1.  Field of the Invention
This invention relates in general to predicting the output of a multiparameter system; and, more particularly, to a system and method for predicting properties of a formation fluid. 
2.  Description of the Prior Art
In drilling wells for the production of hydrocarbons from underground formations, drilling mud is typically cycled through a wellbore as it is being drilled.  In addition to driving a drill motor and cleaning a drilling bit, the drilling mud also provides a column of fluid that exerts pressure on the formation pierced by the wellbore, which prevents or reduces fluid from a reservoir or formation from entering the wellbore.  In addition, drilling mud may infiltrate the formation in the region surrounding the wellbore (the near wellbore region). 
It is often useful in drilling oil wells to test the hydrocarbons present in formations along a wellbore.  This is frequently accomplished through the use of a formation tester, which draws fluid from the formation and stores it for later testing or performs tests in the wellbore. 
An example formation tester is a pumpout wireline formation tester (PWFT).  A PWFT collects formation samples by extending a probe from a wireline tool until the probe presses against the side of the wellbore.  Fluids are then pumped out of the formation and into the PWFT for storage or testing.  Typically, as described above, the near wellbore region contains drilling mud mixed with fluids from the formation. 
Before collecting a sample or running a test, a formation tester may pump the fluid in the formation to purge the mud filtrate contaminates that may have invaded the near wellbore region.  Fluid sensors may monitor fluid properties during pumping.  Commonly used sensors may measure resistivity, capacitance, optical absorption and magnetic resonance (hydrogen index).  These measured properties may be used to evaluate sample fluid properties such as the amount of contamination of a fluid sample. 
Ideally, a sample with an acceptable level of drilling mud contamination is acquired before measuring some of the properties of the formation.  The operator of the formation tester may choose an acceptable level before initiating the test or collection.  Meeting the acceptable mud contamination level may require pumping the formation fluid for a period of time, which could vary from minutes to days.  The pumping duration is a complex function of numerous properties, including properties of the formation, the formation fluid, the drilling mud, and the pump. 
In general, in one aspect, this invention features a method for predicting a property of a fluid being pumped from a formation through a well.  The well may have one or more associated input properties.  The method may include providing one or more input properties to an artificial neural network (ANN).  The ANN may be used to produce a plurality of data points, for which each data point corresponds to a predicted time sample of the property of the fluid sample. 
Implementation of this invention may include one or more of the following.  The plurality of data points may be analyzed to calculate a time duration for pumping of the fluid to achieve a sample quality.  The ANN may be used to predict a sample quality as a function of time.  The ANN may predict a time duration for pumping the fluid to achieve a sample quality.  The ANN may predict pumping differential pressure as a function of time.  The ANN may include a multilayer perceptron (MLP).  The MLP may include at least one hidden layer.  The MLP may be a fully connected MLP.  The MLP may be trained with a training data set. 
The method uses as inputs, one or more input conditions.  The input conditions may include one or more formation properties, one or more wellbore properties, or one or more pumpout properties.  Example formation properties may include permeability, porosity, permeability anisotropy, and viscosity.  Example wellbore properties may include oil-based mud type, water-based mud type, overbalance, filtrate viscosity, mudcake permeability, invasion time, and invasion depth.  Example pumpout properties may include maximum pumping rate, pumping rate, pump pressure differential, number of probes.  An ANN may be selected based in part on a formation property, a wellbore property, or a pumpout property. 
In general, in still another aspect, this invention features a method for predicting a property of a fluid being pumped from a formation through a well.  The well may have one or more input properties associated therewith.  The method includes acquiring a first plurality of data points by measuring a property of the fluid sample at a series of time points, and providing one or more of the input properties to an ANN.  The method also includes predicting, using the ANN, a second plurality of data points corresponding to a predicted property of a fluid sample, the second plurality of data points corresponding to the property predicted at series of time points.  The first and second pluralities of data points are time synchronized, compared.  The inputs to the ANN may be modified if necessary until the comparison meets a threshold. 
In general, in another aspect, this invention features a system for predicting a property of a fluid suitable for formation testing from a formation through a well.  The well may have one or more associated input properties.  The system may include a formation tester, and a computer operably connected to the formation tester.  The computer may include a module, which is configured to provide one or more input properties to an ANN; and receive from the ANN a plurality of data points, each data point corresponding to a predicted time sample of the property of the fluid sample.  The system may be used with one or more packers.  The one or more packers may be used to isolate an interval of a well for formation fluid collection. 
In general, in another aspect, this invention features a system for extracting a fluid suitable for formation testing from a formation through a well.  The well may have one or more associated input properties.  The system may include a formation tester and a computer operably connected to the formation tester.  The formation tester may include a chamber configured to collect the fluid.  The computer may include a module, which is configured to provide one or more input properties to an ANN, predict a time duration using the ANN for pumping the fluid to achieve a sample quality; and send a signal to the formation tester, the signal including a pumping duration, the pumping duration causes the chamber to collect the fluid sample. 
In general, in another aspect, this invention features a system for extracting a fluid suitable for formation testing from a formation through a well.  The well may have one or more associated input properties.  The system may include a formation tester and a computer operably connected to the formation tester.  The formation tester may include a chamber configured to collect the fluid and a measuring section configured to measure one or more properties of the fluid.  The computer may include a module, which is configured to acquire a first plurality of data points from one or more properties of the fluid sample measuring by the measuring section at a series of time points, provide one or more of the input properties to an ANN, predict, using the ANN, a second plurality of data points corresponding to a predicted property of a fluid sample, the second plurality of data points corresponding to the property predicted at series of time points, substantially time synchronize the first and second pluralities of data points, compare first and second plurality of data points that are synchronized, modify one or more of the input properties if tile comparison between the second plurality of data points and the first plurality of data points does not meet a condition; and send a signal to the formation tester causing the fluid sample to be collected by the chamber. 
Other features and advantages will become apparent from the description and claims that follow.