Small pole distance array scanning electrical logging method for detecting silted intercalation in drill hole

Abstract

The invention discloses a small pole distance array scanning electrical logging method for detecting silted intercalation in a drill hole. The method includes the steps: firstly, manufacturing a probe comprising a blind pipe made of insulating materials and a plurality of annular electrodes fixedly sleeving the outer circumferential surface of the blind pipe at intervals; secondly, placing the probe in an electrical logging hole along an electrical logging axis, coupling the probe with drill fluid and then adjusting the voltage of a first shielding electrode and a second shielding electrode to form layered current perpendicular to the electrical logging axis within a certain range by at least three measuring electrodes. The first shielding electrode, at least three spaced measuring electrodes, the second shielding electrode and a negative electrode are sequentially arranged from one end to the other end of the blind pipe, and the layered current flows into a rock stratum. When the measuring electrodes touch the silted intercalation, the current changes due to difference of grounding resistance, and change is reflected on a multi-channel measuring loop formed by the measuring electrodes, so that the silted intercalation is measured.

Description

technical field [0001] The invention relates to a drilling comprehensive logging method for water conservancy projects, in particular to a small pole-spacing array scanning electrical logging method for detecting muddy interlayers in a drilling hole. Background technique [0002] Mud interlayer refers to a weak layer or zone in the rock stratum that is relatively thin in thickness, low in mechanical strength, loose in structure, and weak in intergranular connections. It is usually a special rock formation formed by the long-term physical and chemical action of groundwater after the thin layer of argillaceous rock is broken by structural interlayer dislocation. This special rock formation has microstructure types and mechanical properties different from ordinary rocks and soils. The existence of weak interlayers is one of the key factors leading to the instability and failure of bedding slopes, and muddy interlayers, as the most common secondary weak interlayers, have extrem...

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Problems solved by technology

The muddy interlayer problem is a key geological problem in water conservancy projects. Because the muddy interlayer has the characteristics of discontinuity and local development, the type is mostly debris and mud, and the layer fluctuation is very small. It is difficult to take conventional cores. Complete and accurate acquisition of muddy interlayer information

[0003] At present, the commonly used methods for comprehensive logging of hydraulic engineering drilling include ultrasonic, resistivity, natural gamma ray, optical imaging, etc., but because the thickness of the muddy interlayer in some areas is only 0.5-3.0cm, and the measuring instrument is limited by the data sampling point However, the above logging methods can only identify rock formations of a certain scale and thickness, and the resolution accuracy of muddy interlayers is not enough, so it is difficult to identify them.

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