Abstract: An electromagnetic geophysical survey is performed by transmitting current from a first source into earth, the first source being located in a borehole. An electromagnetic field generated by the current transmitted from the first source is measured to create subsurface data. In addition, a background model is constructed and a leakage current distribution is calculated. A resistivity distribution of the earth is calculated using the subsurface data, the background model and the leakage current distribution, with the leakage current distribution being used as a source current distribution.

Abstract: The integrity of a well is evaluated using a non-invasive and lower cost screening system and method. The system and method identify whether well integrity has degraded and whether there is a clear break in the casing of a well, a corroded patch or faults in the casing. This is accomplished without requiring entry into the well.

Abstract: A downhole drilling tool is adapted to be placed in a borehole formed in the earth. The downhole drilling tool has mounted thereto at least one of a transmitter for generating and a receiver for sensing at least one component of an electromagnetic field within a distant earth region. The tool also has a device configured to acquire subsurface data from the at least one component of the electromagnetic field; and a device configured to calculate a resistivity distribution of the distant earth region from the subsurface data. A geophysical survey is performed with a downhole drilling tool by transmitting at least one component of an electromagnetic field through the distant earth region; acquiring subsurface data from the at least one component of the electromagnetic field; and calculating a resistivity distribution of the distant earth region from the subsurface data.

Abstract: A system measures and/or estimates the distribution of current flowing in or on a Long Conductor, such as a borehole casing. This allows greater precision in data interpretation and in calculating input to geologic models.

Abstract: An electromagnetic geophysical survey is performed by transmitting current from a first source into earth, the first source being located in a borehole. An electromagnetic field generated by the current transmitted from the first source is measured to create subsurface data. In addition, a background model is constructed and a leakage current distribution is calculated. A resistivity distribution of the earth is calculated using the subsurface data, the background model and the leakage current distribution, with the leakage current distribution being used as a source current distribution.