A Brief of the Thin-Wall Diamond Wireline Core Drilling Process in Drillmaster Coring Rigs

Working Principle of Thin-Wall Diamond Wireline Core Drilling Technology

Thin-wall diamond wireline core drilling is an efficient core drilling method that combines diamond bit rock breaking and coring with a wireline core retrieval system. Its basic principle can be divided into the following steps:

Rock Breaking and Coring with the Drill Bit

The thin-wall diamond bit is installed at the forefront of the drilling tool. It utilizes the high hardness and wear resistance of diamond particles to cut through formations.

The center of the bit has a cavity. As drilling progresses, the core (a cylindrical rock sample) is retained in the inner tube behind the bit, enabling continuous coring.

The thin-wall structure reduces cutting resistance and energy consumption, improving drilling efficiency while maximizing core diameter and integrity.

Role of the Wireline Core Retrieval System

The inner tube assembly is placed inside the drill pipe and is responsible for collecting the core.

When the inner tube is full or needs replacement, the entire drill string does not need to be pulled out. Instead, the inner tube is retrieved individually using a wireline and overshot device.

After retrieval, the core is extracted intact. The inner tube is then sent back to the bottom of the hole to resume drilling, ensuring continuous operation.

Circulation Flushing and Cooling

During drilling, flush fluid (usually water or mud) is pumped through the drill pipe to the bottom of the bit to cool the bit and remove rock cuttings.

The flush fluid returns to the surface through the annular space between the drill pipe and the borehole wall, carrying debris with it and maintaining a clean bottom hole, which facilitates continuous cutting.

Advantages of Diamond Drilling in Thin-Wall Diamond Wireline Core Drilling Technology

High Drilling Efficiency

With reasonable process parameters and proper matching of drilling tools and formation conditions, thin-wall diamond bits significantly increase drilling speed. Due to the extreme hardness and wear resistance of diamonds, the bits remain sharp and efficient in hard and abrasive formations, reducing the need for frequent bit changes or downtime. This can double or even multiply drilling efficiency compared to conventional bits. Additionally, the wireline coring system eliminates frequent tripping for core retrieval, greatly reducing non-drilling time and further enhancing overall efficiency.

Excellent Borehole Quality

Thin-wall diamond bits provide stable and uniform cutting, resulting in low borehole deviation and consistent hole diameter. This ensures straight and smooth boreholes. Due to minimal tool vibration, core damage is reduced, and core recovery rates can consistently exceed 95%, providing reliable samples for geological analysis. This is particularly important in complex formations or scientific research.

Lightweight Equipment and Low Labor Intensity

The thin-wall bit and wireline coring system are compact and lightweight, making them suitable for small rigs or fieldwork in challenging conditions. Operators experience reduced labor intensity, improved safety, and easier equipment mobility, meeting the demands of field operations. This is especially advantageous for small-diameter drilling tasks.

Low Accident Rate

The small gap between the thin-wall diamond bit and the borehole wall ensures stable rotation of the drilling tool, minimizing issues such as tool vibration, sticking, or burying. The uniform cutting action results in smooth borehole walls, reducing the risk of collapse or diameter reduction. This stability is crucial for deep drilling or complex formations.

Low Cost

Although diamond bits are more expensive individually, their long service life, high efficiency, and low accident rate make them more cost-effective than conventional bits. Faster drilling shortens project cycles and reduces costs. High core recovery rates minimize the need for redrilling or additional holes, while fewer accidents save expenses associated with handling complications. Overall, this technology offers significant economic benefits.

Wide Applicability

Thin-wall diamond wireline core drilling is suitable for vertical, inclined, directional, and deep holes. It covers a wide range of diameters and can handle formations from soft rock (Grade I) to extremely hard rock (Grade XII). Whether for mineral exploration, geological research, or engineering surveys, this technology delivers excellent results.

Advantages of Wireline Coring in Thin-Wall Diamond Wireline Core Drilling Technology

Reduced Tripping Time and Improved Efficiency

Traditional coring requires full tripping to change bits or retrieve cores, which is time-consuming and reduces efficiency. Wireline coring allows the inner tube and core to be retrieved via a wireline and overshot without tripping the entire drill string. This saves significant auxiliary time and greatly improves drilling efficiency, especially in deep holes.

Reduced Bit and Borehole Wall Contact, Lowering Wear

With less frequent tripping, contact and friction between the bit, drill pipe, and borehole wall are minimized. This reduces premature wear or damage caused by reaming or collisions, lowering tool consumption costs and downtime while extending tool life.

Timely Retrieval of Blocked Cores, Ensuring Core Quality

If core blockage occurs during drilling, traditional methods require full tripping to address the issue, which is labor-intensive and risks core damage. Wireline coring allows quick retrieval of blocked cores, resuming drilling promptly. This ensures core integrity and representativeness, improves recovery rates, and enhances pure drilling hour efficiency while preventing excessive bit wear.

Small Gap Between Drill Pipe and Borehole Wall, Protecting the Borehole

The small annular clearance between the drill pipe and borehole wall in wireline coring provides a shielding effect, reducing stress and erosion on the borehole wall. This minimizes issues like collapse or diameter reduction. Additionally, fewer tripping operations reduce friction and disturbance, enhancing borehole stability, especially in fractured or complex formations.

Rapid Penetration of Complex Sections

In fault zones, loose sand layers, or other complex formations, traditional drilling is prone to borehole collapse or tool sticking. Wireline coring, with its reduced tripping frequency and quick inner tube retrieval, enables faster penetration of challenging sections, reducing downhole accidents and ensuring continuous and safe drilling.

Multi-Functional Retrieval Channel

The retrieval channel in wireline coring is not only for core retrieval and blockage handling but also serves as a multi-functional downhole operation channel. For example, it can be used for borehole deviation surveys, bottomhole temperature or pressure monitoring, and even installing geophysical instruments for in-situ testing. This versatility makes wireline coring not just a coring tool but a comprehensive platform for geological exploration and monitoring, enhancing the application value of boreholes.