gamma environmental pathfinder
TRANSCRIPT
104
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
Chart: POR-1a and POR-1b (Gamma Ray Environmental Corrections - Mud Weight and Borehole Size)
Find the chart for the correct tool size (4.75", 6.75", 8.0", or 9.5") and tool position (centered or eccentered).
Enter the chart on the Borehole Diameter axis at the correct borehole diameter.
Project vertically to the curve corresponding to the correct value of the mud weight, then project horizontally to the GRcor/GR axis and read off the correction factor.
Multiply the log value of the Gamma reading by the correction factor.
Under the standard reference conditions for PathFinder Gamma Ray tools, the tool is centered in an 8.5 inch borehole, and both the tool and the borehole are filled with fresh water. In the field, however, the conditions are usually not standard, and the field logs are generally not presented with gamma ray values corrected for borehole size and mud weight.
Apply any potassium chloride (KCl) correction (charts POR-1c through POR-1j) before correcting for mud weight and borehole size.
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2.
To determine the approximate correction applied to HDS1 and CWR Gamma readings due to mud weight and borehole size.
Assume that a Gamma log taken with a 6.75 inch collar centered in a 9 inch borehole reads 65 API and was drilled with a 12 lb/gal mud. The chart (third down on POR-1a) indicates that the correction factor is 1.12. The corrected reading is then 65*1.12 = 72.8
Applications:
Directions:
Example:
Notes:
POR-1a
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
Gamma Ray Mud Weight and Borehole Size Corrections4.75 inch and 6.75 inch Tools
0.5
0.70.9
1.1
1.31.5
1.7
1.9
2.12.3
2.5
6 7 8 9 10 11 12 13 14Borehole Diameter (in)
GR
co
r/GR
8
12
1618 lb/gal4.75 in tool, centered
0.75
1.00
1.25
1.50
1.75
2.00
6 7 8 9 10 11 12 13 14Borehole Diameter (in)
GR
cor/G
R
8
12
1618 lb/gal
4.75 in tool, eccentered
0.5
1.0
1.5
2.0
2.5
3.0
8 9 10 11 12 13 14 15 16Borehole Diameter (in)
GR
cor/G
R
8
12
1618 lb/gal
6.75 in tool, centered
0.75
1.00
1.25
1.50
1.75
2.00
8 9 10 11 12 13 14 15 16Borehole Diameter (in)
GR
cor/G
R
8
12
1618 lb/gal6.75 in tool, eccentered
POR-1b
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
Gamma Ray Mud Weight and Borehole Size Corrections8.0 inch and 9.5 inch Tools
0.5
1.0
1.5
2.0
2.5
3.0
3.5
10 11 12 13 14 15 16 17 18Borehole Diameter (in)
GR
cor/G
R
8
12
1618 lb/gal8.0 in tool, centered
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
10 11 12 13 14 15 16 17 18Borehole Diameter (in)
GR
cor/G
R
8
12
1618 lb/gal8.0 in tool, eccentered
1.0
1.5
2.0
2.5
3.0
3.5
4.0
12 13 14 15 16 17 18 19 20Borehole Diameter (in)
GR
cor/G
R
8
12
1618 lb/gal9.5 in tool, centered
1.0
1.5
2.0
2.5
3.0
12 13 14 15 16 17 18 19 20Borehole Diameter (in)
GR
cor/G
R
8
12
1618 lb/gal
9.5 in tool, eccentered
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
Chart: POR-1c through 1j (Gamma Ray Environmental Corrections - Potassium Mud)
Find the chart for the correct tool size (4.75", 6.75", 8.0", or 9.5"), tool position (centered or eccentered), and mud weight (10, 12, 14, or 16 lb/gal). If you need corrections for a mud weight other than those given, find the corrections for the given mud weights and interpolate linearly to the needed mud weight.
Enter the chart on the Borehole Diameter axis at the correct borehole diameter.
Project vertically to the curve corresponding to the correct value of the KCl concentration, then project horizontally to the KCl Correction axis and read off the correction.
Subtract the correction from the log value of the Gamma reading..
KCl corrections must be applied before mud weight and hole size corrections.
If you have the potassium concentration in terms of pounds per barrel (ppb) KCl or mg/liter potassium ion (K+), use the following equations to convert to % KCl by weight:
(% KCI) = -0.000378*(ppb KCI)2 + 0.2818*(ppb KCI) + 0.0247
(ppb KCI) = (mg/liter K+)/1500
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2.
3.
4.
1.
2.
To determine the approximate correction applied to HDS1 Gamma readings due to potassium chloride (KCl) in the drilling mud.
Assume that a Gamma log taken with a 4.75 inch collar eccentered in an 8 inch borehole reads 97 API and that the 12 lb/gal drilling mud was made with 10% KCl by weight. The chart (POR-1d, second down) indicates that the KCl correction is 18 API, so the corrected reading is 97 - 18 = 79 API.
Assume that a Gamma log taken with a 8.0 inch collar centered in a 12 inch borehole reads 135 API and that the 12.6 lb/gal drilling mud was made with 15% KCl by weight. The 12 lb/gal chart on POR-1g indicates an 79 API correction, and the 14 lb/gal chart on POR-1g indicates a 68 API correction for 14 lb/gal mud. The interpolated correction for 12.6 lb/gal is
The corrected log reading is then 135 - 76 = 59 API.
Applications:
Directions:
Example:
Notes:
Corection = 79 + (68 - 79) = 76 API (12.6 - 12)
(14 - 12)
POR-1c
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
HDS1 Gamma Ray Potassium Mud Corrections4.75 inch Tool, Centered
0
20
40
60
80
100
120
140
6 7 8 9 10 11 12 13 14
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
10 lb/gal mud, centered tool
0
20
40
60
80
100
120
6 7 8 9 10 11 12 13 14
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
12 lb/gal mud, centered tool
0
10
20
30
40
50
60
70
80
90
100
6 7 8 9 10 11 12 13 14
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
14 lb/gal mud, centered tool
0
10
20
30
40
50
60
70
80
6 7 8 9 10 11 12 13 14
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl16 lb/gal mud, centered tool
POR-1d
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
HDS1 Gamma Ray Potassium Mud Corrections4.75 inch Tool, Eccentered
0
20
40
60
80
100
120
6 7 8 9 10 11 12 13 14
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
10 lb/gal mud, eccentered tool
0
10
20
30
40
50
60
70
80
90
6 7 8 9 10 11 12 13 14
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl12 lb/gal mud, eccentered tool
0
10
20
30
40
50
60
70
80
6 7 8 9 10 11 12 13 14
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
14 lb/gal mud, eccentered tool
0
10
20
30
40
50
60
70
6 7 8 9 10 11 12 13 14
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
16 lb/gal mud, eccentered tool
POR-1e
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
HDS1 Gamma Ray Potassium Mud Corrections6.75 inch Tool, Centered
0
20
40
60
80
100
120
140
160
180
8 9 10 11 12 13 14 15 16Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl10 lb/gal mud, centered tool
0
20
40
60
80
100
120
140
160
8 9 10 11 12 13 14 15 16
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl12 lb/gal mud, centered tool
0
20
40
60
80
100
120
140
8 9 10 11 12 13 14 15 16
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
14 lb/gal mud, centered tool
0
20
40
60
80
100
120
8 9 10 11 12 13 14 15 16
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
16 lb/gal mud, centered tool
POR-1f
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
HDS1 Gamma Ray Potassium Mud Corrections6.75 inch Tool, Eccentered
0
20
40
60
80
100
120
140
160
8 9 10 11 12 13 14 15 16
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl10 lb/gal mud, eccentered tool
0
20
40
60
80
100
120
140
8 9 10 11 12 13 14 15 16
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl12 lb/gal mud, eccentered tool
0
20
40
60
80
100
120
8 9 10 11 12 13 14 15 16Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
14 lb/gal mud, eccentered tool
0
10
20
30
40
50
60
70
80
90
100
8 9 10 11 12 13 14 15 16Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl16 lb/gal mud, eccentered tool
POR-1g
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
HDS1 Gamma Ray Potassium Mud Corrections8.0 inch Tool, Centered
0
50
100
150
200
250
10 11 12 13 14 15 16 17 18
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl10 lb/gal mud, centered tool
0
50
100
150
200
250
10 11 12 13 14 15 16 17 18
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
12 lb/gal mud, centered tool
0
20
40
60
80
100
120
140
160
180
10 11 12 13 14 15 16 17 18
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl14 lb/gal mud, centered tool
0
20
40
60
80
100
120
140
160
10 11 12 13 14 15 16 17 18
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
16 lb/gal mud, centered tool
POR-1h
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
HDS1 Gamma Ray Potassium Mud Corrections8.0 inch Tool, Eccentered
0
50
100
150
200
250
10 11 12 13 14 15 16 17 18
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
10 lb/gal mud, eccentered tool
0
20
40
60
80
100
120
140
160
180
200
10 11 12 13 14 15 16 17 18
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
12 lb/gal mud, eccentered tool
0
20
40
60
80
100
120
140
160
10 11 12 13 14 15 16 17 18
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl14 lb/gal mud, eccentered tool
0
20
40
60
80
100
120
140
10 11 12 13 14 15 16 17 18
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl16 lb/gal mud, eccentered tool
POR-1i
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
HDS1 Gamma Ray Potassium Mud Corrections9.5 inch Tool, Centered
0
50
100
150
200
250
300
350
400
12 13 14 15 16 17 18 19 20
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl10 lb/gal mud, centered tool
0
50
100
150
200
250
300
350
12 13 14 15 16 17 18 19 20
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
12 lb/gal mud, centered tool
0
50
100
150
200
250
300
12 13 14 15 16 17 18 19 20
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
14 lb/gal mud, centered tool
0
50
100
150
200
250
12 13 14 15 16 17 18 19 20
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
16 lb/gal mud, centered tool
POR-1j
LWD Log Interpretation Charts PathFinder Energy Services, Inc., 2002
HDS1 Gamma Ray Potassium Mud Corrections9.5 inch Tool, Eccentered
0
50
100
150
200
250
300
350
400
12 13 14 15 16 17 18 19 20
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
10 lb/gal mud, eccentered tool
0
50
100
150
200
250
300
350
12 13 14 15 16 17 18 19 20
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
12 lb/gal mud, eccentered tool
0
50
100
150
200
250
300
12 13 14 15 16 17 18 19 20
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
14 lb/gal mud, eccentered tool
0
50
100
150
200
250
12 13 14 15 16 17 18 19 20
Borehole Diameter (inches)
KC
l C
orr
ecti
on
(A
PI)
5% KCl
15% KCl
25% KCl
16 lb/gal mud, eccentered tool