Month: June 2023
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Calculating Unit Recovery from Gas Reservoirs under Water Drive
Under initial conditions, one unit (1 ac-ft) of bulk reservoir rock contains Connate water: 43,560 × φ × Swi ft3 Reservoir gas volume: 43,560 × φ × (1 – Swi) ft3 Surface units of gas: 43,560 × φ × (1 – Swi) ÷ Bgi SCF In many reservoirs under water drive, the pressure suffers an initial decline, after which water enters the reservoir at a…
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Calculating Unit Recovery from Volumetric Gas Reservoirs
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:…
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Calculating Hydrocarbon in Place Using Geological, Geophysical, and Fluid Property Data
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…
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Introduction
The contains a discussion of single-phase gas reservoirs (refer to Fig. 1.4). 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…
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The Havlena and Odeh Method of Applying the Material Balance Equation
As early as 1953, van Everdingen, Timmerman, and McMahon recognized a method of applying the material balance equation as a straight line.9 But it wasn’t until Havlena and Odeh published their work that the method became fully exploited.3,4 Normally, when using the material balance equation, an engineer considers each pressure and the corresponding production data as being separate…
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Uses and Limitations of the Material Balance Method
The material balance equation derived in the previous section has been in general use for many years, mainly for the following: 1. Determining the initial hydrocarbon in place 2. Calculating water influx 3. Predicting reservoir pressures Although in some cases it is possible to solve simultaneously to find the initial hydrocarbon and the water influx, generally one or…
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Derivation of the Material Balance Equation
When an oil and gas reservoir is tapped with wells, oil and gas, and frequently some water, are produced, thereby reducing the reservoir pressure and causing the remaining oil and gas to expand to fill the space vacated by the fluids removed. When the oil- and gas-bearing strata are hydraulically connected with water-bearing strata (aquifers) with…
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Introduction
Fluid does not leave a void space behind, as it is produced from a hydrocarbon reservoir. As the pressure in the reservoir drops during the production of fluids, the remaining fluids and/or reservoir rock expand or nearby water encroaches to fill the space created by any produced fluids. The volume of oil produced on the…
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Review of Reservoir Water Properties
The properties of formation waters are affected by temperature, pressure, and the quantity of solution gas and dissolved solids, but to a much smaller degree than crude oils. The compressibility of the formation, or connate, water contributes materially in some cases to the production of volumetric reservoirs above the bubble point and accounts for much…
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Isothermal Compressibility
Sometimes it is desirable to work with values of the liquid compressibility rather than the formation or relative volume factors. The isothermal compressibility, or the bulk modulus of elasticity of a liquid, is defined by Eq. (2.1): The compressibility, c, is written in general terms since the equation applies for both liquids and solids. For a…