Evaluation of Geochemical Approaches to Heavy Oil Viscosity Mapping in San Joaquin Valley, California

Abstract

Areal and vertical distributions of petroleum viscosities within heavy oil reservoirs are important in designing well completions, optimizing field development and planning thermal and other recovery operations. Viscosities of oils in closely-spaced reservoir zones in heavy oil fields can vary substantially. Unfortunately, oil samples are often unavailable or too small for conventional laboratory viscosity measurements. In such cases, correlations between heavy oil viscosity and geochemical, chemical and physical parameters can be valuable for estimating working viscosities. Various geochemical-viscosity correlations were evaluated using a suite of heavy crude oils (API gravities < 150) from fields in the San Joaquin Valley, California. Whole, dewatered, crude oils where studied. Kinematic viscosities were measured at multiple temperatures. Elemental, organic acid, pour point and gravity analyses were completed, followed by compound class separations and gas chromatographic analyses. Statistical methods were used to assess correlations of various parameters with viscosity. Results were compared with correlations reported in the literature and evaluated in terms of linkage to models of field-wide degradation processes believed to account for formation of the heavy oils, with the goal of assessing these predictive models for viscosity variations with applications to viscosity mapping.

Prediction of Heavy-Oil Viscosities With a Simple Correlation Approach

“…Therefore, care must be exercised when the correlation is used in the assessment of viscosity (in °API) and temperature ranges outside of those of the data used in calibrating the correlation. Table 2-Viscosity data used in developing the new correlation (Al-Maamari et al 2006;Henshaw et al 1998). Unlike complex mathematical approaches for estimating the viscosity of heavy oils, the proposed correlation is straightforward and would be greatly helpful for engineers, especially those dealing with petroleum engineering and heavy-oil production.…”

“…The data required to develop this correlation include the viscosity of heavy oil as a function of temperature and the corrected API (CAPI) (Henshaw et al 1998;Al-Maamari et al 2006). The following methodology (Bahadori and Vuthaluru 2009;Bahadori 2010Bahadori , 2011 has been applied to develop this correlation by use of Matlab® technical computing language (Matlab 2008):…”

“…Fig. 1 shows the proposed correlation curves in comparison with the literature data (Henshaw et al 1998;Al-Maamari et al 2006) that were used to calibrate the correlation. Note that the data that were used in developing and calibrating the correlation had gravities less than 15 °API [corrected API (CAPI) less than 6] and temperatures in the range of 40 to 177°C.…”