Rotary steerable drilling tool and associated method of use
The device contemplated provides a method for positioning the drill bit in a drilling operation to achieve small changes in hole angle or azimuth as drilling proceeds. Two different positions are available to the operator. The first is a straight ahead position where the tool essentially becomes a packed hole stabilizer assembly. The second position tilts the bit across a rotating fulcrum to give a calculated offset at the bit-formation interface. The direction that the bit offset is applied in relation to current hole direction is controlled by positioning the orienting pistons prior to each drilling cycle, through the use of current measurement-while-drilling (MWD) technology. Components of the tool comprise a MWD housing, upper steering and drive mandrel, non-rotating position housing, lower drive mandrel splined with the upper mandrel, rotating fulcrum stabilizer and drill bit.
1. A rotary steerable drilling tool, comprising:
(a) a mandrel;
(b) a housing mounted on the mandrel for rotation in relation to the mandrel; and
(c) an adjustable offset mechanism on the housing, the adjustable offset mechanism being surface adjustable to move the rotary steerable drilling tool to and from a straight ahead drilling position and an offset drilling position:
(d) a first sensor on the mandrel that is sensitive to a rotary orientation of the housing, the first sensor providing a signal indicative of the rotary orientation of the housing on the mandrel, for use in controlling the rotary steerable drilling tool;
(e) a second sensor on the mandrel, the second sensor being longitudinally offset from the first sensor;
(f) the first sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the rotary steerable drilling tool is an on-bottom drilling position; and
(g) the second sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the rotary steerable drilling tool is in a pulled back position.
2. The rotary steerable drilling tool of claim 1 in which the adjustable offset mechanism comprises plural pistons radially mounted in the housing, the plural pistons being radially adjustable by actuation of the mandrel.
3. The rotary steerable drilling tool of claim 2 in which the plural pistons comprise first and second pistons located on opposed sides of the housing, the first piston being extended and the second piston being retracted in the straight ahead drilling position, and the first piston being retracted and the second piston being extended in the offset drilling position.
4. The rotary steerable drilling tool of claim 3 in which the pistons are actuated by a cam sleeve mounted on the mandrel.
5. The rotary steerable drilling tool of claim 1 in combination with a drill string comprising a measurement-while-drilling (MWD) tool, a drill bit terminating the drill string and a stabilizer located on the drill string between the rotary steerable drilling tool and the drill bit.
6. The rotary steerable drilling tool of claim 1 in which the first sensor comprises a switch on the mandrel that is sensitive to a trigger on the housing.
7. The rotary steerable drilling tool of claim 6 in which the trigger is a magnet.
8. A rotary orientable drilling tool for use in combination with a MWD tool, the rotary orientable drilling tool comprising:
(a) a mandrel;
(b) an asymmetrical housing mounted on the mandrel for rotation in relation to the mandrel;
(c) a first sensor on the mandrel that is sensitive to a rotary orientation of the housing in relation to the mandrel, the first sensor providing a signal indicative of the rotary orientation of the housing on the mandrel to a communication link;
(d) a second sensor on the mandrel, the second sensor being longitudinally offset from the first sensor;
(e) the first sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the rotary steerable drilling tool is in an on-bottom drilling position; and
(f) the second sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the rotary steerable drilling tool is in a pulled back position and providing a signal indicative of the rotary orientation of the housing in relation to the mandrel to the communication link.
9. The rotary orientable drilling tool of claim 8 in which the first sensor comprises a switch on the mandrel that is sensitive to a trigger on the housing.
10. The rotary orientable drilling tool of claim 9 in which the trigger is a magnet.
11. A drill string, comprising:
(a) a mandrel;
(b) a housing mounted on the mandrel for rotation in relation to the mandrel;
(c) an adjustable offset mechanism on the housing, the adjustable offset mechanism being surface adjustable to move the drill string to and from a straight ahead drilling position and an offset drilling position;
(d) a drill bit terminating the drill string;
(e) a stabilizer on the drill string between the drill bit and mandrel;
(f) a first sensor on the mandrel that is sensitive to a rotary orientation of the housing in relation to the mandrel, the first sensor providing a signal indicative of the rotary orientation of the housing on the mandrel to a communication link;
(g) a second sensor on the mandrel, the second sensor being longitudinally offset from the first sensor;
(h) the first sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the drill string is in an on-bottom drilling position; and
(i) the second sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the drill string is in a pulled back position and also providing a signal indicative thereof to the communication link.
12. A drill string, comprising:
(a) a mandrel;
(b) a housing mounted on the mandrel for rotation in relation to the mandrel;
(c) an adjustable offset mechanism on the housing, the adjustable offset mechanism being surface adjustable to move the drill string to and from a straight ahead drilling position and an offset drilling position;
(d) plural pistons radially mounted in the housing, the plural pistons being radially adjustable by actuation of the mandrel;
(e) a drill bit terminating the drill string;
(f) a stabilizer on the drill string between the drill bit and mandrel;
(g) a first sensor on the mandrel that is sensitive to the rotary orientation of the housing in relation to the mandrel, the first sensor providing a signal indicative of the rotary orientation of the housing on the mandrel to the communication link;
(h) a second sensor on the mandrel, the second sensor being longitudinally offset from the first sensor;
(i) the first sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the drill string is in an on-bottom drilling position; and
(j) the second sensor being sensitive to the orientation of the housing in relation to the mandrel when the string is in a pulled back position.
13. A drill string, comprising:
(a) a mandrel;
(b) a housing mounted on the mandrel for rotation in relation to the mandrel;
(c) an adjustable offset mechanism on the housing, the adjustable offset mechanism being surface adjustable to move the drill string to and from a straight ahead drilling position and an offset drilling position;
(d) first piston and second piston radially mounted in the housing, the first piston and second piston being radially adjustable by actuation of the mandrel; the first piston being extended and the second piston being retracted in the straight ahead drilling position, and the first piston being retracted and the second piston being extended in the offset drilling position;
(e) a drill bit terminating the drill string;
(f) a stabilizer on the drill string between the drill bit and mandrel;
(g) a first sensor on the mandrel that is sensitive to a rotary orientation of the housing in relation to the mandrel, the first sensor providing a signal indicative of the rotary orientation of the housing on the mandrel to the communication link;
(h) a second sensor on the mandrel, the second sensor being longitudinally offset from the first sensor;
(i) the first sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the drill string is in an on-bottom drilling position; and
(j) the second sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the string is in the pulled back position.
14. A drill string, comprising:
(a) a mandrel;
(b) a housing mounted on the mandrel for rotation in relation to the mandrel;
(c) an adjustable offset mechanism on the housing, the adjustable offset mechanism being surface adjustable to move the drill string to and from a straight ahead drilling position and an offset drilling postion;
(d) first piston and second piston radially mounted in the housing, the first piston and second piston being radially adjustable by actuation of the mandrel, the first piston being extended and the second piston being retracted in the straight ahead drilling position, and the first piston being retracted and the second piston being extended in the offset drilling position;
(e) a cam sleeve mounted on the mandrel for actuating the first piston and second piston;
(f) a drill bit terminating the drill string;
(g) a stabilizer on the drill string between the drill bit and mandrel;
(h) a first sensor on the mandrel that is sensitive to a rotary orientation of the housing in relation to the mandrel, the first sensor providing a signal indicative of the rotary orientation of the housing on the mandrel to the communication link;
(i) a second sensor on the mandrel, the second sensor being longitudinally offset from the first sensor;
(j) the first sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the drill string is in an on-bottom drilling position; and
(k) the second sensor being sensitive to the rotary orientation of the housing in relation to the mandrel when the string is in a pulled back position.
15. A method of drilling a hole, the method comprising the steps of:
(a) rotating a drill string while the drill string is bottomed out in the hole, said drill string having a housing and a mandrel disposed at a drill bit on the drill string;
(b) pulling the drill string off bottom;
(c) offsetting the drill string in the hole above a fulcrum to offset the drill bit in the hole and controlling the drill string in response to signals produced by first and second sensors that are each responsive to a rotary orientation of the housing on the mandrel; and
(d) continuing to rotate the drill string with the drill string bottomed out in the hole and the drill bit offset in the hole.
16. The method of claim 15 in which the drill string is offset above the fulcrum using a non-rotating sleeve that is held against movement in relation to the hole.
17. The method of claim 16 in which offsetting the drill string comprises the step of driving pistons radially outward from the housing to hold the housing in the hole and offset the drill string in the hole.