# US 2021/0278560 A1 · Systems and methods to monitor downhole reservoirs > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0278560 A1 - Document ID: US20210278560A1 - Status: Published application - Kind: A1 - Application number: 16/336,831 - Filed: 2017-09-26 - Published: 2021-09-09 - Earliest claimed: 2017-09-26 - Assignees: Halliburton Energy Services, Inc. - Applicants: Halliburton Energy Services, Inc. - Inventors: Ilker R. CAPOGLU; Burkay Donderici - Web page: https://patentgrep.com/patent/US20210278560A1 ## CPC - G01V 3/28: using induction coils - E21B 49/00: Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells - G01V 3/26: operating with magnetic or electric fields produced or modified either by the surrounding earth formation or by the detecting device (with electromagnetic waves G01V3/30) - G01V 3/38: Processing data, e.g. for analysis, for interpretation, for correction - E21B 43/20: Displacing by water - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract The disclosed embodiments include downhole electromagnetic reservoir monitors, and systems and methods to monitor downhole reservoirs. In one embodiment, the electromagnetic reservoir monitor includes a galvanic transmitter deployed proximate a wellbore casing and having a source electrode and a return electrode, where a current flowing from the source electrode, through a formation, to the return electrode is altered by a fluid reservoir of the formation, and where an altered component of the current induces a secondary magnetic field. The electromagnetic reservoir monitor also includes a magnetic receiver having a tilted coil deployed proximate the wellbore casing, the tilted coil having an orientation relative to a cross sectional plane normal to a longitudinal axis of the wellbore casing, and the tilted coil operable to detect a component of the secondary magnetic field, where the secondary magnetic field is indicative of at least one property of the fluid reservoir. ## Claims ### Claim 1 An electromagnetic reservoir monitor comprising: a galvanic transmitter deployed proximate a wellbore casing and having a first source electrode and a first return electrode, wherein a current flowing from the first source electrode, through a formation, to the first return electrode is altered by a first fluid reservoir of the formation, and wherein an altered component of the current induces a first secondary magnetic field; and a magnetic receiver having a first tilted coil deployed proximate the wellbore casing, the first tilted coil having a first orientation relative to a cross sectional plane normal to a longitudinal axis of the wellbore casing, and the first tilted coil operable to detect a component of the first secondary magnetic field, wherein the secondary magnetic field is indicative of at least one property of the fluid reservoir. ### Claim 2 (depends on 1) The electromagnetic reservoir monitor of claim 1, wherein the at least one property of the first fluid reservoir comprises a resistivity of the first fluid reservoir, a conductivity of the first fluid reservoir, a position of the first fluid reservoir relative to the first tilted coil, dimensions of the first fluid reservoir, and a distance from the first fluid reservoir to the first tilted coil. ### Claim 3 (depends on 1) The electromagnetic reservoir monitor of claim 1, wherein the galvanic transmitter operates within a range of approximately 1 kHz to 50 kHz. ### Claim 4 (depends on 1) The electromagnetic reservoir monitor of claim 1, wherein the first source electrode and the first return electrode reside in a first source region and a first return region, respectively, and wherein the first source region and the first return region are separated by a gap region to prevent the current from shorting. ### Claim 5 (depends on 1) The electromagnetic reservoir monitor of claim 1, wherein the magnetic receiver comprises a second tilted coil deployed proximate the wellbore casing, the second tilted coil having a second orientation relative to the cross sectional plane. ### Claim 6 (depends on 5) The electromagnetic reservoir monitor of claim 5, wherein the second tilted coil is operable to detect a second component of the first secondary magnetic field. ### Claim 7 (depends on 1) The electromagnetic reservoir monitor of claim 1, wherein the first source electrode and the first return electrode are positioned at different azimuths around a perimeter of the wellbore casing. ### Claim 8 (depends on 7) The electromagnetic reservoir monitor of claim 7, wherein the galvanic transmitter further comprises: a second source electrode and a second return electrode positioned at different azimuths around the perimeter of the wellbore casing, wherein a second current flowing from the second source electrode, through the formation, to the second return electrode is altered by a second fluid reservoir of the formation, and wherein an altered component of the second current induces a second secondary magnetic field, and wherein the second tilted coil is operable to detect a component of the second secondary magnetic field. ### Claim 9 (depends on 8) The electromagnetic reservoir monitor of claim 8, wherein the first source electrode and the second source electrode alternatively transmit the current and the second current across the formation to the first return electrode and the second return electrode, respectively. ### Claim 10 (depends on 1) The electromagnetic reservoir monitor of claim 1, wherein the galvanic transmitter further comprises a focusing electrode operable to facilitate the current to penetrate the formation. ### Claim 11 (depends on 10) The electromagnetic reservoir monitor of claim 10, further comprising: a first gap region separating the first source electrode and the focusing electrode; and a second gap region separating the first return electrode and the focusing electrode, wherein the first source electrode and the first return electrode reside in a first source region and a first return region, respectively. ### Claim 12 A method to monitor a downhole reservoir, comprising: deploying a first source electrode of a galvanic transmitter on a wellbore casing; deploying a first return electrode of the galvanic transmitter on the wellbore casing; deploying a first tilted coil of a magnetic receiver on the wellbore casing, the first tilted coil being having a first orientation relative to a cross sectional plane normal to a longitudinal axis of the wellbore casing; applying a voltage to the first source and return electrodes to generate a current, the current being transmitted from the first source electrode, through a formation, to the first return electrode, wherein the current is altered by a water flood region of the formation, and wherein an altered component of the current induces a secondary magnetic field; and measuring a first component of the secondary magnetic field detected by the first tilted coil. ### Claim 13 (depends on 12) The method of claim 12, further comprising determining one or more of properties of the water flood region based on the secondary magnetic field. ### Claim 14 (depends on 13) The method of claim 13, wherein determining the one or more properties of the water flood region comprises determining at least one of a resistivity of the water flood region, a conductivity of the water flood region, dimensions of the water flood region, and a distance from the water flood region to the first tilted coil based on the secondary magnetic field. ### Claim 15 (depends on 12) The method of claim 12, further comprising: deploying a second tilted coil of the magnetic receiver on the casing, the second tilted coil having a second orientation relative to the cross sectional plane; and measuring a second component of the secondary magnetic field detected by the tilted coil. ### Claim 16 (depends on 12) The method of claim 12, further comprising deploying a focusing electrode operable to facilitate the current to penetrate the formation. ### Claim 17 (depends on 16) The method of claim 16, further comprising adjusting a voltage difference between the focus electrode and the source electrode to augment a penetration level of the current. ### Claim 18 (depends on 12) The method of claim 12, further comprising: deploying a second source electrode of the galvanic transmitter on the casing; deploying a second return electrode of the galvanic transmitter on the casing; applying a second voltage to the second source and return electrodes to generate a second current, wherein the second current is transmitted from the second source electrode, through the formation, to the second return electrode, wherein the second current is altered by a second water flood region of the formation, and wherein an altered component of the second current induces a second secondary magnetic field; and measuring a first component of the second secondary magnetic field detected by a second tilted coil. ### Claim 19 An electromagnetic reservoir monitoring system, comprising: a downhole reservoir monitor comprising: a galvanic transmitter deployed proximate a wellbore casing and having a source electrode and a return electrode, wherein a current flowing from the source electrode, through a formation, to the wellbore casing, to the return electrode, is altered by a fluid reservoir of the formation, and wherein an altered component of the current induces a secondary magnetic field; and a magnetic receiver having a tilted coil deployed proximate the wellbore casing, the tilted coil having an orientation relative to a cross sectional plane normal to a longitudinal axis of the wellbore casing, the tilted coil operable to detect a component of the secondary magnetic field; a storage medium operable to store instructions to determine at least one property of the fluid reservoir; and a processor operable to execute the instructions to determine the at least one property of the fluid reservoir based on the secondary magnetic field. ### Claim 20 (depends on 19) The electromagnetic monitoring system of claim 19, wherein the at least one property of the fluid reservoir comprises a resistivity of the fluid reservoir, a conductivity of the water flood region, dimensions of the fluid reservoir, and a distance from the fluid reservoir to the tilted coil.