| 摘要 |
Detecting in an earth formation (51) a boundary (56) between first and secon d formation regions (54, 55) having different resistivities, wherein the first formation region (54) is traversed by a wellbore, using a logging tool (60) provided with a number of electrodes (61, 62, 63) including a monitoring electrode (63), the method comprising: a) selecting a location (65) of the logging tool (60) in the wellbore (57); b) assuming a position of the bounda ry (56) relative to the selected location (65), selecting outside the wellbore (57) a target point (67) relative to the selected location (65), and selecti ng a target value for a selected parameter in the target point (67); c) assumin g a model wherein the logging tool (60) in the wellbore is surrounded by a homogeneous formation having the resistivity of the first formation region (54), and determining how two of the electrodes (61, 62, 63) have to be energized in order that in the target point (67) the selected parameter has the target value; d) selecting a monitoring parameter at the monitoring electrode (63); e) placing the logging tool (60) at the selected location (6 5) in the wellbore (57); f) determining a detection value of the monitoring parameter resulting from energizing the two electrodes (61, 62, 63) as determined in step; c) and g) interpreting the detection value of the monitoring parameter in order to detect the boundary (56).
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