Schlumberger Technology Corporation

James J Dunlap

Oliver Clinton Mullins

Edward Harrigan

Ricardo Vasques

Chengli Dong

Go Fujisawa

Soraya Sofia Betancourt

Andrew Carnegie

Nicolas Adur

Alejandro Duran

Matheus Nogueira

A method and apparatus for sampling formation fluid includes drawing formation fluid from the subterranean formation into the downhole tool and collecting the formation fluid in a sample chamber. An exit flow line is operatively connected to the sample chamber for selectively removing a contaminated and/or clean portion of the formation fluid from the sample chamber whereby contamination is removed from the sample chamber. For example, a clean portion of the formation fluid may be passed to another sample chamber for collection, or a contaminated portion may be dumped into the borehole.

Downhole sampling apparatus and method for using same

The invention provides a method for determining phase transition pressure of downhole retrograde condensate. An OBM-contamination value is produced from a time-series of fluorescence values produced by measuring fluorescence emitted from a single-phase flow of OBM-contaminated formation fluid in a downhole cell during a cycle of time. The pressure of fluid in the cell is set at a transition boundary by incrementing drawdown pressure and monitoring the presence or absence of a phase transition. An apparent phase transition pressure value associated with the cycle of time is produced by setting apparent phase transition pressure value equal to cell pressure. This process is repeated for several cycles of time to produce a number of pairs of OBM-contamination value and apparent phase transition pressure value as OBM-contamination decreases over time. The value of phase transition pressure is determined by extrapolating from a representation of apparent phase transition pressure values versus OBM-contamination values.

Determining phase transition pressure of downhole retrograde condensate

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Sugar Land, TX, United States of America

James J Dunlap