Schlumberger Technology Corporation

Services Petroliers Schlumberger

Schlumberger Holdings Limited

Prad Research and Development Limited

Hong Zhang

Richard A Rosthal

David Lee Alumbaugh

Edward Nichols

Luis Eduardo DePavia

Cyrille Levesque

H Frank Morrison

Guozhong Gao

Frank Morrison

Brian Oliver Clark

Yuji Hosoda

Richard A Roshtal

Thor Johnsen

Vamsi Vytla

Luis E Depavia

Methods and related systems are described for making measurements of an electromagnetic field in a subterranean formation that has been induced by a current loop. The current loop uses one or more steel wellbore casings as electrodes. Receiver arrays are positioned either at surface/seafloor, in the same, or in nearby wells. In the most general case, the receivers are tri-axial. A section of metallic casing in one well can be used as a current source and the electromagnetic field at surface can be measured using an array of EM receivers placed at a range of distances from the wellbore.

Surface to borehole electromagnetic surveying using metallic well casings as electrodes

The present disclosure relates to systems and methods for conducting an electromagnetic borehole-to-surface survey of a formation surrounding a borehole. Such methods include deploying a dipole transmitter into the borehole to a depth of investigation, deploying an array of electromagnetic receivers outside of the wellbore, and measuring a response of the formation at the array of electromagnetic receivers deployed outside of the wellbore, for example at the surface. From the response of the formation a property of the formation can be determined based on the response of the formation measured at the array of electromagnetic receivers. For the scenario of a cased well, a local reference receiver may be added at a location proximate the borehole to measure the effective magnetic moment of the transmitter inside the casing, and normalize the formation response in order for a more accurate determination of a formation characteristic, such as resistivity. These receivers can also be used for other types of surveys.

Electromagnetic logging between a cased borehole and surface

Methods and related systems are described for making an electromagnetic induction survey of a formation surrounding a cased section of a borehole. An electromagnetic transmitter and/or receiver is deployed into the cased section of the borehole. Electromagnetic survey measurements and impedance measurements relating to impedance of the transmitter and/or receiver are made while deployed in the section of the borehole. Compensation is made for the attenuation amplitude and/or phase in the electromagnetic survey measurements due to the conductive casing. The compensation is based on the impedance measurements and equivalent circuit parameters. The impedance measurements are correlated with numerical modeling results of a purely inductive electromagnetic transducer, and calculated equivalent circuit parameters are combined with the numerical modeling results.

Induction coil impedance modeling using equivalent circuit parameters

Methods and related systems are described for making an electromagnetic induction survey of a formation surrounding a cased section of a borehole. An electromagnetic transmitter and/or receiver are deployed into the cased section of the borehole. One or more additional devices are used to measure the properties of a conductive casing relating to conductivity, thickness and magnetic permeability. A casing coefficient is then calculated that can then be used for the processing of the deep-sensing induction measurements.

Measuring casing attenuation coefficient for electro-magnetics measurements

The present disclosure relates to determining the attenuation of an electromagnetic signal passing through a conductive material. An antenna is provided and placed in relatively close proximity to the conductive material. An alternating current is passed through the antenna and the impedance of the antenna is measured. The attenuation is determined using the measured impedance. A single frequency measurement may be made, or multiple measurements using different frequencies may be made. Grouped parameters based on properties of the material and the frequency of the current are used to relate the coil impedance to the attenuation. A current frequency for which the ratio of the antenna's resistive part of the impedance to the angular frequency of the current is substantially insensitive to at least one of the parameters is preferred.

Attenuation of electromagnetic signals passing through conductive material

Methods and related systems are described for making electromagnetic measurements of a subterranean rock formation through a conductive casing of a borehole. A number of transmitters/receivers are deployed into single well having a conductive casing. A magnetic field is induced through the conductive casing and into a surrounding subterranean rock formation, and the magnetic field is detected by the receivers. The receivers have main windings, feedback winding and bucking windings. One of the receiver coils in the tool string is excited at a time, and induced voltages at all of the other receiver coils, either in straight mode, or in feedback mode, are measured.

Single-well through casing induction logging tool

The present disclosure relates to determining attenuation factors relating to an electromagnetic signal passing through, a conductive material seen by a real sensor. A sensor is provided and disposed proximate to the material. An alternating current is passed through the sensor and the impedance of the sensor is measured. The impedance of an ideal coil is obtained from the measured impedance using electromagnetic modeling combined with a circuit analysis of the coil impedance, and the attenuation factors for the real coil in straight or feedback mode are determined by electromagnetic modeling of casing attenuation factors and impedance of an ideal coil combined with equivalent circuit modeling of the sensor transfer functions. The attenuation factors seen by the real sensor may be determined in real-time or post-survey. The material may be magnetic or non-magnetic.

Correction factors for electromagnetic measurements made through conductive material

Impedances of an electromagnetic (EM) coil positioned in a well lined with an electrically conductive liner are determined. The impedances correspond to plural frequencies of operation of the EM coil. Based on the impedances of the EM coil corresponding to the plural frequencies, an attenuation factor associated with the electrically conductive liner is determined.

Characterizing at least one property of a liner that lines a well

A current sensor measures an electrical current flowing in well casing or other magnetic structure. The current sensor can be installed in a tool for performing electromagnetic (EM) induction surveying in a wellbore lined with an electrically conductive casing. The tool includes an EM element to transmit or receive a magnetic field through the casing. The measured current using the current sensor can be used to relate the change of casing effect on the EM element (e.g., an induction receiver) placed inside the well casing for performing the EM induction survey.

Detecting electrical current in a magnetic structure

To synchronize units of a formation evaluation/drilling operation evaluation system, a time delay associated with a communications link between a master unit and a slave unit of the formation evaluation/drilling operation evaluation system is determined. The master unit has a master time clock that provides universal time. The time delay associated with the communications link is used to enable synchronization of time provided by a slave time clock in the slave unit to the universal time.

Time synchronization in units at different locations

To determine effect on a magnetic field caused by a lining structure in a wellbore, an array may be deployed into the wellbore lined with the lining structure. The array comprises a plurality of sensors including sensor A configured to operate as a transmitter, sensor B configured to operate as either a transmitter or a receiver, and sensor C configured to operate as a receiver. The array measures magnetic fields using sensor B as a receiver and sensor C in response to activation of sensor B as a transmitter and sensor A. A plurality of lining structure correction factors can be calculated based on the measured magnetic fields, based on the reciprocity of the sensors.

Growing community of inventors

El Sobrante, CA, United States of America

Hong Zhang