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EP-4244660-B1 - METHOD FOR MAKING DIRECTIONAL RESISTIVITY MEASUREMENTS OF A SUBTERRANEAN FORMATION

EP4244660B1EP 4244660 B1EP4244660 B1EP 4244660B1EP-4244660-B1

Inventors

  • Sun, Keli
  • ZHONG, XIAOYAN
  • MIRTO, Ettore
  • TAN, Kong Hauw Sarwa Bakti

Dates

Publication Date
20260506
Application Date
20211110

Claims (14)

  1. A method (100) for making electromagnetic directional resistivity measurements of a subterranean formation, the method comprising: (a) rotating (102) an electromagnetic logging tool (50) in a subterranean wellbore penetrating the formation, the logging tool (50) including a transmitting antenna (52, 54, 56, 58, 60, 62; Tl, T2, T3, T4, T5, T6) and a receiving antenna (52, 54, 56, 58, 60, 62; R1, R2, R3, R4) spaced along a tool body (51), at least one of the transmitting antenna (52, 54, 56, 58, 60, 62) and the receiving antenna (64, 66, 68, 69) being a tilted antenna; (b) causing (104) the electromagnetic logging tool (50) to make a plurality of electromagnetic measurements at a corresponding plurality of frequencies while rotating in (a); and (c) processing (108) the plurality of measurements made at the corresponding plurality of frequencies in (b) to compute a combined apparent resistivity of the subterranean formation, wherein the processing includes minimizing a difference between a plurality of modeled measurements and the plurality of measurements made in (b), the modeled measurements being computed using a model assuming a homogenous formation.
  2. The method of claim 1, wherein the processing includes minimizing a sum of the differences between the modelled measurements and the plurality of measurements made at the corresponding plurality of frequencies.
  3. The method of claim 2, wherein step (c) further comprises: (c1) processing a plurality of measurements at each of the plurality of frequencies to compute a gain compensated measurement quantity at each frequency; and (c2) processing the plurality of gain compensated measurement quantities obtained in (c1) to compute the combined apparent resistivity of the subterranean formation, wherein the processing includes minimizing a sum of the differences between modelled gain compensated measurements and the plurality of gain compensated measurements computed in (c1).
  4. The method of claim 3, wherein the combined apparent resistivity Rapp ( ϕ ) is computed in (c2) using at least one of the following mathematical equations: Rapp ϕ = arg min R ∑ i = 1 N f g m fi R − g d fi ϕ ; Rapp ϕ = arg min R ∑ i = 1 N f g m fi R − g d fi ϕ n ⋅ w i ; Rapp ϕ = arg min R ∑ i = 1 N f g m fi R − g d fi ϕ 2 w i 2 ∑ i = 1 N f g d fi ϕ 2 w i 2 ; wherein g m fi R represent the modelled measurements and g d fi ϕ represent the gain compensated measurement quantities at frequencies i = 1,2, ..., N f , ϕ represents the toolface angle, w i represents a weighting factor or function, and n > 0.
  5. The method of claim 2, wherein step (c) further comprises: (c1) processing the plurality of measurements made at the corresponding plurality of frequencies in (b) to compute a plurality of combined apparent resistivity values at a corresponding plurality of discrete toolface angles; and (c2) processing the plurality of combined apparent resistivity values to generate an image depicting the plurality of combined apparent resistivity values versus toolface angle and measured depth of the wellbore.
  6. The method of claim 1, further comprising: (d) evaluating (110) the combined apparent resistivity computed in (c) to control a direction of drilling of the subterranean wellbore.
  7. The method of claim 1, wherein the combined apparent resistivity of the subterranean formation is computed in (c) using a downhole processor deployed in the electromagnetic logging tool.
  8. An electromagnetic logging while drilling tool (50) comprising: a logging while drilling tool body (51); at least one transmitting antenna (52, 54, 56, 58, 60, 62; Tl, T2, T3, T4, T5, T6) and at least one receiving antenna (64, 66, 68, 69; R1, R2, R3, R4) deployed on the tool body (51), wherein at least one of the transmitting antenna (52, 54, 56, 58, 60, 62) and the receiving antenna (64, 66, 68, 69) is a tilted antenna; and an electronic controller configured to perform steps (b) and (c) of the method of any of claims 2 to 7.
  9. The tool of claim 8, wherein the controller is further configured to (iii) communicate with a controller in a steering tool to perform the method of claim 6.
  10. The tool of claim 8, wherein the transmitting antenna comprises first and second axial transmitting antennas (72) and the receiving antenna comprises first and second tilted receiving antennas (74A, 74B).
  11. The tool of claim 8, wherein the transmitting antenna comprises first and second tilted transmitting antennas (78) and the receiving antenna comprises first and second axial receiving antennas (80).
  12. The tool of claim 8, wherein the transmitting antenna comprises first and second transverse transmitting antennas (86) and the receiving antenna comprises first and second tilted receiving antennas (88).
  13. The tool of claim 8, wherein the transmitting antenna comprises first and second tilted transmitting antennas (82) and the receiving antenna comprises first and second transverse receiving antennas (84).
  14. The tool of claim 8, wherein the transmitting antenna comprises first and second tilted transmitting antennas (90) and the receiving antenna comprises first and second tilted receiving antennas (92), wherein the transmitting antennas (90) have a different tilt angle than the receiving antennas (92).

Description

BACKGROUND INFORMATION Electromagnetic measurements, such as logging while drilling (LWD) and wireline logging measurements, may be utilized to determine a subterranean formation resistivity, which, along with formation porosity measurements, can be used to indicate the presence of hydrocarbons in a subterranean formation. Moreover, azimuthally sensitive directional resistivity measurements may be employed, for example, in pay-zone steering applications, to provide information upon which steering decisions may be made. Symmetrized directional resistivity measurements have been used to evaluate formation resistivity in the region above and bellows formation boundaries. The sign (positive or negative) of the symmetrized measurement indicates whether the formation above the logging tool is more or less resistive than the formation below the logging tool. While symmetrized measurements have been used in geosteering applications, their interpretation may not be intuitive and may commonly require expert analysis. US 2018/003853 A1 discloses a method to obtain multi-component signal measurements from an electromagnetic logging tool conveyed along a borehole through a formation, and invert the measurements for a single frequency using an anisotropic formation model having at least dip, horizontal and vertical resistivity, and horizontal and vertical permittivity, as parameters. SUMMARY A method for making electromagnetic directional resistivity measurements of a subterranean formation is disclosed. The method includes rotating an electromagnetic logging tool in a subterranean wellbore penetrating the formation. The logging tool includes a transmitting antenna and a receiving antenna spaced along a tool body with at least one of the transmitting antenna and the receiving antenna being a tilted antenna. The electromagnetic logging tool is used to make a plurality of electromagnetic measurements at a corresponding plurality of frequencies while rotating in the wellbore. The plurality of measurements made at the corresponding plurality of frequencies is processed to compute a combined apparent resistivity of the subterranean formation. The processing includes minimizing a difference between a plurality of modeled measurements and the plurality of wellbore measurements in which the modeled measurements are computed using a model assuming a homogenous formation. This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS For a more complete understanding of the disclosed subject matter, and advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: FIG. 1 depicts an example drilling rig on which disclosed embodiments may be utilized.FIG. 2 depicts one example embodiment of the electromagnetic directional resistivity logging tool depicted on FIG. 1.FIGS. 3A-3F (collectively FIG. 3) depict coupled transceiver (coupled transmitter and receiver) arrangements suitable for making directional electromagnetic logging measurements for the disclosed method embodiments.FIG. 4 depicts a flow chart of one disclosed method embodiment.FIGS. 5A and 5B depict attenuation AD (5A) and phase shift PS (5B) as a function of the resistivity of a formation.FIGS. 6A and 6B depict an example implementation with FIG 6A depicting a 16 bin (sector) resistivity image showing apparent resistivity values in pseudo-color versus azimuth angle and total vertical depth of the well and FIG. 6B depicting a plot of Rapptop, Rappbottom, Rappup, and Rappdown versus vertical depth of the well. DETAILED DESCRIPTION Disclosed embodiments relate generally to electromagnetic wellbore logging measurements and more particularly to a method for making directional resistivity measurements of a subterranean formation at multiple frequencies. This Application recognizes a need in the industry for a simpler and more intuitive measurement for use in geosteering applications. A method for making electromagnetic directional resistivity measurements of a subterranean formation is disclosed. The method includes rotating an electromagnetic logging tool in a subterranean wellbore penetrating the formation. The logging tool includes a transmitting antenna and a receiving antenna spaced along a tool body with at least one of the transmitting antenna and the receiving antenna being a tilted antenna. The electromagnetic logging tool is used to make a plurality of electromagnetic measurements at a corresponding plurality of frequencies while rotating in the wellbore. The plurality of measurements made at the corresponding plurality of frequencies is processed to compute a combined apparent resistivity of the subterranean forma