Real time radioactive
A method, a system, tools for use by the system, and an interpretation method for injecting and detecting tracers and conducting flow characterizing of a petroleum well are provided. The method describes monitoring of travel time and slip velocity between two/three different phases (oil/water and possibly gas) in the well. The travel time and slip velocity are determined using an injection tool for injection of an over pressurized injection, thus simultaneous injection to all phases, of the partitioning tracers each of which would follow certain phase. The tracers are detected by a tracer detector downstream the injector. The slip velocity is obtained from the difference of travel time of two tracers which partition to two different phases.
1. A method of characterizing flow behavior of a petroleum well, comprising:
a) using at least two locally arranged injection devices, each of the injection devices provided at an injection position along the petroleum well, each of the injection positions being associated with a local production flow, wherein each of the injection devices injects a set of at least a first tracer with water-affinity and a second tracer with hydrocarbon-affinity into a base pipe of the petroleum well, the first and the second tracers being detectable downstream by an online detector, the injections by the injection devices occurring simultaneously into water and hydrocarbon-containing fluids present in the local production flow associated with each of the injection position, and wherein overpressure in each of the injection devices during the injection is at least 5 bars relative to the pressure in the base pipe;
b) allowing transport of each of the local production flows to the online detector at a detection point downstream of the injection positions;
c) at the detection point, conducting monitoring for detection of the first and the second tracers in a production flow comprising one or more of the local production flows to determine arrival time of the first and second tracers;
d) calculating detection point slip times between corresponding arrival times of the first and the second tracers as measured at the detection point;
e) based on the detection point slip times, determining transport times and local zonal slip times for the first and second tracers; and
f) based on the determined transport times and local zonal slip times, characterizing the flow behavior of the petroleum well.
2. The method according to claim 1 , wherein the first and second tracers include radioactive elements.
3. The method according to claim 2 , wherein the online detector is further configured to detect radiation from the radioactive elements in the first and second tracers.
4. The method of claim 3 , further comprising defining the arrival times of each of the detected tracers by defining a characteristic feature in a record or a graph of registered radiation.
5. The method of claim 1 , further comprising placing a reference injection position at or near a downstream end of a production zone of the petroleum well and measuring transport times of fluids from said reference injection position to the detection point downstream.
6. The method of claim 1 , further wherein each of said first and the second tracers has a property of partitioning less than 1:10 with respect to the hydrocarbon-containing fluids and the water, respectively.
7. The method of claim 1 , further comprising injecting the first tracer with water-affinity and the second tracer with hydrocarbon-affinity by one and same carrier fluid.
8. The method of claim 1 , further wherein the injected set of tracers is identical, in two of the injection positions that neighbor each other.
9. The method of claim 1 , further wherein the injected set of tracers is different, in two of the injection positions that neighbor each other.
10. The method of claim 1 , further comprising injecting a neutral, non-affinity tracer, wherein said neutral tracer fractionates between the water and the hydrocarbon-containing fluids.
11. The method of claim 1 , further comprising repeating, after a desired time, method steps (a)-(e) so as to make one or more further injections at further injection positions along the well.