Abstract

Objective of this study is to introduce a novel derivative screening technique using a field sandpack based on modified Seright's filterability apparatus to deliver fast and effective results. For polymer manufacturers, it is often important to understand injectivity of several polymers for a particular EOR application. Space, time and labor constraints can make polymer screening by core flood testing quite cumbersome and expensive. This technique could be of help in such situations. For oil operator companies, it could be useful to screen and reduce the number of polymers to evaluate through third party tests. This technique also could be used at a field location to understand if there is blocking potential of polymer solution for different batches and estimate the resistance factor (RF). This new technique, sandpack filterability, could act as effective tool to screen various polymers for a particular EOR application using field sand instead of core flood techniques currently utilized.

Sandpacks can be prepared from field or generic sand. A chromatography column is used to prepare a sandpack, which is connected to a pressure tank. Different polymers are chosen for a particular field application. Polymer solution corresponding to throughput of 1000 cm3/cm2 of polymer is passed through the sandpack and sandpack resistance is calculated over throughput at a constant pressure of 20 psi. Polymers showing increase in sandpack resistance with increase in throughput could potentially block the formation.

For RF measurements- flow rates of brine and polymer solutions through sandpacks are measured at different pressures. Using Darcy's law, RF is the ratio of flow rate of brine to that of polymer at constant pressure. RF against shear rate (or flux) is plotted. This technique effectively measures RF that is in close agreement with the core flooding data. Case study of 5 Kemira polymers is shown for a particular field.

Although 5 polymers pass traditional tests with a filter ratio of less than 1.2 through 1.2 microns polycarbonate filter, sand pack filterability results differ. Based on mineralogy of field sand and pore throat size distribution, the flow of polymer through the porous media can change. Flow through the sandpack should demonstrate more realistic behavior of the polymer in the field. This technique narrowed down the polymer selections to 2 polymers based on filterability and sand pack filterability results.

Those 2 polymer were screened for RFs in sand packs and core floods at different shear rates for correlation. Differences and similarities between these two techniques (novel sand pack filterability and core flooding) are compared in this study to understand strengths and weaknesses of the novel test. This novel testing could help in many scenarios to understand injectivity of the polymer and help measuring RFs with minimal equipment, time and cost.

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