquire un-aliased gravity data coincident with the seismic source and receiver locations.
• Remove elevation, topographic and regional effects from the gravity data.
• Invert the high frequency residual gravity data into a surface consistent static correction.
• Calculate and apply the statics optimizing the regional gravity and the GravStat™ inversion.
• Analyze the processed seismic data for clarity and accuracy to known geology.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
The GravStat™ Method
• Acquire un-aliased gravity data coincident with the seismic source and receiver locations.
• Remove elevation, topographic and regional effects from the gravity data.
• Invert the high frequency residual gravity data into a surface consistent static correction.
• Calculate and apply the statics optimizing the regional gravity and the GravStat™ inversion.
• Analyze the processed seismic data for clarity and accuracy to known geology.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Spatial Aliasing of Gravity Data
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Typical 3D Survey Designs
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
3D Survey Design-1 (660 feet)
0.
1320.
2640.
3960.
5280.
5280. 3960. 2640. 1320. 0.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
3D Survey Design-2 (660 feet)
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
3D Survey Design-3 (660 feet)
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
3D Survey Design-4 (440 feet)
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
3D Survey Design-5 (300 feet)
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
The GravStat™ Method
• Acquire un-aliased gravity data coincident with the seismic source and receiver locations.
• Remove elevation, topographic and regional effects from the gravity data.
• Invert the high frequency residual gravity data into a surface consistent static correction.
• Calculate and apply the statics optimizing the regional gravity and the GravStat™ inversion.
• Analyze the processed seismic data for clarity and accuracy to known geology.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Bouguer Gravity Map (Delaware Basin)
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
The GravStat™ Method
• Acquire un-aliased gravity data coincident with the seismic source and receiver locations.
• Remove elevation, topographic and regional effects from the gravity data.
• Invert the high frequency residual gravity data into a surface consistent static correction.
• Calculate and apply the statics optimizing the regional gravity and the GravStat™ inversion.
• Analyze the processed seismic data for clarity and accuracy to known geology.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ Static Map (Delaware Basin)
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
The GravStat Method
• Acquire un-aliased gravity data coincident with the seismic source and receiver locations.
• Remove elevation, topographic and regional effects from the gravity data.
• Invert the high frequency residual gravity data into a surface consistent static correction.
• Calculate and apply the statics optimizing the regional gravity and the GravStat™ inversion.
• Analyze the processed seismic data for clarity and accuracy to known geology.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
3D Shot RecordOnly elevation statics applied
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
3D Shot RecordElevation andGravstat™ statics
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
The GravStat Method
• Acquire un-aliased gravity data coincident with the seismic source and receiver locations.
• Remove elevation, topographic and regional effects from the gravity data.
• Invert the high frequency residual gravity data into a surface consistent static correction.
• Calculate and apply the statics optimizing the regional gravity and the GravStat™ inversion.
• Analyze the processed seismic data for clarity and accuracy to known geology.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Refraction Statics Section (glacial till)
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ Statics Section (glacial till)
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Set A - Refraction Statics without Autostatics
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Set B - GravStat Statics without Autostatics
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Set C - Final Refraction Static Section
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Set D - Final GravStat Static Section
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Advantages of GravStat™
• High velocity over low.• Not dependent on the quality of the seismic first
breaks.• Automatically compensates for velocity
variations in the weathering and sub-weathering.• Long period statics are resolved.• Subtle features such as faults are more clearly
imaged with GravStat™ reason less autostatic smear.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Advantages of GravStat™
• High velocity over low.• Not dependent on the quality of the seismic first
breaks.• Automatically compensates for velocity
variations in the weathering and sub-weathering.• Long period statics are resolved.• Subtle features such as faults are more clearly
imaged with GravStat™ reason less autostatic smear.
• THE SEISMIC WILL NOW TIE TO THE WELLS
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
A Kansas example how GravStat™ was used to tie to
known well control.
This example is a comparison of two interpretations; one using seismic data processed with refraction, and the other
using seismic data processed using GravStat™.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Refraction - Interpretation
• The following three slides show a structural interpretation using seismic data processed with refraction statics.
• The survey is over a producing field - well control is shown by the green dots.
• Note how much the refraction velocity map must be distorted to tie to the known well control.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Refraction - Time Structure1046
104510
44
1044
1043
10
43
10
42
1041
10
41
10
40
1040
10
39
1039
10
38
1038
1038
10
38
1038
1037
10
37
10
37
1036
1036
1036
1035
1035
10
34
10
34
1033
1033
1032
886,399
886,399
887,592
887,592
888,785
888,785
889,978
889,978
891,171
891,171
892,364
892,364
893,557
893,557
894,750
894,7505
69
,06
15
70
,25
45
71
,44
75
72
,64
05
73
,83
35
75
,02
6
56
9,0
61
57
0,2
54
57
1,4
47
57
2,6
40
57
3,8
33
57
5,0
26
Contour interval = 1ms
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Refraction - Velocity to Depth4675
4675
4675
4650
4650
46504625
4625
46
25
4600
887,000
887,000
888,000
888,000
889,000
889,000
890,000
890,000
891,000
891,000
892,000
892,000
893,000
893,000
894,000
894,000
895,000
895,000
896,000
896,0005
69
,00
05
70
,00
05
71
,00
05
72
,00
05
73
,00
05
74
,00
05
75
,00
0
56
9,0
00
57
0,0
00
57
1,0
00
57
2,0
00
57
3,0
00
57
4,0
00
57
5,0
00
Contour interval = 5’/sec.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Refraction - Depth Map
-1080-1080
-1100-1100 -1120
-1120
-1120
-1140
-1140
-114
0
-1160
-116
0
887,000
887,000
888,000
888,000
889,000
889,000
890,000
890,000
891,000
891,000
892,000
892,000
893,000
893,000
894,000
894,000
895,000
895,000
896,000
896,0005
69
,00
05
70
,00
05
71
,00
05
72
,00
05
73
,00
05
74
,00
05
75
,00
0
56
9,0
00
57
0,0
00
57
1,0
00
57
2,0
00
57
3,0
00
57
4,0
00
57
5,0
00
Contour interval = 4 feet
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ - Interpretation
• The following three slides show a structural interpretation using seismic data processed with GravStat™ statics.
• As before, the well control is shown by the green dots.• Note how well-behaved and generally-flat the
calculated velocity map is compared to the refraction velocity map.
• Also note the similarities between the GravStat™ Time and Depth Maps.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ - Time Structure1210
12
08
1207
12
07
12
06
1206
1205
12
05
12
04
12
04
1203
12
03
1203
1202
12
02
1201
1201
1200
12
00
1199
119
9
119
8
119
8
119
7
119
7
119
7
119
6
1196
119611
95
1195
119
5
119
4
119
4
1194
119
4
119411
93
119
3
1193
1193
1193
1192
119
2
1192
1192
119
1
1191
119
1
1191
119
1
119
0
1190
1190
1190
118
9
1189
118
9
1189
118
81188
1188
118
7
1187
118
7
118
6
1186
1185
1184
887,000
887,000
888,000
888,000
889,000
889,000
890,000
890,000
891,000
891,000
892,000
892,000
893,000
893,000
894,000
894,000
895,000
895,000
896,000
896,0005
69
,00
05
70
,00
05
71
,00
05
72
,00
05
73
,00
05
74
,00
05
75
,00
0
56
9,0
00
57
0,0
00
57
1,0
00
57
2,0
00
57
3,0
00
57
4,0
00
57
5,0
00
Contour interval = 1ms
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ - Velocity to Depth
4050
4050
4050
4050
887,000
887,000
888,000
888,000
889,000
889,000
890,000
890,000
891,000
891,000
892,000
892,000
893,000
893,000
894,000
894,000
895,000
895,000
896,000
896,0005
69
,00
05
70
,00
05
71
,00
05
72
,00
05
73
,00
05
74
,00
05
75
,00
0
56
9,0
00
57
0,0
00
57
1,0
00
57
2,0
00
57
3,0
00
57
4,0
00
57
5,0
00
Contour interval = 5’/sec.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ - Depth Map
-1120-1120
-112
0
-112
0
-1140-1140
-1140
-1140
-1160
-1160
-11
80
-118
0
887,000
887,000
888,000
888,000
889,000
889,000
890,000
890,000
891,000
891,000
892,000
892,000
893,000
893,000
894,000
894,000
895,000
895,000
896,000
896,0005
69
,00
05
70
,00
05
71
,00
05
72
,00
05
73
,00
05
74
,00
05
75
,00
0
56
9,0
00
57
0,0
00
57
1,0
00
57
2,0
00
57
3,0
00
57
4,0
00
57
5,0
00
Contour interval = 4 feet
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Refraction - Depth Map
-1080-1080
-1100-1100 -1120
-1120
-1120
-1140
-1140
-114
0
-1160
-116
0
887,000
887,000
888,000
888,000
889,000
889,000
890,000
890,000
891,000
891,000
892,000
892,000
893,000
893,000
894,000
894,000
895,000
895,000
896,000
896,0005
69
,00
05
70
,00
05
71
,00
05
72
,00
05
73
,00
05
74
,00
05
75
,00
0
56
9,0
00
57
0,0
00
57
1,0
00
57
2,0
00
57
3,0
00
57
4,0
00
57
5,0
00
Contour interval = 4 feet
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ - Depth Map
-1120-1120
-112
0
-112
0
-1140-1140
-1140
-1140
-1160
-1160
-11
80
-118
0
887,000
887,000
888,000
888,000
889,000
889,000
890,000
890,000
891,000
891,000
892,000
892,000
893,000
893,000
894,000
894,000
895,000
895,000
896,000
896,0005
69
,00
05
70
,00
05
71
,00
05
72
,00
05
73
,00
05
74
,00
05
75
,00
0
56
9,0
00
57
0,0
00
57
1,0
00
57
2,0
00
57
3,0
00
57
4,0
00
57
5,0
00
Contour interval = 4 feet
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
GravStat™ - Time Structure1210
12
08
1207
12
07
12
06
1206
1205
12
05
12
04
12
04
1203
12
03
1203
1202
12
02
1201
1201
1200
12
00
1199
119
9
119
8
119
8
119
7
119
7
119
7
119
6
1196
119611
95
1195
119
5
119
4
119
4
1194
119
4
119411
93
119
3
1193
1193
1193
1192
119
2
1192
1192
119
1
1191
119
1
1191
119
1
119
0
1190
1190
1190
118
9
1189
118
9
1189
118
81188
1188
118
7
1187
118
7
118
6
1186
1185
1184
887,000
887,000
888,000
888,000
889,000
889,000
890,000
890,000
891,000
891,000
892,000
892,000
893,000
893,000
894,000
894,000
895,000
895,000
896,000
896,0005
69
,00
05
70
,00
05
71
,00
05
72
,00
05
73
,00
05
74
,00
05
75
,00
0
56
9,0
00
57
0,0
00
57
1,0
00
57
2,0
00
57
3,0
00
57
4,0
00
57
5,0
00
Contour interval = 1ms
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Refraction - Time Structure1046
104510
44
1044
1043
10
43
10
42
1041
10
41
10
40
1040
10
39
1039
10
38
1038
1038
10
38
1038
1037
10
37
10
37
1036
1036
1036
1035
1035
10
34
10
34
1033
1033
1032
886,399
886,399
887,592
887,592
888,785
888,785
889,978
889,978
891,171
891,171
892,364
892,364
893,557
893,557
894,750
894,7505
69
,06
15
70
,25
45
71
,44
75
72
,64
05
73
,83
35
75
,02
6
56
9,0
61
57
0,2
54
57
1,4
47
57
2,6
40
57
3,8
33
57
5,0
26
Contour interval = 1ms
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Conclusions
• The GravStat™ time structure map mimics the actual well control more accurately than the refraction time structure map.
• The GravStat™ velocity map is flatter, allowing for greater confidence in predicting prospects away from the existing well control.
• The time structure on the refraction static interpretation in the SW corner of the survey is probably not a valid prospect.
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Predicted Well Tie Results
GravStat
Refraction
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
ZEN...........ZEN........... and the Art of Small, Prospect Specific 3D Seismic Surveys in Oil and Gas Exploration
William A. Miller, CPG, PE
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
AN ATTEMPT TO QUANTIFY AN ATTEMPT TO QUANTIFY CONFIDENCE IN MAPPING CONFIDENCE IN MAPPING
STRUCTURESSTRUCTURES
Assuming Vint=7 ft/msec and picking accuracy of 1 msec, then express ConfidenceConfidence as:1-(accuracy in ft/structural relief)1-(accuracy in ft/structural relief)
– for 10’ of structure: Confidence=1-7/10 or 30%– for 14’ of structure: Confidence=1-7/14 or 50%– for 21’ of structure: Confidence=1-7/21 or 66%– for 28’ of structure: Confidence=1-7/28 or 75%
William A. Miller, CPG, PE
GravStat™ A OEX TechnologyRegistered in the U. S. Patent and Trademark Office and offered
through Lockhart Geophysical
Economics of GravStat™
A typically GravStat™ survey only adds 10% to the 3D seismic survey.
The true cost of a GravStat™ survey is considerably less if one considers the cost of drilling a dry hole!