Patent ID: 9068438
Filing Date: 2015-06-30
Classification: E21B

Abstract:
1. A formation testing tool for extracting formation fluid from an earth formation penetrated by a borehole having a drilling fluid, the tool comprising: a sample flow element configured to extract formation fluid from the formation in a sample zone; a sample zone seal forming a perimeter defining the sample zone; a contamination removal flow element configured to extract formation fluid contaminated with the drilling fluid from a contamination removal zone in the formation; a contamination removal zone seal forming a perimeter defining the contamination removal zone, which surrounds and excludes the sample zone; one or more sensors configured to measure a property of the formation fluid extracted by the sample flow element and/or the contamination flow element; a sample flow control device configured to control flow of extracted formation fluid from the sample flow element; a contamination removal flow control device configured to control flow of extracted formation fluid contaminated with the drilling fluid from the contamination removal flow element; and a controller comprising an input and an output and being configured to: (i) receive input from the one or more sensors; (ii) receive as input a first amount of contamination in the formation fluid extracted by the sample flow element; (iii) receive as input a constraint related to extracting the formation fluid using at least one of the sample flow element and the contamination removal flow element and to control at least one of the sample flow rate and the contamination removal flow rate to be within the constraint; (iv) calculate a first derivative of the first amount of contamination over time; and (v) provide a control output to control a sample flow rate in the sample flow element by modulating or adjusting the sample flow control device and a contamination removal flow rate in the contamination flow removal element by modulating or adjusting the contamination removal flow control device according to a calculation of a change in an amount of contamination in extracted formation fluid over an interval of time in order to decrease an amount of time required to acquire a sample of the formation fluid having an acceptable amount of contamination; wherein the controller is further configured to control the sample flow rate and the contamination flow rate to maximize the first derivative of the first amount of contamination over time as a negative value within the constraint.