New Modified Black-Oil Correlations for Gas Condensate and Volatile Oil Fluids

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSeveral authors have shown the applicability of modified black oil (MBO) approach for modeling gas condensate and volatile oil reservoirs. It was shown before that MBO could adequately replace compositional simulation in many applications. In this work, a new set of MBO PVT correlations was developed. The four PVT functions (oil-gas ratio, R v , solution gas-oil ratio, R s , oil formation volume factor, B o , and gas formation volume factor, B g ) were investigated. According to our knowledge, no other correlation for calculating oil-gas ratio exists in the petroleum literature. Alternatively, oil-gas ratio (needed for material balance and reservoir simulation calculations of gas condensate and volatile oil reservoirs) had to be generated from a combination of laboratory experiments and elaborate calculation procedures using EOS models. In previous work, we found that Whitson and Torp method for generating Modified Black Oil (MBO) PVT properties yielded best results when compared with compositional simulation. This method (and the others available in the literature such as Coats' and Walsh's) requires the use of data from PVT laboratory experiments and proper construction of EOS models. We used Whitson and Torp's method to generate our database of the MBO PVT curves used in developing our correlations after matching the PVT experimental results with an EOS model. For each one of the four PVT parameters, we used 1850 values obtained from PVT analysis of eight gas condensate fluid samples and 1180 values obtained from PVT analysis of five volatile oil fluid samples. The samples were selected to cover a wide range of fluid composition, condensate yield, reservoir temperature, and pressure. The data points were generated by extracting the PVT properties of each sample at six different separator conditions. We then used multi-variable regression techniques to calculate our correlation constants.The new correlations were validated using the generalized material balance equation calculations with data generated from a compositional reservoir simulator. These new correlations depend only on readily available parameters in the field and can have wide applications when representative fluid samples are not available.

Modified Black Oil PVT Properties Correlations for Volatile Oil and Gas Condensate Reservoirs

“…They also take into consideration the effect of surface separator conditions. Also, all parameters used in the correlations are readily available especially for the surface gas gravity term that was a point of confusion in previous MBO correlations 9,17 .…”

The effects of the volatile oil-gas ratio on reserve estimation (GMBE versus CMBE) in undersaturated volumetric reservoirs

“…The correlation proposed by El-Banbi et al (2006), was used to determine the volatile oil-gas ratio Rv for gas condensate and volatile reservoir. The results obtained from both fluids were 58108.09 MMstb/scf for gas condensate reservoir and 91.58283 MMstb/scf for volatile oil reservoir.…”

Fuzzy modeling of volume reduction of oil due to dissolved gas runoff and pressure release

“…Furthermore, sampling should be done at early stage of reservoir production which imposes some limitation on providing reliable samples (Dake 1998). Owing to these limitations, researchers have tried to establish empirical correlations for estimating oil FVF from available measured oil properties, including gas specific gravity, temperature, stock-tank oil gravity, and solution gas oil ratio (Katz 1942;Knopp and Ramsey 1960;Vazquez and Beggs 1980;Glaso 1980;Al-Marhoun 1988;Dokla and Osman 1992;Farshad et al 1996;Petrosky and Farshad 1993;Omar and Todd 1993;Almehaideb 1997;Al-Shammasi 1999;Dindoruk and Christman 2001;El-Banbi et al 2006;Hemmati and Kharrat 2007;Elmabrouk et al 2010). These empirical correlations do not have flexible structure and consequently do not serve satisfying generalization.…”