TY - THES

T1 - Pore pressure influence on ultrasonic measurements simulated with Nitrogen in sandstones

AU - Baumgartinger, Dominik

N1 - no embargo

PY - 2023

Y1 - 2023

N2 - Gas storage in former oil or natural gas reservoirs is becoming more and more important, especially due to gas consumption fluctuations between summer and winter. In this context, injection and extraction processes occur. This raises the question of whether and to what extent these loadings or processes damage the reservoir rock. In the present thesis, different sandstones were loaded with gas trying to induce damage and detect this damage with ultrasonic measurements. Under specific pressure conditions of 30 MPa vertical loading and 10 MPa circumferential loading, two experiments were performed. The test setup was built in a rock testing machine, where a piping system assures the gas flow as well as the regulation of the gas pressure which should simulate the pore pressure. For the first experiment, the gas pressure is increased by 10 bar every test. The second experiment should simulate the injection and extraction processes by cyclical loading with 10 and 90 bar (5 repetitions). Ultrasonic measurements are done before and after every test. The used samples are sandstones from the Trattnach oil field (1R,2R), Ruhr sandstone of the Imberg company (DBA1, DBA2), red sandstone (DBA5, DBA6) and sandstone from Groß Lessen of the Exxon Mobile company (4.1, 4.2). Porosity measurements were performed before and after loading. These measurements show a clear decreasing trend. The Trattnach sandstone is an exception because it shows an increasing porosity, which can be explained by residual organic matter and severe mechanical damage to the sample. Through the ultrasonic measurements, travel times were measured and out of those p-wave velocities were calculated. These velocities decrease after loading in every sample, which clearly indicates that damage was done to the samples. By a Fourier transformation of the ultrasonic data, conclusions about damage or cracks can be made. The indicator here is the presence or absence of frequency components. In conclusion, damage can be induced through loading the sample with certain gas pressures. Some loading stages show more difference than others. Ultrasonic measurements detect p-wave velocities, which provide information about the damage to the sample. Higher velocities indicate greater damage to the specimen. Porosity behaviour supports these observations and Fourier analysis provides a good complement. With this procedure it was not possible to quantify the damage in the sample.

AB - Gas storage in former oil or natural gas reservoirs is becoming more and more important, especially due to gas consumption fluctuations between summer and winter. In this context, injection and extraction processes occur. This raises the question of whether and to what extent these loadings or processes damage the reservoir rock. In the present thesis, different sandstones were loaded with gas trying to induce damage and detect this damage with ultrasonic measurements. Under specific pressure conditions of 30 MPa vertical loading and 10 MPa circumferential loading, two experiments were performed. The test setup was built in a rock testing machine, where a piping system assures the gas flow as well as the regulation of the gas pressure which should simulate the pore pressure. For the first experiment, the gas pressure is increased by 10 bar every test. The second experiment should simulate the injection and extraction processes by cyclical loading with 10 and 90 bar (5 repetitions). Ultrasonic measurements are done before and after every test. The used samples are sandstones from the Trattnach oil field (1R,2R), Ruhr sandstone of the Imberg company (DBA1, DBA2), red sandstone (DBA5, DBA6) and sandstone from Groß Lessen of the Exxon Mobile company (4.1, 4.2). Porosity measurements were performed before and after loading. These measurements show a clear decreasing trend. The Trattnach sandstone is an exception because it shows an increasing porosity, which can be explained by residual organic matter and severe mechanical damage to the sample. Through the ultrasonic measurements, travel times were measured and out of those p-wave velocities were calculated. These velocities decrease after loading in every sample, which clearly indicates that damage was done to the samples. By a Fourier transformation of the ultrasonic data, conclusions about damage or cracks can be made. The indicator here is the presence or absence of frequency components. In conclusion, damage can be induced through loading the sample with certain gas pressures. Some loading stages show more difference than others. Ultrasonic measurements detect p-wave velocities, which provide information about the damage to the sample. Higher velocities indicate greater damage to the specimen. Porosity behaviour supports these observations and Fourier analysis provides a good complement. With this procedure it was not possible to quantify the damage in the sample.

KW - Porendruck

KW - Ultraschallmessungen

KW - P-Wellen Geschwindigkeit

KW - mechanischer Schaden

KW - Porosität

KW - Gasspeicherung

KW - Speichergestein

KW - pore pressure

KW - ultrasonic measurements

KW - p-wave velocity

KW - mechanical damage

KW - porosity

KW - gas storage

KW - reservoir rocks

U2 - 10.34901/MUL.PUB.2023.24

DO - 10.34901/MUL.PUB.2023.24

M3 - Master's Thesis

ER -