Method and system for detecting downhole magnetic interference on measurement while drilling operations
A method and a system implementing the method, are disclosed for computing magnetic interferences in measurement while drilling operations, using the retrieved lateral, and axial magnetic interferences of the measurement while drilling downhole tool system. With the disclosed method and system of implementing the method, it can be determined whether the source of the magnetic interference is from the measurement while drilling downhole tool system lateral direction or its axial direction. When magnetic field strength is abnormal, the lateral and axial magnetic interferences are monitored, and then compared against their values before the abnormal magnetic field strength. This way the direction of the magnetic interference is analyzed to eliminate or judge the cause of the interference, and properly guide the measurement while drilling downhole tool system towards its reservoir or well location.
1. A system for detecting magnetic interferences, comprising:
a measurement while drilling downhole tool system comprising a three-axis accelerometer sensor, a three-axis magnetometer sensor, a temperature sensor, a memory resource for storing data corresponding to operations of acquiring, computing, and generating, and a non-transitory computer readable memory device;
a telemetry system for sending and receiving data of inclination, azimuth, gravity tool face, magnetic tool face, magnetic dip, total gravity field strength, and total magnetic field strength, connected to the measurement while drilling downhole tool system;
a computer system output device;
wherein the non-transitory computer readable memory device is coupled to the memory resource, coupled to the telemetry system, coupled to the computer system output device, and is programmed to perform operations of:
storing the received data of inclination, azimuth, gravity tool face, magnetic tool face, magnetic dip, total gravity field strength, and total magnetic field strength to the memory resource;
retrieving the stored data of inclination, azimuth, gravity tool face, magnetic tool face, magnetic dip, total gravity field strength, and total magnetic field strength from the memory resource;
computing a magnetic field intensity using the retrieved data of inclination, azimuth, gravity tool face, magnetic tool face, magnetic dip, total gravity field strength, and total magnetic field strength;
generating a magnetic field intensity from a computed total magnetic field strength;
storing the generated magnetic field intensity to the memory resource;
retrieving the stored magnetic field intensity from the memory resource;
computing a lateral magnetic field intensity using the retrieved data of inclination, azimuth, gravity tool face, magnetic tool face, magnetic dip, total gravity field strength, and total magnetic field strength, and the retrieved magnetic field intensity;
storing the computed lateral magnetic field intensity to the memory resource;
computing an axial magnetic field strength using the retrieved data of inclination, azimuth, gravity tool face, magnetic tool face, magnetic dip, total gravity field strength, and total magnetic field strength, and the retrieved magnetic field intensity;
storing the computed axial magnetic field strength to the memory resource;
repeating the steps of storing received data, retrieving the stored data, generating a magnetic field intensity, storing the generated magnetic field intensity, retrieving the stored magnetic field intensity, computing a lateral magnetic field intensity, storing the lateral magnetic field intensity, computing an axial magnetic field strength, and storing the axial magnetic field strength;
monitoring a stored magnetic field intensity, a stored lateral magnetic field intensity, and a stored axial magnetic field strength for every repeated step;
determining a difference between the stored magnetic field intensity and a local magnetic field intensity after every repeated step;
determining a presence of magnetic interference based on a magnitude of the difference; and
computing the magnetic interference for a measurement while drilling downhole tool system by calculating a change in the stored lateral magnetic field intensity and a change in the stored axial magnetic field strength.
2. The system of claim 1 , wherein computing the lateral magnetic field intensity comprises an expression:
B
xy
=
B
m
×
{
1
-
[
1
2
×
(
cos
(
AZI
)
×
sin
(
INC
)
cos
(
DIP
)
+
1
cos
(
AZI
)
×
sin
(
INC
)
cos
(
DIP
)
-
sin
2
(
AZI
)
×
cos
(
DIP
)
×
sin
(
INC
)
cos
(
AZI
)
-
sin
2
(
DIP
)
×
cos
(
AZI
)
×
sin
(
INC
)
cos
(
DIP
)
-
cos
2
(
INC
)
×
cos
(
DIP
)
cos
(
AZI
)
)
-
cos
(
INC
)
×
sin
(
DIP
)
]
2
}
1
2
.
3. The system of claim 1 , wherein computing the axial magnetic field strength comprises an expression:
B
z
=
B
m
×
(
1
2
×
(
cos
(
AZI
)
×
sin
(
INC
)
cos
(
DIP
)
+
1
cos
(
AZI
)
×
sin
(
INC
)
cos
(
DIP
)
-
sin
2
(
AZI
)
×
cos
(
DIP
)
×
sin
(
INC
)
cos
(
AZI
)
-
sin
2
(
DIP
)
×
cos
(
AZI
)
×
sin
(
INC
)
cos
(
DIP
)
-
cos
2
(
INC
)
×
cos
(
DIP
)
cos
(
AZI
)
)
-
cos
(
INC
)
×
sin
(
DIP
)
)
.