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Bubble point pressure (pb) determination from T1 over T2app ratio

IP.com Disclosure Number: IPCOM000181380D
Publication Date: 2009-Mar-31

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The bubble point pressure is defined as the pressure at which the first gas bubble appears while decreasing the pressure on the fluid sample. To determine when the first gas bubble appears is a very challenge experimental task. I propose here a way how to estimate the bubble point from NMR measurements: The loss of gas in solution appears together with an increase of viscosity. It is possible to extract from the plot R vs. pressure the bubble point pressure by looking at the crossover point between the asymptotic lines of the R-p curve below and above the bubble pressure. This method is analogue to the determination of the bubble point pressure from the J-function vs. pressure plot. The R-p method can be used in the lab or in downhole services for on lived oil, or lived oil saturated core samples; it can be used in the field as well by means of correlations (R as function of p) or direct measurement of R under variation of the reservoir pressure.