Subsurface formation anisotropy determination with tilted or transverse magnetic dipole antennas
AssigneeSchlumberger Technology Corporation
InventorsDzevat Omeragic, Jacques R. Tabanou, Alain Dumont
Life of this patent
Estimating the term…
Abstract
Transverse or tilted magnetic dipole antenna systems are used for electromagnetic logging measurements to determine the anisotropic resistivity of subsurface formations. Combined measurements between transverse or tilted antennas, as well as axial antennas, are used to compensate for receiver antenna mismatch in the system. Some embodiments use model-based parametric inversion to estimate the anisotropic resistivity in the presence of invasion and shoulder-bed effects.
Claims27
A well logging system for determining an anisotropy parameter of a subsurface formation, comprising:
- an elongated support having a longitudinal axis and adapted for subsurface disposal while drilling a borehole through said formation;
- a plurality of transmitter antennas disposed on the support, at least one of said antennas having its magnetic moment oriented at an angle with respect to the support axis, each of said antennas adapted to transmit electromagnetic energy;
- a pair of receiver antennas disposed on the support with their axes oriented at an angle with respect to the support axis, said antennas adapted to detect electromagnetic signals associated with the energy transmitted from said transmitter antennas;
- wherein the at least one angled transmitter antenna or one of said receiver antennas is disposed with its respective magnetic moment or axis at a ninety-degree angle with respect to the support axis;
- and
- processor means adapted to combine detected electromagnetic signals associated with said transmitter or receiver antenna oriented at the ninety-degree angle with detected electromagnetic signals associated with another antenna of said plurality of transmitter antennas to determine the anisotropy parameter.
A well logging system for determining an anisotropy parameter of a subsurface formation, comprising:
- an elongated support having a longitudinal axis and adapted for subsurface disposal while drilling a borehole through said formation;
- first and second transmitter antennas disposed on the support with their magnetic moments having matching orientations with respect to the support axis, said antennas adapted to transmit electromagnetic energy;
- a pair of receiver antennas disposed on the support with their axes oriented at an angle with respect to the support axis and located between said first and second transmitter antennas, said receiver antennas adapted to detect electromagnetic signals;
- and
- processor means adapted to combine detected electromagnetic signals relating to a phase difference or a magnitude ratio to compensate for a mismatch between said pair of receiver antennas to determine the anisotropy parameter.
A method for determining an anisotropy parameter of a subsurface formation in which an elongated support having a longitudinal axis and adapted for subsurface disposal while drilling a borehole through said formation is received, comprising:
- a) selectively transmitting electromagnetic energy into the formation from a plurality of transmitter antennas disposed on the support, at least one of said antennas having its magnetic moment oriented at an angle with respect to the support axis;
- b) detecting electromagnetic signals associated with the energy transmitted from said transmitter antennas with a pair of receiver antennas disposed on the support with their axes oriented at an angle with respect to the support axis, wherein one of said receiver antennas or the at least one angled transmitter antenna is disposed with its respective axis or magnetic moment at a ninety-degree angle with respect to the support axis;
- and
- c) combining detected electromagnetic signals associated with said transmitter or receiver antenna oriented at the ninety-degree angle with detected electromagnetic signals associated with another antenna of said plurality of transmitter antennas to determine the anisotropy parameter.
Dependencies are inferred from the claim text.