Crude oil compatibility testing with completion brine is necessary to prevent the formation of crude oil-brine emulsions that cause formation damage and limit hydrocarbon production. Furthermore, required remedial action is costly. Conventional testing for the formation of oil-brine emulsions requires large volumes of oil, typically 50 to 75 mL oil for each test. Completion brine projects can require more than forty tests to identify adequately all fluid compatibility issues, which translates to about three liters of crude oil. However, high profile projects often deliver only limited quantities of crude oil, sometimes only 500 milliliters or less are available for emulsion testing.
To accommodate the growing demand for oil volume, researchers developed a new high-shear method and apparatus that uses a total per test volume of 10 milliliters, including crude oil and brine, fracturing gels, fluid loss control gels, broken gels, filtrates or stimulation fluids, and combinations thereof. With this methodology, a series of 40 crude oil compatibility tests requires only 200 mL of crude oil. The apparatus is constructed from common laboratory equipment and readily available devices. Markedly, the equipment delivers consistent high-shear mixing, clear visualization of fluid interfaces, capacity to stack three or more test fluids in a single test, and the ability to heat age samples to about 82°C (180°F).
Testing demonstrated that the new high-shear method and device produce reliable results using small volumes of crude oil and compare positively with conventional test methods. Since this method is applicable to all fluid-fluid testing, a proposal will be presented for inclusion into ISO-13503-3 (API RP-13J), Testing of heavy brines.