Method and apparatus for real time oil based mud contamination monitoring

A computer readable medium having a computer program product stored thereon for determining oil based mud contamination of a hydrocarbon fluid obtained from a wellbore during formation testing that when executed on a computer comprises:

• receiving a reservoir model for simulating the contamination;
• receiving an empirical equation for computing the contamination;
• for a first pumping time, separately generating a simulated contamination based on the reservoir model and an empirically computed contamination based on the empirical equation;
• comparing the simulated contamination and the empirically computed contamination;
• selecting one of the reservoir model and the empirical equation as more reliable and another one as less reliable for the first pumping time;
• and
• revising the less reliable one of the reservoir model and the empirical equation based on a result of the comparing.

An apparatus comprising:

• a) a system for implementing a reservoir model for simulating the contamination;
• b) a system for implementing an empirical equation for computing the contamination, for a first pumping time, separately generating a simulated contamination based on the reservoir model and an empirically computed contamination based on the empirical equation;
• c) a system for comparing the simulated contamination and the empirically computed contamination;
• d) a system for selecting one of the reservoir model and the empirical equation as more reliable and another one as less reliable for the first pumping time;
• e) a system for revising the less reliable one of the reservoir model and the empirical equation based on a result of the comparing until the simulated contamination and the empirically computed contaimination are within a preset limit;
• and
• f) a system determining whether the simulated contamination and the empirically computed contaimination are sufficiently small such that the hydrocarbon fluid qualifies as a representative fluid sample for the formation testing, and if not implementing the system for selecting for a second pumping time.