Laboratory data show that the gas-oil ratio performance of non-uniform porosity limestones produced by solution gas drive is sensitive to producing rate and to fluid properties. Non-uniform porosity limestones are those for which laboratory solution and external gas drive tests yield considerably different relative permeability ratio characteristics.The oil recovery performance by solution gas drive depends directly on the number of gas bubbles formed. Laboratory rates of pressure decline, which are 100 to 10,000 times greater than normal field rates, cause the formation of an unusually large number of gas bubbles. This results in abnormally high oil recovery efficiencies. Since it is impractical to reproduce the number of bubbles formed under field conditions, laboratory solution gas drive data on non-uniform porosity limestones are therefore not directly applicable to field operations. However, certain laboratory data can be used to make a conservative estimate of field performance.The concepts presented in this paper indicate the possibility that increased field oil recoveries may be obtained from non-uniform porosity limestones by rap-

The experimental data, when extrapolated t o zero feed volume and plotted on a vaporization-composition diagram like Figure 5, indicate the validity of the following generalizations:1. The change of residual spray composition with vaporization is a function of initial composition, chamber air tcmperature, and nozzle characteristics for the particular binary, in this case orthodichlorobenzrne-tctrachlorocth ylene.2. Thc other variables inyestigatedfeed pressure, feed temperature, and nozzle-to-tray distancc-have the effect of locating the position on the vaporizution-composition curve but do not affect the shape of the c'iirvc.The calculated rcsults for the binary based on the assumption of liquiddiffusion-controlling mass transfrr indicate the smaller droplets slowing down, increasing in temperature, changing in composition, and decreasing in radius more rapidly than the larger drops. Such behavior is consistent with experience.

Well pressure transient tests provide a means for directly obtaining information about formation pressure and reserooir flow capacity. Such tests have also been proposed for determining presence and location of faults or other reservoir closures and for measuring oil in place. For mathematical convenience, most theoretical studies have considered the reserooirs to be homogeneous. Definitive information is not yet available to show whether the actual presence of nonuniformities will make pressure transient behavior different from that of a uniform reservoir. The conclusions reached from actual transient tests are questionable, therefore, insofar as they rely on the original assumption of homogeneity. One type of nonuniformity commonly assumed to exist is that of stratification. In most reserooirs the strata are thought to be in vertical communication. Equations for the transient flow of a singlephase, compressible fluid in a one-well, bounded, circular reservoir have been solved for several situations involving crossflow between multiple strata of various thicknesses and permeabilities. The results show that except for the very early flow period, which usually is too short to be analyzed, the transient performance observed at the well is substantially identical with that of a homogeneous reservoir having the same dimensions and having the same steady-state flow capacity. Thus, stratification does not adversely affect interpretation of well transient tests. This conclusion holds for all commonly encountered combinations of reservoir thickness and external radius. Deviations are observed for unusually thick reservoirs whose outer radii are relatively small. The results of these studies also show that the presence and the amount of stratification cannot be simply diagnosed from reserooir pressure transient data when there is crossflow between strata.

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