Category: Single-Phase Fluid Flow In Reservoirs

Now that Darcy’s law has been reviewed and the classification of flow systems has been discussed, the actual models that relate flow rate to reservoir pressure can be developed. The next several sections contain a discussion of the steady-state models. Both linear and radial flow geometries are discussed since there are many applications for these… Continue reading Steady-State Flow

Reservoir flow systems are usually classed according to (1) the compressibility of fluid, (2) the geometry of the reservoir or portion thereof, and (3) the relative rate at which the flow approaches a steady-state condition following a disturbance. For most engineering purposes, the reservoir fluid may be classed as (1) incompressible, (2) slightly compressible, or… Continue reading The Classification of Reservoir Flow Systems

In 1856, as a result of experimental studies on the flow of water through unconsolidated sand filter beds, Henry Darcy formulated the law that bears his name. This law has been extended to describe, with some limitations, the movement of other fluids, including two or more immiscible fluids, in consolidated rocks and other porous media.… Continue reading Darcy’s Law and Permeability

The material balance equations for each of the four reservoir types defined in were developed. These material balance equations may be used to calculate the production of oil and/or gas as a function of reservoir pressure. The reservoir engineer, however, would like to know the production as a function of time. To learn this, it is… Continue reading Introduction

The precision of the reserve calculations by the volumetric method depends on the accuracy of the data that enter the computations. The precision of the initial gas in place depends on the probable errors in the averages of the porosity, connate water, pressure, and gas deviation factor and in the error in the determination of… Continue reading Limitations of Equations and Errors

Normal pressure gradients observed in gas reservoirs are in the range of 0.4 to 0.5 psi per foot of depth. Reservoirs with abnormal pressures may have gradients as high as 0.7 to 1.0 psi per foot of depth.14,15,16,17 Bernard has reported that more than 300 gas reservoirs have been discovered in the offshore Gulf Coast alone,… Continue reading Abnormally Pressured Gas Reservoirs

The demand for natural gas is seasonal. During winter months, there is a much greater demand for natural gas than during the warmer summer months. To meet this variable demand, several means of storing natural gas are used in the industry. One of the best methods of storing natural gas is with the use of… Continue reading Gas Reservoirs as Storage Reservoirs

In the study of gas reservoirs in the preceding section, it was implicitly assumed that the fluid in the reservoir at all pressures as well as on the surface was in a single (gas) phase. Most gas reservoirs, however, produce some hydrocarbon liquid, commonly called condensate, in the range of a few to a hundred or more… Continue reading The Gas Equivalent of Produced Condensate and Water

In water-drive reservoirs, the relation between Gp and p/z is not linear, as can be seen by an inspection of Eqs. (4.13) and (4.16). Because of the water influx, the pressure drops less rapidly with production than under volumetric control, as shown in the upper curve of Fig. 4.2. Consequently, the extrapolation technique described for volumetric reservoirs is not applicable.… Continue reading Material Balance in Water-Drive Gas Reservoirs

For a volumetric gas reservoir, Eq. (4.13) can be reduced to a simple application of a straight line involving the gas produced, its composition, and the reservoir pressure. This relationship is routinely used by reservoir engineers to predict recoveries from volumetric reservoirs. Since there is neither water encroachment nor water production in this type of… Continue reading Material Balance in Volumetric Gas Reservoirs