Method of detecting fluid in-flows downhole

1. A method of measuring fluid in-flow in a region of interest in a wellbore, comprising:

a) deploying a fiber optic cable concurrently with placement of a downhole tubular;

b) transmitting a light signal along the cable and receiving a reflected signal from the region of interest; and

c) interpreting the received signal to obtain information about fluid flowing into or out of the wellbore in the region of interest;

wherein step c) comprises:

i) assessing amplitude and frequency spectra across an array of channels;

ii) conditioning the received signal by removing at least a portion of the signal that is not related to flow;

iii) assessing flow regimes across depths and times;

iv) calculating axial flow/s within the wellbore using relationships for axial flow; and

v) calculating flow into or out of the wellbore at one or more points using relationships for flow through an orifice.

2. The method according to claim 1 wherein the wellbore contains a velocity string and step c) is carried out without removing the velocity string.

3. The method according to claim 1 wherein the wellbore includes a horizontal portion.

4. The method according to claim 1 wherein the fiber optic cable is free of Bragg gratings.

5. The method according to claim 1 wherein step c) further includes:

c1) detecting a change over time in said received signal; and

c2) interpreting said change so as to obtain information about a change in fluid inflow.

6. The method according to claim 1 wherein step c) further includes the step of:

vi) comparing the results of steps iv) and v), and minimizing errors using additional constraining information.

7. The method according to claim 6 wherein the addition constraining information is selected from the group consisting of wellhead flowrates, and temperature measurements.

8. The method according to claim 1 , further including the steps of:

d) repeating steps a) and b) over time so as to obtain information about a change in fluid inflow.