Estimating contamination during focused sampling

A method comprising:

• obtaining in-situ, real-time data associated with fluid obtained by a downhole sampling tool disposed in a borehole that extends into a subterranean formation, wherein the obtained fluid comprises native formation fluid and filtrate contamination resulting from formation of the borehole, wherein the downhole sampling tool is in electrical communication with surface equipment disposed at a wellsite surface from which the borehole extends, and wherein the obtained data includes a plurality of values of a fluid property of the obtained fluid relative to:
• a pumpout volume of the fluid pumped from the subterranean formation by the downhole sampling tool;
• or
• a pumpout time during which the fluid is pumped from the subterranean formation by the downhole sampling tool;
• and
• via operation of at least one of the downhole sampling tool and the surface equipment:
• generating a population of values for Ĉ, wherein each value of Ĉ is an estimated value of the fluid property for the native formation fluid;
• determining which one of the values for Ĉ has an integral error of nonlinearity (IEN) in logarithmic space that is lower than the IENs for each of the other ones of the values for Ĉ;
• characterizing the native formation fluid based on which one of the values for Ĉ near Ĉ has an IEN in logarithmic space that is lower than the IENs for the other ones of the values for Ĉ;
• and
• controlling one or more operational elements of the downhole sampling tool based on the characterization of the native formation fluid.

A method comprising:

• obtaining in-situ, real-time data associated with fluid obtained by a downhole sampling tool disposed in a borehole that extends into a subterranean formation, wherein the downhole sampling tool is in electrical communication with surface equipment disposed at a wellsite surface from which the borehole extends, and wherein the obtained data includes a plurality of values of a fluid property of the obtained fluid;
• and
• via operation of at least one of the downhole sampling tool and the surface equipment, filtering the obtained data utilizing a robust moving percentile (RMP) filter by:
• obtaining parameters for a data window to be moved through a plurality of window locations individually utilized to collectively filter the obtained data, wherein the parameters include a window size and a window target percentile range between upper and lower percentiles;
• and
• at each of the plurality of window locations:
• determining which of the obtained data values correspond to the upper and lower percentiles of the obtained data within the window at a current window location;
• replacing the obtained data within the window at the current window location with random data having values ranging between the obtained data values determined to correspond to the upper and lower percentiles;
• smoothing the random data;
• determining a filtered data point for the current window location based on the smoothed random data;
• characterizing the obtained fluid based on the filtered data point;
• and
• controlling one or more operational elements of the downhole sampling tool based on the characterization of the obtained fluid.