With the continuous development and progress of rope coring drilling methods, the efficiency and transformation of core drilling work have been greatly promoted, and it has great advantages over traditional drilling methods. However, in the long-term application process, we have also found that when drilling in complex formations, using mud to protect the hole, the inner wall of the drill pipe will often form a layer of mud to varying degrees, which will seriously hinder the placement of the inner pipe, thus directly affecting the application of rope coring drilling.
Phenomenon and analysis
When drilling in complex formations using coring drilling methods, measures such as using mud hole protection will form a layer of solid mud skin on the inner wall of the drill pipe to varying degrees, affecting the lowering or extraction of the corer. The formation of mud skin is related to mud properties, water loss, drilling speed and return time. The solidified materials on the inner wall of the Wireline drill rod were extracted for analysis, among which larger solid particles in the mud and rock powder particles accounted for the majority.
Discussion on the mechanism of mud skin formation on the inner wall of Wireline drill rod
In production practice, we can find that the formation of mud skin consolidation on the inner wall of drill pipe during rope coring drilling requires the following elements:
(1) Drilling in complex formations requires the use of mud and polymer materials to protect the borehole, and the viscosity of the borehole protection fluid is relatively high.
(2) Higher rotation speed
(3) The flow rate of the flushing fluid in the Wireline drill rod is relatively low.
The main reason for the formation of mud skin on the inner wall of Wireline drill rod is that when the drill pipe rotates at high speed, the solid particles in the flushing fluid are thrown to the wall of the drill pipe under the action of centrifugal inertia. The high-viscosity polymer in the borehole protection fluid forms a mesh structure that wraps the solid particles. When the radial flushing force of the flushing fluid cannot flush them away, a stable mud skin layer is gradually formed. In this process, the polymer materials in the borehole protection fluid and the tiny particles in the mud are indispensable conditions for maintaining the stability of the borehole wall. Therefore, how to solve the borehole protection problem and the contradiction between the mud skin consolidation problem in the drill pipe are what needs to be discussed in the following chapters.
The influence of various factors on the formation of mud skin on the inner wall of Wireline drill rod and the solution.
Among the various factors that cause the consolidation of mud skin inside the Wireline drill rod, some factors are the key factors that reflect the advantages of rope drilling and are difficult to change, while some factors can be optimized and combined to find a balance without changing the stability of the hole wall and the drilling efficiency, thus solving the problem.
