Methods and systems for drilling boreholes
A system for drilling a borehole according includes a drill rig and a control system. The control system receives information from the drill rig that relates to at least one drill parameter. The control system processes information relating to the drill parameter, determines whether the drill parameter is within a predetermined specification for the monitored drill parameter, chooses a hole defect mitigation routine based on the monitored drill parameter when the monitored drill parameter is outside the predetermined specification, and controls the drill rig to implement the chosen hole defect mitigation routine.
1. A method for collaring a borehole, comprising:
performing a first phase collaring operation from a surface start to a point at which a drill bit reaches a dynamically determined collaring depth or a maximum collaring depth at a hole collar bottom; and
performing a second phase collaring operation to form a hole collar, the second phase collaring operation, comprising:
retracting the drill bit until the drill bit is above the surface;
activating a water injection system during the retracting of the drill bit and deactivating the water injection system when the drill bit is above the surface.
2. The method of claim 1 , wherein the dynamically determined collaring depth comprises a depth determined when a drill penetration rate falls below a predetermined drill penetration rate.
3. The method of claim 1 , further comprising re-lowering the drill bit into the hole collar to the dynamically determined collaring depth or the maximum collaring depth, and confirming that competent ground is present at the hole collar bottom.
4. The method of claim 3 , wherein the re-lowering comprises re-lowering the drill bit at a speed that is slower than normal drilling speed.
5. The method of claim 1 , further comprising lifting the drill bit above the surface and spinning the drill bit prior to beginning the first phase collaring operation.
6. The method of claim 1 , wherein the second phase collaring operation comprises:
re-lowering the drill bit to the hole collar;
determining whether competent ground is present at the hole collar bottom; and,
if competent ground is not present, drilling until it is determined that competent ground is present.
7. The method of claim 6 , wherein determining whether competent ground is present comprises determining if a drill penetration rate falls below a predetermined penetration level for a predetermined period of time.
8. A method for collaring a borehole, comprising:
performing a first phase collaring operation from a surface start to a point at which a drill bit reaches a dynamically determined collaring depth or a maximum collaring depth at a hole collar bottom; and
performing a second phase collaring operation to form a hole collar, the second phase collaring operation, comprising:
retracting the drill bit until the drill bit is above the surface;
activating a water injection system during the retracting of the drill bit; and
activating an air injection system when the drill bit is above the surface.
9. A method for collaring a borehole, comprising:
before drilling, preparing a surface location to receive a drill bit by removing any obstructions to a hole collar opening at the surface location;
performing a first phase collaring operation beginning at the surface location, the first phase collaring operation, comprising:
dynamically determining a collaring depth at a hole collar bottom; and
conducting the first phase collaring operation until the drill bit reaches the collaring depth at the hole collar bottom, the first phase collaring operation producing cuttings around the hole collar opening; and,
performing a second phase collaring operation, the second phase collaring operation, comprising:
retracting the drill bit from the hole collar bottom;
activating a water injection system during the retracting of the drill bit;
continuing the retracting until the drill bit is above the surface location;
deactivating the water injection system when the drill bit is above the surface; and
moving cuttings away from the hole collar opening when the drill bit is above the surface location.
10. The method of claim 9 , wherein performing the second phase collaring operation comprises determining that competent ground exists at the hole collar bottom.
11. The method of claim 10 , wherein determining that competent ground exists comprises:
returning the drill bit to the hole collar bottom at a reduced speed; and
determining whether a drill penetration rate of the drill bit follows below a predetermined drill penetration rate.
12. The method of claim 11 , wherein the reduced speed is between about 30 percent and about 50 percent of normal drill speed.
13. The method of claim 9 , wherein moving cuttings away from the hole collar opening comprises:
raising the drill bit above the surface location; and
activating an air injection system operatively associated with the drill bit to move cuttings away from the hole collar opening.