Month: June 2023

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

In the previous sections, the initial gas in place was calculated on a unit basis of 1 ac-ft of bulk productive rock, given information on the porosity and connate water. To calculate the initial gas in place on any particular portion of a reservoir, it is necessary to know, in addition, the bulk volume of… Continue reading Calculating Gas in Place Using Material Balance