Utilization of dynamic downhole surveying measurements
View Patent ↗A method for making dynamic gravity toolface measurements while rotating a downhole measurement tool in a borehole is disclosed. The method includes processing magnetic field measurements and accelerometer measurements to compute a toolface offset and further processing the toolface offset in combination with a magnetic toolface to obtain the dynamic gravity toolface. Methods for correcting dynamic and static navigational sensor measurements to remove sensor biases, for example, are also disclosed.
1. A method of drilling in a borehole, comprising:
(a) deploying and rotating a bottom hole assembly (BHA) in the borehole, the bottom hole assembly comprising a downhole tool, a drill bit, and a steering tool, the downhole tool including first and second cross-axial magnetic field sensors and first and second cross-axial accelerometers;
(b) causing the downhole tool to make first and second cross-axial magnetic field measurements and first and second cross-axial accelerometer measurements while the downhole tool is rotating in (a), wherein the first and the second cross-axial magnetic field measurements do not include a z-axis magnetic field measurement;
(c) processing the cross-axial magnetic field measurements obtained in (b) to compute a magnetic toolface;
(d) processing the cross-axial magnetic field measurements and the cross-axial accelerometer measurements obtained in (b) to compute a dynamic toolface offset, wherein the dynamic toolface offset is computed over a plurality of measurements according to the following equation:
T
-
M
=
arc
tan
[
∑
(
B
x
A
y
-
B
y
A
x
)
-
∑
(
B
x
A
x
+
B
y
A
y
)
]
wherein T−M represents the dynamic toolface offset with T representing a gravity toolface and M representing the magnetic toolface, B x and B y represent the first and second cross-axial magnetic field measurements, and A x and A y represent the first and second cross-axial accelerometer measurements;
(e) processing the magnetic toolface computed in (c) and the dynamic toolface offset computed in (d) to compute a dynamic gravity toolface;
(f) processing the gravity toolface computed in (e) in a rotary steerable tool deployed in the BHA to compute a direction of subsequent drilling of the wellbore; and
(g) adjusting the rotary steerable tool to change a direction of drilling along the direction of subsequent drilling computed in (f).
2. The method of claim 1 , wherein the magnetic toolface is computed in (c) according to a following mathematical equation of:
M
=
arc
tan
B
x
B
y
3. The method of claim 1 , wherein (d) further comprises:
(i) processing the cross-axial magnetic field measurements and the cross-axial accelerometer measurements obtained in (b) to compute a preliminary dynamic toolface offset;
(ii) processing the magnetic tool face obtained in (c) to compute a rotation rate of the downhole tool; and
(iii) processing the preliminary dynamic toolface offset and the rotation rate of the downhole tool to compute the dynamic toolface offset.
4. The method of claim 3 , wherein (iii) comprises correcting the preliminary dynamic toolface offset to a zero-rpm equivalent value.
5. The method of claim 1 , further comprising:
(h) processing the dynamic gravity toolface computed in (e) in combination with logging while drilling data to create a logging while drilling image.
6. The method of claim 1 , wherein the downhole tool is one of a logging while drilling tool and a rotary steerable tool.
7. The method of claim 1 , where (a) further comprises utilizing a downhole controller to control a rotation rate of the downhole tool with respect to the borehole.
8. The method of claim 1 , wherein the downhole tool and the steering tool are within the same housing.
9. The method of claim 1 , wherein (g) comprises extending one or more blades on the rotary steerable tool to change the direction of drilling along the direction of subsequent drilling computed in (f).