High resolution resistivity measurements on core plugs

A method, comprising:

• providing a tool having a plurality of voltage electrodes in electrical contact with a sample and a pair of current electrodes in electrical contact with the sample, wherein the voltage electrodes are disposed on the sample intermediate the current electrodes;
• providing desired depths of investigation and levels of resolution by configuring the spacing of the voltage electrodes;
• passing an electric current through the sample;
• using a measurement device to make electrical measurements between various electrode pairs;
• comparing the electrical measurements from the various electrode pairs;
• inferring that the sample has heterogeneous electrical properties using the compared electrical measurements;
• and
• adjusting, based on the electrical measurements, a finite element model (FEM) to approximate heterogeneous electrical property values.

A system, comprising:

• a tool having two current electrodes, three or more voltage electrodes, and a measurement device capable of making electrical measurements;
• a sample with electrical connectivity to one of the current electrodes at one location on the sample, the other current electrode at another location on the sample, and the three or more voltage electrodes disposed intermediate the two current electrodes;
• and
• a processor capable of:
• passing an electric current through the sample;
• using the measurement device to make a first set of electrical measurements that involve a first pair of voltage electrodes;
• using the measurement device to make a second set of electrical measurements that involve a second pair of voltage electrodes;
• comparing the first set of electrical measurements to the second set of electrical measurements;
• inferring that the sample has heterogeneous electrical properties using the compared electrical measurements;
• and
• adjusting, based on the first set and the second set of electrical measurements, a finite element model (FEM) to approximate heterogeneous electrical property values.