METHOD TO DETECT FORMATION PORE PRESSURE FROM RESISTIVITY MEASUREMENTS AHEAD OF THE BIT DURING DRILLING OF A WELL

• US 20100000791A1
• Filed: 07/07/2008
• Published: 01/07/2010
• Est. Priority Date: 07/07/2008
• Status: Active Grant

• Current Assignee: BP Corporation North America Incorporated (BP PLC)
• Original Assignee: BP Corporation North America Incorporated (BP PLC)
• Inventors: Alberty, Mark William
• Granted Patent: US 8,061,442 B2
• Time in Patent Office: Days
• US Class Current: 175/45
• CPC Class Codes: E21B 47/06 Measuring temperature or pressure
• CPC Class Codes: G01V 3/20 operating with propagation of electric current

Abstract

Methods are described using resistivity ahead of a drill bit measurements obtained while drilling a subterranean well using a drilling mud. Resistivity data ahead of the bit is gathered during drilling and prior to penetrating a region of interest of a known subterranean formation using the drill bit and the drilling mud. The drill string progresses at known dip and azimuth angles toward the subterranean formation. The resistivity data is used to determine pore pressure ahead of the drill bit in the formation as a function of resistivity ahead of the drill bit in the formation while the drill bit advances toward but before the bit penetrates the formation while drilling. In certain embodiments, the methods include redirecting the drill bit while drilling toward locations in the formation where pore pressure is within an acceptable range. In other embodiments, a drilling mud parameter is adjusted based on the pore pressure in front of the bit.

Claims

1. A method of using resistivity ahead of a drill bit measurements obtained while drilling a subterranean well using a drilling mud, the method comprising:

a) gathering resistivity data ahead of the bit during drilling and prior to penetrating a known subterranean formation using the drill bit and the drilling mud, the drill string progressing at known dip and azimuth angles toward the subterranean formation; and

b) using the resistivity data to determine pore pressure ahead of the drill bit in the formation as a function of resistivity ahead of the drill bit in the formation while the drill bit advances toward but before the bit penetrates the formation while drilling.

2. The method of claim 1 further comprising redirecting the drill bit while drilling toward locations in the formation where pore pressure is within an acceptable range for the mud and pressure control equipment being used.

3. The method of claim 1 further comprising adjusting the density, specific gravity, weight, viscosity, water content, oil content, composition, pH, flow rate, solids content, solids particle size distribution, resistivity, conductivity, or any combination of any of these, of the drilling mud based on measured resistivity of the formation prior to the drill bit entering the formation.

4. The method of claim 1 further comprising adjusting the density, specific gravity, weight, viscosity, water content, oil content, composition, pH, flow rate, solids content, solids particle size distribution, resistivity, conductivity, or any combination of any of these, of the drilling mud based on calculated pore pressure of the formation prior to the drill bit entering the formation.

5. The method of claim 1 wherein the gathering of resistivity data ahead of the bit comprises a method selected from contact resistivity measurement focused in front to the bit, use of a transient electromagnetic survey, continuous deep directional electromagnetic measurements, and use of guided electromagnetic waves along the drill pipe.

6. The method of claim 1 wherein the mud is selected from oil-based muds, water-based muds, and synthetic-based muds.

7. The method of claim 1 wherein the measuring resistivity and determining pore pressure occur continuously.

8. The method of claim 3 wherein the adjusting occurs continuously.

9. The method of claim 2 wherein the redirecting occurs continuously.

10. A method of using resistivity ahead of a drill bit measurements obtained while drilling a subterranean well using a drilling mud, the method comprising:

a) gathering resistivity data ahead of the bit during drilling and prior to penetrating a known subterranean formation using the drill bit and the drilling mud, the drill string progressing at known dip and azimuth angles toward the subterranean formation; and

b) using the resistivity data to determine change of pore pressure ahead of the drill bit in the formation as a function of change of resistivity ahead of the drill bit in the formation while the drill bit advances toward but before the bit penetrates the formation while drilling.

11. The method of claim 10 further comprising redirecting the drill bit while drilling toward locations in the formation where pore pressure is within an acceptable range for the mud and pressure control equipment being used.

12. The method of claim 10 further comprising adjusting the density, specific gravity, weight, viscosity, water content, oil content, composition, pH, flow rate, solids content, solids particle size distribution, resistivity, conductivity, or any combination of any of these, of the drilling mud based on measured resistivity of the formation prior to the drill bit entering the formation.

13. The method of claim 10 further comprising adjusting the density, specific gravity, weight, viscosity, water content, oil content, composition, pH, flow rate, solids content, solids particle size distribution, resistivity, conductivity, or any combination of any of these, of the drilling mud based on calculated pore pressure of the formation prior to the drill bit entering the formation.

14. The method of claim 10 wherein the gathering of resistivity data ahead of the bit comprises a method selected from contact resistivity measurement focused in front to the bit, use of a transient electromagnetic survey, continuous deep directional electromagnetic measurements, and use of guided electromagnetic waves along the drill pipe.

15. The method of claim 12 wherein the mud is selected from oil-based muds, water-based muds, and synthetic-based muds.

16. A method of reducing risk of a subterranean well collapse into a subterranean well being drilled toward a formation using resistivity ahead of the bit measurements obtained while drilling the well using a drilling mud, the method comprising;

a) gathering resistivity data ahead of the bit during drilling and prior to penetrating a known subterranean formation using the drill bit and the drilling mud, the drill string progressing at known dip and azimuth angles toward the subterranean formation;

b) using the resistivity data to determine pore pressure of the formation while the drill bit advances toward but before the bit penetrates the formation while drilling;

c) estimating the likelihood of well wall collapse using the pore pressure; and

d) adjusting the density, specific gravity, weight, viscosity, water content, oil content, composition, pH, flow rate, solids content, solids particle size distribution, resistivity, conductivity, or any combination of any of these, of the drilling mud based on the pore pressure of the formation.

17. The method of claim 16 wherein the gathering of resistivity data ahead of the bit comprises a method selected from contact resistivity measurement focused in front to the bit, use of a transient electromagnetic survey, continuous deep directional electromagnetic measurements, and use of guided electromagnetic waves along the drill pipe.

18. The method of claim 16 wherein the measuring resistivity and determining pore pressure occur continuously.

19. The method of claim 16 wherein the estimating occurs continuously.

20. The method of claim 16 wherein the adjusting occurs continuously.

21. A method of reducing risk of differentially sticking the drill string in a well being drilled toward a formation using resistivity ahead of the bit measurements obtained while drilling the well using a drilling mud, the method comprising:

a) gathering resistivity data ahead of the bit during drilling and prior to penetrating a known subterranean formation using the drill bit and the drilling mud, the drill string progressing at known dip and azimuth angles toward the subterranean formation;

b) using the resistivity data to determine pore pressure of the formation while the drill bit advances toward but before the bit penetrates the formation while drilling;

c) adjusting the density, specific gravity, weight, viscosity, water content, oil content, composition, pH, flow rate, solids content, solids particle size distribution, resistivity, conductivity, or any combination of any of these, of the drilling mud based on the pore pressure of the formation so as to minimize the differential pressure across the formation thereby reducing the risk of differential sticking.

22. The method of claim 21 wherein the gathering of resistivity data ahead of the bit comprises a method selected from contact resistivity measurement focused in front to the bit, use of a transient electromagnetic survey, continuous deep directional electromagnetic measurements, and use of guided electromagnetic waves along the drill pipe.

23. The method of claim 21 wherein the measuring resistivity and determining pore pressure occur continuously.

24. The method of claim 21 wherein the estimating occurs continuously.

25. The method of claim 21 wherein the adjusting occurs continuously.