摘要:
The present invention relates to a method of investigating the wall (2) of a borehole in a geological formation by means of two injectors (4, 5) with a potential V being applied between them and in measuring the potential difference δV between two electrically isolated measurement electrodes (6) situated between the two injectors (4, 5) and spaced apart from the formation by an insulating layer (1), in which the resistivity of the formation is obtained from the measured values of δV, V and I, with corrections being made for the effects due to the nature and the thickness of the insulating layer (1). In a first variant these corrections are based on a correction factor obtained from curves of K=Rt.I/δV as a function of the impedance V/I of the injector. In a second variant these corrections are obtained by estimating the current IF actually injected into the formation while taking account of leakage current IL, and calculating the resistivity of the formation from the equation (I). The invention also provides an investigation device enabling the values of IF and/or IL to be estimated. Rt = k c δ V I F = k c δ V I - I L ( I )
摘要:
The present invention relates to apparatus for a tool for investigating the wall of a borehole in a geological formation, the apparatus comprising: a non-conductive pad having an inside face and an outside face for pressing against the wall; a set of measurement electrodes mounted on the outside face of the pad and means for measuring the potential difference between two measurement electrodes; and both a source electrode adapted to inject current into the geological formation and a return electrode, the set of measurement electrodes being situated between the source electrode and the return electrode for the current; the apparatus being characterized in that the pad comprises an electrically conductive portion covering the entire measurement electrode zone and electrically insulated from the measurement electrodes.
摘要:
The invention concerns an apparatus for investigating the wall of a borehole filled with non-conductive mud, said apparatus comprising: a pad having an inside face and an outside face for pressing against the wall of the borehole; a set of measurement electrodes mounted on the outside face of the pad, potentials differences being measured between said measurement electrodes in order to provide measured points representative of the resistivity of the formation; both a source electrode and a return electrode adapted to inject current into the formation, the set of measurement electrodes being situated between the source electrode and the return electrode.
摘要:
The invention concerns an apparatus for investigating the wall of a borehole tilled with non-conductive mud, said apparatus comprising: a pad having an inside face and an outside face for pressing against the wall of the borehole; a set of measurement electrodes mounted on the outside face of the pad, potentials differences being measured between said measurement electrodes in order to provide measured points representative of the resistivity of the formation; both a source electrode and a return electrode adapted to inject current into the formation, the set of measurement electrodes being situated between the source electrode and the return electrode.
摘要:
A method for electrically investigating a wall of a borehole in a geologic formation including injecting a current into the formation at a first position along the wall and returning the current at a second position along the wall, the formation current having a frequency below about 100 kHz, measuring a voltage in the formation between a third position and a fourth position along the wall, the third and fourth positions being located between the first and second positions, and determining an amplitude of a component of the voltage in phase with the current.
摘要:
A system and method for imaging properties of subterranean formations in a wellbore is provided. The system comprises a formation sensor for collecting currents injected into the subterranean formations, the formation sensor positionable on a downhole tool deployable into the wellbore. The system comprises a controller for controlling the formation sensor and a formation imaging unit. The formation imaging unit comprises a current management unit for collecting data from the currents injected into the subterranean formations, the currents having at least two different frequencies. The formation imaging unit comprises a drilling mud data unit for determining at least one drilling mud parameter, a formation data unit for determining at least one formation parameter from the collected data, and an inversion unit for determining at least one formation property by inverting the at least one formation parameter.
摘要:
A system and method for imaging properties of subterranean formations in a wellbore is provided. The system comprises a formation sensor for collecting currents injected into the subterranean formations, the formation sensor positionable on a downhole tool deployable into the wellbore. The system comprises a controller for controlling the formation sensor and a formation imaging unit. The formation imaging unit comprises a current management unit for collecting data from the currents injected into the subterranean formations, the currents having at least two different frequencies. The formation imaging unit comprises a drilling mud data unit for determining at least one drilling mud parameter, a formation data unit for determining at least one formation parameter from the collected data, and an inversion unit for determining at least one formation property by inverting the at least one formation parameter.
摘要:
A method for electrically investigating a wall of a borehole in a geologic formation including injecting a current into the formation at a first position along the wall and returning the current at a second position along the wall, the formation current having a frequency below about 100 kHz, measuring a voltage in the formation between a third position and a fourth position along the wall, the third and fourth positions being located between the first and second positions, and determining an amplitude of a component of the voltage in phase with the current.
摘要:
The invention is concerned with a tool for imaging a formation, the tool comprising: a pad capable of alignment adjacent a wall of the formation. The pad has located thereon an imaging electrode for injecting current into the formation. There is a first return electrode separated from the imaging electrode for receiving the injected current. There is at least one recessed electrode that is located at a different distance from the wall of the formation as the other electrodes.
摘要:
The invention is concerned with a tool and method for imaging a formation through a substantially non-conductive medium. The tool comprises first circuitry for injecting a current into the formation, wherein a complex impedance to the current is measured. Second circuitry for determining a phase angle of an impedance of the non-conductive medium and third circuitry for determining a component of the complex impedance that is orthogonal to the phase angle.