Pressure sensor arrangement using an optical fiber and methodologies for performing an analysis of a subterranean formation

1. A sensor cable for measuring pressure at a plurality of spaced apart locations in a subterranean formation, the sensor cable comprising:

(a) a first sensing portion including an elongated outer casing having a first end portion, a second opposite end portion and a side portion extending between the first end portion and the second end portion, the first sensing portion including a pressure sensor to measure pressure acting on the side portion;

(b) a second sensing portion including an elongated outer casing having a first end portion, a second opposite end portion and a side portion extending between the first and second end portions of the second sensing portion, the second sensing portion including a pressure sensor to measure pressure acting on the side portion of the second sensing portion;

(c) an interconnection portion located between the first sensing portion and the second sensing portion, the interconnection portion including a first end portion and a second opposite end portion;

(d) the first end portion of the first sensing portion being coupled to the first end portion of the interconnection portion;

(e) the first end portion of the second sensing portion being coupled to the second end portion of the interconnection portion;

(f) said first sensing portion, said second sensing portion and said interconnection portion when coupled to one another forming an elongated string-like structure;

(g) an optical fiber defining a continuous optical path extending through said first sensing portion, said interconnection portion and said second sensing portion, said optical path configured for transporting an optical signal conveying pressure information generated by the pressure sensor of said first sensing portion and the pressure sensor of said second sensing portion;

(h) said first sensing portion, said second sensing portion and said interconnection portion having a cross-sectional dimension that remains substantially constant along the string-like structure;

(i) the first sensing portion, the second sensing portion and the interconnection portion include respective first, second and third internal cavities, the sensor cable including a fluid-tight partition between the first internal cavity and the third internal cavity.

2. A sensor cable as defined in claim 1 , wherein:

(a) one of said first end portion of said first sensing portion and said first end portion of said interconnection portion including a projection;

(b) the other of said first end portion of said first sensing portion and said first end portion of said interconnection portion including a recess;

(c) said recess receiving said projection when the first end portion of said first sensing portion is coupled to the first end portion of said interconnection portion.

3. A sensor cable as defined in claim 2 , wherein said projection has a cross-sectional dimension that generally corresponds to a cross-sectional dimension of said recess.

4. A sensor cable as defined in claim 3 , wherein when said projection is received in said recess, an outer wall portion of the said first sensing portion is substantially flush with an outer wall portion of the interconnection portion.

5. A sensor cable as defined in claim 1 , wherein the string-like structure has a round cross-sectional shape.

6. A sensor cable as defined in claim 1 , wherein the string-like structure has a cross-sectional dimension less than 1 inch.

7. A sensor cable as defined in claim 1 , wherein the string-like structure has a cross-sectional dimension less than 0.625 inch.

8. A sensor cable as defined in claim 1 , wherein the string-like structure has a cross-sectional dimension less than 0.5 inch.

9. A sensor cable as defined in claim 1 , wherein the string-like structure has a cross-sectional dimension less than 0.25 inch.

10. A sensor cable as defined in claim 1 , wherein the pressure sensor of said first sensing portion includes a deformable component coupled to the optical fiber, the deformable component being responsive to outside pressure acting against the side portion of said first sensing portion to locally alter an optical property of the optical fiber.

11. sensor cable as defined in claim 10 , wherein the deformable component imparts a bending movement in the optical fiber.

12. A sensor cable as defined in claim 11 , wherein the deformable component causes the optical fiber to axially stretch as the optical fiber bends.

13. A sensor cable as defined in claim 12 , wherein the pressure sensor includes a mechanical link between the deformable component and the optical fiber, the mechanical link causing the optical fiber to bend in response to deformation of the deformable component.

14. A sensor cable as defined in claim 13 , wherein the mechanical link extends generally along a longitudinal axis of the first sensing portion.

15. A sensor cable as defined in claim 11 , wherein the first sensing portion has a longitudinal axis, the bending movement occurring in a direction that is non co-axial with the longitudinal axis.

16. A sensor cable for measuring pressure at a plurality of spaced apart locations in a subterranean formation, the sensor cable comprising:

(a) a first sensing portion including an elongated outer casing having a first end portion, a second opposite end portion and a side portion extending between the first end portion and the second end portion, the first sensing portion including a pressure sensor to measure pressure acting on the side portion;

(b) a second sensing portion including an elongated outer casing having a first end portion, a second opposite end portion and a side portion extending between the first and second end portions of the second sensing portion, the second sensing portion including a pressure sensor to measure pressure acting on the side portion of the second sensing portion;

(c) an interconnection portion located between the first sensing portion and the second sensing portion, the interconnection portion including a first end portion and a second opposite end portion;

(d) the first end portion of the first sensing portion being coupled to the first end portion of the interconnection portion;

(e) the first end portion of the second sensing portion being coupled to the second end portion of the interconnection portion;

(f) said first sensing portion, said second sensing portion and said interconnection portion when coupled to one another forming an elongated string-like structure;

(g) an optical fiber defining a continuous optical path extending through said first sensing portion, said interconnection portion and said second sensing portion, said optical path configured for transporting an optical signal conveying pressure information generated by the pressure sensor of said first sensing portion and the pressure sensor of said second sensing portion;

(h) said first sensing portion, said second sensing portion and said interconnection portion having a cross-sectional dimension that remains substantially constant along the string-like structure;

(i) one of said first end portion of said first sensing portion and said first end portion of said interconnection portion including a projection;

(j) the other of said first end portion of said first sensing portion and said first end portion of said interconnection portion including a recess;

(k) said recess receiving said projection when the first end portion of said first sensing portion is coupled to the first end portion of said interconnection portion.

17. A sensor cable as defined in claim 16 , wherein the first sensing portion, the second sensing portion and the interconnection portion include respective first, second and third internal cavities, the sensor cable including a fluid-tight partition between the first internal cavity and the third internal cavity.

18. A sensor cable as defined in claim 16 , wherein said projection has a cross-sectional dimension that generally corresponds to a cross-sectional dimension of said recess.

19. A sensor cable as defined in claim 18 , wherein when said projection is received in said recess, an outer wall portion of the said first sensing portion is substantially flush with an outer wall portion of the interconnection portion.

20. A sensor cable as defined in claim 16 , wherein the string-like structure has a round cross-sectional shape.

21. A sensor cable as defined in claim 16 , wherein the string-like structure has a cross-sectional dimension less than 1 inch.

22. A sensor cable as defined in claim 16 , wherein the string-like structure has a cross-sectional dimension less than 0.625 inch.

23. A sensor cable as defined in claim 16 , wherein the string-like structure has a cross-sectional dimension less than 0.5 inch.

24. A sensor cable as defined in claim 16 , wherein the string-like structure has a cross-sectional dimension less than 0.25 inch.

25. A sensor cable as defined in claim 16 , wherein the pressure sensor of said first sensing portion includes a deformable component coupled to the optical fiber, the deformable component being responsive to outside pressure acting against the side portion of said first sensing portion to locally alter an optical property of the optical fiber.

26. A sensor cable as defined in claim 25 , wherein the deformable component imparting a bending movement to the optical fiber.

27. A sensor cable as defined in claim 26 , wherein the deformable component causes the optical fiber to axially stretch as the optical fiber bends.

28. A sensor cable as defined in claim 27 , wherein the first sensing portion has a longitudinal axis, the bending movement occurring in a direction that is non co-axial with the longitudinal axis.

29. A sensor cable for measuring pressure at a plurality of spaced apart locations in a subterranean formation, the sensor cable comprising:

(a) a first sensing portion including an elongated outer casing having a first end portion, a second opposite end portion and a side portion extending between the first end portion and the second end portion, the first sensing portion including a pressure sensor to measure pressure acting on the side portion;

(b) a second sensing portion including an elongated outer casing having a first end portion, a second opposite end portion and a side portion extending between the first and second end portions of the second sensing portion, the second sensing portion including a pressure sensor to measure pressure acting on the side portion of the second sensing portion;

(c) an interconnection portion located between the first sensing portion and the second sensing portion, the interconnection portion including a first end portion and a second opposite end portion;

(d) the first end portion of the first sensing portion being coupled to the first end portion of the interconnection portion;

(e) the first end portion of the second sensing portion being coupled to the second end portion of the interconnection portion;

(f) said first sensing portion, said second sensing portion and said interconnection portion when coupled to one another forming an elongated string-like structure;

(g) an optical fiber defining a continuous optical path extending through said first sensing portion, said interconnection portion and said second sensing portion, said optical path configured for transporting an optical signal conveying pressure information generated by the pressure sensor of said first sensing portion and the pressure sensor of said second sensing portion;

(h) said first sensing portion, said second sensing portion and said interconnection portion having a cross-sectional dimension that remains substantially constant along the string-like structure;

(i) the string-like structure has a cross-sectional dimension less than 0.625 inch.

30. A sensor cable as defined in claim 29 , wherein the first sensing portion, the second sensing portion and the interconnection portion include respective first, second and third internal cavities, the sensor cable including a fluid-tight partition between the first internal cavity and the third internal cavity.

31. A sensor cable as defined in claim 29 , wherein:

(a) one of said first end portion of said first sensing portion and said first end portion of said interconnection portion including a projection;

(b) the other of said first end portion of said first sensing portion and said first end portion of said interconnection portion including a recess;

(c) said recess receiving said projection when the first end portion of said first sensing portion is coupled to the first end portion of said interconnection portion.

32. A sensor cable as defined in claim 31 , wherein said projection has a cross-sectional dimension that generally corresponds to a cross-sectional dimension of said recess.

33. A sensor cable as defined in claim 32 , wherein when said projection is received in said recess, an outer wall portion of the said first sensing portion is generally flush with an outer wall portion of the interconnection portion.

34. A sensor cable as defined in claim 29 , wherein the string-like structure has a round cross-sectional shape.

35. A sensor cable as defined in claim 29 , wherein the string-like structure has a cross-sectional dimension less than 0.5 inch.

36. A sensor cable as defined in claim 29 , wherein the string-like structure has a cross-sectional dimension less than 0.25 inch.

37. A sensor cable as defined in claim 29 , wherein the pressure sensor of said first sensing portion includes a deformable component coupled to the optical fiber, the deformable component being responsive to outside pressure acting against the side portion of said first sensing portion to locally alter an optical property of the optical fiber.

38. A sensor cable as defined in claim 37 , wherein the deformable component imparting a bending movement in the optical fiber.

39. A sensor cable as defined in claim 38 , wherein the deformable component causes the optical fiber to axially stretch as the optical fiber bends.

40. A sensor cable as defined in claim 39 , wherein the first sensing portion has a longitudinal axis, the bending movement occurring in a direction that is non co-axial with the longitudinal axis.

41. A sensing device for measuring pressure of a gas or a liquid in a well bore extending in a subterranean formation, the sensing device comprising:

(a) an elongated casing having an end and a side, the elongated casing having a longitudinal axis;

(b) an optical fiber extending in the elongated casing;

(c) a pressure sensor in the elongated casing, the pressure sensor including a deformable component responsive to pressure of gas or liquid in the well bore to locally alter an optical property of the optical fiber;

(d) the pressure sensor being configured such that the deformable component applies a force on the optical fiber which has a direction that is non co-axial with the longitudinal axis, the force creating a strain in the optical fiber, wherein the elongated casing has a plurality of pressure sensors in a spaced apart relationship to measure pressure at respective measuring points along the side, the optical fiber defining a continuous optical path linking the plurality of pressure sensors to transport an optical signal conveying outside pressure information from the plurality of measuring points.

42. A sensing device as defined in claim 41 , wherein the force causes the optical fiber to bend sideways of the longitudinal axis.

43. A sensing device as defined in claim 42 , wherein the bend stretches the optical fiber.

44. A sensing device as defined in claim 41 , wherein the pressure sensor includes a grating in the optical fiber, the grating being located within a section of the optical fiber that is subjected to the strain such that the strain alters an optical property of the grating.

45. A sensing device for measuring pressure of a gas or a liquid in a well bore extending in a subterranean formation, the sensing device comprising:

(a) an elongated casing having an end and a side, the elongated casing having a longitudinal axis;

(b) an optical fiber extending in the elongated casing;

(c) a pressure sensor in the elongated casing, the pressure sensor including a deformable component responsive to pressure of gas or liquid in the well bore to locally alter an optical property of the optical fiber;

(d) the pressure sensor being configured such that the deformable component applies a force on the optical fiber which has a direction that is non co-axial with the longitudinal axis, the force creating a strain in the optical fiber, wherein the pressure sensor includes a grating in the optical fiber, the grating being located within a section of the optical fiber that is subjected to the strain such that the strain alters an optical property of the grating;

wherein the force causes the optical fiber to bend sideways of the longitudinal axis, wherein the bend stretches the optical fiber, and wherein the elongated casing has a plurality of pressure sensors in a spaced apart relationship to measure pressure at respective measuring points along the side, the optical fiber defining a continuous optical path linking the plurality of pressure sensors to transport an optical signal conveying outside pressure information from the plurality of measuring points.