Equi-pressure geosteering

• US 6,464,021 B1
• Filed: 12/30/1999
• Issued: 10/15/2002
• Est. Priority Date: 06/02/1997
• Status: Expired due to Term

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Edwards, John E.
• Primary Examiner(s): DANG, HOANG C
• Application Number:
  US09/475,871
• Time in Patent Office: 1,020 Days
• Field of Search: 175/45, 175/40, 175/61, 175/62, 166/254.1, 166/254.2, 166/250.07, 731/524.6, 731/525.1, 731/525.2
• US Class Current: 175/61
• CPC Class Codes: E21B 23/00 Apparatus for displacing, setting, locking, releasing or removing tools, packers or the like in boreholes or wells setting of casings, screens or liners E21B43/10
• CPC Class Codes: E21B 47/01 Devices for supporting measuring instruments on drill bits, pipes, rods or wirelines; Protecting measuring instruments in boreholes against heat, shock, pressure or the like
• CPC Class Codes: E21B 47/017 Protecting measuring instruments
• CPC Class Codes: E21B 47/04 Measuring depth or liquid level
• CPC Class Codes: E21B 47/12 Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
• CPC Class Codes: E21B 47/13 by electromagnetic energy, e.g. radio frequency
• CPC Class Codes: 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
• CPC Class Codes: E21B 49/10 using side-wall fluid samplers or testers
• CPC Class Codes: E21B 7/06 Deflecting the direction of boreholes

Abstract

A method for determining a desirable depth for drilling a horizontal well within an oil reservoir includes the steps of deploying a plurality of data sensors at discrete depths in a subsurface formation penetrated by a wellbore, gathering formation pressure data for the discrete depths using the data sensors, and determining the depth of a reservoir using the gathered formation pressure data. The depth within the reservoir may be determined by identifying from the gathered formation pressure data at least one depth whose corresponding formation pressure is suggestive of a reservoir. Once such a depth is identified, the wellbore itself or a lateral drainhole depending from the wellbore may be steered into the reservoir by maintaining the trajectory of the wellbore or drainhole at a substantially constant distance from a fluid contact within the reservoir.

Claims

1. A method for indicating a desirable vertical depth for drilling a horizontal well within a reservoir, comprising:

deploying a plurality of data sensors at discrete depths in a subsurface formation penetrated by a wellbore;

gathering formation pressure data for the discrete depths using the data sensors; and

determining the vertical depth within a reservoir using the gathered formation pressure data.

2. The method of claim 1, wherein the formation pressure is gathered using receivers for receiving the formation pressure data transmitted by the data sensors.

3. The method of claim 2, wherein the receivers are disposed within a downhole tool.

4. The method of claim 3, wherein the downhole tool is part of a drill string.

5. The method of claim 3, wherein the downhole tool is part of a wireline sonde.

6. The method of claim 1, wherein the depth within the reservoir is determined by identifying from the gathered formation pressure data at least one depth whose corresponding formation pressure is suggestive of a reservoir.

7. The method of claim 6, further comprising steering a lateral drainhole from the wellbore at a substantially constant distance from a fluid contact within the reservoir.

8. The method of claim 7, wherein the lateral drainhole is steered by maintaining the trajectory of the drainhole substantially at the one identified depth.

9. The method of claim 6, further comprising steering the wellbore laterally into the reservoir.

10. The method of claim 9, wherein the wellbore is steered laterally by maintaining the trajectory of the drainhole substantially at the one identified depth.

11. The method of claim 1, wherein the depth of the reservoir is determined by identifying from the gathered formation pressure data a formation pressure-versus-depth profile.

12. The method of claim 11, further comprising identifying the gas-oil contact depth and the oil-water contact depth.

13. The method of claim 11, further comprising steering a lateral drainhole from the wellbore at a substantially constant distance from a fluid contact within the reservoir.

14. The method of claim 12, wherein the lateral drainhole is steered by maintaining the trajectory of the drainhole substantially at a depth between the gas-oil contact depth and the oil-water contact depth.

15. The method of claim 1 further comprising steering the wellbore laterally into the reservoir.

16. The method of claim 15, wherein the wellbore is steered laterally by maintaining the trajectory of the drainhole substantially at a depth between the gas-oil contact depth and the oil-water contact depth.

17. The method of claim 1, wherein the vertical depth within the reservoir is determined by comparing the gathered formation pressure data with a pre-determined formation pressure gradient.

18. The method of claim 17, wherein the pre-determined formation pressure gradient is established from vertical or near vertical offset wells using wireline formation pressure measurements.

19. The method of claim 17, wherein the pre-determined formation pressure gradient is established from a near vertical section of the wellbore using LWD formation pressure measurements.