Method and apparatus using pad carrying electrodes for electrically investigating a borehole
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 formation over a circumferentially effectively contiguous segment of the borehole. Discrete portions of the flow of current are separably measurable so as to obtain a plurality of survey signals representative of the current density from the array and from which a detailed electrical picture of a circumferentially continuous segment of the borehole wall can be derived as the tool is moved along the borehole. In another form of an array of meausre electrodes, they are arranged in a closed loop, such as a circle, to enable direct measurements of orientations of resistivity of anomalies.
- Assignee:
- Schlumberger Technology Corp.
- Patent Number(s):
- US 4468623
- OSTI ID:
- 6374043
- Resource Relation:
- Patent File Date: Filed date 30 Jul 1981; Other Information: PAT-APPL-288554
- Country of Publication:
- United States
- Language:
- English
Similar Records
Apparatus and method for investigating wellbores and the like
Method of interpreting impedance distribution of an earth formation penetrated by a borehole
Related Subjects
03 NATURAL GAS
BOREHOLES
ELECTRIC LOGGING
WELL LOGGING EQUIPMENT
DESIGN
CRACK PROPAGATION
ELECTRIC CURRENTS
ELECTRODES
FORMATION DAMAGE
FRACTURE MECHANICS
FRACTURES
PROCESS CONTROL
CAVITIES
CONTROL
CURRENTS
EQUIPMENT
FAILURES
MECHANICS
WELL LOGGING
020200* - Petroleum- Reserves
Geology
& Exploration
030200 - Natural Gas- Reserves
Geology
& Exploration