Tracer Flowback Analysis for Estimating Multi-Zone Well Inflow
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Solution Overview
Problem
Existing tracer systems in oil and gas wells have short active release periods and are based on erosion or dissolution, making it difficult to predict longevity and requiring different interpretation methods, while constant tracer release rates over time are needed for accurate reservoir monitoring.
Innovation Solution
Implementing tracer carriers that release tracer material at a near-constant rate over time, allowing for the analysis of tracer transients during changes in well production rate to estimate downhole inflow profiles by sampling and analyzing tracer concentrations at the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If erosion or dissolution-based tracer release is used, then tracer release can be achieved, but the active release period is short and longevity cannot be predicted
Solution Approach 1:
The patent changes the release mechanism from erosion/dissolution (time-dependent degradation) to diffusion-controlled release (constant concentration gradient). This parameter change transforms the release profile from short-term to long-term constant release, resolving the contradiction between release duration and predictability.
Solution Approach 2:
The patent replaces mechanical/chemical degradation mechanisms (erosion, dissolution) with a physical diffusion process. The tracer carrier uses diffusion through a matrix or coating, which provides a more predictable and sustained release mechanism compared to mechanical wear or chemical dissolution.
2Measurement precision
If constant tracer release rate is implemented, then accurate reservoir monitoring is enabled, but the system complexity increases
Solution Approach 1:
The patent employs porous materials (porous matrix or coating) as the tracer carrier. The porous structure provides a large surface area for diffusion while maintaining a simple overall device geometry. This resolves the contradiction by achieving constant release through material properties rather than complex mechanical systems.
Solution Approach 2:
The tracer carrier system is designed to be self-regulating through diffusion processes. The constant concentration gradient maintained by the porous structure automatically provides constant release rates without requiring external control mechanisms, reducing system complexity while ensuring measurement precision.
3Measurement precision
If tracer carriers with long constant release period are used, then downhole inflow profile estimation is improved, but the quantity of tracer material required increases
Solution Approach 1:
The porous matrix or coating provides high surface area to volume ratio, enabling efficient diffusion of tracer material over extended periods. This allows using smaller quantities of tracer material while maintaining long constant release capability, resolving the contradiction between release duration and material quantity.
Solution Approach 2:
The diffusion process provides continuous periodic release of tracer material over the entire production life of the well. This sustained periodic action ensures that tracer is continuously available for measurement without requiring large initial quantities, as the release is distributed over time rather than concentrated.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate estimation of downhole inflow profiles by utilizing tracer transients, providing a reliable method for reservoir monitoring and improving the understanding of fluid influx zones.
Implementation Method 1
tracers creating small volumes of equally high tracer concentration in the local fluid... utilising the release of the tracer from a polymer arranged in the actual influx zone... tracer carriers with a generally even leak-out rate such as by diffusion to the well fluid under wetting
Implementation Method 2
Tracer transients formed by shut-in or otherwise changes in the flow will propagate to the surface as concentration slugs or shots. The tracer transients are driven by the velocity field in the well.
Data Source
Figure 1
Figure 2~3
Figure 4~5b
AI summary
A method of estimating influx profile for at least one well fluid to a producing petroleum well with two or more influx zones or influx locations to a production flow. The method comprising providing measured concentrations and type of tracer material data from samples collected from the production flow at a location downstream of the tracer sources at known sampling times after inducing a transient in the production rate of the production flow thereby changing the local exposure times of the tracer sources to the fluid to create a tracer transient. Based on said concentrations and sampling sequence, calculating said influx volumes (qi).