Schlumberger s Formation MicroScanner (FMS) is similar to the SHDT Dual Dipmeter tool in all respects except that in one of the configurations it has two arrays of electrodes on pads three and four (Standen, 1986). Currently on the market is another version of the tool with four imaging pads perpendicular to each other.

In one configuration the arrays consist of three rows of seven buttons and one row of six. Each of the buttons is 2/10 of an in. in diameter with the entire array 2.7 in. wide by 1.4 in. deep. The configuration allows for a 60% overlap of the electrical signals. With arrays on two pads, a 20% coverage of the well bore is obtained in an 8 1/2 in. diameter hole. With the four pad configuration, a 45% circumferential coverage is obtained in an 8 1/2 in. diameter hole.

Increases in borehole coverage have been advancing at a rapid pace. Table 3 1 shows a summary of characteristics of the FMS tool and the BHTV discussed in a previous section.

In addition to the array electrodes, the tool also has 10 standard SHTD electrodes (8 measure electrodes plus 2 speed electrodes) as well as a directional cartridge containing accelerometers and magnetometers (GPIT). Thus the total number of electrodes in this set-up is 27+27+10=64 electrodes. Acquisition of the data is by two modes; either as an SHDT without image data or in imaging mode with all 64 electrodes being recorded.

The image processing...