Method and system for reservoir inflow quantification

Abstract

The invention provides a method and system of estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well and includes installing a liner 12 with at least

Description

The present invention relates to apparatus and methods for reservoir monitoring. Aspects of the invention include a system and method for monitoring characteristics of influx to a producing well. Aspects of the invention also include estimating and / or calculating a distribution of influx rates from a reservoir to a production well. Background to the invention Downhole tracers released into a production flow in a producing well has been previously used for estimating which fluids flow in parts of the well. Methods of monitoring fluid rate based on transient flow where distinct tracers are arranged at different influx locations in a well are known. EP2633152 discloses a method of estimating influx profile for well fluids to hydrocarbon well. The method comprises inducing a transient in the production rate of the entire production flow by shutting in the well. The well is shut-in for a period of time to allow a high concentration of tracers to build up in the well and then the well is re-started to carry the tracers to surface. Sampling and analysis of the concentration of the different tracers is used to provide qualitative and quantitative production data. These methods require the capture of tracer released during or shortly after well restart. High frequency sampling must be regularly taken to ensure that the transient tracer data is captured. If samples are not taken at sufficient frequency or over a long enough period, aspects of the tracer data may be lost. These method may also limit the number of opportunities for obtaining tracer data, as shutting in the well is a complex and highly expensive operation requiring significant project planning and resulting in loss of revenue due to interruption to production. Summary of the invention It is amongst the aims and objects of the invention to provide a method and system for monitoring influx zone contributions of well fluid to production flow in a hydrocarbon production well. It is a further object of an aspect of the invention to provide a method and system for estimating the distribution of inflow rates in hydrocarbon wells without requiring the well to be shut in. It is another object of the present invention to provide a tracer chamber associated with a production liner for accurately locating tracer at a known position in the well. It is a further object to accurately deposit tracer in the formation at one or more influx locations by perforating a tracer chamber, liner section and formation at one or more known position to create the one or more influx locations and deposit the tracer. It is another object of the present invention to deposit distinct tracer in perforations in the formation at multiple known positions of the well and inducing production to determine an influx profile for the well. Further aims and objects of the invention will become apparent from reading the following description. According to a first aspect of the invention, there is provided a method of estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well; wherein the method comprises installing a liner with at least one tracer chamber in a well; wherein the at least one tracer chamber comprises at least one distinct tracer material; perforating a section of the liner, at least one tracer chamber and surrounding formation to create an influx location and deposit tracer from the at least one tracer chamber into the formation; inducing production flow from the reservoir into the well; collecting at least one sample downstream of the at least one influx location; analysing the at least one sample for concentration and type of tracer material; and based on the analysed concentrations characterising flow from the at least one influx location. The method may comprise perforating the liner, tracer chamber and surrounding formation to deposit tracer materials and / or tracer molecules from the tracer chamber into the perforation holes in the formation. The method may comprise perforating the liner, tracer chamber and surrounding formation to deposit tracer material or molecules from the tracer chamber into the formation. The method may comprise perforating the liner, tracer chamber and surrounding formation to establish a pathway for the reservoir fluids to flow into the well. The method may comprise perforating the liner, tracer chamber and surrounding formation to create an influx location. The method may comprise perforating cement or resin surrounding or partially surrounding the liner and / or the tracer chamber. The method may comprise perforating cement or resin surrounding or partially surrounding a liner section and / or the tracer chamber. The method may comprise installing the at least one tracer chamber at known levels or positions of the well. The liner may be a cementable liner or a cemented liner. The method may comprise perforating the liner, tracer chamber, cement and surrounding formation to deposit at least one tracer material and / or tracer molecules from the at least one tracer into perforations in the formation. The method may comprise perforating the liner, tracer chamber, resin and / or surrounding formation to deposit at least one tracer material and / or tracer molecules from the at least one tracer into perforations in the formation. The at least one well fluid may be at least one of oil, gas and / or water. The method may comprise collecting samples of the at least one well fluid downstream of the influx locations such as at surface. By providing tracer chambers at known positions in the well and perforating the liner, tracer chamber and / or surrounding formation distinct tracer material or molecules may be accurately deposited into in precise areas of the formation. Deposited tracer materials or molecules may return through the perforations in the selected influx locations into the well during production. The at least one tracer chamber may comprise a shroud. The at least one tracer chamber may be made of metal such as steel. The at least one tracer chamber may comprise a shroud. The at least one tracer chamber may comprise a jacket. The at least one tracer chamber may comprise a carrier. The at least one tracer chamber may comprise a jacket carrier. The at least one tracer chamber may be a sealed chamber. The at least one tracer chamber may circumferentially cover at least part of a production liner section. The tracer chamber may have any shape or profile. The at least one tracer chamber may be non-perforated. The at least one tracer chamber may be sealed. At least one wall or surface of the tracer chamber may be a wall or surface of a production liner section. The at least one tracer chamber may be mounted on or in the production liner. The at least one tracer chamber may comprise at least one port, aperture or opening. The at least one port, aperture or opening may be a pressure equalising port, aperture or opening. The at least one tracer chamber may be installed by arranging, fixing and / or immobilising the tracer chamber to an outer surface and / or an inner surface of the production liner. The at least one tracer chamber may be located on and around the production liner. The at least one tracer chamber may be located around the entire circumference of a section of the production liner or partially around the outer circumference of a section of the production liner. The at least one tracer chamber may be located on an inner surface of the production liner. The at least one tracer chamber may be located around the entire inner circumference of a section of the production liner or partially around the inner circumference of a section of the production liner. The production liner may comprise a plurality of production liner sections. At least one tracer chamber may be installed, arranged, associated with or mounted on or to at least one production liner section. The tracer chamber may be located adjacent to a target influx location or zone of interest in a well. The at least one tracer material may be a solid, liquid or gas. The at least one tracer may comprise tracer molecules and a carrier. The at least one tracer may be a powder, particles, pellets or fragmented solid pieces. The tracer material may be selected from the group comprising chemical, fluorescent, phosphorescent, magnetic, DNA and radioactive compounds. The tracer may be a non-radioactive tracer. The tracer material may comprise chemical tracers selected from the group comprising perfluorinate hydrocarbons or perfluoroethers. The perfluorinated hydrocarbons may be selected from the group of perfluoro butane (PB), perfluoro methyl cyclopentane (PMCP), perfluoro methyl cyclohexane (PMCH). The tracer material may be a solid, liquid and / or a gas form. The tracer material may be a powder or dissolved or mixed with other components. The tracer material may be in a concentrated form. The at least one tracer may comprise a tracer and a carrier. The at least one tracer may be encapsulated, partially encapsulated and / or contained within a carrier. The carrier may be a matrix material. The carrier may be dissolvable or erodable substance. The carrier may be a polymeric material. The tracer material may be inside, partially encapsulated and / or encapsulated by the carrier. The tracer material may be uniformly distributed in the carrier. The tracer material may be inhomogeneously distributed in the carrier. The tracer material may be chemically immobilized within and / or to the carrier. The tracer material may be chemically immobilized by a chemical interaction between the tracer and the carrier. The tracer material may be chemically immobilized in a way that it releases tracer molecules or particles in the presence of a chemical and / or physical trigger. The carrier may be engineered to dissolve or degrade at a pre-determined rate upon exposure to a specific fluid or condition. The carrier may be engineered to dissolve or degrade at a pre-determined rate upon exposure to a formation fluid, temperature change, pressure change, or acid. The carrier may be dissolvable or degradable or perforated by a mechanical device. Each of the two or more tracers may have a different carrier type or material designed to provide a different release rate of tracer from the carrier. The tracer and / or carrier may be moulded into any shape. The tracer material may be moulded into rods of tracer molecules in matrix material. The tracer may be encapsulated or contained within a bag, tube or wrap. The bag, tube or wrap may comprise a polymer material. The tracer material may be fluid specific. The release of tracer from the polymeric material may be fluid specific. By distributing tracer mass in space a dependency on (phase) rate may be obtained. A larger influx rate may carry more tracer located in the spatially distributed phase into the production flow. The tracer may have an even release rate or a known release rate from the carrier. The tracer material may be lodged or deposited into the formation. The tracer material may be lodged or deposited into perforation holes in the formation The tracer material may be designed to fragment, disintegrate or break down into particles in response to a perforation event. The tracer material may be designed to partially fragment, disintegrate or break down into particles in response to a perforation event. The tracer may be a liquid tracer encapsulated or contained within a bag or tube. The bag or tube may be designed to fragment, disintegrate or break down into particles in response to a perforation event. The liquid tracer may be configured to be carried or injected into the perforations in response to a perforation event. The at least one tracer may release tracer molecules into fluid by dissolution, perforation or degradation of the carrier and / or the tracer into the fluid. The carrier may be selected to controllable degrade on contact with a fluid. The at least one tracer chamber may comprise two or more distinct tracer materials. Each of the two or more tracers may have a different physical form. The two or more tracers may be selected from the group comprising solid, liquid, gas, gel and / or a dispersion. Each of the two or more tracers may have a different phase. Each of the two or more tracers may have a different state of matter. Each of the two or more tracers may have the same state or phase in a different physical form. Each of the two or more tracers may have the same state of matter in a different physical form. The two or more tracers may be a solid in a different physical form. The two or more two tracers may comprise different forms of solids. The different forms of solid may comprise particles, fragmented solids, grains, pellets or a powder. The different forms of solid may comprise solids of different discrete masses or granular size. The two or more tracers may be liquids of different compressibility, pressure, buoyancy, viscosity and / or surface tension. The two or more tracers may be liquids of different compressibility and / or density. Preferably each of the two or more tracers are distinct tracers. Each of the two or more tracers may be chemically distinct tracers. The tracer chamber may comprise at least one solid tracer. The tracer chamber may comprise at least one fluid tracer. The tracer chamber may comprise a combination of at least one solid tracer and at least one liquid tracer. The two or more tracers may comprise a coating or carrier in a different state or phase to the tracer. At least one of the two or more tracers may be in a concentrated form. The two or more tracers may be surrounded by a fluid or mass to fill any void or space in the at least one tracer chamber not occupied with tracer. Filling any empty void or space with a fluid or mass may mitigate or avoid the at least one tracer chamber collapsing due to downhole pressure. The at least one tracer chamber may comprise at least one solid tracer. The at least one tracer chamber may comprise at least one fluid tracer. The at least one tracer chamber may comprise a combination of at least one solid tracer and at least one liquid tracer. At least one of the tracers may be lodged or deposited into the formation. At least one of the tracers may be lodged or deposited into the formation in response to a perforation event. The method may comprise depositing two or more tracers into the formation. The method may comprise depositing two or more tracers into each perforation. Each of the tracers may be lodged or deposited into perforation holes in the formation At least one of the tracers may be designed to fragment, disintegrate or break down into particles in response to a perforation event. At least one tracers may be designed to partially fragment, disintegrate or break down into particles in response to a perforation event. The tracer may be a liquid tracer encapsulated or contained within a bag or tube. The carrier, bag, tube and / or wrap may be designed to fragment, disintegrate or break down into particles in response to a perforation event. At least one tracer may be a fluid tracer and may be configured to be carried or injected into the perforations in response to a perforation event. At least one tracer may be a solid tracer and particles may be configured to be carried or injected into the perforations in response to a perforation event. At least one tracer may be a fragmented solid tracer and fragment or particles may be configured to be carried or injected into the perforations in response to a perforation event. Each of the two or more tracers may have a different release rate into a well fluid. Each of the two or more tracers may have a different release profile into a well fluid. Each of the two or more tracers may have a different release rate into a well fluid from the at least one tracer chamber. Each of the two or more tracers may have a different release rate from the at least one tracer chamber. Each of the two or more tracers may have different structure and / or flow behaviour. At least one tracer may be solid and may have a continuous mass. At least one tracer may be a granular solid with discrete particles able to move independently and / or move like a fluid. At least one tracer may have a rapid release profile from the at least one tracer chamber. At least one tracer may have a slow or sustained release profile from the at least one tracer chamber. At least one tracer may be configured to be released from the at least one tracer chamber as a burst or a pulse. At least one tracer may be configured to be released from the at least one tracer chamber as a sustained or continuous release. At least one tracer may be a fluid tracer configured to be released from the at least one tracer chamber as a burst or a pulse. At least one tracer may be a solid tracer configured to be released from the at least one tracer chamber as a sustained or continuous release. At least one tracer may be a fragment solid tracer configured to be released initially from the at least one chamber as a burst or a pulse and then as a sustained or continuous release. At least one tracer may have a rapid release profile from a perforation hole. At least one tracer may have a slow or sustained release profile from a perforation hole. At least one tracer may be configured to be released from a perforation hole as a burst or a pulse. At least one tracer may be configured to be released from a perforation hole as a sustained or continuous release. At least one tracer may be a fluid tracer configured to be released from a perforation hole as a burst or a pulse. At least one tracer may be a solid tracer configured to be released from a perforation hole as a sustained or continuous release. At least one tracer may be a fragment solid tracer configured to be released initially from a perforation hole as a burst or a pulse and then as a sustained or continuous release. The method may comprise releasing at least one of the tracers in response to a mechanical or chemical actuation. The method may comprise releasing two or more of tracers in response to a mechanical or chemical actuation. The method may comprise releasing each of the two or more tracers in response to a mechanical or chemical actuation. The method may comprise releasing the two or more tracers at different times and / or rates in response to at least one mechanical or chemical actuation. The mechanical or chemical actuation may be selected from the group comprising a mechanical valve, mechanical sleeve opening, pressure induced rupture, pressure induced release, pressure induced fracture and / or chemical dissolution or degradation of a carrier. Each of the two or more tracers may have a distinct release mechanism. The method may comprise sequentially releasing tracers from the tracer chamber and / or a carrier. The method may comprise releasing simultaneously releasing tracers from the tracer chamber and / or a carrier. The method may comprise inducing production to allow tracer material and / or tracer molecules in the formation to enter the production flow through a specific influx location and propagate downstream with the production flow. The method may comprise inducing a steady state production flow from the reservoir into the well. The method may comprise inducing a steady state flow. The method may comprise inducing a steady state flow condition in the production rate of the entire production flow or for at least one of the influx locations. The method may comprise adjusting the production flow to a different steady state flow. The method may comprise inducing multiple steady state flow conditions in the production rate of the entire production flow or for at least one of the influx locations and collecting samples. The tracer may be detectable downstream of the influx location and / or topside as tracer response signal and / or spike at the downstream detection point. The method may comprise depositing tracer material or molecules into the formation through at least one perforation. The method may comprise depositing tracer material or molecules into the formation through at least one perforation by actuating a perforation tool to perforate a liner section, at least one tracer chamber and surrounding formation. The perforating tool may be a perforating gun. The perforating tool may be a perforating gun with at least one explosive charge. The method may comprise detonating at least one explosive charge to perforate a liner section, at least one tracer chamber and surrounding formation. The method may comprise perforating the liner section, at least one tracer chamber and surrounding formation at two or more locations in the well to create two or more influx locations. The method may comprise depositing distinct tracer material and / or tracer molecules into the formation through each of the perforations at the two or more influx locations. The method may comprise depositing a first type of tracer into at least one perforation at a first influx location. The method may comprise depositing a second type of tracer into at least one perforation at a second influx location. The method may comprise depositing tracer material or molecules into at least one perforation at each zone or influx location sequentially or simultaneously. The method may comprise depositing the tracer material molecules into at least one perforation at more than one of the influx location or influx location at a time. The method may comprise pumping a fluid downhole to push remaining tracer material and / or tracer molecules in the tracer chamber into the at least one perforations into the formation. The method may comprise pumping a fluid downhole to push remaining tracer material and / or tracer molecules in each tracer chamber into each of the at least one perforations into the formation. The method may comprise collecting at least one sample before, during and / or after a steady state production flow rate. The method may comprise calculating rate fractions from each influx location into the production flow using mass conservation equations. The method may comprise collecting at least one sample at known sampling times. The method may comprise collecting samples at known sampling times. The method may comprise collecting two or more samples. The method may comprise collecting a plurality of samples. The method may comprise collecting samples at known sampling times. One or more of the method steps may be repeated to estimate an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well at different points in time. The method or one or more steps of the method may be repeated periodically. One or more of the method steps may be repeated and the contribution of flow from the two or more influx locations may be adjusted. According to a second aspect of the invention, there is provided a method of estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well; wherein the method comprises installing a liner with two or more tracer chambers in a well; wherein each tracer chamber is installed at a known level of the well; wherein each tracer chamber comprises at least one distinct tracer material; perforating the liner, the two or more chambers and surrounding formation to create two or more influx locations and deposit tracer from each tracer chamber into the formation at each influx location; inducing production flow from the reservoir into the well; collecting at least one sample downstream of the two or more influx locations; analysing the at least one sample for concentration and type of tracer material; and based on the analysed concentrations calculating contribution of flow from each influx location. The tracer chamber may be mounted on, in or to the production liner. The tracer chamber may be mounted on, in or to a section of the production liner. The tracer chamber may be installed on, arranged on, or associated with a section of the production liner by fixing or mounting the tracer chamber on or to an outer surface of a section of the production liner. The tracer chamber may be installed on, arranged on, or associated with a section of the production liner by fixing or mounting the tracer chamber on or to an inner surface of the production liner. The tracer chamber may be located on and / or around the production liner. The tracer chamber may be located around an entire circumference of a section of the production liner or partially around the outer circumference of a section of the production liner. The tracer chamber may be located on an inner surface of the production liner. The tracer chamber may be located around the entire inner circumference of a section of the production liner or partially around the inner circumference of a section of the production liner. The tracer chamber may be integral with the structure of the production liner section. The tracer chamber may be a structure component the production liner section. The tracer chamber may be a discrete component connectable to the production liner section. Each of the two or more tracer chambers may be associated with, mounted on or mounted to a different section of liner. The method may comprise perforating the two or more liner sections associated with the two or more tracer chambers. The method may comprise collecting at least one sample at known sampling times. The method may comprise collecting samples at known sampling times. The method may comprise collecting two or more samples. The method may comprise collecting a plurality of samples. The method may comprise collecting samples at known sampling times. The method may comprise inducing production flow from the reservoir into the well. The at least one tracer chamber may comprise two or more distinct tracer materials. Each of the two or more tracers may have a different physical form. Embodiments of the second aspect of the invention may comprise features corresponding to the preferred or optional features of the first aspect of the invention or vice versa. According to a third aspect of the invention, there is provided a system for estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well the system comprising: at least one production liner section comprising at least one tracer chamber; wherein the at least one production liner section is configured to be installed at a known level of the well. The at least one well fluid may be oil, gas and / or water. The at least one tracer chamber may comprise at least one distinct tracer material. The at least one tracer chamber may comprise two or more distinct tracer materials. Each of the two or more tracers may have a different physical form. The tracer chamber and the production liner section may be configured to be perforated by a perforation tool. The tracer chamber and the production liner section may be configured to be perforated by a perforation tool to create an influx location. The tracer chamber and the production liner section may be configured to be perforated by a perforation tool to deposit tracer material or molecules from the tracer chamber into perforation holes in the formation. The tracer chamber and the production liner section may be configured to be perforated by a perforation tool to deposit tracer material or molecules from the tracer chamber into the formation. The at least one tracer chamber may be mounted on, in or to the production liner. The at least one tracer chamber may be mounted on, in or to a section of the production liner. The at least one tracer chamber may be integrated with the production liner. The at least one tracer chamber may be integrated with a section of the production liner. The at least one tracer chamber may be installed on, arranged on, or associated with a section of the production liner by fixing or mounting the tracer chamber on or to an outer surface of a section of the production liner. The at least one tracer chamber may be mounted on or to a surface of the production liner section. The at least one tracer chamber may be installed on, arranged on, or associated with a section of the production liner by fixing or mounting the tracer chamber on or to an inner surface of the production liner. The at least one tracer chamber may be located on and / or around the production liner. The at least one tracer chamber may be located around an entire circumference of a section of the production liner or partially around the outer circumference of a section of the production liner. The at least one tracer chamber may be located on an inner surface of the production liner. The tracer chamber may be located around the entire inner circumference of a section of the production liner or partially around the inner circumference of a section of the production liner. The at least one tracer chamber may be integral with the structure of the production liner section. The at least one tracer chamber may be integrally formed with the structure of the production liner section The at least one tracer chamber may be a structure component the production liner section. The at least one tracer chamber may be incorporated into the structure of the production liner section. The at least one tracer chamber may be a discrete component connectable to the production liner section. The system may comprise a sampling device for collecting samples downstream of the influx location at known sampling times. The sampling device may be a real time sampling probe. The system may comprise a tracer analyser for analysing samples concentration and type of tracer material. The production liner section may be connectable or connected to a plurality of production liner sections. The plurality of production liner sections may be connectable or connected together to form a production liner. The production liner may comprise two or more production liner sections each comprising a tracer chamber. The position of the two or more tracer chambers along the length of the production liner may be selected to target sections or zones of the wellbore formation. The at least one tracer chamber may be installed in known levels of the well by arranging the production liner section with the tracer chamber mounted on or to a surface of the production liner section at a known level in the well. The at least one tracer chamber may be installed in known levels of the well by arranging the production liner section with the integrated tracer chamber at a known level in the well. The at least one tracer chamber may be configured to outwardly vent tracer towards the formation during a perforation event. The at least one tracer chamber may be configured to inwardly vent fluid and tracer from a perforation hole during production. The tracer chamber may be configured to inwardly vent fluid and tracer from the perforation hole through the tracer chamber. Any remaining tracer in the tracer chamber after the perforation may be configured to be carried with the influx flow through the tracer chamber to the well. The system may comprise a perforating tool. The perforating tool may be a perforating gun. The perforating gun may comprise at least one explosive charge. The perforating tool may be configured to travel inside the production liner. The perforating tool may be configured to perforate the tracer chamber and the production liner section when actuated. The perforating tool may be configured to detonate the at least one explosive charge to perforate the tracer chamber and the production liner section. The at least one tracer chamber may comprise a shroud. The at least one tracer chamber may be made of metal such as steel. The tracer chamber may comprise a shroud. The at least one tracer chamber may comprise a jacket. The tracer chamber may comprise a carrier. The at least one tracer chamber may comprise a jacket carrier. The tracer chamber may be a sealed chamber. The at least one tracer chamber may circumferentially cover at least part of a production liner section. The at least one tracer chamber may have any shape or profile. The at least one tracer chamber may be non-perforated. The tracer chamber may be sealed. The at least one tracer chamber may be sealed to outside flow before being perforated. At least one wall or surface of the tracer chamber may be a wall or surface of a production liner section. The tracer chamber may be mounted on or in the production liner. The at least one tracer chamber may comprise at least one port, aperture or opening. The at least one port, aperture or opening may be a pressure equalising port, aperture or opening. The tracer material may be a solid or liquid. The tracer material may be a powder, particles, pellets or fragmented solid pieces. The tracer material may be surrounded by a fluid or mass to fill any void or space in the tracer chamber not occupied with tracer material. The tracer material may be surrounded by a fluid or mass to fill any void or space in the tracer chamber not occupied with tracer material. Filling any empty void or space with a fluid or mass may mitigate or avoid the tracer chamber collapsing due to downhole pressure. The tracer may be a solid, liquid or gas. The tracer may be selected from the group comprising chemical, fluorescent, phosphorescent, metallic complex, particles, nano particles, quantum dots, magnetic, poly functionalized PEG and PPGs, DNA, antibodies and / or radioactive compounds. The tracer may be non-radioactive. The tracer may comprise chemical tracers selected from the group comprising perfluorinated hydrocarbons or perfluoroethers. The perfluorinated hydrocarbons may be selected from the group of perfluoro buthane (PB), perfluoro methyl cyclopentane (PMCP), perfluoro methyl cyclohexane (PMCH). The tracer may be chemically immobilized within and / or to the tracer chamber. The at least one tracer may be encapsulated, partially encapsulated and / or contained within a carrier. The tracer release apparatus may comprise tracer molecules and a carrier. The carrier may be a matrix material. The matrix material may be a polymeric material. The tracer molecules may be chemically immobilized within and / or to the carrier. The tracer molecules may be chemically immobilized by a chemical interaction between the tracer and the carrier. The tracer may be encapsulated or partially encapsulated in a protective coating. The protective coating may be a polymeric material. The tracer material may be wrapped in the protective coating. The carrier may be selected from poly methyl methacrylates (PMMA), poly methylcrylates, poly ethylenglycols (PEG), poly lactic acid (PLA) or poly glycolic acid (PGA) commercially available polymers or copolymers thereof. The carrier may be selected from polymers with higher rates of tracer molecules release such as polyethylene and polypropylene. The tracer may be physically dispersed and / or physically encapsulated in the carrier. The tracer may release tracer molecules into fluid by dissolution or degradation of the carrier and / or the tracer into the fluid. The carrier may be selected to controllable degrade on contact with a fluid. The tracer molecules may be detected and its concentration measured by different techniques such as optical detection, optical fibers, spectrophotometric methods, PCR techniques combined with sequential analysis, chromatographic methods, or radioactivity analysis. The tracer molecules may be detected and its concentration measured by sampling production fluid. The sampling may be conducted at the one or more of said sampling times. One or more samples may be collected for later analysis. At least one sample of fluid may be collected downstream of the tracer chamber or influx location. Two or more samples may be collected. A plurality of samples may be collected. Samples may be collected and / or measured downstream at known sampling times. Based on the measured concentrations and their sampling sequence and the well geometry the influx volumes may be calculated. The method may comprise estimating or calculating an influx profile based on the concentration and type of tracer as a function of the sampling time. The influx volumes may be used to estimate an influx profile of the well. The tracer molecules may be detected by a detection device such a probe. The detection device may facilitate real time monitoring and / or analysis of the tracer in the production fluid. The collection, detection, analysis and / or interpretation of tracer data in production fluid may be separate methods from one another and performed at different times or jurisdictions. The detection, analysis and / or interpretation of tracer in production fluid may be separate methods to the separation of phases, release of tracer cloud from the tracer chamber and / or the collection of samples. Samples may be collected and the tracer detected, analysed and / or interpreted at a time or jurisdiction which is separate and distinct from the location of well and therefore the collection of the samples. Embodiments of the third aspect of the invention may comprise features corresponding to the preferred or optional features of the first or second aspects of the invention or vice versa. According to a fourth aspect of the invention, there is provided a system for estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well the system comprising: a production liner comprising a plurality of production liner sections; wherein at least one production liner section comprises at least one tracer chamber; wherein the production liner section is configured to be installed at a known level of the well. The plurality of production liner sections are joined end to end to form the production liner. The at least one tracer chamber may be mounted on, in or to the production liner. The at least one tracer chamber may be mounted on, in or to a section of the production liner. The at least one tracer chamber may be installed on, arranged on, or associated with a section of the production liner by fixing or mounting the at least one tracer chamber on or to an outer surface of a section of the production liner. The at least one tracer chamber may be mounted on or to a surface of the production liner section. The at least one tracer chamber may be installed on, arranged on, or associated with a section of the production liner by fixing or mounting the tracer chamber on or to an inner surface of the production liner. The tracer chamber may be located on and / or around the production liner. The at least one tracer chamber may be located around an entire circumference of a section of the production liner or partially around the outer circumference of a section of the production liner. The at least one tracer chamber may be located on an inner surface of the production liner. The tracer chamber may be located around the entire inner circumference of a section of the production liner or partially around the inner circumference of a section of the production liner. The at least one tracer chamber may be arranged, fixed, installed and / or immobilised to an outer surface and / or an inner surface of the production liner section. The tracer chamber may be located on and / or around the production liner. The at least one tracer chamber may be integral with the structure of the production liner section. The at least one tracer chamber may be integrally formed with the structure of the production liner section The at least one tracer chamber may be a structure component the production liner section. The at least one tracer chamber may be incorporated into the structure of the production liner section. The at least one tracer chamber may be a discrete component connectable to the production liner section. The tracer chamber may comprise at least one distinct tracer material. The at least one tracer chamber may comprise two or more distinct tracer materials. Each of the two or more tracers may have a different physical form. The at least one tracer chamber and the production liner section may be configured to be perforated by a perforation tool. The tracer chamber and the production liner section may be configured to be perforated by a perforation tool to create an influx location. The tracer chamber and the production liner section may be configured to be perforated by a perforation tool to deposit tracer material or molecules from the tracer chamber into perforation holes in the formation. The system may comprise a sampling device for collecting samples downstream of the influx location at known sampling times. The sampling device may be a real time sampling probe. The system may comprise a tracer analyser for analysing samples concentration and type of tracer material. The production liner section may be connectable or connected to a plurality of production liner sections. The plurality of production liner sections may be connectable or connected together to form a production liner. The production liner may comprise two or more production liner section comprising a tracer chamber. The position of the two or more tracer chambers along the length of the production liner may be selected to target sections of the wellbore formation. The at least one tracer chamber may be installed in known levels of the well by arranging the production liner section with the tracer chamber mounted on a surface of the production liner section at a known level in the well. The tracer chamber may be configured to outwardly vent tracer towards the formation during a perforation event. The tracer chamber may be configured to inwardly vent fluid and tracer from a perforation hole during production. The system may comprise a perforating tool. The perforating tool may be a perforating gun. The perforating gun may comprise at least one explosive charge. The perforating tool may be configured to travel inside the production liner. The perforating tool may be configured to perforate the tracer chamber and the production liner section when actuated. The perforating tool may be configured to detonate the at least one explosive charge to perforate the tracer chamber and the production liner section. The tracer chamber may be non-perforated. The tracer chamber may comprise a shroud. The tracer chamber may comprise a jacket. The tracer chamber may comprise a carrier. The tracer chamber may comprise a jacket carrier. The tracer chamber may be a sealed chamber. The tracer material may be a solid or liquid. The tracer chamber may comprise two or more distinct tracer materials. The tracer chamber may comprise at least one solid tracer. The tracer chamber may comprise at least one fluid tracer. The tracer chamber may comprise a combination of at least one solid tracer and at least one liquid tracer. The fluid tracer may be encapsulated or contained within a polymer before perforation. The fluid tracer may be encapsulated or contained within a bag or tube before perforation. The bag or tube may comprise a polymer material. The solid tracer may be a powder, particles, pellets or fragmented solid piece encapsulated or contained within a polymer before perforation. The powder, particles, pellets or fragmented solid pieces may be encapsulated or contained within a bag, wrap or tube before perforation. The bag, wrap or tube may comprise a polymer material. The tracer material may be surrounded by a fluid or mass to fill any void or space in the tracer not occupied with tracer material. The tracer material may be surrounded by a fluid or mass to fill any void or space in the tracer chamber not occupied with tracer material. Filling any empty voids or spaces with a fluid or mass may mitigate or avoid the tracer chamber collapsing due to downhole pressure. The tracer chamber may comprise at least one port, aperture or opening. The tracer chamber may comprise at least one port, aperture or opening before perforation. The at least one port, aperture or opening may be a pressure equalising port, aperture or opening. Embodiments of the fourth aspect of the invention may comprise features corresponding to the preferred or optional features of the first, second or third aspects of the invention or vice versa. According to a fifth aspect of the invention, there is provided a method of estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well; wherein the method comprises installing a production liner comprising a plurality of production liner sections in a well; wherein at least one production liner section comprises at least one tracer chamber; wherein the at least one production liner section is configured to be installed at a known level of the well; wherein the at least one tracer chamber comprises at least one distinct tracer material; perforating the at least one production liner section, the tracer chamber and surrounding formation to create an influx location and deposit tracer from the at least one tracer chamber into the formation; inducing production flow in the well; collecting at least one sample downstream of the influx location; analysing the at least one sample for concentration and type of tracer material; and based on the analysed concentrations calculating flow data from the influx location. The method may comprise inducing a steady state flow. The method may comprise inducing a steady state flow condition in the production rate of the entire production flow or for influx location. The method may comprise inducing a transient in the production flow. The method may comprise collecting at least one sample at known sampling times. The method may comprise collecting samples at known sampling times. The method may comprise collecting two or more samples. The method may comprise collecting a plurality of samples. The method may comprise collecting samples at known sampling times. The method may comprise inducing multiple steady state flow conditions in the production rate of the entire production flow or for the influx location and collecting samples. The method may comprise producing at least one well fluid from the well at a first production flow rate in the production tubing and collecting samples at the first production flow rate and then modifying the production flow rate in the production tubing to a second production flow rate and collecting samples at the second production flow rate. The method may comprise producing at least one well fluid from the well at a third production flow rate in the production tubing and collecting samples at the third production flow rate. The second production flow rate may be higher than the first production flow rate. Alternatively, the second production flow rate may be lower than the first production flow rate. The third production flow rate may be higher than the first and / or second production flow rate. Alternatively, the third production flow rate may be lower than the first and / or second production flow rate. The tracer chamber may comprise two or more distinct tracer materials. Each of the two or more tracers may have a different physical form. The method may comprise releasing each of the two or more distinct tracers from the at least one tracer chamber at different rates. The method may comprise depositing or injecting different amounts of each of the two or more distinct tracers into the formation and / or into the at least one perforation. Embodiments of the fifth aspect of the invention may include one or more features of the first to fourth aspects of the invention or their embodiments, or vice versa. According to a sixth aspect of the invention, there is provided a method of estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well; wherein the method comprises installing a production liner comprising a plurality of production liner sections in a well; wherein two or more production liner sections each comprise at least one tracer chamber; wherein each tracer chamber comprises at least one distinct tracer material; perforating the two or more production liner sections, the tracer chambers and surrounding formation to create two or more influx locations and deposit tracer from each tracer chamber into the formation at the two or more influx locations; inducing production flow in the well; collecting at least one sample downstream of the two or more influx locations; analysing the at least one sample for concentration and type of tracer material; and based on the analysed concentrations calculating said contribution of flow from the two or more influx locations. Each of the at least one production liner section may be configured to be installed at a known level of the well. The method may comprise collecting at least one sample at known sampling times. The method may comprise collecting samples at known sampling times. The method may comprise collecting two or more samples. The method may comprise collecting a plurality of samples. The method may comprise collecting samples at known sampling times. The method may comprise inducing a steady state flow. The method may comprise inducing a steady state flow condition in the production rate of the entire production flow or for at least one influx location. The method may comprise inducing multiple steady state flow conditions in the production rate of the entire production flow or for at least one of the influx locations and collecting samples. The method may comprise producing at least one well fluid from the well at a first production flow rate in the production tubing and collecting samples at the first production flow rate and then modifying the production flow rate in the production tubing to a second production flow rate and collecting samples at the second production flow rate. The method may comprise producing at least one well fluid from the well at a third production flow rate in the production tubing and collecting samples at the third production flow rate. The second production flow rate may be higher than the first production flow rate. Alternatively, the second production flow rate may be lower than the first production flow rate. The third production flow rate may be higher than the first and / or second production flow rate. Alternatively, the third production flow rate may be lower than the first and / or second production flow rate. Each of the tracer chambers may comprise two or more distinct tracer materials. Each of the two or more tracers may have a different physical form. The method may comprise releasing each of the two or more distinct tracers from each tracer chamber at different rates. The method may comprise depositing or injecting different amounts of each of the two or more distinct tracers into the formation and / or into the at least one perforation. Embodiments of the sixth aspect of the invention may include one or more features of the first to fifth aspects of the invention or their embodiments, or vice versa. According to a seventh aspect of the invention there is provided a method of collecting at least one sample for later analysis in estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well with two or more influx locations; wherein the formation comprises distinct tracer molecules for each of the two or more influx locations; wherein the method comprises: inducing production flow in the well; and collecting at least one sample downstream of the two or more influx locations. The method may comprise analysing the at least one sample for concentration and type of tracer material from said possible tracer sources; and based on the analysed concentrations calculating the contribution of flow from the two or more influx locations. The method may comprise inducing steady state production flow. The method may comprise collecting the at least one sample at a location downstream of the tracer sources at known sampling times (t) after inducing a steady state flow in the production rate of the entire production flow or for at least one of the influx locations. The method may comprise collecting at least one sample at known sampling times. The method may comprise collecting samples at known sampling times. The method may comprise collecting two or more samples. The method may comprise collecting a plurality of samples. The method may comprise collecting samples at known sampling times. The method may comprise collecting samples wherein the formation comprises tracer material and / or tracer molecules deposited into the formation by perforating a tracer chamber associated with a production liner at each of the two or more influx locations. Embodiments of the seventh aspect of the invention may include one or more features of the first to sixth aspects of the invention or their embodiments, or vice versa. According to an eighth aspect of the invention there is provided a method of estimating an influx profile for at least one well fluid from a reservoir formation to a producing hydrocarbon well; wherein the formation comprises at least one influx location with at least one distinct tracer deposited in at least one perforation in the formation; the method comprises: analysing at least one sample collected at a location downstream of the at least one influx location; analysing the at least one sample for concentration and type of tracer material; and based on the analysed concentrations calculating flow data for the at least one influx location. The method may comprise analysing the at least one sample collected during a steady state flow in the production rate of the entire production flow or for at least one of the influx locations. The method may comprise analysing the at least one sample collected during a transient flow in the production rate of the entire production flow or for at least one of the influx locations. The method may comprise collecting at least one sample at known sampling times. The method may comprise collecting samples at known sampling times. The method may comprise collecting two or more samples. The method may comprise collecting a plurality of samples. The method may comprise collecting samples at known sampling times. The formation may comprise two or more distinct tracer materials deposited by perforating a tracer chamber comprising two or more distinct tracers. Embodiments of the eighth aspect of the invention may include one or more features of the first to seventh aspects of the invention or their embodiments, or vice versa. According to a ninth aspect of the invention there is provided a method of estimating an influx profile for at least one well fluid from a reservoir formation to a producing hydrocarbon well; wherein the formation comprises two or more influx locations each with at least one distinct tracer deposited in at least one perforation in the formation at the two or more influx locations; the method comprises: analysing at least one sample collected at a location downstream of the two or more influx locations; analysing the at least one sample for concentration and type of tracer material; and based on the analysed concentrations calculating the contribution of flow from the two or more influx locations. The method may comprise collecting at least one sample at known sampling times. The method may comprise collecting samples at known sampling times. The method may comprise collecting two or more samples. The method may comprise collecting a plurality of samples. The method may comprise collecting samples at known sampling times. Each influx location may comprise two or more distinct tracer materials deposited by perforating a tracer chamber comprising two or more distinct tracers. Embodiments of the ninth aspect of the invention may include one or more features of the first to eighth aspects of the invention or their embodiments, or vice versa. According to a tenth aspect of the invention there is provided a method of estimating an influx profile for at least one well fluid to a producing hydrocarbon well, wherein the formation comprises two or more influx locations each with at least one distinct tracer deposited in at least one perforations in the formation at the two or more influx locations; the method comprising: providing measured concentrations and type of tracer material data from at least one sample previously collected from the production flow at a location downstream of the two or more influx locations; and based on the measured concentrations calculating influx volumes and / or contribution of flow from the two or more influx locations. The method may comprise providing measured concentrations and type of tracer material data from the at least one sample collected during a steady state flow in the production rate of the entire production flow or for at least one of the influx locations. The method may comprise providing measured concentrations and type of tracer material data from two or more samples previously collected from the production flow. The method may comprise providing measured concentrations and type of tracer material data from a plurality of samples previously collected from the production flow. The method may comprise providing measured concentrations and type of tracer material data from samples previously collected from the production flow. The method may comprise collecting samples wherein the formation comprises tracer materials and / or tracer molecules deposited into the formation by perforating a tracer chamber associated with a production liner at each of the two or more influx locations. Embodiments of the tenth aspect of the invention may include one or more features of the first to ninth aspects of the invention or their embodiments, or vice versa. According to an eleventh aspect of the invention, there is provided a method of depositing tracer in a reservoir formation, the method comprising; installing a production liner comprising a plurality of production liner sections; wherein at least one production liner section comprises at least one tracer chamber; wherein the at least one production liner section is configured to be installed at a known level of the well; perforating the at least one production liner section, the tracer chamber and surrounding formation to deposit tracer from the at least one tracer chamber into the formation. The method may comprise depositing tracer materials and / or tracer molecules in a reservoir formation. The method may comprise perforating a set material surrounding or partially surround the at least one production liner section and / or the tracer chamber. The set material may be cement or resin material. The tracer chamber may comprise at least one distinct tracer. The tracer chamber may comprise two or more distinct tracers. Each of the two or more tracers may have a different physical form. Embodiments of the eleventh aspect of the invention may include one or more features of the first to tenth aspects of the invention or their embodiments, or vice versa. According to a twelfth aspect of the invention, there is provided method of estimating influx data for at least one well fluid to a producing hydrocarbon well, wherein the formation comprises at least one influx location with at least one distinct tracer deposited in the formation; the method comprising the steps of: providing measured concentrations and type of tracer material data from at least one samples previously collected from the production flow at a location downstream of the at least one influx location; and based on the measured concentrations calculating influx data from the at least one influx location. The at least one tracer may be deposited in at least one perforation in the formation. The at least one tracer may be deposited in at least one perforation in the formation by perforating a production liner comprising at least one tracer chamber in a well. The tracer chamber may comprise two or more distinct tracers. Two or more tracers may be deposited in at least one perforation in the formation. The method may comprise providing measured concentrations and type of tracer material data from at least one sample previously collected from the production flow at a location downstream of the tracer sources at known sampling times after inducing steady state production flow. The method may comprise providing measured concentrations and type of tracer material data from at least one sample previously collected during a steady state flow in the production rate of the entire production flow or for at least one of the influx locations. The method may comprise providing measured concentrations and type of tracer material data from two or more samples previously collected from the production flow. The method may comprise providing measured concentrations and type of tracer material data from a plurality of samples previously collected from the production flow. The method may comprise providing measured concentrations and type of tracer material data from samples previously collected from the production flow. Embodiments of the twelfth aspect of the invention may include one or more features of the first to eleventh aspects of the invention or their embodiments, or vice versa. According to a thirteenth aspect of the invention, there is provided a method of installing a production liner with associated tracer material in a wellbore, the method comprising; installing a production liner comprising a plurality of production liner sections; wherein at least one production liner section comprises at least one tracer chamber; pumping a settable fluid in a gap between an outer wall of the production wall and wellbore surface wherein the settable material is configured to set to form a solid material. The at least one production liner section may be configured to be installed at a known level of the well. The method may comprise perforating the at least one production liner section, the tracer chamber, the settable material and surrounding formation to deposit tracer material and / or molecules from the at least one tracer chamber into the formation. The settable material may be cement or a resin material. The tracer chamber may comprise at least one distinct tracer. The tracer chamber may comprise two or more distinct tracers. Each of the two or more tracers may have a different physical form. Embodiments of the thirteenth aspect of the invention may include one or more features of the first to twelfth aspects of the invention or their embodiments, or vice versa. According to a fourteenth aspect of the invention there is provided a method of estimating an influx profile for at least one well fluid from a reservoir formation to a producing hydrocarbon well; wherein the well comprises a production liner comprising a plurality of production liner sections in the well; wherein two or more production liner sections each comprise at least one tracer chamber; wherein each tracer chamber comprises at least one distinct tracer; the method comprising: perforating the two or more production liner sections, the at least one tracer chambers and surrounding formation to create two or more influx locations and deposit tracer from each tracer chamber into the formation at the two or more influx locations; inducing production flow in the well; collecting at least one sample downstream of the two or more influx locations; analysing the at least one sample for concentration and type of tracer material; and based on the analysed concentrations calculating said contribution of flow from the two or more influx locations. The method may comprise inducing a steady state flow. Embodiments of the fourteenth aspect of the invention may include one or more features of the first to thirteenth aspects of the invention or their embodiments, or vice versa. According to a fifteenth aspect of the invention there is provided a method of estimating an influx profile for at least one well fluid from a reservoir formation to a producing hydrocarbon well; wherein the well comprises a production liner comprising a plurality of production liner sections in the well; wherein at least one production liner section comprises at least one tracer chamber; wherein each tracer chamber comprises at least one distinct tracer; the method comprising: perforating the at least one production liner section, the at least one tracer chamber and surrounding formation to create at least one influx location and deposit tracer from the at least one tracer chamber into the formation at the at least one influx location; inducing production flow in the well; collecting at least one sample downstream of the at least one influx location; analysing the at least one sample for concentration and type of tracer material; and based on the analysed concentrations calculating said contribution of flow from the at least one more influx location. The method may comprise inducing a steady state flow. The method may comprise inducing a transient in the production flow. Two or more production liner sections may each comprise at least one tracer chamber; wherein each tracer chamber may comprise at least one distinct tracer material. The method may comprise perforating the two or more production liner sections, the tracer chambers and surrounding formation to create two or more influx locations and deposit tracer from each tracer chamber into the formation at the two or more influx locations. The method may comprise calculating contribution of flow from the two or more influx locations based on the analysed concentrations. The tracer chamber may comprise two or more distinct tracers. Each of the two or more tracers may have a different physical form. Embodiments of the fifteenth aspect of the invention may include one or more features of the first to fourteenth aspects of the invention or their embodiments, or vice versa. Brief description of the drawings There will now be described, by way of example only, various embodiments of the invention with reference to the following drawings (like reference numerals referring to like features) in which: Figure 1A to 1D are simplified sectional diagrams through a wellbore showing steps of installing and perforating a production liner with an associated tracer chamber in accordance with an aspect of the invention; Figure 2A to 2C are enlarged sectional diagrams of the production liner section with an associated tracer chamber of Figure 1A showing the perforation of the production liner section with an associated tracer chamber in accordance with an aspect of the invention; Figure 3A and 3B are simplified sectional diagrams through a production well showing three tracer chambers associated with three production liner sections of a production liner in a well during production in accordance with an aspect of the invention; Figure 4A is a graphical representation of example tracer concentration levels measured at surface at a flow rate of 2000m3 / day of where dispersion is varied in accordance with an aspect of the invention; Figure 4B is a graphical representation of example tracer concentration levels measured at surface at a flow rate of 200m3 / day of where dispersion is varied in accordance with an aspect of the invention; Figure 4C is a graphical representation of example tracer concentration levels measured at surface, with characteristic time scales (t1, t2 and t3) in tracer signals annotated as lines; Figure 5 is a simplified sectional diagram showing concentration downstream of a junction from upstream concentrations and rates in accordance with an aspect of the invention; Figure 6 is a graphical representation of example tracer concentration levels measured at surface for three different steady state conditions in accordance with an aspect of the invention; Figure 7A is a graph showing percentage of influx rate contribution for seven influx locations in a well based on tracer response data collected during two transient production flow events; Figure 7B is a graph showing percentage of influx rate contribution for seven influx locations in a well based on tracer response data collected during a steady state production flow; Figure 8A to 8C are enlarged sectional diagrams of a production liner section with an associated tracer chamber containing a liquid tracer showing the perforation steps of the liner; Figure 9A to 9C are enlarged sectional diagrams of a production liner section with an associated tracer chamber containing a fragmented solid tracer showing the perforation steps of the liner; and Figure 10A to 10D are enlarged sectional diagrams of four different production liner sections each with an associated tracer chamber containing different tracer arrangements. Detailed description of preferred embodiments Figures 1A to 1D are simplified sectional views through a wellbore 10 showing stages of installing and perforating a production liner with incorporated tracer system 20 into a wellbore 10. The production liner may also be known as a casing. The production liner 12 comprises a plurality of liner sections 14, for clarity one is shown in Figures 1A to 1D. At least one production liner section 14 of the production liner comprises a tracer chamber 16. In this example the tracer chamber is located around an outer surface of the production liner section 14. The tracer chamber 16 comprises an inner void 18 which accommodates tracer material 22. In this example the outer diameter of the tracer chamber is less than an outer diameter of a production liner collar. The tracer material 22 may be a solid or liquid. In this example the tracer is a solid and is surrounded by a fluid 17. In this example the tracer chamber 16 has a length of up to 3m and optionally has at least one open port 15 into the void to allow for pressure equalisation between the void and the wellbore while the production tubing is run in hole to prevent collapse of the void. As shown in Figure 1A the production liner with incorporated tracer system 20 is run into the wellbore 10 in the direction shown as arrows “A”. As shown in Figure 1B cement 30 is pumped down the production liner and up into the space 31 between the outer surface of the production liner with incorporated tracer system 20 and the wellbore formation. The position of the open port 15 at the uphole position on the tracer chamber prevents the fluid 17 from leaking from the void. Due to the pressure equalisation between the void and the wellbore and the small diameter of the port 15 there is no ingress into the void from the cement. Once the cement sets the production liner with incorporated tracer system 20 is bonded to the formation by cement 30 as shown in Figure 1C. A perforation tool 40 (best shown in Figure 2B) is lowered through the production liner 12. In this example the perforation tool is a perforation gun with explosive charges. The perforated gun is actuated to detonate the explosive charges which perforate the tracer chamber 16, cement 30 and surrounding formation 11 to create perforation holes 34. During the perforation, tracer molecules 23 are carried with the explosive force from the tracer chamber 16 into the perforation holes 34 in the formation 11. The tracer material and / or molecules are deposited into the formation via the perforation holes. It will be appreciated that tracer material comprising carrier material may be deposited into the formation via the perforation holes. As shown in Figure 1D once a production flow starts the inflow of fluids from the formation 11 carries the deposited tracer materials and / or tracer molecules 23 from the perforation holes 34 into the well shown as arrows “B” in Figure 1D, where they are carried to the surface with the production flow shown as arrow “F”. The production of tracer at surface may be dependent on the rate of influx through the perforation holes 34 into the well. Figures 2A to 2C are enlarged sectional views of a production liner section 14 with incorporated tracer chamber 16. Figure 2A shows the production liner section 14 and tracer chamber 16 intact before they are perforated by a perforation tool. In this example the tracer is a solid tracer encapsulated and uniformly distributed in a polymer. The tracer material is moulded into rods of tracer molecules in matrix material. The tracer material is arranged in the void of the tracer chamber. In this example an open port 15 is provided in the wall of the tracer chamber into the void to allow for pressure equalisation between the void and the wellbore while the production tubing is run in hole to prevent collapse of the void. It will be appreciated in other examples the void may be sealed and the void completely filled with a solid and / or fluid to prevent collapse. In this example the perforation tool is a perforation gun 40. The perforation gun is lowered downhole to a position adjacent to the tracer chamber. The perforation gun is actuated to detonate a group of positioned explosive charges to perforate the liner section 14, the tracer chamber 16, the tracer material 22, the cement 30 and the surrounding formation 11. The explosions carry tracer molecules 23 from the tracer material 22 into the perforation holes 34 in the formation 11. Figure 3A and 3B are simplified sectional views through a production well 100. The central production liner 112 in the well is cemented in place by cement 130. The central production liner 112 comprises a plurality of liner sections 114 joined to each other to form the liner 112. In this example three of the liner sections 114a have a tracer chamber 116 located around an outer surface of the production liner section 114a. The tracer chambers are installed at known positions along the well. The regions around the well 100 in a reservoir 13 are divided into a number of zones. In this example three tracer chambers 116a, 116b, 116c are shown each located at a different position or zone in the well. In this example each of the three perforated tracer chambers 116a, 116b, 116c has a distinct tracer material 122a, 122b, 122c with unique characteristics for each tracer chamber. It will be appreciated that there may be a different number of tracer chambers at different positions along the production liner or well than illustrated in Figures 3A and 3B. The three tracer chambers and surrounding formation 11 are perforated as described in Figures 1A to 2C above creating three influx locations 150a, 150b and 150c. The explosive force deposits tracer molecules 123a, 123b, 123c from the tracer chambers 116a, 116b, 116c into the perforation holes 134a, 134b, 134c respectively in the formation 11. Figure 3B shows an enlarged section of the well showing the three influx locations 150a, 150b and 150c created through perforations through the liner sections, tracer chambers 116a, 116b, 116c cement 130 and into the formation. During production influx, volumes of fluids enter the well 100 from the reservoir 13 into the central production liner 112 via each of the separate an influx locations 150a, 150b and 150c show as arrows “A”, "B” and “C” in Figure 3B. In the above examples each of the tracer chamber 116a, 116b, 116c is located on and around a different section of the production liner. The tracer chamber may be located around the entire circumference of a section of the production liner or partially around the outer circumference of a section of the production liner. It will be appreciated that additionally or alternatively the tracer chamber may be located on an inner surface of the production liner. The tracer chamber may be located around the entire inner circumference of a section of the production liner or partially around the inner circumference of a section of the production liner. By accurately locating tracer chambers with distinct tracers in specific zones and perforating the tracer chambers to create influx locations fluid samples may be obtained downstream and tracer concentrations measurements taken that may provide inflow contribution from each influx location. The tracer concentrations measured at surface may be dependent on the rate of influx at each influx location. It will be appreciated the sequence in which the tracer chambers are perforated may be in any order. Once the tracer chambers have been perforated and the perforating tool withdrawn production can be started. During production, the rate Q' of each phase is recorded downstream of the influx locations such as at surface. Additionally, fluid samples are taken downstream of the influx location such as at surface and concentrations (Q, C2, ••• , CN) of the tracers are measured in the fluid samples. During production the time to travel to surface from each influx inlet points is not the same, because the distance from the influx locations to the point of sampling such as surface are not the same for each influx locations and because the fluid velocity vary (typically increases) as the fluid moves from the influx locations along the well bore towards the surface. This implies that tracer found at the point of sampling entered the well-bore at different times, that can vary by several minutes or even hours, depending on the specific conditions in the well. In some examples it may be advantageous to keep the fluid production rate constant during a period of sampling to ensure that the tracer concentration from each influx locations changes little over time. This generally cannot be achieved if a transient in the production flow is present. In this example, maintaining a steady state flow condition allows a comparison of the concentration and rates at the influx locations to the measured concentration and rates at the sampling point, such as at surface. The calculation of rate fractions from each influx location into the production flow uses the fundamental principle of mass-conservation that applies for each tracer in the individual tracer systems. If we define a small control volume V = Q • At, corresponding to a sample at surface, and if we assume that no tracer mass leaves or enters this control volume during transport from the entry point to the sampling point, then the mass in this control volume is conserved. The mass of a tracer i = 1,2,.., N, entering into the wellbore with a carrying fluid at a rate Qt and a concentration Ct, must equal the mass topside where the rate Q' and concentration C'i is measured. We thus have: mi = Qi • Q • At = Q • C't • At (1) Eliminating the time interval and re-arranging: Qt / Q' = C’jCt (2) This relationship shows that the fraction of fluid originating from influx location i, ft = QJQ is given as the concentration of tracer i at the influx location relative to the concentration of that tracer in the sample. The concentrations q are unknown - however, we can assume that these concentrations are similar for each reservoir volume attached to individual influx locations, in other words that Q = C2 = C3 =.. = CN = k. We would like to express the unknown k by known properties. If we use the relationship Qi / Q = ci / k, a summation over all i gives: N N IF St i=l i=l The constant Q can be taken out of the summation and continuity for the flow (Q = X gives that the left-hand side of Equation (3) must equal 1. Since k is a constant, it can also be moved out of the summation, and we obtain the desired result. N k=^C[ (4) i = l Finally, we can express the desired inflow contribution from each zone as: N / ^C[ (5) i = l This relationship assumes that no tracer mass leaves or enters the control volume during transport from the influx location to the surface. In practice this means that mixing in the wellbore must be negligible, which occurs if the dispersion is small. This is a valid assumption if the flow in the wellbore is turbulent, which is a condition met in many cases relevant for the technology. Equation (5) developed above is based on the approximation that all concentrations Q, C2, •••, CN are equal. To ensure that this approximation is good various operational steps can be tuned. First, it is possible to ensure that the amount of tracer released from the individual tracer systems (tracer chambers) is equal, by equating the amount available in each system. Additionally, the release parameters can be adjusted to ensure that the 1 gradient dC / dt is constant. Finally, the process used to place the tracer material in the 2 formation surrounding the well (e.g. the rock surrounding a well bore) can be adapted in 3 such a way that the tracer material is distributed in an isotropic fashion. This can be 4 achieved e.g. by tuning perforation guns to perform in a repeatable and consistent manner 5 and by placing material along the wellbore in a systematic and distributed manner adapted 6 to the perforation process. In some cases, it can be desirable to have a flexibility to choose 7 the parameters affecting individual concentrations Q, C2, •••, CN. If the parameter choices 8 are made systematically and recorded it is possible to take this into account and revise 9 relation (5) accordingly. As an example, let us assume that the amount of tracer in system 10 # j is a times the amounts in the other systems, i.e. that Q = C2 = ••• = ^Cj = ••• = CN = 11 k. In that case we find that: 12 N J-1 , N , y«i=y£i+^+y £< (6) A 0 A k «k A k ' ' i=l i=l 1=7+1 13 14 and hence that: (7—1 N \ £c‘+;h + 2c‘ (7) i=l i=j+l ] 15 16 for systems i = 1,2, ■■■ ,j - l,j + l,--,fV. For system # j we have: IN \ a= / + Zc- <8) / \i=l i=7+l / 17 18 Similar expressions can be developed for other special cases, as long as the relationship 19 between the individual concentrations can be quantified. In one embodiment of the 20 invention the fraction of oil and water along production wells can be obtained. The inflow 21 contribution per influx location along the well, established using the expressions developed 22 above are available for each phase for which a system is installed. For example, if water 23 and oil tracer specific systems are installed at each influx location point, the production 24 allocation of both oil (fot) and water (fwt) along the wellbore is available, by use of 25 expression (5) using oil and water tracer concentrations, respectively. To obtain the water and oil rates at specific influx location points (j) we can then simply multiply the rates of oil (Qo) and water at the surface to the respective allocation factors. The expressions for oil and water then read Qo i = fot ■ Q'o and Qw i = fwt ■ Q'w. In the event that there is gas produced at the surface, it is necessary to take this into account when calculating the downhole oil rate. In most cases this can be achieved by applying the formation volume factors b0 and bfl.The quantities Q', as well as the concentrations Q, C2, •••, CN represents values of corresponding continuous functions of time Q'(t) and ^(¢), C2(t),(t). In the descriptions (figures included) all quantities are for brevity denoted without the time variable. This notational choice does not in any way restrict the derived expressions and methods to one specific time (tt) or to a series of discrete times t2, •••, tM). All embodiments of the invention are therefore unrestricted by the discrete representation used in the description given herein. A series of fluid samples, e.g., would give a time-series of results. A measurement system that could provide continuous functions Q'(t) and would likewise provide continuous results. Modification of equations 1 to 4 above may be made to incorporate systematic known variation in the tracers and tracer systems, as exemplified through equations 6 to 8. Modification of expressions equations 1 to 4 to incorporate systematic known variation in the rate assessment can be generalized to unknown variations by means of calibration. This can be used to exploit a relative stability of concentration fractions to assess zonal inflow rate proportions even in situations where variations cannot be inferred from known systematic differences between the tracers or tracer systems. One example may be to use a standard production logging tool (PLT) to measure rate proportions at one time interval and use these to estimate values on concentration proportions. This may provide a constant correction factor that can then be used to correct for concentration-based flow quantifications for times outside the time interval for which the PLT provide proportional rate measurements. Other calibration methods may comprise flush out analysis and / or arrival analysis. These methods may comprise inducing a tracer transient in the flow. The method may comprise inducing a transient in the flow rate. The method may comprise releasing a build-up of tracer in a pulse or short duration to create a tracer transient. The transients may be induced by shutting-in the well or otherwise changes in the flow. Inducing a transient may create a build-up tracer concentration in the locality of the tracer source. On production the built up tracer concentration may propagate to the surface as a high concentration tracer clouds, slugs or shots. The tracer transients are driven by the velocity field in the well. The topside arrivals of the onset of the different tracers, or the full transient of the different tracers, can be used to estimate the downhole velocity field. From the velocity field the inflow profile may be calculated. The concentration of tracers at surface as a function of time may be related to the influx into the well, by the velocity field. The tracer concentrations may be governed by the velocity field. The velocity field may be influenced by the well geometry and transport path of the fluid flow. The tracer concentration may be calculated as a function of time. The measured tracer concentrations may be compared with modelled tracer concentrations to derive information about downhole inflow profiles. Model concentrations for each tracer material may be calculated in a modelled downstream well flow transport path as a function of time under a modelled transient occurring in the model. In an arrival time method a model may be used based on the well geometry of the production well such as influx location, that assumes a specific scenario of inflow distribution, simulates the arrival time of the tracer peaks, and compares the simulated results to the actual peak arrivals. After several iterations, the model may converge on a solution that provides an inflow distribution that best fits the actual data. The model may include a model transport path corresponding to the actual well's transport path downstream of the influx zones. In a flush out method tracer released from the tracer release apparatus may create a characteristic signal called a flush-out signal. The flush-out signal has a peak concentration followed by the decay of the concentration. The decay of the concentration after the peak may be expressed by a slowly decaying function such as exponential function or power law function. The coefficient in the functions describing the steepness of the decay is proportional to the fluid velocity inside the tracer release apparatus and thus the fluid velocity inside the tracer release apparatus can be calculated based on the measured tracer concentration decay curve. Steeper curve, i.e., shorter flush-out time, corresponds to the higher fluid velocity inside the tracer release apparatus. The duration of the tracer signal may be captured by sampling or real time measurement. The signal should be long enough that it is not destroyed by the dispersion during the travel to the detection point which may be located after the upper completion and a long tie-back. Tracer release and dispersion may be modelled by flow models. The dispersion of the signal during the travel to the detection point may be compensated by modelling based on the well geometry and / or a model of the well. Other calibration methods may comprise temperature-based flow quantification, micro seismic methods or flow metering devices. Fluid rate information from tracer signals Mass conservation of a tracer in a flow stream may be described by a partial differential equation known as the advection-dispersion equation. It follows directly from the advection-dispersion equation that fluid rate and tracer signals in the form of concentration versus time are related, and that concentration signals therefore bear information about fluid rates in a system. One specific form of the advection-dispersion equation for single phase transport in a one dimensional system, given as: dC dC d2C — +U — -D— = 0 (9) Ot OX OX2 where C(x, t) is concentration (unit M / L3), U is velocity of the moving phase (unit L / T) and D is dispersion (L / T2) of the tracer in the one dimensional system. In Equation (9) it is assumed that dispersion and velocity are constant and thus independent of time and the spatial coordinate. This equation can be solved analytically or numerically. Examples of solutions to this equation, with initial conditions: C (x, 0) = 0 for x >0 C(0,t) = Co fort >t >0 C(0, t) = 0 for t >t C(oo, 0) = 0 for t >0 for various values of the parameters Co, U = Q / (jir2f t, and D are displayed in Figure 4B. Figures 4A and 4B shows graphical representations of examples of solutions to the convection-dispersion equation for various parameter values. Data is based on a well length L = 2000 m, an inner well radius r = 0.15 m and t = 5 h. An arbitrary value Co = 10 was set in all cases. The parameter t is the duration of a constant concentration in the boundary condition given above. It is set equal for all cases displayed in Figure 4A and 4B, hence the mass is the same in all cases. In a preferred embodiment t corresponds to the time from production start until the concentrations Q, C2,.. deviate from their initial constant levels by a level above an accepted uncertainty for a particular application (e.g. 10%, 25%, 50% etc). As shown in Figure 4A the dispersion was varied at 1, 10 and 100 m2 / s which changed the appearance of the resulting tracer curve but all of the curves maintained a generally rectangular shaped curve. In Figure 4A the rectangular shaped curve is maintained due to a high flow rate in this example a rate Q = 2000 m31 day was applied. In Figures 4A and 4B Dispersion at 1 m2 / s is shown as curve “A”, dispersion at 10 m2 / s is shown as curve “B” and 100 m2 / s as curve “C”. However, Figure 4B shows how the appearance of the tracer curves change to generally bell-shaped curves for each of the dispersion values (1,10 and 100 m2 / s) when the well flow rate is reduced to Q = 200 m3 / day. If the well flow rates is high then the dispersion of the tracer during its transport in the well to surface is small and mixing in the wellbore is negligible this results is a high gradient concentration spike followed by a high gradient drop when the tracer has reached the surface. In contrast, if the well flow rate is low then the tracer spends more time dispersing and mixing in the well during its transport this results is a lower gradient concentration spike followed by a lower gradient drop when the tracer has reached the surface. From Figures 4A and 4B it is clear that the appearance of tracer curves depends on the characteristics of the system in which the tracer is transported. The characteristics of the tracer signals can be analysed by comparing the time scales in the problem. Three timescales of particular interest are: 1) h is the time to travel from influx location to surface by advection = L • nr2 / Q\, 2) t2 is a characteristic time for mixing t2 = L2 / D’, and 3) t3 is the duration of constant influx concentration (t3 = t ). Figure 4C is a graphical representation of example tracer concentration levels measured at surface, with characteristic time scales (h, t2 and ta) in tracer signals annotated as lines. The characteristic times of the tracer signals are valuable to assess the suitability of signals from one particular parameter setting to provide useful information. For example to assess if the dispersion is too large for a particular parameter setting to provide accurate tracer signals, ti and t2 can be compared. In similar manners t2 and t3 can be compared, as well as ti and t3. Applied to the embodiment described here, the characteristic times may be used as shown in Figure 4C, to determine suitable rate settings in the well such as appropriate sample frequencies. In this example, steady state flow occurs when t3 are larger than such as shown in Figure 4A and also large compared to t2. For two or more sources of well fluid meet at a junction and results in a combined flow with a flow rate of Q = + Q2 -----1- CN. One such example is where tracer from one influx location meet the production flow in the wellbore. Another example is the junction of individual laterals and the main well-bore in multilateral wells. Downstream of a junction the tracer concentration is diluted given as C = q • Qi / (Qi + ^2-1-----h Qn\ where Ct is the concentration in the flow carrying tracer to the junction at a flowrate QL. Hence the downstream concentration depends on the flowrates into the junction and the concentration in the flow. A simple illustration where two fluid streams meet is illustrated in Figure 5. Figure 5 show the concentration C downstream of a junction, given from upstream concentration and rates. In one upstream flow of the junction Q2, C2 = 0, in a second upstream flow Qr, Cr = k and in the combined downstream flow of the junction Q = Qr + Q2 and C = kQJ(Qr + Q2). Although a transient or change in production flow is not required to calculate relative inflow from each zone the method may comprise adjusting the production flow rate to a set a different steady state condition in the well to verify that the method may provide reliable results at different flow conditions. In a production well the flow rate into the well bore from individual influx locations depend on the reservoir pressure as well as the pressure in the well. The latter can be adjusted by various means - e.g. by changing choke-settings or other means that increases or decreases flowrate at the surface. Such adjustments will change the relative inflow from individual sections of the well. For example in Figure 5 it is clear that such adjustments will change the concentrations of tracer measured at the surface. If the characteristics of the flow and the initial conditions are such that tracer concentrations into the wellbore at the influx location from the reservoir are quasi-constant over time (t3 is large) and rate adjustment changes concentrations at the surface we will expect behaviour with step-wise changes to the concentration, similar to that seen in Figure 6. Figure 6 is an illustration of measured surface concentrations in a well as function of time when the tracer concentrations at an influx location is constant and the surface tracer concentrations are measured during a first steady state condition, the production flow rate is adjusted and the tracer concentrations is measured at a second steady state condition different to the first steady state condition. The example concentrations provided in Figure 6 is based on a case with only two influx locations as known as influx zones, denoted zone 1 (dashed line) and zone 2 (solid line). The contribution to the total flow from zone 1 is given as = 6 / / (6 / + C2), where 6 / and C2 are concentrations at surface of tracer from zone 1 and 2 as described by Equation (5). The fraction from zone 2 is given as f2 = C2 / (C1 + C2). If changes to the well are applied (e.g. choke charges) that affect the distribution of inflow rates, this will affect the concentrations. In the example shown in Figure 6, for time below 10h the well conditions are set so that zone 2 contributes four times more fluid than zone 1 (Q2 = 4 • QJ and the concentration of tracer from zone 2 (20 on the graph) is thus four times larger than the concentration from zone 1 (5 on the graph). The fraction of fluid produced from zone 1 is 5 / (20+5)=20%, and the fraction from zone 2 is 20 / (20+5)=80%. At a time t = lOh the choke settings are changed so that the inflow contribution to zone 1 is increased from 20% to 40%. This is reflected in the concentration of tracer from zone 1 - that doubles from 5 to 10. At the same time, the concentration from zone 2 drops from 20 to 15. At time t = 20h the well conditions are again changed to a third production rate where Q2 = 5(^ and a third measured concentration during steady state condition is measured at surface at 6 = 20-^ / (6-^) = 10 / 3-3.3. Additionally or optionally analysing reservoir tracer samples of the initial production fluid from each influx zone addition information on the influx profile of the well may be provided. As an example the initial high concentration tracer from the influx fluid in each zone decreases as production continues until it reaches a steady state constant influx tracer concentration. The rate of change in tracer concentration is a function of cumulative production. Influx zones with high inflow rates flush out the tracer faster than zones with low inflow rates thereby preserving the high concentration of tracer molecules and generating a profile with steep rates of decline. In contrast, the concentration of tracer flushed out of a low inflow rate becomes more diluted as mixes with production flow and travels to the surface. As a result the tracer concentration profile presents a noticeably less steep rate of decline when compared to a high-performing zone. By modelling the flush out of the tracer during initial production when the tracer concentration is high and decreasing as a function of cumulative volume and comparing the measured concentrations from samples to simulated data the percentage of total inflow for each monitored zone may be identified. Additionally or optionally analysis may be performed on the arrival time at surface of tracer from the reservoir during the initial production fluid. During production the time to travel to surface from each influx zone is not the same, because the well geometry and distance from the influx locations to the surface are not the same for each influx locations and because the fluid velocity vary (typically increases) as the fluid moves from the influx locations along the well bore to the surface. During initial production, the distinctive tracer in the reservoir at each influx zones enters the production flow and is carried to the sampling point where the fluid is sampled to measure the high concentration peaks as they arrival at surface. The volume between the arrival of each tracer peak is proportional to the inflow that occurs upstream of each tracer. The measured results are compared with simulations to determine the inflow distribution. The system may use an iterative technique that assumes a specific scenario of inflow distribution, simulates the arrival time of the tracer peaks based on that scenario, and compares the simulated results to the actual peak arrivals. After several iterations, the system converges on a solution that provides an inflow distribution that best fits the actual measured data. Figure 7A and 7B show a graph of percentage of influx rate contribution data based on tracer response for seven influx locations in a well determined using a transient flow method (Figure 7A) and the present invention (Figure 7B) which in this example uses tracer data collected during a steady state production flow. In the transient flow method one or more transients are induced in the production flow by shutting in and restarting the production. The response tracer signals are interpreted based on the samples taken during the transient. Figure 7A shows tracer data collected during two transient flow events. Figure 7A show that the tracer data is consistent between each of the transient events. The transient flow method requires high frequency sampling to be regularly taken to ensure that the transient tracer data is captured. If samples are not taken at sufficient frequency or over a long enough period, aspects of the tracer data are be lost. In the transient method a high concentration of tracer is build up at each influx location during the shut in period. When the well is restarted the high concentration of tracer is flushed to surface as a tracer cloud. A high concentration of tracer is initially seen in the samples which declines over time as the tracer cloud is flushed from the well. The arrival time of the tracer cloud from each influx location and their rate of decline provide information on the influx rate distribution of the well. From this information the influx rate contribution data for the two transient events were plotted in Figure 7A. Figure 7B is a graph showing percentage of influx rate contribution for seven influx locations in a well based on tracer response data collected during a steady state production flow. In this example, no production flow transient is required. The tracer concentration in the collected samples can be interpreted independently from the remaining tracer concentrations in the sampling time series. Each individual data line in the histogram represents a single sample and the lines are graded from dark to light for every zone to illustrate time (the darkest colour is the sample taken initially and the lightest colour is the last sample in the time series). The results show that samples collected on Day 1 are consistent with samples collected on Day 2 and Day 3. Each sample provides an overall consistent influx distribution from each influx location to the well. Figures 8A to 8C are enlarged sectional views of production liner section shown generally at 214 with an incorporated tracer chamber 216. Figure 8A shows the production liner section 214 and tracer chamber 216 intact before they are perforated by a perforation tool. In this example the tracer chamber 216 comprise a liquid tracer 222. The liquid tracer 222 is contained within a carrier. In this example the carrier is a bag or tube 225 made of a polymer material. During manufacture the plastic bag or tube 225 is filled with a known amount and / or volume of liquid tracer before the bag or tube 225 is sealed and placed in the tracer chamber 216. Optionally an open port 215 is provided in the wall of the tracer chamber into the void. It will be appreciated in other examples the void may be sealed and the void completely filled with a solid and / or fluid to prevent collapse. In this example a perforation gun 240 is lowered downhole to a position adjacent to the tracer chamber. The perforation gun is actuated to detonate a group of positioned explosive charges to perforate the liner section 214, the tracer chamber 216, the bag or tube 225, the cement and the surrounding formation. The explosions carry the liquid tracer 222 into the perforation holes 234 in the formation. Although Figure 8C shows the empty bag or tube 225 after the explosion, this is for explanation purposes to show substantially all of the liquid tracer 222 is carried into the formation rather than remain in the chamber. In practice the bag or tube would be significantly destroyed or damaged during the perforation explosion. By providing a liquid tracer in the tracer chamber, most if not all of the liquid tracer will be transported from the chamber to the perforations after the perforation explosion. This may allow a known amount of fluid tracer to be transported into the formation. Figures 9A to 9C are enlarged sectional views of production liner section shown generally at 314 with an incorporated tracer chamber 316. Figure 9A shows the production liner section 314 and tracer chamber 316 intact before they are perforated by a perforation tool. In this example the tracer 322 comprises fragmented solid tracer 322. The fragmented solid tracer 322 is made of solid fragments or particles. During manufacture the tracer 322 may be encapsuled or attached to a solid carrier material. The tracer 322 may be encapsuled or attached to a solid polymer material. The tracer 322 may be moulded into rods of tracer molecules in matrix material which may be broken up or fragmented into small pieces or particles of tracer at least partially encapsuled with polymer material. The fragmented tracer 322 may be loosely positioned within the tracer chamber 316. The pieces of the fragmented tracer 322 may be located in carrier which in this example is a polymer tube 325. Optionally an open port 315 is provided in the wall of the tracer chamber into the void. It will be appreciated in other examples the void may be sealed and the void completely filled with a solid and / or fluid to prevent collapse. In this example a perforation gun 340 is lowered downhole to a position adjacent to the tracer chamber. The perforation gun is actuated to detonate a group of positioned explosive charges to perforate the liner section 314, the tracer chamber 316, polymer tube 325, the cement and the surrounding formation. The explosions carry the fragmented tracer pieces 322a into the perforation holes 334 in the formation. Although Figure 9C shows the empty tube 225 after the explosion, this is for explanation purposes to show the fragmented tracer 322 is carried into the formation rather than remain in the chamber. In practice the tube would be significant destroyed or damaged during the perforation explosion. By providing a fragmented solid tracer in the tracer chamber, most if not all of the tracer fragments will be transported from the chamber to the perforations after the perforation explosion. This may allow a known amount of tracer to be transported into the formation. By providing fragmented solid tracer may provide a different release profile from the tracer chamber and / or well fluid than a liquid tracer or a solid rod tracer. Also a different ratio of an amount tracer injected into the formation to the amount of tracer remaining in the tracer chamber may be achieved with a fragmented solid tracer compared to a liquid tracer or a solid rod tracer. In the example described in Figures 8A to 9A that one tracer type is located in the tracer chamber. It will be appreciated that two or more tracers may be located in each tracer chamber or release apparatus. The two or more tracers may have different physical forms. At least two tracers may have different physical forms in the tracer chamber. The two or more tracers may have different physical forms from one another. The two or more tracers may be selected from the group comprising solid, liquid, gas, gel and / or a dispersion. Each of the two or more tracers may have a different phase. Each of the two or more tracers may have a different state of matter. Figures 10A to 10D show different tracer arrangements in a production liner section shown generally at 414 with an incorporated tracer chamber 416a. Figure 10A shows a tracer chamber 416 comprising a combination of distinct solid tracer rod 422a and distinct fragmented solid tracer 422b. Figure 10B shows a tracer chamber 416b comprising a combination of distinct liquid tracer 422c and distinct fragmented solid tracer 422b. Figure 10C shows a tracer chamber 416c comprising a combination of a distinct solid tracer rod 422a and a distinct liquid tracer 422c. Figure 10D shows a tracer chamber 416d comprising a combination of distinct solid tracer rod 422a, distinct liquid tracer 422c and distinct fragmented solid tracer 422b. It will be appreciated that in other examples the solid, fragmented solid and / or liquid tracer may be contained or encapsulated in other forms of carrier such as dissolvable or degradable carriers which may be fluid specific. The fluid specific carrier may be designed to release the tracer when in contact with a specific well fluid. It will be appreciated that in the above examples the number of distinct solid tracer rods, size of distinct solid tracer rods, shape of distinct solid tracer rods, carrier type, carrier material and / or release mechanism in the tracer chamber may be varied. It will be appreciated that in the above examples the number of fragmented solid tracer, size of fragmented solid tracer, shape of fragmented solid tracer, carrier type, carrier material and / or release mechanism in the tracer chamber may be varied. It will be appreciated that in the above examples the number of liquid tracer containers, size or volume of liquid tracer containers, shape of liquid tracer containers, carrier type, carrier material and / or release mechanism in the tracer chamber may be varied. By providing a combination of tracer types such as solid tracer rods, liquid tracer and / or fragmented solid tracer in a tracer chamber it may be possible to provide tracers with different delivery mechanisms or release rates from the tracer chamber and / or from a carrier. It may be possible to control the amount or type of tracer deposited in the formation and / or retained in the tracer chamber. During a perforation it may be possible to distinguish between tracer signals which originate from tracer located in the perforations / formation from tracer signals which originate from tracer located in the well or remaining in the tracer chamber. Each of the above production liner sections shown in Figures 10A to 10D may be installed in a well as part of a liner and perforated in a manner similar to the methods described in relation to Figures 2A to 2C, 8A to 8C and 9A to 9C. A benefit of an embodiment of the invention is that a combination of two or more tracers with different physical forms may be provided in a tracer chamber which offer a wide range of different tracer release profiles to be selected. In some embodiments this may also enable one tracer type to be rapidly injected or released ensuring a known amount of tracer to be injected or released from a tracer chamber into a well, fracture or perforation within a known time frame and a second tracer to be partially injected or released from the tracer chamber and provided a slow gradually release from the chamber, well, fracture or perforation over time. By analysing the different tracer response information may be provided on characteristics of the well, fracture or perforation. A further benefit of an embodiment of the invention is that the use of different tracers with different release profiles may offer a combination of short-term diagnostics which may provide immediate data on well characteristics as well as longer term monitoring over time. This may provide an operator with information to distinguish between early production performance and longer-term inflow trends. A benefit of an embodiment of the invention is that by depositing tracer into perforations in the formation using the perforation method described above and producing flow a tracer response in samples collected downstream of the influx / perforation location may allow estimation of influx rate at the influx / perforation location. A benefit of an embodiment of the invention is that by depositing tracer into perforations in the formation using the perforation method described above and producing under steady state conditions a tracer response in samples collected downstream of the influx location may be dependent on the influx rate at the influx location. By positioning multiple tracer chambers at different locations in the well and perforating each tracer chamber to create an influx location the influx contribution of each influx location may be determined. This avoids the requirement to induce transients in the production flow which may affect or even stop production. A further benefit of an embodiment of the invention is the method may also mitigate or reduce the requirement to take multiple samples and monitor tracer concentrations in samples over an extended period of time. In steady production flow examples of the invention, tracer concentrations in individual samples collected using this method may reliably inform the influx contribution of influx locations to the well. While the disclosure is not bound by any particular theory or mechanism of action the tracer deposited in the formation via the perforation holes may be carried with the influx flow and the tracer concentration detected at surface may be dependent on the influx flow rate at the perforation location. By distributing tracer mass in the space in the formation a dependency on rate may be created as a larger influx rate may carry more tracer located in that spatially distributed formation space into the production flow. The invention may provide a method and system of estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well. The method comprises installing a liner with at least one tracer chamber wherein each tracer chamber is installed at a known level of the well and wherein each tracer chamber comprises at least one distinct tracer material. The method comprises perforating a liner section, the at least one chamber and surrounding formation to create at least one influx locations and deposit tracer material and / or tracer molecules from each tracer chamber into the formation at the at least one influx location. The method comprises inducing production flow from the reservoir into the well and collecting samples downstream of the at least one influx location at known sampling times. The method comprises analysing samples for concentration and type of tracer material. Based on the analysed concentrations the contribution of flow from the at least one influx location may be calculated. Throughout the specification, unless the context demands otherwise, the terms 'comprise' or 'include', or variations such as 'comprises' or 'comprising', 'includes' or 'including' will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers. Furthermore, relative terms such as “up”, “down”, “top”, “bottom”, “upper”, “lower”, “upward”, “downward”, “horizontal”, “vertical”, “and the like are used herein to indicate directions and locations as they apply to the appended drawings and will not be construed as limiting the invention and features thereof to particular arrangements or orientations. The foregoing description of the invention has been presented for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention as defined by the appended claims.

Claims

1. A method of estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well;wherein the method comprises installing a liner with at least one tracer chamber in a well;wherein the at least one tracer chamber comprises at least one distinct tracer;perforating a section of the liner, the at least one tracer chamber and a surrounding formation to create an influx location and deposit tracer from the at least one tracer chamber into the formation;inducing a production flow from the reservoir into the well;collecting at least one sample downstream of the at least one influx location;analysing the at least one sample for tracer concentration;and based on the analysed concentration characterising flow from the at least one influx location.

2. The method according to claim 1 comprising perforating the liner, at least one tracer chamber and surrounding formation to deposit at least one tracer from the tracer chamber into the perforation holes in the formation.

3. The method according to claim 1 or claim 2 comprising inducing a production flow from the reservoir into the well to carry tracer through the perforations at the influx locations into the well during production.

4. The method according to any preceding claim comprising inducing a production flow from the reservoir into the well to carry tracer remaining in the at least one tracer chamber after the perforation into the well.

5. The method according to any preceding claim wherein the at least one tracer chamber comprises at least one port or aperture before perforation.

6. The method according to any preceding claim wherein the at least one tracer chamber is arranged, fixed and / or immobilised to an outer surface and / or an inner surface of the at least one production liner section.

7. The method according to any preceding claim comprising inducing a change in theproduction rate of the entire production flow or for the at least one influx location.

8. The method according to any preceding claim wherein the liner comprises two or more tracer chambers and the method comprising perforating the liner, tracer chambers and surrounding formation at two or more locations in the well to create two or more influx locations.

9. The method according to claim 8 comprising depositing at least one distinct tracer into the formation through each of the perforations at the two or more influx locations.

10. The method according to any preceding claim comprising depositing at least one distinct tracer from a first tracer chamber into at least one perforation at a first influx location and depositing at least one distinct tracer from a second tracer chamber into at least one perforation at a second influx location.

11. The method according to any preceding claim comprising depositing at least one tracer into at least one perforation at each zone or influx location sequentially or simultaneously.

12. The method according to any preceding claim comprising pumping a fluid downhole to push tracer and / or tracer molecules remaining in the at least tracer chamber into the at least one perforations into the formation.

13. The method according to any preceding claim comprising inducing a steady state production flow from the reservoir into the well and collecting at least one sample before, during and / or after a steady state production flow rate.

14. The method according to any preceding claim comprising inducing multiple steady state flow conditions in the production rate of the entire production flow or for the at least one influx location and collecting samples.

15. The method according to any preceding wherein the at least one tracer chamber comprises two or more distinct tracers.

16. The method according to any preceding wherein the at least one distinct tracer is solid, liquid or gas.

17. The method according to any preceding wherein the at least one tracer chamber comprises two or more distinct tracers wherein at least one distinct tracer is a liquid tracer.

18. The method according to any preceding comprising calibrating an influx profile estimation by comparing measured tracer data with calibration data obtained from a calibration method selected from the group comprising production logs, micro seismic methods, flow metering devices, temperature-based flow quantification and / or flow-quantification data obtained from quantification of tracer signals during a transient period.

19. A system for estimating an influx profile for at least one well fluid from a reservoir to a producing hydrocarbon well the system comprising:at least one production liner section comprising at least one tracer chamber; wherein the at least one production liner section is configured to be installed at a known level of the well;wherein the tracer chamber and the production liner section is configured to be perforated by a perforation tool to create an influx location and deposit at least one tracer from the tracer chamber into perforation holes in the formation.

20. The system according to claim 19 wherein the at least one tracer chamber is integrated with a section of the production liner, mounted on, in or to a section of the production liner.

21. The system according to any of claims 19 or 20 wherein the at least one tracer chamber is located on an inner or outer surface of the production liner.

22. The system according to any of claims 19 to 21 comprising a sampling device for collecting samples downstream of the influx location at known sampling times.

23. The system according to any of claims 19 to 22 wherein the at least one tracer is solid, liquid and / or gas.

24. The system according to any of claims 19 to 23 wherein the at least one tracer chamber comprises at least one port or aperture.

25. The system according to any of claims 19 to 24 wherein the at least one tracer is surrounded by a fluid or mass to fill any void or space in the at least one tracer chamber not occupied with tracer.

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