Analysis of abnormally pressured gas reservoirs /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Two new methods to predict gas reserves in abnormally pressured gas reservoirs are presented. The first method, which requires stabilized reservoir pressures, correlates early production data to the original gas in place. Reservoir simulation studies, material balance calculations and real production data indicate that abnormally pressured gas reservoirs exhibit a linear p vs G[p] behavior at pressures above 5.000 psia. The extrapolation of this early straight line leads to under estimate of gas in place. This method correlates both the conventional plz vs G[p] curve and the p vs G[p] line to the correct value of original gas in place. A correction parameter alpha (α), establishes the relationships between G. p and plz. The correlation was determined from a study of numerous abnormally pressured gas reservoirs case histories of the Gulf Coast of Louisiana and Texas. The new method does not require the "z" factor be calculated at each pressure point. The original gas in place estimate calculated by this method was accurate within 5 % when compared to nine case histories studies. The relationship between α, the material balance equation and effective compressibility (c[e]) is also presented. The second method, which mainly requires transient or unstabilized pressures, is an extension of the isochronal short time buildup pressure procedure presented by Chen and Vu^37- The influence of rock and water compressibility were included in this new approach. A plz(1-c[e]Δp) vs G[p] plot is constructed with isochronal, transient or unstabilized pressures instead of with static pressures. The slope of this line was found to be close to the static plz(1-c[e]Δp) vs G[p] plot. An extrapolation of the slope generated from two or more isochronal short-time build-up tests to initial conditions is used to estimate gas reserves. The method was developed by combining the material balance equation for abnormally pressured gas reservoirs and the solution of the diffusivity equation. The theoretical basis for the constant rate and constant bottom hole pressure cases is presented. The method has its main application in tight gas reservoirs when the shut-in time required to attain stabilized reservoir pressures can be very long. Reservoir simulation as well as theoretical results indicates this technique may be applied to abnormally pressured gas reservoirs with a permeability of 1 md or greater... |
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| Item Description: | Vita. "Major subject: Petroleum Engineering." |
| Physical Description: | xi, 72 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |