DTH Hammer Sealing for Overburden Drilling Pressure Loss
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Solution Overview
Problem
Existing drilling devices, such as down-the-hole hammers, face challenges with insufficient drill depth, small borehole diameter, and high flushing medium flow rates, which affect drilling efficiency.
Innovation Solution
The proposed solution involves a drilling device with a DTH-hammer, a drilling tube with a waste conduit for cuttings and a supply conduit for the flushing medium, and an overburden tube connected to the drill bit, featuring a seal assembly with rubber and plastic disks to reduce pressure losses and a method where the flushing medium is supplied peripherally to carry away cuttings, with an overburden tube dragged adjacent to the surrounding rock, maintaining a sufficient pressure gradient and constant borehole volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high flushing medium flow rates are used, then cuttings are effectively carried away, but energy loss increases and drilling depth is insufficient
Solution Approach 1:
The sealing system is segmented into multiple sealing elements (packer with sealing elements, valve members with sealing surfaces) distributed at different locations along the drill string. This segmentation allows pressure control at multiple zones, reducing energy loss while maintaining effective flushing medium flow rates for cuttings removal
Solution Approach 2:
The invention changes the pressure parameters of the flushing medium by using sealing elements and valve members to maintain pressure gradients. This allows the flushing medium to effectively carry away cuttings without requiring excessively high flow rates, thereby reducing energy loss while increasing drilling depth
2Productivity
If larger borehole diameter is achieved, then drilling capacity increases, but flushing medium pressure losses through gaps increase
Solution Approach 1:
The invention extracts and eliminates the harmful gaps between the drill string and borehole wall by introducing a packer with sealing elements. This packer is positioned to seal the annular space, preventing flushing medium from leaking through gaps and reducing pressure losses, thereby allowing larger borehole diameters without compromising flushing efficiency
Solution Approach 2:
The packer acts as an intermediary element between the flushing medium and the annular space. It mediates the pressure transmission by sealing the gaps, ensuring that the flushing medium maintains sufficient pressure to carry away cuttings even in larger boreholes, thus reducing energy loss while maintaining drilling capacity
3Productivity
If borehole volume increases during drilling, then more cuttings can be accommodated, but additional pressure loss occurs
Solution Approach 1:
The invention performs preliminary sealing of the borehole annulus using the packer with sealing elements before the flushing medium needs to traverse the entire borehole volume. This preliminary action creates a controlled pressure environment that prevents flushing medium from lost through expanding borehole gaps, thereby accommodating cuttings capacity without additional pressure loss
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances drilling efficiency by reducing energy loss, allowing for greater drill depth and larger borehole diameters with reduced flushing medium flow rates, independently of the rock's nature, and maintains a high flow velocity to effectively carry away cuttings.
Implementation Method 1
rubber disks separated by smaller diameter plastic disks are used, where an outer diameter of the rubber disks corresponds to, i.e. is about equal to or slightly larger than, an inner diameter of the overburden tube
Implementation Method 2
a method of overburden drilling using air lifting
Implementation Method 3
dragging along an overburden tube adjacent the surrounding rock
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a DTH-hammer drilling device, comprising a down-the-hole- (DTH-) hammer (6) with a percussion drill bit (9), a drill pipe (2) with a waste conduit for the cuttings and at least one supply conduit for the flushing medium and a flushing medium supply device, wherein a seal (18) for sealing the borehole against the borehole opening is provided in a fixed distance from the drilling head (6), or wherein a casing tube (12) is connected to the drill bit (9). The invention further relates to an overburden drilling method, comprising rotating a drill bit (9), supplying an energy transfer medium through a drill pipe (2) to the rotating drill bit (9) for transmitting a percussive action thereonto, dragging a casing tube (12) along with the drill bit (9) and flushing away cuttings through the drill pipe (2).