EOR Solutions
Identifying Injector to Producer Connectivity
Injector to producer connectivity is identified through the use of chemical tracers.
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APPLICATION
Chemical tracers can be pumped into waterflood injection wells while production wells are monitored for chemical breakthrough. By measuring tracer concentration in offset producing wells as a function of time, the following interpretations can be made:
Poor Sweep Efficiency: Breakthrough time that is significantly lower than predicted matrix flow rates would suggest that fractures or high permeability anomalies communicate between the injection wells and producing wells. This rapid channeling leads to poor sweep efficiency and low oil recoveries.
DESCRIPTION
The tracer is made of a stable salt that is not naturally present in oilfield waters. Before injection, baseline water samples are collected at the injector and the offset producers. The tracer is injected in a low volume high concentration slug. The salt propagates through the reservoir and adsorption is minimal. Samples are collected at the offset producers daily and sent to the laboratory for evaluation. Sampling period and frequency are dependent on anticipated breakthrough time.
| Advantages |
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Low cost chemical with no radioactive properties |
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Can be used in almost any type of mix water |
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Pumped with standard oilfield equipment |
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Minimal interruption in waterflood operation |
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Laboratory evaluation included in technology package |
| Critical Design Factors |
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Patterns with known injector-producer connectivity are excellent candidates |
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Minimum efficient injection rate must be sustained |
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Breakthrough times of manageable length must be anticipated – breakthrough times of more than two months are inconclusive |
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| Chemical Tracers |
| The ability to quantify transit times between injectors and producers is an important step in implementing any type of EOR process.
The use of chemical tracers in a waterflood will help to quantify both transit times and an apparent breakthrough or channel volume. This data assists in characterizing the reservoir heterogeneity and ultimately the need for conformance.
TIORCO has the ability to run up to a three well tracer survey which includes the delivery of the product and all associated lab testing. Tracer surveys are normally done at cost as they are intended to be a preliminary reservoir screening tool and will be used to design any of our chemical EOR processes. |
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| Tracer Application |
| TIORCO’s goal in the Vizcacheras field in Western Argentina’s Cuyo Basin was to improve volumetric sweep efficiency in the subject pattern and reduce water injection and water production rates in the producers. A pilot was begun in 2002 with laboratory studies, initial polymer gel treatment design, tracer studies and numerical simulation. Tracer analysis confirmed water channeling between injector and producer wells.
Based on preliminary analysis in November of 2004, the pilot treatment resulted in incremental oil reserves of 130,800 barrels at a development cost of $2.30 U.S. per barrel. As a result of the pilot project, TIORCO performed three more injection well treatments in the Vizcacheras field in December 2004 in a first-step expansion project that is still underway today.
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