System and method for performing distant geophysical survey
A downhole drilling tool is adapted to be placed in a borehole formed in the earth. The downhole drilling tool has mounted thereto at least one of a transmitter for generating and a receiver for sensing at least one component of an electromagnetic field within a distant earth region. The tool also has a device configured to acquire subsurface data from the at least one component of the electromagnetic field; and a device configured to calculate a resistivity distribution of the distant earth region from the subsurface data. A geophysical survey is performed with a downhole drilling tool by transmitting at least one component of an electromagnetic field through the distant earth region; acquiring subsurface data from the at least one component of the electromagnetic field; and calculating a resistivity distribution of the distant earth region from the subsurface data.
1. A method of performing a geophysical survey in a borehole made with a downhole drilling tool, the method comprising:
transmitting at least one component of an electromagnetic field through the earth between the downhole drilling tool and a distant earth region located in front of the downhole drilling tool, wherein the downhole drilling tool establishes a transmission point or a receiving point for the at least one component of the electromagnetic field;
acquiring subsurface data about the distant earth region from the at least one component of the electromagnetic field;
calculating a resistivity distribution of the distant earth region from the subsurface data while the downhole drilling tool is moving; and
steering the downhole drilling tool, wherein the downhole drilling tool is guided based on at least a portion of the subsurface data and the resistivity distribution of the distant earth region.
2. The method of claim 1 , wherein the downhole drilling tool establishes the transmission point for the at least one component of the electromagnetic field.
3. The method of claim 2 , further comprising measuring the electromagnetic field with a plurality of spaced, surface or near surface sensors.
4. The method of claim 3 , wherein at least two of the plurality of surface or near surface sensors are spaced by at least ⅕ mile.
5. The method of claim 1 , wherein the downhole drilling tool establishes the receiving point for the at least one component of the electromagnetic field.
6. The method of claim 5 , wherein the receiving point is established by a capacitive sensor carried by the downhole drilling tool.
7. The method of claim 6 , wherein the at least one component of the electromagnetic field is transmitted from a plurality of spaced, surface or near surface transmitters to the capacitive sensor.
8. The method of claim 7 , wherein at least two of the plurality of spaced, surface or near surface sensors are spaced by at least ⅕ mile.
9. The method of claim 5 , wherein the at least one component of the electromagnetic field is transmitted from a plurality of spaced, surface or near surface transmitters to a sensor carried by the downhole drilling tool.
10. The method of claim 1 , wherein the distant earth region extends from a borehole in which the downhole drilling tool is located to at or near a surface region of the earth.
11. The method of claim 1 , wherein the distant earth region extends from a first borehole in which the downhole drilling tool is located to a second borehole located remote from the first borehole.
12. The method of claim 1 , further comprising:
determining a position or trajectory of the downhole drilling tool based on the resistivity distribution.
13. A system for performing a geophysical survey comprising:
a downhole drilling tool adapted to be placed in a borehole formed in the earth, said downhole drilling tool having mounted thereto at least one of a transmitter for generating and a receiver for sensing at least one component of an electromagnetic field within the earth between the downhole drilling tool and a distant earth region located in front of the downhole drilling tool;
a device configured to acquire subsurface data about the distant earth region from the at least one component of the electromagnetic field; and
a device configured to calculate a resistivity distribution of the distant earth region from the subsurface data while the downhole drilling tool is moving, wherein at least a portion of the subsurface data and the resistivity distribution of the distant earth region is used in steering the downhole drilling tool.
14. The system of claim 13 , wherein the downhole drilling tool establishes a transmission point for the at least one component of the electromagnetic field.
15. The system of claim 14 , wherein the device configured to measure the subsurface data includes a plurality of spaced, surface or near surface sensors.
16. The system of claim 15 , wherein at least two of the plurality of surface or near surface sensors are spaced by at least ⅕ mile.
17. The system of claim 13 , wherein the downhole drilling tool establishes a receiving point for the at least one component of the electromagnetic field.
18. The system of claim 17 , wherein the receiving point is established by a capacitive sensor carried by the downhole drilling tool.
19. The system of claim 18 , further comprising: a plurality of spaced, surface or near surface transmitters for transmitting the at least one component of the electromagnetic field to the capacitive sensor.
20. The system of claim 19 , wherein at least two of the plurality of spaced, surface or near surface sensors are spaced by at least ⅕ mile.
21. The system of claim 13 , wherein the distant earth region extends from a borehole in which the downhole drilling tool is located to at or near a surface region of the earth.
22. The system of claim 13 , wherein the distant earth region extends from a first borehole in which the downhole drilling tool is located to a second borehole located remote from the first borehole.
23. The system of claim 13 , wherein the resistivity distribution is used to determine a position or a trajectory of the downhole drilling tool.