WO2006052145A1 - Procédé d’identification pour réservoirs d’hydrocarbure - Google Patents

Procédé d’identification pour réservoirs d’hydrocarbure Download PDF

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Publication number
WO2006052145A1
WO2006052145A1 PCT/NO2005/000423 NO2005000423W WO2006052145A1 WO 2006052145 A1 WO2006052145 A1 WO 2006052145A1 NO 2005000423 W NO2005000423 W NO 2005000423W WO 2006052145 A1 WO2006052145 A1 WO 2006052145A1
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WO
WIPO (PCT)
Prior art keywords
resistivity
source
anisotropy
mapping
determination
Prior art date
Application number
PCT/NO2005/000423
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English (en)
Inventor
Mikhail Boulaenko
Jonny Hesthammer
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Rocksource Geotech As
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Rocksource Geotech As filed Critical Rocksource Geotech As
Publication of WO2006052145A1 publication Critical patent/WO2006052145A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/12—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with electromagnetic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
    • G01V3/08—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices
    • G01V3/083—Controlled source electromagnetic [CSEM] surveying

Definitions

  • the present invention relates to geophysical mapping and more specifically to the prospecting for hydrocarbon reservoirs.
  • the electrical resistivity of hydrocarbon-filled sediments is 10-1000 higher than water-filled sediments. This resistivity contrast can be used to discriminate between hydrocarbon-filled and water-filled sediments as described by US patents 4,617,518; 4,633,182; 6,603,313; 6,739,165.
  • US 5886526 discloses a method and an apparatus for determining the anisotropy of a formation comprising multiple layers with different resistivity.
  • the system further comprises deployment of an electromagnetic source and multiple receivers for detecting vertical and horizontal conductivities in the formation.
  • GB Pat.app. 2390904 discloses an apparatus and a method for electromagnetic surveying of an area of seafloor that potentially contains a subterranean hydrocarbon reservoir by using a vertical electric dipole (VED-source) and a horizontal magnetic dipole (VMD-source) for determining the resistivity in both directions.
  • VED-source vertical electric dipole
  • VMD-source horizontal magnetic dipole
  • Controlled source electromagnetic (CSEM) sounding is a well known geophysical method for mapping resistivity of the subsurface (Kaufman A. and Keller G., 1983, Frequency and transient soundings.). Due to the highly conductive nature of sediments (e.g. 1 ohm-m) high frequency electromagnetic waves are rapidly attenuated. This significantly lowers the resolution with depth and makes detection of thin resistive layers at depth a challenging task.
  • CSEM Controlled source electromagnetic
  • the concept of the present invention is based on inversion for anisotropic conductivity of the earth formations related to hydrocarbon exploration and production and can use any survey configuration, including the methods described in GB 2390904 and US 6628119.
  • the method according to the present invention is not survey specific, but a method for detecting thin resistive layers using any type of EM data and survey configurations.
  • the present invention relates to surface resistivity mapping, not 5 mapping within or between wells using well equipment.
  • the method for geophysical prospecting for thin hydrocarbon-filled reservoirs is based on analysis of anisotropy in electrical resistivity of the target formation.
  • a remote resistivity mapping survey preferably optimized for anisotropic mapping is performed.
  • High values in electrical anisotropy along with high vertical resistivity of a formation 20 correspond to presence of thin resistive layers.
  • the presence of conductive layers such as shales will decrease horizontal resistivity and further increase the value of anisotropy.
  • thick resistive rock bodies such as salt diapirs and volcanic rocks will have high values of both horizontal and vertical resistivity, but low anisotropy values.
  • the object of the present invention is to address and alleviate the above mentioned problems and shortcomings of the prior art.
  • Figure 1 shows an example of a vertical profile through a cell.
  • Figure 2 shows a recommended optimized survey acquisition.
  • FIG. 35 A typical example of a setting suitable of the proposed method is shown in Figure 1. 35 The figure shows a vertical profile through a cell comprising background formation 1, a shale layer 2 and a hydrocarbon-filled layer 3. An anisotropic electrical resistivity tensor is constructed based on sub-wavelength isotropic resistivity values and geometry. A cell filled with background formation 1 is intersected by a horizontal layer 2 of shale and a horizontal hydrocarbon-filled layer 3.
  • Figure 2 shows a recommended optimized survey acquisition in which reference number 4 represents receivers, reference number 5 represents a vertical electric dipole source and reference number 6 represents a vertical magnetic dipole source.
  • Receivers 4 capable of recording the electromagnetic field are deployed on the sea floor at N predefined positions above the target zone.
  • VED vertical electric dipole
  • VMD vertical magnetic dipole
  • Emission of electromagnetic signal from each VMD source position is performed using a specified waveform, preferentially similar to that used for the VED source.
  • VED and VMD sources can be used and/or deployed simultaneously at a source position.
  • the sources and/or receivers can be towed at any speed.
  • VMD source it is also possible to use a VMD source at M specified positions first, and then use the VED source at M specified positions. Also, the VMD and VED sources may be used simultaneously. The source(s) may be stationary or towed and can emit energy constantly or at certain time intervals.
  • the advantage of the above method is that a VED source generates currents which are mostly oriented in a vertical direction. As a result, the sounding will be most sensitive to the vertical resistivity of the formations.
  • a VMD source generates electrical currents which flow mostly in the horizontal planes. As a result, the sounding will be most sensitive to horizontal resistivity of the formations. The combination of these will provide an advantage with respect to anisotropic resistivity imaging. Examples
  • a controlled source survey is performed in a marine environment, on land, or in the air.
  • the source used in the example is a dipole, including horizontal electric dipole, vertical electric dipole, horizontal magnetic dipole, vertical magnetic dipole, or any combination of these.
  • Receivers are deployed on the ground or at the sea floor at specified positions and record variations from six components of the electromagnetic field with time.
  • the source(s) is activated at specified positions. Short or/and long offset recording maybe used.
  • passive source electromagnetic survey can be performed.
  • other geophysical surveys can be performed, including galvanic resistivity surveys, seismic surveys, magnetic surveys and gravity surveys, hi a marine environment the water depth must be sufficient to deploy both sources and receivers.
  • the source emits a square waveform with 0.1 Hz emitting frequency.
  • any emitting frequencies may be used. Several frequencies preferably should be used.
  • time domain analysis of the data can be performed.
  • the examples contain a possible reservoir located 2000 meters below the sea floor.
  • the reservoir has a thickness of 20 meters, and with a resistivity of 100 ohm-m.
  • This reservoir is covered by a shale layer with a resistivity of 0.1 ohm-m and a thickness of 20 meters.
  • the formation rock resistivity is 1 ohm-m.
  • the lateral extent of the reservoir is 200 meters.
  • the method proposed is suitable for a variety of different settings and includes both deep and shallow reservoirs.
  • a low resolution anisotropic resistivity model is obtained by the process of mathematical inversion (Tikhonov A.N. and Arsenin V.A., 1977, Solutions of Ill-posed Problems. Winston & Sons, Washington).
  • the cell size is chosen to correspond to wavelengths present at the relevant depth (the cell size increases with depth). Li the presented examples, the cell size at target depth is 200x200x200 meters.
  • Each model grid cell represents a specific volume in the subsurface. Any geometrical features in the volume will be significantly smaller than the wavelength and thus of sub- wavelength resolution. Fluids like hydrocarbons such as oil, gas can be sealed by shale layers which are relatively conductive. These layers are commonly thin and thus also of sub-wavelength resolution.
  • Figure 1 shows a vertical profile of a cell where an anisotropic electrical resistivity tensor is constructed based on sub-wavelength isotropic resistivity values and geometry.
  • a cell filled with background formation 1 is intersected by a horizontal layer 2 of shale and a horizontal hydrocarbon-filled layer 3.
  • Shale, hydrocarbon, and the background formation are assumed to have isotropic resistivity values, identified respectively by rs, rh and rb.
  • the cell size is 200x200x200 meters, with a shale thickness of 20 meters and a hydrocarbon reservoir thickness of 20 meters.
  • the horizontal and vertical macroscopic resistivity of the cell can be computed according to the following rules:
  • Rh l/ ⁇ l/r_i > (1)
  • Rv ⁇ r_i > (2)
  • Rh is the horizontal cell resistivity
  • Rv is the vertical cell resistivity
  • ⁇ . > denotes averaging
  • r_i is the resistivity of the i th layer where all layers have the same thickness.
  • Vertical and horizontal resistivity of cells filled with complex sub- wavelength structures can be computed numerically or analytically.
  • Anisotropy is defined as:
  • resistivity tensors can be used in order to estimate various parameters of a sub-wavelength model (e.g. dip, strike etc.)
  • the presence of a thin horizontal resistive layer will significantly increase the vertical resistivity of the cell while horizontal resistivity will be less affected. This will cause an increase of the anisotropy value.
  • the presence of a thin horizontal conductive layer will significantly decrease the horizontal resistivity of the cell, while the vertical resistivity will be less affected. This will also cause an increase of the anisotropy value, but the values of Rh and Rv will be low.
  • the cell is intersected by a single hydrocarbon filled layer with a thickness that is 10% of the cell size.
  • Example 2 The cell is intersected by a single shale layer with a thickness that is 10% of the cell size.
  • the resistivity of the shale layer is 0.1 ohm-m, and the background resistivity is 1 ohm-m. This leads to the following parameters:
  • the cell is intersected by a hydrocarbon filled layer and a shale layer, both with a thickness that is 10% of the cell size.
  • the resistivity of the hydrocarbon- filled reservoir layer is 100 ohm-m
  • the resistivity of the shale layer is 0.1 ohm-m
  • the background resistivity is 1 ohm-m.
  • a thick salt body will have high values of both vertical and horizontal resistivity but the anisotropy values will be close to unit.
  • a thick volcanic rock body will have high values of vertical and horizontal resistivity but the anisotropy values will be close to unit.
  • a thick, non permeable carbonate rock body will have high values of vertical and horizontal resistivity but the anisotropy values will be close to unit.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Remote Sensing (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Electromagnetism (AREA)
  • Environmental & Geological Engineering (AREA)
  • Geology (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics (AREA)
  • Geophysics And Detection Of Objects (AREA)

Abstract

L’invention concerne un procédé de prospection géophysique pour réservoirs remplis d’hydrocarbure sur la base de l’analyse d’anisotropie en matière de résistivité électrique de la formation cible. On réalise une étude de cartographie de résistivité à distance optimisée de préférence pour une cartographie anisotrope. Les valeurs élevées d’anisotropie électrique de même que la résistivité verticale élevée d’une formation correspondent à la présence de fines couches résistives. En outre, la présence de couches conductrices comme des schistes va abaisser la résistivité horizontale et renforcer la valeur d’anisotropie. Par contraste, des corps de roches épaisses résistives comme des diapirs de sel et des roches volcaniques auront des valeurs élevées à la fois de résistivité horizontale et de résistivité verticale, mais de faibles valeurs d’anisotropie.
PCT/NO2005/000423 2004-11-09 2005-11-09 Procédé d’identification pour réservoirs d’hydrocarbure WO2006052145A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO20044888 2004-11-09
NO20044888A NO20044888L (no) 2004-11-09 2004-11-09 Metode for identifikasjon av hydrokarbonreservoar.

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WO2006052145A1 true WO2006052145A1 (fr) 2006-05-18

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2433604A (en) * 2005-12-22 2007-06-27 Schlumberger Holdings Multi-component field sources for subsea exploration
WO2007136276A1 (fr) * 2006-05-24 2007-11-29 Norsk Hydro Asa Procédé d'étude géophysique électromagnétique de formations rocheuses sous-marines
WO2008054888A2 (fr) * 2006-10-31 2008-05-08 Schlumberger Canada Limited Suppression de champs électromagnétiques liés à la surface de la mer pour réalisation d'une étude électromagnétique
US7894989B2 (en) 2005-06-09 2011-02-22 Exxonmobil Upstream Research Co. Method for determining earth vertical electrical anisotropy in marine electromagnetic surveys
US9195783B2 (en) 2010-08-16 2015-11-24 Exxonmobil Upstream Research Company Reducing the dimensionality of the joint inversion problem
US9453929B2 (en) 2011-06-02 2016-09-27 Exxonmobil Upstream Research Company Joint inversion with unknown lithology
US9494711B2 (en) 2011-07-21 2016-11-15 Garrett M Leahy Adaptive weighting of geophysical data types in joint inversion
US9702995B2 (en) 2011-06-17 2017-07-11 Exxonmobil Upstream Research Company Domain freezing in joint inversion
EP2149058A4 (fr) * 2007-04-30 2017-07-12 KJT Enterprises, Inc. Câble d'acquisition de signal électromagnétique maritime multicomposant, système et procédé
US9846255B2 (en) 2013-04-22 2017-12-19 Exxonmobil Upstream Research Company Reverse semi-airborne electromagnetic prospecting
US10379255B2 (en) 2010-07-27 2019-08-13 Exxonmobil Upstream Research Company Inverting geophysical data for geological parameters or lithology
US10571592B2 (en) 2015-08-31 2020-02-25 Pgs Geophysical As Direct resistivity determination
US10591638B2 (en) 2013-03-06 2020-03-17 Exxonmobil Upstream Research Company Inversion of geophysical data on computer system having parallel processors

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5886526A (en) * 1996-06-19 1999-03-23 Schlumberger Technology Corporation Apparatus and method for determining properties of anisotropic earth formations
US6603313B1 (en) * 1999-09-15 2003-08-05 Exxonmobil Upstream Research Company Remote reservoir resistivity mapping
GB2390904A (en) * 2002-07-16 2004-01-21 Univ Southampton Electromagnetic surveying for hydrocarbon reservoirs

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5886526A (en) * 1996-06-19 1999-03-23 Schlumberger Technology Corporation Apparatus and method for determining properties of anisotropic earth formations
US6603313B1 (en) * 1999-09-15 2003-08-05 Exxonmobil Upstream Research Company Remote reservoir resistivity mapping
GB2390904A (en) * 2002-07-16 2004-01-21 Univ Southampton Electromagnetic surveying for hydrocarbon reservoirs

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7894989B2 (en) 2005-06-09 2011-02-22 Exxonmobil Upstream Research Co. Method for determining earth vertical electrical anisotropy in marine electromagnetic surveys
GB2433604B (en) * 2005-12-22 2010-05-26 Schlumberger Holdings Multi-component field sources for subsea exploration
GB2433604A (en) * 2005-12-22 2007-06-27 Schlumberger Holdings Multi-component field sources for subsea exploration
US7884612B2 (en) 2005-12-22 2011-02-08 Westerngeco L.L.C. Multi-component field sources for subsea exploration
US8299794B2 (en) 2006-05-24 2012-10-30 Norsk Hydro Asa Method for electromagnetic geophysical surveying of subsea rock formations
NO342904B1 (no) * 2006-05-24 2018-08-27 Statoil Petroleum As Fremgangsmåte for elektromagnetisk geofysisk undersøkelse av undersjøiske bergartsformasjoner
WO2007136276A1 (fr) * 2006-05-24 2007-11-29 Norsk Hydro Asa Procédé d'étude géophysique électromagnétique de formations rocheuses sous-marines
AU2007252339B2 (en) * 2006-05-24 2010-08-12 Equinor Energy As Method for electromagnetic geophysical surveying of subsea rock formations
WO2008054888A3 (fr) * 2006-10-31 2008-10-02 Schlumberger Ca Ltd Suppression de champs électromagnétiques liés à la surface de la mer pour réalisation d'une étude électromagnétique
WO2008054888A2 (fr) * 2006-10-31 2008-05-08 Schlumberger Canada Limited Suppression de champs électromagnétiques liés à la surface de la mer pour réalisation d'une étude électromagnétique
EP2149058A4 (fr) * 2007-04-30 2017-07-12 KJT Enterprises, Inc. Câble d'acquisition de signal électromagnétique maritime multicomposant, système et procédé
US10379255B2 (en) 2010-07-27 2019-08-13 Exxonmobil Upstream Research Company Inverting geophysical data for geological parameters or lithology
US9195783B2 (en) 2010-08-16 2015-11-24 Exxonmobil Upstream Research Company Reducing the dimensionality of the joint inversion problem
US9453929B2 (en) 2011-06-02 2016-09-27 Exxonmobil Upstream Research Company Joint inversion with unknown lithology
US9702995B2 (en) 2011-06-17 2017-07-11 Exxonmobil Upstream Research Company Domain freezing in joint inversion
US9494711B2 (en) 2011-07-21 2016-11-15 Garrett M Leahy Adaptive weighting of geophysical data types in joint inversion
US10591638B2 (en) 2013-03-06 2020-03-17 Exxonmobil Upstream Research Company Inversion of geophysical data on computer system having parallel processors
US9846255B2 (en) 2013-04-22 2017-12-19 Exxonmobil Upstream Research Company Reverse semi-airborne electromagnetic prospecting
US10571592B2 (en) 2015-08-31 2020-02-25 Pgs Geophysical As Direct resistivity determination

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NO20044888D0 (no) 2004-11-09
NO20044888L (no) 2006-05-10

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