Data extraction for OBM contamination monitoring

A method comprising:

• obtaining in-situ, real-time data associated with a sample stream obtained by a downhole sampling apparatus disposed in a borehole that extends into a subterranean formation, wherein the downhole sampling apparatus is in electrical communication with surface equipment disposed at a wellsite surface from which the borehole extends, wherein the downhole sampling apparatus is operable to obtain apparent optical density (OD), apparent mass density (ρ), and apparent gas-oil ratio (GOR) of the sample stream such that the obtained data comprises OD data, ρ data, and GOR data, and wherein the sample stream comprises:
• native formation fluid from the subterranean formation;
• and
• filtrate contamination resulting from formation of the borehole in the subterranean formation;
• and
• via operation of a processor at at least one of the downhole sampling apparatus and the surface equipment:
• using the processor to statistically filter the obtained data to remove outliers from the OD data, the ρ data, and the GOR data;
• fitting the filtered OD, ρ, and GOR data to a corresponding one of a plurality of models each characterizing a corresponding one of OD, ρ, and GOR as a function of a pumpout volume (V) or time (t) of the sample stream, wherein fitting the filtered OD, ρ, and GOR data to the corresponding models includes determining an adjustable parameter y relating the filtered OD, ρ, and GOR data to V or t;
• and
• identifying a start of a developed flow regime of the native formation fluid within the subterranean formation surrounding the borehole by:
• generating a flow regime identification (FRID) plot by collectively plotting, relative to V or t:
• the fitted OD data;
• the fitted ρ data;
• the fitted GOR data;
• and
• one of V−y or t−y;
• and
• identifying from the FRID plot the minimum V or t at which the plotted OD, ρ, and GOR data each substantially coincide with the one of V−y or t−y, wherein the start of the developed flow regime is the identified minimum V or t;
• and
• operating the downhole sampling apparatus based on the identified start of the developed flow regime of the native formation fluid.

An apparatus comprising:

• a downhole sampling apparatus operable within a borehole extending from a wellsite surface into a subterranean formation;
• and
• surface equipment disposed at the wellsite surface and in communication with the downhole sampling apparatus, wherein the downhole sampling apparatus and the surface equipment are collectively operable to:
• obtain in-situ, real-time data associated with a sample stream obtained by the downhole sampling apparatus disposed within the borehole, wherein the obtained data includes a plurality of fluid properties of the sample stream, and wherein the sample stream comprises:
• native formation fluid from the subterranean formation;
• and
• filtrate contamination resulting from formation of the borehole in the subterranean formation;
• using a processor at at least one of the downhole sampling apparatus and the surface equipment, statistically filter the obtained data to remove outliers from the obtained data;
• fit the filtered data to each of a plurality of models each characterizing a corresponding one of the fluid properties as a function of a pumpout volume (V) or time (t) of the sample stream;
• identify, based on the fitted data, a start of a developed flow regime of the native formation fluid within the subterranean formation surrounding the borehole;
• and
• apply the identified start of the developed flow regime of the native formation fluid in an operation of the downhole sampling apparatus.