Category: Single-Phase Gas Reservoirs

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…

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,…

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…

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…

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.…

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…

In many gas reservoirs, particularly during the development period, the bulk volume is not known. In this case, it is better to place the reservoir calculations on a unit basis, usually 1 ac-ft of bulk reservoir rock. This one unit, or 1 ac-ft, of bulk reservoir rock contains Connate water: 43,560 × φ × Sw ft3 Reservoir gas volume:…

In order for the reservoir engineer to calculate the amount of hydrocarbon in place from geological information, the reservoir bulk volume must first be calculated. Many methods exist to estimate the reservoir bulk volume but only two will be discussed here. The first method involves the reservoir engineer using well logs, core data, well test…

In a single-phase gas reservoir, the reservoir fluid, usually called natural gas, remains as nonassociated gas during the entire producing life of the reservoir. This type of reservoir is frequently referred to as a dry gas reservoir because no condensate is formed in the reservoir during the life of production. However, many of these wells…