Effects of cyclic cryogenic treatment on rock physical and mechanical properties of Eagle Ford shale samples - An experimental study

Altawati, Faisal; Emadi, Hossein

doi:10.1016/j.jngse.2020.103772

Cited by 16 publications

(7 citation statements)

References 48 publications

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“…Increasing porosity or permeability makes the rock sample less brittle. The existence of pore spaces and microcracks in the rock affects the rock-mechanical properties, such as uniaxial compressive strength (UCS) and tensile strength, where UCS and tensile strength of rock decrease with increasing porosity and permeability (Al-Harthi et al 1999;Altawati and Emadi 2021;Gharahbagh and Fakhimi 2011;Koncagül Rajabzadeh et al 2012). Thus, alteration in the rock brittleness occurs.…”

Section: Resultsmentioning

confidence: 99%

An experimental study to investigate the physical and dynamic elastic properties of Eagle Ford shale rock samples

Altawati

Emadi

Khalil

2021

J Petrol Explor Prod Technol

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Unconventional resources, such as Eagle Ford formation, are commonly classified for their ultra-low permeability, where pore sizes are in nano-scale and pore-conductivity is low, causing several challenges in evaluating unconventional-rock properties. Several experimental parameters (e.g., diffusion time of gas, gas injection pressure, method of permeability measurement, and confining pressure cycling) must be considered when evaluating the ultra-low permeability rock's physical and dynamic elastic properties measurements, where erroneous evaluations could be avoided. Characterizing ultra-low permeability samples' physical and elastic properties helps researchers obtain more reliable information leading to successful evaluations. In this study, 24 Eagle Ford core samples' physical and dynamic elastic properties were evaluated. Utilizing longer diffusion time and higher helium injection pressure, applying complex transient method, and cycling confining pressure were considered for porosity, permeability, and velocities measurements. Computerized tomography (CT) scan, porosity, permeability, and ultrasonic wave velocities were conducted on the core samples. Additionally, X-ray Diffraction (XRD) analysis was conducted to determine the mineralogical compositions. Porosity was measured at 2.07 MPa injection pressure for 24 h, and the permeability was measured using a complex transient method. P- and S-wave velocities were measured at two cycles of five confining pressures (up to 68.95 MPa). The XRD analysis results showed that the tested core samples had an average of 81.44% and 11.68% calcite and quartz, respectively, with a minor amount of clay minerals. The high content of calcite and quartz in shale yields higher velocities, higher Young's modulus, and lower Poisson's ratio, which enhances the brittleness that is an important parameter for well stimulation design (e.g., hydraulic fracturing). The results of porosity and permeability showed that porosity and permeability vary between 5.3–9.79% and 0.006–12 µD, respectively. The Permeability–porosity relation of samples shows a very weak correlation. P- and S-wave velocities results display a range of velocity up to 6206 m/s and 3285 m/s at 68.95 MPa confining pressure, respectively. Additionally, S-wave velocity is approximately 55% of P-wave velocity. A correlation between both velocities is established at each confining pressure, indicating a strong correlation. Results illustrated that applying two cycles of confining pressure impacts both velocities and dynamic elastic moduli. Ramping up the confining pressure increases both velocities owing to compaction of the samples and, in turn, increases dynamic Young's modulus and Poisson's ratio while decreasing bulk compressibility. Moreover, the results demonstrated that the above-mentioned parameters' values (after decreasing the confining pressure to 13.79 MPa) differ from the initial values due to the hysteresis loop, where the loop is slightly opened, indicating that the alteration is non-elastic. The findings of this study provide detailed information about the rock physical and dynamic elastic properties of one of the largest unconventional resources in the U.S.A, the Eagle Ford formation, where direct measurements may not be cost-effective or feasible.

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Section: Resultsmentioning

confidence: 99%

An experimental study to investigate the physical and dynamic elastic properties of Eagle Ford shale rock samples

Altawati

Emadi

Khalil

2021

J Petrol Explor Prod Technol

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“…Figure shows the distribution of wells in the field, where eight horizontal wells were completed in the Eagle Ford between 2011 and 2013, as shown by the black line in Figure . Similar to the Bakken, the Eagle Ford formation has an extremely tight rock matrix, where the permeability is at a nano-darcy to micro-darcy level. − The crude oil produced from Eagle Ford shale is also volatile because of the high percentage of light components in the oil. , At this site, the oil production rate dropped nearly 90% in the first 5 years of production, from a peak rate of 40,863 bbl/month (6.5 × 10 3 m 3 /month) (in August 2011) to 4500 bbl/month (0.715 × 10 3 m 3 /month) (in April 2016).…”

Section: Assessment Of Immiscible and Miscible Field Casesmentioning

confidence: 94%

“…A variety of laboratory experiments and simulation studies were performed to investigate EOR mechanisms and predictive potential EOR responses in unconventional reservoirs. − ,,− However, very few of these studies were correlated with actual field performance. One of the reasons was the limited access to actual field data. , In this section, a series of experiments were collected for gas injection pressure, MMP, and oil recovery factor assessment in the Bakken and Eagle Ford, and then a set of new experimental and simulation activities were carried out to correlate the laboratory/simulation observations with actual field performance.…”

Section: Laboratory and Simulation Investigationsmentioning

confidence: 99%

Investigating Enhanced Oil Recovery in Unconventional Reservoirs Based on Field Case Review, Laboratory, and Simulation Studies

et al. 2022

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Aimed at advancing gas injection enhanced oil recovery (EOR) technologies in unconventional reservoirs, this study comprised a series of activities to bridge the gap between the theoretical study and actual field applications. Twenty-four EOR pilot tests were collected from the major unconventional plays in North America to evaluate the performance of different EOR technologies. Fit-for-purpose experiments and simulations were performed to investigate the effects of injection rate and pressure on EOR performance, as well as to reveal the effectiveness of huff "n" puff (HnP) cycles in actual field operations. The selection of injection rate and pressure as key parameters for investigation was based on field observations and communications with oil and gas operators because these two parameters play critical roles in both facility design and overall cost for an EOR project. Results showed that miscible EOR with a high gas injection rate and pressure is required for field operations because the injected gas needs to penetrate and extract oil from the tight matrix. Experimental results indicated that there is a correlation between oil recovery and the logarithm of core volume for miscible EOR. Immiscible gas EOR could not yield a satisfactory EOR response in actual reservoirs because the injected gas tends to flow through fractures instead of penetrating the matrix to interact with oil. Results also showed that reaching minimum miscibility pressure (MMP) does not guarantee an optimum EOR operation in unconventional reservoirs. Pressure higher than MMP is preferred in field operations. When designed properly, up to a tenfold oil production rate boost is achievable in field applications within a short period. However, such a high-performance operation is only effective in the first several HnP cycles due to the limited gas penetration depth into the rock matrix.

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“…Coal is a complex material composed of inorganic and organic matter with complex internal structural characteristics. , CBM mainly exists in the coal seam in an adsorbed state and partially exists in the fractures and pores of the coal seam in a free state. , In order to improve the permeability of coal seams, researchers have proposed a variety of methods to increase the permeability of coal reservoirs, including loose blasting, hydraulic slitting, hydraulic fracturing, etc. , However, these methods all have a certain scope of application. For example, in loose blasting, it is difficult to control the drilling depth, the number of drilling holes, and the sealing position. , Hydraulic slitting has problems such as high cost of use, large demand for water and sand, and large pollution to the production environment . The addition of hydraulic fracturing can cause groundwater pollution .…”

Section: Introductionmentioning

confidence: 99%

“…For example, in loose blasting, it is difficult to control the drilling depth, the number of drilling holes, and the sealing position. 16,17 Hydraulic slitting has problems such as high cost of use, large demand for water and sand, and large pollution to the production environment. 18 The addition of hydraulic fracturing can cause groundwater pollution.…”

Section: Introductionmentioning

confidence: 99%

Mechanical Strength Damage of Bitumite in Different Freezing States after the Freezing of Liquid Nitrogen at Ultralow Temperature

et al. 2022

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In order to explore the evolution law of mechanical strength of frozen and thawed coal samples after the freezing of liquid nitrogen (LN 2 ) at ultralow temperature, the Yuanzhuang bitumite is cored to make standard samples. The MTS testing machine and ultrasonic detector are used for testing, and the stress−strain curve and ultrasonic time domain image of coal samples are obtained. The evolution law of mechanical strength of coal samples is studied. The results showed that (1) uniaxial compressive strength, elastic modulus, and ultrasonic longitudinal wave velocity of frozen coal samples are positively correlated with the freezing time of LN 2 in 0−50 min and negatively correlated with the freezing time of LN 2 in 50−150 min. (2) The uniaxial compressive strength, elastic modulus, and ultrasonic longitudinal wave velocity of thawed coal samples decrease with the increase of LN 2 freezing time. (3) With the increase of the LN 2 freezing time, the time-domain waveform of coal samples begins to be disordered, and the frequency-domain waveform begins to shift to low peaks, and branch peaks are generated. (4) The brittleness index of frozen coal samples increases with the increase of freezing time, and the brittleness index of thawed coal samples decreases with the increase of freezing time. Compared with the frozen coal samples, the thawed coal samples are subjected to greater thermal stress under the freezing of LN 2 at the same time, which shows a stronger deterioration of mechanical properties. The results can provide a reference for LN 2 fracturing and antireflection.

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Effects of cyclic cryogenic treatment on rock physical and mechanical properties of Eagle Ford shale samples - An experimental study

Cited by 16 publications

References 48 publications

An experimental study to investigate the physical and dynamic elastic properties of Eagle Ford shale rock samples

An experimental study to investigate the physical and dynamic elastic properties of Eagle Ford shale rock samples

Investigating Enhanced Oil Recovery in Unconventional Reservoirs Based on Field Case Review, Laboratory, and Simulation Studies

Mechanical Strength Damage of Bitumite in Different Freezing States after the Freezing of Liquid Nitrogen at Ultralow Temperature

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