Method and apparatus using pad carrying electrodes for electrically investigating a borehole

US4468623A · kind A · utility

Assignee

• SCHLUMBERGER TECHNOLOGY CORPORATION · US

Inventors

• Stanley C. Gianzero · Austin, US
• David E. Palaith · Washington, US
• David Chan · Bethel, US

Key dates

• Filing date: Jul 30, 1981
• Grant date: Aug 28, 1984
• Expiry date: Jul 30, 2001

Classification

• Technology area (CPC G): Physics
• CPC primary: G01V3/20
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Methods and apparatuses for electrically investigating a borehole are described. Tool mounted pads are provided, each with a plurality of small measure electrodes from which individually measurable survey currents are injected toward the wall of the borehole. The measure electrodes are arranged in an array in which the measure electrodes are so placed at intervals along at least a circumferential direction (about the borehole axis) as to inject survey currents into the borehole wall segments which overlap with each other to a predetermined extent as the tool is moved along the borehole. The measure electrodes are made small to enable a detailed electrical investigation over a circumferentially contiguous segment of the borehole so as to obtain indications of the stratigraphy of the formation near the borehole wall as well as fractures and their orientations. In one technique, a spatially closed loop array of measure electrodes is provided around a central electrode with the array used to detect the spatial pattern of electrical energy injected by the central electrode. In another embodiment, a linear array of measure electrodes is provided to inject a flow of current into the forma…