AU2012101959A4

AU2012101959A4 - Pressure Feed System for a Down Hole Drill

Info

Publication number: AU2012101959A4
Application number: AU2012101959A
Authority: AU
Inventors: Ian SPEER
Original assignee: Strada Design Ltd
Current assignee: Strada Design Ltd
Priority date: 2011-11-18
Filing date: 2012-11-19
Publication date: 2016-10-13
Anticipated expiration: 2020-11-19
Also published as: AU2013201651A1; AU2013201651A2; WO2013071369A1

Abstract

- 20 A pressure feed system 10 for a down hole drill has a housing 19 through which a down hole drill is able to move when being operated to drill a hole and a sealing 5 system capable of forming first and second seals about the drill at respective spaced apart first and second sealing locations within the housing 19. The sealing system has a first sealing mechanism 20a and a second sealing mechanism 20b. An inlet 26 is provided in the housing 19 enabling fluid to flow into the housing at location between the first and second sealing locations.

Description

PRESSURE FEED SYSTEM FOR A DOWN HOLE DRILL

Field of the Invention

The present invention relates to the drilling of holes using a down hole drill.

Background of the Invention

Many different types of down hole drills are available which utilise a fluid under pressure to assist in advancing the drill. The fluid may act to either drive a cutting tool at a down hole end of an associated drill string, or to flush drill cuttings from an associated hole, or both. The fluid can be a gas such as air or nitrogen, a liquid/slurry such as water or drilling mud, or a combination of a gas and liquid. Throughout this specification the expression “pressurised fluid” is intended to denote a fluid under pressure, irrespective of whether or not the fluid is compressible. A down hole drill may comprise a rotation head, a drill string connected via a sub to the rotation head and a drill tool or bit at a down hole end of the drill string drill. The drill string is formed by connecting together a number of drill pipes (also known as drill rods). The rotation head imparts torque to the drill string and connected drill bit. The rotation head is slidably mounted on a tower. Hydraulic rams are usually used to linearly translate the rotation head along the tower and provide hold down and pull back forces for the drill. The depth of drilling is increased by sequentially adding dill pipes, one at a time to the string. The type of drill bit or tool connected to the down hole end of the string will vary depending on many factors including hole geology and application at hand, for example exploration, production, blasting. Examples of the drill bit or tool include but are not limited to DTH (“Down The Hole”) hammer, tricone, drag bit or diamond (core) bit.

Consider for example a down hole drill with a DTH hammer. The DTH hammer is driven by a pressurised fluid such as air. The pressurised (and thus compressed) air serves two functions. It drives a piston onto a hammer bit at an end of a drill string to effect an impact of the bit onto the toe (i.e bottom) of the hole being drilled. In addition, the compressed air may entrain drill cuttings and deliver the cuttings to the surface to clear the hole of debris and for possible analysis.

The air pressure and volume at which the DTH hammer is operated is critical in terms

Claims

The claims defining the invention are as follows:

1. A method of operating a drill having a drill string composed of one or more end-to-end connected drill pipes and a down the hole hammer (DTH) coupled to a down hole end of the drill string wherein the DTH is operated by a flow of pressurized air, the method comprising: passing the drill string through a pressure feed system having a housing and first and second sealing mechanisms that are axially spaced apart and fixed in an axial direction relative to each other within the housing, the pressure feed system further having an air inlet located between the first and second sealing mechanisms; delivering torque to rotate the drill string to facilitate drilling of a hole while the drill string passes through the housing; supplying pressurised air to the hole through the drill from a first location upstream of the housing to operate the DTH by: establishing a circulating flow of the pressurised air down through the drill string and up the hole created by the drill; and establishing a desired hole pressurisation in the hole; and upon operating the drill to advance the hole by a length substantially equal to a length of a drill pipe: (a) ceasing the delivery of torque to the drill string; (b) lifting the drill from a toe of a hole being drilled; (c) coupling an additional drill pipe in the drill string while substantially maintaining both the circulating flow of pressurized air and the desired hole pressurisation by selectively suppling pressurised air to the hole from the first location and the air inlet; (d) after coupling of the additional drill pipe, lowering the drill onto the toe of the hole and delivering torque to the drill string, and supplying pressurised air to the drill from the first location to enable recommencement of drilling; and (e) repeating steps (a) to (d) each time the drill is advanced in the hole by a length substantially equal to a length of a drill pipe until a desired hole depth is achieved.
2. The method according to claim 1 wherein step (c) comprises: operating the first and second sealing mechanisms to form first and second seats about the drill string at first and second sealing locations within the housing; breaking a joint in the drill string between the first and second sealing locations to form up hole and down hole drill portions wherein pressurised airflow is maintained in the drill across the broken joint between the first and second sealing locations through the housing; and, switching the supply of pressurized air from the first location to the air inlet in the housing.
3. The method according to claim 2, comprising isolating the up hole and down hole drill portions from fluid communication with each other wherein the pressurised airflows into the down hole drill portion of the drill string and into the hole from the air inlet.
4. The method according to claim 3, wherein isolating the up hole and down hole drill portions comprises translating the up hole drill portion from the down hole drill portion while maintaining the first seal to form a gap there between and closing a valve in the housing between the up hole and down hole drill portions.
5. The method according to claim 3 or 4, wherein isolating the up hole and down hole drill portions comprises supporting the down hole drill portion from resting on a toe of the hole.