Method of generating a deep resistivity image in LWD measurements
A pseudo-image is produced by combining deep-reading azimuthally sensitive resistivity measurements with azimuthally insensitive resistivity measurements made by a multiple propagation resistivity tool. This image is useful in reservoir navigation. Features on the azimuthally sensitive measurements such as saddle-points and mid-points are diagnostic of bed geometry relative to the borehole.
1. A method of developing a reservoir in an earth formation, the method comprising:
(a) conveying a bottomhole assembly (BHA) into a borehole in the earth formation;
(b) obtaining azimuthally sensitive propagation resistivity measurements;
(c) identifying a feature selected from (A) an electrical midpoint, and (B) an electrical saddle-point in the azimuthally sensitive propagation resistivity measurements; and
(d) identifying a geometric relation of a position of the BHA relative to a bed boundary in the earth formation using the identified feature.
2. The method of claim 1 further comprising controlling a drilling direction of the BHA using the identified geometric relation.
3. The method of claim 2 wherein controlling a drilling direction of the BHA further comprises at least one of (i) staying below a shale roof, (ii) staying above an oil-water contact, (iii) identifying an azimuth and a distance of a resistivity boundary in the earth formation, (iv) avoiding a shale lens, and (v) avoiding a calcite stringer.
4. The method of claim 1 wherein obtaining the azimuthally sensitive measurements further comprises correcting for an eccentering of the logging tool in the borehole.
5. The method of claim 1 wherein obtaining the azimuthally sensitive measurements further comprises correcting for a bending of the logging tool in the borehole.
6. An apparatus for developing a reservoir in an earth formation, the apparatus comprising:
(a) a bottomhole assembly (BHA) conveyed into a borehole in the earth formation;
(b) a logging tool on the BHA which obtains azimuthally sensitive propagation resistivity measurements;
(c) a processor configured to:
(I) identifies a feature selected from (A) an electrical midpoint, and(B) an electrical saddle-point in the azimuthally sensitive propagation resistivity measurements; and
(II) identifies a geometric relation of a position of the BHA relative to a bed boundary in the earth formation.
7. The apparatus of claim 6 wherein the processor is further configured to control a drilling direction of the BHA using the identified geometric relation.
8. The apparatus of claim 7 wherein processor is configured to control the drilling direction of the BHA by at least one of (i) staying below a shale roof, (ii) staying above an oil-water contact, (iii) identifying an azimuth and a distance of a resistivity boundary in the earth formation, (iv) avoiding a shale lens, and (v) avoiding a calcite stringer.
9. The apparatus of claim 6 further comprising a drilling tubular which conveys the BHA into the borehole.
10. A computer-readable medium for use with an apparatus for developing a reservoir in an earth formation, the apparatus comprising:
(a) a bottomhole assembly (BHA) configured to be conveyed into a borehole in the earth formation; and
(b) a logging tool on the BHA configured to obtain azimuthally sensitive propagation resistivity measurements;
the medium comprising instructions that enable at least one processor to:
(c) identify a feature selected from (A) an electrical midpoint, and (B) an electrical saddle-point in the azimuthally sensitive propagation resistivity measurements; and
(d) identify a geometric relation of a position of the BHA relative to a bed boundary in the earth formation.
11. The medium of claim 10 further comprising at least one of:
(i) a ROM, (ii) an EPROM, (iii) an EEPROM, (iv) a flash memory, and (v) an optical disk.