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API PUBL 4711-2001 pdf free download

API PUBL 4711-2001 pdf free download.Methods for Determining Inputs to Environmental Petroleum Hydrocarbon Mobility and Recovery Models.
4.7 Relative Permeability vs. Saturation ( r k vs. S ) Table 7 lists methods for measuring relative permeability as a function of saturation. Two general categories of methods are steady-state and unsteady state. Significant debate has been given to which of these approaches is best (e.g., Honarpour et al., (1986) and Rose (1987)). While it can be argued that steady-state methods are more rigorous, it is the authorÕs opinion that the potential for better results is not significant when one considers the magnitude of uncertainty introduced by the heterogeneity of the subsurface environment. As such, Table 7 gives preference (order follows preference) to unsteady state methods due to their advantage of lower cost. It is noted that several of the reviewers of this document stated a preference for steady-state methods due to greater accuracy. In light of the lack of clear consensus, the best approach should be evaluated within the context of the objectives of individual projects. The rationale for determining permeability as a function of saturation includes: · The data can be used to identify whether the Brooks-Corey model (as presented in Equations 4-6) or the van Genuchten model (as presented in Equations 7-9) provides the best results. · Insight can be gained into the wetting properties of the matrix. · Relative permeability data can be used to directly obtain inputs to relative permeability models.
Discussions in the previous sections address determination of porous media properties at a scale of a few centimeters. Using centimeter-scale values to address field-scale problems, it is necessary to assume that centimeter-scale properties are representative of field-scale properties. Reflecting on the heterogeneous nature of geologic materials, extrapolation of centimeter-scale properties to field-scale may not always be appropriate. To overcome this limitation, porous media properties can be measured at a field scale. This is analogous to measuring hydraulic conductivity in a laboratory core test versus measuring hydraulic conductivity through an aquifer test. The core study provides a point value. The aquifer test provides a volume-averaged result for the portion of the aquifer stressed by the test. While field-scale determinations are appealing, their development for analysis of product mobility has been limited. The following describes use of baildown tests and hydrocarbon production data to address product mobility. 5.1 Baildown Tests Baildown tests involve instantaneously removing product from a conventional monitoring well that is screened across the water table. Responses of the air-product and product-water interfaces are measured through time. The procedure is roughly analogous to a slug test. Baildown tests have been used to obtain qualitative evidence of the potential for free-product recovery (e.g., Testa and Winegardner [1991]) and estimates of specific product volume (e.g., Lundy and Zimmerman [1996] and Lundy et al., [1998]). It has also been proposed that baildown tests can be used to determine formation transmissivity to product (e.g., Lundy and Zimmerman [1996] and Huntley [2000]). Techniques for estimating product transmissivity using baildown tests are outlined in Table 9.
A derivation for Equations (19) through (21) is presented in Appendix C. Figure 11 illustrates a graphic approach for estimating α and m V . As shown, production rate is plotted as a function of cumulative production. Typically, late data will fit a straight line. The primary condition here is that the system is operated in a near consistent mode (near constant rate of total fluid production). The slope of the straight line is α . The x intercept of the line is m V . The modeled results presented in Figure 9 (see solid line) illustrate that the technique provides a reasonable match to cumulative production data. Sale and Applegate (1997) describe use of decline curve analysis to estimate the maximum recoverable volume and operation of free product recovery systems to an endpoint of 95% of the maximum recoverable volume.

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