USE OF ENCAPSULATED TRACERS

• US 20100307745A1
• Filed: 06/03/2009
• Published: 12/09/2010
• Est. Priority Date: 06/03/2009
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (SLB)
• Original Assignee: Schlumberger Technology Corporation (SLB)
• Inventors: Tustin, Gary, Miller, Mathew, Lafitte, Valerie, Hughes, Trevor, Wang, Shiyi, Kefi, Slaheddine
• Granted Patent: US 9,290,689 B2
• Time in Patent Office: Days
• US Class Current: 166/250.12
• CPC Class Codes: C09K 8/62 Compositions for forming crevices or fractures
• CPC Class Codes: E21B 43/26 by forming crevices or fractures
• CPC Class Codes: E21B 47/11 using tracers; using radioactivity

Abstract

A process of making observations of a subterranean reservoir penetrated by a wellbore uses distinguishable sets of tracer particles and comprises steps of:

• (i) delivering a plurality of sets of tracer particles to respective subterranean locations via the wellbore, the particles in each set comprising a tracer substance which distinguishes that set form the other sets;
• (ii) causing or allowing the tracer substances to flow out from the tracer particles whilst the particles are at the respective subterranean locations;
• (iii) causing or allowing production of fluid out of said reservoir via the wellbore; and
• (iv) detecting the presence or absence of the tracer substances in the produced fluid.

The tracer substances are sufficiently distinguishable from each other to enable a tracer substance detected in the produced fluid to identify the set of tracer particles from which it has come and hence identify the location from which it has come. The process may be used in conjunction with hydraulic fracturing, placing sets of particles at different locations within a fracture and/or in different fractures extending from a single wellbore.

Claims

1. A process of making observations of a subterranean reservoir penetrated by a wellbore, using tracer particles, comprising steps of

delivering a plurality of sets of tracer particles to respective subterranean locations via the wellbore, the particles in each set comprising a tracer substance which distinguishes that set form the other sets and a carrier;

causing or allowing the tracer substances to flow out from the tracer particles whilst the particles are at the respective subterranean locations;

causing or allowing production of fluid out of said reservoir via the wellbore; and

detecting the presence or absence of the tracer substances in the produced fluid.

2. The process of claim 1 wherein the plurality of sets of tracer particles comprises at least three sets, which are delivered to respective different subterranean locations.

3. The process of claim 1 wherein at least two sets of particles differ in median particle size.

4. The process of claim 3 wherein the particles of a first set are sufficiently small to enter pores of the rock which constitutes the subterranean reservoir formation but particles of another set are too large to do so.

5. The process of claim 4 wherein the first set of particles has a median particle size of no more than 10 microns.

6. The process of claim 5 wherein not more than 10 wt % of the particles of the first set have a particle size larger than 20 microns.

7. The process of claim 3 wherein a first set of particles has a median particle size of no more than 10 microns and a second set of particles has a median particle size in a range from 20 to 100 microns.

8. The process of claim 7 wherein not more than 10 wt % of the particles in the second set have a particle size smaller than 10 microns.

9. The process of claim 3 wherein a third set of particles differs in median particle size from the first and second sets of particles.

10. The process of claim 9 wherein the third set of particles has a median particle size of over 200 microns.

11. The process of claim 10 wherein not more than 10 wt % of the first particles have a particle size larger than 20 microns, not more than 10 wt % of the second particles have a particle size smaller than 15 microns, not more than 10 wt % of the second particles have a particle size larger than 200 microns and not more than 10 wt % of the third particles have a particle size smaller than 150 microns.

12. The process of claim 1 wherein a plurality of sets of particles are transported down the wellbore concurrently.

13. The process of claim 1 carried out in the course of hydraulic fracturing of the subterranean reservoir.

14. The process of claim 13 wherein proppant is transported down the wellbore and a plurality of sets of particles are transported down the wellbore concurrently with proppant.

15. The process of claim 13 wherein a plurality of fractures are formed in the reservoir and the process comprises delivering a plurality of sets of tracer particles to respective fractures via the wellbore, a set of particles in each fracture comprising a tracer substance which distinguishes that fracture from the other fractures.

16. The process of claim 1 wherein the tracer particles comprise tracer substance encapsulated by carrier material.

17. The process of claim 16 wherein the carrier material comprises organic polymer and has a Tg value which is above ambient temperature at the surface but below the temperature at the subterranean locations to which the particles are delivered.

18. The process of claim 16 wherein the carrier material comprises organic polymer with hydrolysable groups in the polymer chain which are labile to hydrolysis to break the polymer chain.