Electromagnetic downlink while drilling
Communication between the surface and a downhole location, such as a bottomhole assembly and/or an RSS is performed by electromagnetic downlink. Electromagnetic signals are transmitted from the surface through the formation at a frequency of 8 Hz or greater. Electromagnetic signals are transmitted and received while drilling or during drilling activities. In this manner, information and instructions may be transmitted to the BHA while drilling.
1. A method for downhole communication, comprising:
Providing an oil-based fluid to a bottomhole assembly;
selecting a frequency of at least 8 Hz for an electromagnetic signal based, in part, on the oil-based fluid;
transmitting the electromagnetic signal from a surface location without interrupting downhole drilling activities, wherein the downhole drilling activities comprise removing material from a wellbore;
receiving the electromagnetic signal downhole at a bottomhole assembly while performing the downhole drilling activities; and
demodulating the electromagnetic signal at the bottomhole assembly while performing the downhole drilling activities.
2. The method of claim 1 , wherein transmitting the electromagnetic signal includes transmitting instructions for the bottomhole assembly or transmitting information to the bottomhole assembly.
3. The method of claim 2 , comprising changing at least one drilling parameter of the bottomhole assembly based on the transmitted instructions.
4. The method of claim 1 , wherein receiving the electromagnetic signal includes receiving the electromagnetic signal at a rotary steerable system of the bottomhole assembly.
5. The method of claim 1 , wherein the downhole drilling activities comprise drilling formation of the wellbore, reaming formation of the wellbore, or cutting casing of the wellbore.
6. The method of claim 1 , wherein transmitting the electromagnetic signal includes transmitting the electromagnetic signal while maintaining a volumetric flow rate of a drilling fluid.
7. A method for downhole communication, comprising:
providing an oil-based fluid to a bottomhole assembly;
selecting a frequency of at least 8 Hz for an electromagnetic signal based in part on the oil-based fluid;
transmitting the electromagnetic signal from a surface location; and
receiving the electromagnetic signal downhole at an uphole location of a length of drill pipe of the bottomhole assembly;
insulating the length of drill pipe of the bottomhole assembly from the formation with the oil-based fluid; and
transmitting the electromagnetic signal to a gap sub of the bottomhole assembly.
8. The method of claim 7 , wherein transmitting the electromagnetic signal includes transmitting at a bit rate of greater than 1 bit per second.
9. The method of claim 8 , wherein transmitting the electromagnetic signal includes transmitting at a bit rate of greater than 8 bits per second.
10. The method of claim 7 , wherein transmitting the electromagnetic signal includes transmitting instructions for the bottomhole assembly.
11. The method of claim 10 , comprising receiving the instructions and changing at least one drilling parameter of the bottomhole assembly.
12. The method of claim 7 , comprising demodulating the electromagnetic signal.
13. The method of claim 12 , wherein demodulating the electromagnetic signal includes filtering noise from the electromagnetic signal.
14. The method of claim 7 , wherein transmitting the electromagnetic signal includes transmitting a plurality of electromagnetic signals at a plurality of frequencies.
15. A method for downhole communication, comprising:
performing drilling activities comprising drilling, reaming, or milling using an oil-based fluid;
selecting a frequency of at least 8 Hz for an electromagnetic signal based, in part, on the oil-based fluid
while performing the drilling activities, transmitting the electromagnetic signal from a surface location to a bottomhole assembly;
while performing the drilling activities, receiving the electromagnetic signal downhole at the bottomhole assembly; and
demodulating the electromagnetic signal at the bottomhole assembly.
16. The method of claim 15 , wherein transmitting the electromagnetic signal includes transmitting at a frequency of greater than 8 Hz.
17. The method of claim 15 , wherein performing the drilling activities includes tripping drill pipe into a wellbore or tripping drill pipe out of the wellbore.
18. The method of claim 15 , wherein demodulating the electromagnetic signal includes demodulating the electromagnetic signal with a signal-to-noise ratio of greater than 1:1.