Method of tracing flow of hydrocarbon from a subterranean reservoir

Abstract

A method of tracing flow of hydrocarbon from a subterranean reservoir including forming a dispersion, injecting a hydraulic fracturing fluid containing the dispersion down a well penetrating a hydrocarbon reservoir, thereafter collecting a sample of hydrocarbon fluid flowing from the reservoir, and analysing the sample to determine whether the tracer compound is present in the sample. The dispersion includes a discontinuous condensed phase having a hydrocarbon-soluble tracer compound and a continuous phase which includes an aqueous liquid.

What is claimed: 
     
         1 . A method of tracing flow of hydrocarbon from a subterranean reservoir comprising the steps of forming a dispersion consisting of a discontinuous condensed phase and a continuous liquid phase, said discontinuous condensed phase comprising a hydrocarbon-soluble tracer compound and said continuous liquid phase comprising an aqueous liquid, injecting a hydraulic fracturing fluid containing the dispersion down a well penetrating a hydrocarbon reservoir, thereafter collecting a sample of hydrocarbon fluid flowing from the reservoir and analysing the sample to determine whether the tracer compound is present in the sample. 
     
     
         2 . A method according to  claim 1  wherein the tracer compound has a solubility in water between 50 and 120 degrees Celsius of less than 0.1 g/litre. 
     
     
         3 . A method according to  claim 1  wherein the partition coefficient of the tracer compound between the hydrocarbon/water is selected to be at least 1,000. 
     
     
         4 . A method according to  claim 1  wherein the dispersion comprises an emulsion and said discontinuous phase comprises an organic liquid. 
     
     
         5 . A method according to  claim 4  wherein the discontinuous phase of the emulsion comprises a solution of a tracer compound in an organic solvent. 
     
     
         6 . A method according to  claim 1  wherein the dispersion comprises a colloidal dispersion and said discontinuous phase comprises particles of a colloidal solid. 
     
     
         7 . A method according to  claim 1  wherein said dispersion contains an additive selected from the group consisting of emulsifiers, stabilisers and rheology modifiers. 
     
     
         8 . A method according to  claim 1  wherein the tracer compound is selected from the group consisting of a halogenated aromatic compound, a halogenated cycloalkane or a halogenated aliphatic compound all wherein the halogen is selected from the group consisting of Cl, Br and I. 
     
     
         9 . A method according to  claim 5  wherein the tracer compound is selected from the group consisting of 4-iodotoluene, 1,4-dibromobenzene, 1-chloro-4-iodobenzene, 5-iodo-m-xylene, 4-iodo-o-xylene, 3,5-dibromotoluene, 1,4-diiodobenzene, 1,2-diiodobenzene, 2,4-dibromomesitylene, 2,4,6-tribromotoluene, 1-iodonaphthalene, 2-iodobiphenyl, 9-bromophenanthrene, 2-bromonaphthalene, bromocyclohexane, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1-bromododecane, bromooctane, 1-bromo-4-chlorobenzene, bromobenzene, 1,2,3-trichlorobenzene, 4-chlorobenzalchloride and 1-bromo-4-fluorobenzene. 
     
     
         10 . A method according to  claim 1  wherein the discontinuous phase of the dispersion contains more than one tracer compound. 
     
     
         11 . A method according to  claim 1  wherein the dispersion is formed prior to the injection of hydraulic fracturing fluid and then added to the hydraulic fracturing fluid injection during a fracturing operation. 
     
     
         12 . A method according to  claim 1  wherein the tracer compound is added to and mixed directly with the hydraulic fracturing fluids during the injection, so that the dispersion is formed in situ, with the fracturing fluid forming the continuous aqueous phase. 
     
     
         13 . A method according to  claim 1  wherein a formation fracturing operation is carried out in more than one stage and a known amount of tracer is added to the hydraulic fracturing fluid injected into the well during each stage. 
     
     
         14 . A method according to  claim 1  wherein the injection of hydraulic fracturing fluid containing the dispersion occurs after the initial injection of hydraulic fracture fluid creating the initial rock fracture matrix. 
     
     
         15 . A method according to  claim 1  wherein solid proppant particles are injected into the well with hydraulic fracturing fluid and the injection of hydraulic fracturing fluid containing the dispersion occurs during the initial injection of such solid proppant particles at the front of a solids injection. 
     
     
         16 . A method according to  claim 1 , comprising the steps of forming at least two tracer emulsions, each tracer emulsion comprising a discontinuous phase comprising a hydrocarbon-soluble tracer compound in a continuous phase comprising an aqueous liquid and each tracer compound having a tracer characteristic which is different from the corresponding tracer characteristic of the tracer compound of each other tracer emulsion; adding each said tracer emulsion to a hydraulic fracture fluid, injecting said hydraulic fracture fluid containing the tracer emulsion down a well penetrating a hydrocarbon reservoir, thereafter collecting a sample of hydrocarbon fluid flowing from the reservoir and analysing the sample to determine whether any of the tracer compounds is present in the sample. 
     
     
         17 . A method according to  claim 16 , wherein said subterranean reservoir is fractured in stages and a hydraulic fracture fluid containing at least one unique tracer emulsion is injected into the well at each stage. 
     
     
         18 . A method according to  claim 16  wherein each tracer compound has a solubility in water between 50 and 120 degrees Celsius of less than 0.1 g/litre. 
     
     
         19 . A method according to  claim 16  wherein the partition coefficient of each tracer between the hydrocarbon/water is selected to be at least 1,000. 
     
     
         20 . A method according to  claim 16  wherein the tracer compound is selected from the group consisting of a halogenated aromatic compound, a halogenated cycloalkane or a halogenated aliphatic compound all wherein the halogen is selected from the group consisting of Cl, Br and I. 
     
     
         21 . A method according to  claim 20  wherein each tracer compound is selected from the group consisting of 4-iodotoluene, 1,4-dibromobenzene, 1-chloro-4-iodobenzene, 5-iodo-m-xylene, 4-iodo-o-xylene, 3,5-dibromotoluene, 1,4-diiodobenzene, 1,2-diiodobenzene, 2,4-dibromomesitylene, 2,4,6-tribromotoluene, 1-iodonaphthalene, 2-iodobiphenyl, 9-bromophenanthrene, 2-bromonaphthalene, bromocyclohexane, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1-bromododecane, bromooctane, 1-bromo-4-chlorobenzene, bromobenzene, 1,2,3-trichlorobenzene, 4-chlorobenzalchloride and 1-bromo-4-fluorobenzene. 
     
     
         22 . A method according to  claim 16  wherein at least one of the emulsions is formed prior to the injection of hydraulic fracturing fluid and then added to the hydraulic fluid injection during a fracturing operation. 
     
     
         23 . A method according to  claim 16  wherein at least one tracer compound is added to and mixed directly with the hydraulic fracturing fluid during the injection, so that the emulsion is formed in situ, the hydraulic fracturing fluid forming the continuous aqueous phase of the emulsion. 
     
     
         24 . A method according to  claim 16  wherein the hydraulic fracturing fluid containing the emulsion is introduced into the well after the initial injection of fracture fluid creating the initial rock fracture matrix in each stage. 
     
     
         25 . A method according to  claim 16 , wherein solid proppant particles are injected into the well with hydraulic fracturing fluid and the injection of hydraulic fracturing fluid containing the dispersion occurs during the initial injection of such solid proppant particles at the front of a solids injection. 
     
     
         26 . A method of identifying the flow of a hydrocarbon from a first location in a subterranean reservoir to a well located at a second location in said reservoir comprising the steps of
 a) forming a dispersion of at least one hydrocarbon-soluble tracer compound in an aqueous liquid,   b) injecting a hydraulic fracture fluid containing the emulsion down a well penetrating a hydrocarbon reservoir at said first location,   c) thereafter collecting a sample of hydrocarbon flowing from the well located at said second location,   d) analysing the sample to determine whether the tracer compound is present in the sample and   e) determining, from the results of said analysis, whether a flow of hydrocarbon has occurred from the first location to the second location.   
     
     
         27 . A method of confirming the presence at a first location in a well of a barrier which would, if present, restrict flow of a hydrocarbon from a location in a well upstream of said first location to a location downstream of said first location, comprising the steps of
 a) forming a dispersion of a hydrocarbon-soluble tracer compound in an aqueous liquid,   b) injecting a hydraulic fracture fluid containing the dispersion down a well penetrating a hydrocarbon reservoir at said location upstream of said first location,   c) thereafter collecting a sample of hydrocarbon flowing from the reservoir at a location downstream of said first location,   d) analysing the sample to determine whether the tracer compound is present in the sample,   e) inferring from the presence or absence of tracer compound in the sample whether said sample contains hydrocarbon which has flowed from a location upstream of said first location, thereby to determine whether said barrier exists at said first location.   
     
     
         28 . A method according to  claim 27 , wherein at least one said barrier is placed in the well and further comprising the step of releasing a barrier after the tracer dispersion has been injected into the well and before the sample is collected. 
     
     
         29 . A method according to  claim 27 , wherein the barrier comprises a plug which has been placed in the well. 
     
     
         30 . A method according to  claim 27 , wherein said barrier comprises a well-completion device having at least one flow control means comprising at least one hole and which, in a first condition allows flow through said hole and in a second condition blocks flow through said hole. 
     
     
         31 . A composition comprising a dispersion consisting of a discontinuous condensed phase and a continuous liquid phase, the discontinuous condensed phase comprising a hydrocarbon-soluble tracer compound and the continuous liquid phase comprising an aqueous liquid.