scholarly journals The Effect of Thermal Shocking with Nitrogen Gas on the Porosities, Permeabilities, and Rock Mechanical Properties of Unconventional Reservoirs

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2131 ◽  
Author(s):  
Khalid Elwegaa ◽  
Hossein Emadi
Keyword(s):  
Mechanical Properties ◽  
Hydraulic Fracturing ◽  
Wave Velocity ◽  
Ultrasonic Waves ◽  
P Wave ◽  
Unconventional Reservoirs ◽  
Nitrogen Gas ◽  
P Wave Velocity ◽  
Cryogenic Fracturing ◽  
Rock Mechanical Properties

Cryogenic fracturing is a type of thermal shocking in which a cold liquid or gas is injected into a hot formation to create fractures. Research has shown that like traditional hydraulic fracturing, cryogenic fracturing could improve oil/gas recovery from unconventional reservoirs. Research has also shown, though, that, unlike traditional hydraulic fracturing, which uses water-based fluids, cryogenic fracturing limits and can even heal damage that is near the wellbore. Previous studies on thermal shocking, however, have generally examined only a few parameters at a time. To provide a more complete overview of the process, this study examines the effects of thermal shocking with low-temperature nitrogen gas on the porosities, permeabilities, and rock mechanical properties of unconventional reservoirs. Three cycles of thermal shocking were applied to a core sample and an outcrop sample from an unconventional reservoir. Each sample was heated at 82 °C for 1 h, and then nitrogen at −18 °C was injected at 6.89 MPa for 5 min. The porosities and permeabilities of the cores and the velocities at which ultrasonic waves travelled through them were measured both before and after each thermal shock. The results strongly suggest that the thermal shocking produced cracks. The porosity increased by between 1.34% and 14.3%, the permeability increased by between 17.4% and 920%, and the average P-wave velocity decreased by up to 100 m/s. From the reduction in P-wave velocity, it was determined that the brittleness ratio increased by between 2 and 4 and the fracability index increased by between 0.2 and 0.8.

scholarly journals Experimental Investigation on the Correlation between Dynamic Ultrasonic and Mechanical Properties of Sandstone Subjected to Uniaxial Compression

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-22
Author(s):  
Yunjiang Sun ◽  
Jianping Zuo ◽  
Yue Shi ◽  
Zhengdai Li ◽  
Changning Mi ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Ultrasonic Wave ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Poisson’S Ratio ◽  
P Wave ◽  
Poisson's Ratio ◽  
Ultrasonic Wave Velocity ◽  
P Wave Velocity

Ultrasonic wave velocity is effective to evaluate anisotropy property and predict rock failure. This paper investigates the correlation between dynamic ultrasonic and mechanical properties of sandstones with different buried depths subjected to uniaxial compression tests. The circumferential anisotropy and axial wave velocity of sandstone are obtained by means of ultrasonic wave velocity measurements. The mechanical properties, including Young’s modulus and uniaxial compressive strength, are positively correlated with the axial P wave velocity. The average angles between the sandstone failure plane and the minimum and maximum wave directions are 35.8° and 63.3°, respectively. The axial P wave velocity almost keeps constant, and the axial S wave velocity has a decreasing trend before the failure of rock specimen. In most rock samples under uniaxial compression, shear failure occurs in the middle and splitting appears near both sides. Additionally, the dynamic Young’s modulus and dynamic Poisson’s ratio during loading are obtained, and the negative values of the Poisson’s ratio occur at the initial compression stage. Distortion and rotation of micro/mesorock structures may be responsible for the negative Poisson’s ratio.

S-wave velocity prediction in unconventional shale reservoirs

Geophysics ◽  
2018 ◽  
Vol 83 (1) ◽  
pp. MR35-MR45 ◽  
Author(s):  
Lev Vernik ◽  
John Castagna ◽  
Sheyore John Omovie
Keyword(s):  
Wave Velocity ◽  
Prediction Method ◽  
Organic Content ◽  
P Wave ◽  
Unconventional Reservoirs ◽  
Hybrid Technique ◽  
S Wave ◽  
P Wave Velocity ◽  
Velocity Prediction ◽  
Shale Reservoirs

In unconventional reservoirs with significant organic content, the Greenberg-Castagna (GC) S-wave velocity prediction method does not yield accurate S-wave velocity predictions, with observed mean errors varying from 6% to 16% in a variety of unconventional reservoirs rich in organic content. This is because kerogen content is not explicitly taken into account in the GC S-wave velocity prediction method. Two alternative approaches for bedding-normal S-wave velocity prediction from P-wave velocity and other well logs in relatively straight holes drilled in unconventional reservoirs are investigated. The first method is purely empirical, requiring minimal information such as P-wave velocity and total organic carbon content. This approach implicitly accounts for compositional and stress effects on mudrock elasticity. The second method can be classified as a hybrid technique, comprising the following three steps: (1) computing a nonkerogen phase P-wave velocity using the Vernik-Kachanov (VK) model, (2) determination of the nonkerogen S-wave velocity from the GC approach, and (3) using a simplified VK model to mix the nonkerogen matrix with nanoporous kerogen to predict the bedding-normal S-wave velocity of the organic mudrock. The second method explicitly takes into account all the variables that control elastic properties of organic mudrock reservoirs. Tests in nine wells from seven different oil and gas shale reservoirs indicate that both methods have prediction accuracy better than 3% error when input data are accurate.

scholarly journals Frost Damage in Tight Sandstone: Experimental Evaluation and Interpretation of Damage Mechanisms

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4617
Author(s):  
Shun Ding ◽  
Hailiang Jia ◽  
Fan Zi ◽  
Yuanhong Dong ◽  
Yuan Yao
Keyword(s):  
Mechanical Properties ◽  
Wave Velocity ◽  
Building Materials ◽  
Frost Damage ◽  
P Wave ◽  
Tight Sandstone ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
P Wave Velocity ◽  
Tight Rocks

Low-porosity tight rocks are widely used as building and engineering materials. The freeze–thaw cycle is a common weathering effect that damages building materials in cold climates. Tight rocks are generally supposed to be highly frost-resistant; thus, studies on frost damage in tight sandstone are rare. In this study, we investigated the deterioration in mechanical properties and changes in P-wave velocity with freeze–thaw cycles in a tight sandstone. We also studied changes to its pore structure using nuclear magnetic resonance (NMR) technology. The results demonstrate that, with increasing freeze–thaw cycles, (1) the mechanical strength (uniaxial compressive, tensile, shear strengths) exhibits a similar decreasing trend, while (2) the P-wave velocity and total pore volume do not obviously increase or decrease. (3) Nanopores account for >70% of the pores in tight sandstone but do not change greatly with freeze–thaw cycles; however, the micropore volume has a continuously increasing trend that corresponds to the decay in mechanical properties. We calculated the pressure-dependent freezing points in pores of different diameters, finding that water in nanopores (diameter <5.9 nm) remains unfrozen at –20 °C, and micropores >5.9 nm control the evolution of frost damage in tight sandstone. We suggest that pore ice grows from larger pores into smaller ones, generating excess pressure that causes frost damage in micropores and then nanopores, which is manifested in the decrease in mechanical properties.

A correlation between P-wave velocity and Schmidt hardness with mechanical properties of travertine building stones

2016 ◽  
Vol 9 (10) ◽  
Author(s):  
Amin Jamshidi ◽  
Mohammad Reza Nikudel ◽  
Mashallah Khamehchiyan ◽  
Reza Zarei Sahamieh ◽  
Yasin Abdi
Keyword(s):  
Mechanical Properties ◽  
Wave Velocity ◽  
P Wave ◽  
Building Stones ◽  
P Wave Velocity ◽  
Schmidt Hardness

scholarly journals Effects of Saturation Levels on the Ultrasonic Pulse Velocities and Mechanical Properties of Concrete

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 152
Author(s):  
Ma. Doreen Esplana Candelaria ◽  
Seong-Hoon Kee ◽  
Jurng-Jae Yee ◽  
Jin-Wook Lee
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Wave Velocity ◽  
Water Saturation ◽  
P Wave ◽  
Saturation Level ◽  
Saturation Condition ◽  
P Wave Velocity ◽  
Compressive Strength Of Concrete ◽  
The Relationship

The main objective of this research is to investigate the effect of water content in concrete on the velocities of ultrasonic waves (P- and S-waves) and mechanical properties (elastic modulus and compressive strength) of concrete. For this study, concrete specimens (100 mm × 200 mm cylinders) were fabricated with three different water-to-binder ratios (0.52, 0.35, and 0.26). These cylinders were then submerged in water to be saturated in different degrees from 25% to 100% with an interval of 25% saturation. Another set of cylinders was also oven-dried to represent the dry condition. The dynamic properties of concrete were then assessed using a measurement of elastic wave accordance with ASTM C597-16 and using resonance tests following ASTM C215-19, before and after immersion in water. The static properties of saturated concrete were also assessed by the uniaxial compressive testing according to ASTM C39/C39M-20 and ASTM C469/C469M-14. It was observed that the saturation level of concrete affected the two ultrasonic wave velocities and the two static mechanical properties of concrete in various ways. The relationship between P-wave velocity and compressive strength of concrete was highly sensitive to saturation condition of concrete. In contrast, S-wave velocity of concrete was closely correlated with compressive strength of concrete, which was much less sensitive to water saturation level compared to P-wave velocity of concrete. Finally, it was noticed that water saturation condition only little affects the relationship between the dynamic and elastic moduli of elasticity of concrete studies in this study.

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