Method and device for determining asphaltene precipitation onset pressure

摘要

A process is provided for determining asphaltene precipitation onset pressure in formation fluid. In one embodiment the process includes the steps of: (a) isolating a downhole sample of formation fluid; (b) illuminating the sample with UV light; (c) measuring fluorescence energy emanating from the sample; (d) reducing pressure on the sample; (e) repeating steps (b) to (d); and (f) setting asphaltene precipitation onset pressure equal to pressure on the sample when an abrupt change in fluorescence energy is detected. A downhole optical analyzer includes a UV lamp; a piston adapted to decrease pressure of the fluid in an optical cell region by increasing the volume of an isolated sample of formation fluid; and a pressure sensor for sensing pressure of the isolated sample.