Design and Experimental Study of Core Bit for Hard Rock Drilling in Deep-Sea

 

Part 1 of 3 – Introduction to Drilling with Matrix Dual Tube and Reverse Air Methods

 

Reverse Circulation Drilling with Air using a Rock Bit (Tri-cone/PDC)

 

Over the past few years, dual-tube drilling techniques have become increasingly popular in industries such as mining, geothermal exploration, and large-diameter borehole construction. Despite their widespread adoption, detailed explanations of how these systems function remain surprisingly scarce. This series aims to demystify some of the key principles behind Matrix's dual-tube product line as utilized by our clients. Please remember that we are not professional drillers; instead, we specialize in custom manufacturing tailored specifically for the drilling sector. For further inquiries or deeper insights, feel free to reach out to us directly.

 

All dual-tube operations rely on the principle of reverse circulation drilling, where debris travels upward through the interior of the inner tube rather than along the annular gap surrounding the drill string. It’s crucial to understand that while reverse circulation drilling can also be achieved with traditional drill rods via various configurations, these approaches differ significantly from the dual-tube methods discussed herein. Two primary categories of dual-tube reverse circulation exist—reverse circulation using air and flooded reverse circulation. Below, we delve into these methodologies and explore the innovative products crafted by Matrix to bring them to life.

 

Let’s begin with reverse circulation drilling employing a rock bit (Tri-cone/PDC) powered by compressed air (as illustrated in Figure 1). In this setup, compressed air enters the annular region between the outer tube’s inner diameter and the inner tube’s outer diameter via a side-entry air swivel positioned beneath the top-head drive mechanism. From there, the air flows downward through the drill string until reaching an adapter assembly mounted just above the cutting tool. This assembly includes a wear sleeve designed to release pressurized air close to the bit face. Upon exiting the adapter, the air expands rapidly, creating a significant pressure drop that propels cuttings away from the bit face and upward through the API pin-up connection of the tri-cone bit into the inner tube. A lift-check valve ensures that no backflow occurs, preventing potential blockages within the annular space. High-velocity cuttings ascend through the inner tube and exit via the top-head discharge hose. During mineral exploration, these cuttings are redirected toward a collection system capable of separating geological materials for subsequent sampling and documentation. This continuous, real-time sampling process enables drill operators to identify the precise depth and stratigraphic layer they are working within mere minutes.

 

 

Figure 1: Sample Flow Diagram. Dual Tube Reverse Circulation Drilling with Air using a Rock Bit (Tri-cone/PDC)

 

Keen to learn more? Stay tuned for Parts 2 and 3 of our "Introduction to Drilling with Matrix Dual Tube" series! Part 2 will cover conventional DTH hammers and DTH RC hammers, while Part 3 focuses on dual-tube flooded reverse circulation drilling.

 

Disclaimer: The opinions expressed in this article reflect the author’s personal views based on engineering knowledge, technical expertise, and practical experience acquired while collaborating with numerous clients across the industry. None of this content is intended to override or supersede official guidelines provided by other sources. Furthermore, the information contained herein should not be utilized for legal proceedings of any kind.

 

 

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