Rock Physics Relationships between Compressional, Shear, and Density Logs in Unconventional Formations, Including Deviated Wells

Quirein, John; Far, Mehdi E.; Gu, Miao; Gokaraju, Deepak; Mekic, Natasa

doi:10.2118/176964-ms

Cited by 3 publications

(2 citation statements)

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“…It had been determined that the compressional and shear wave velocities will change when a large number of rock fractures exist (Quirein et al 2015;Carcione et al 2013). Fractures led the velocities to become abnormal.…”

Section: Introductionmentioning

confidence: 99%

Experiments on acoustic measurement of fractured rocks and application of acoustic logging data to evaluation of fractures

et al. 2017

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Fractures in oil and gas reservoirs have been the topic of many studies and have attracted reservoir research all over the world. Because of the complexities of the fractures, it is difficult to use fractured reservoir core samples to investigate true underground conditions. Due to the diversity of the fracture parameters, the simulation and evaluation of fractured rock in the laboratory setting is also difficult. Previous researchers have typically used a single material, such as resin, to simulate fractures. There has been a great deal of simplifying of the materials and conditions, which has led to disappointing results in application. In the present study, sandstone core samples were selected and sectioned to simulate fractures, and the changes of the compressional and shear waves were measured with the gradual increasing of the fracture width. The effects of the simulated fracture width on the acoustic wave velocity and amplitude were analyzed. Two variables were defined: H represents the amplitude attenuation ratio of the compressional and shear wave, and x represents the transit time difference value of the shear wave and compressional wave divided by the transit time of the compressional wave. The effect of fracture width on these two physical quantities was then analyzed. Finally, the methods of quantitative evaluation for fracture width with H and x were obtained. The experimental results showed that the rock fractures linearly reduced the velocity of the shear and compressional waves. The effect of twin fractures on the compressional velocity was almost equal to that of a single fracture which had the same fracture width as the sum of the twin fractures. At the same time, the existence of fractures led to acoustic wave amplitude attenuations, and the compressional wave attenuation was two times greater than that of the shear wave. In this paper, a method was proposed to calculate the fracture width with x and H, then this was applied to the array acoustic imaging logging data. The application examples showed that the calculated fracture width could be compared with fractures on the electric imaging logs. These rules were applied in the well logs to effectively evaluate the fractures, under the case of no image logs, which had significance to prospecting and development of oil and gas in fractured reservoirs.

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Section: Introductionmentioning

confidence: 99%

Experiments on acoustic measurement of fractured rocks and application of acoustic logging data to evaluation of fractures

et al. 2017

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“…Quirein et al (2015) investigated both the laboratory and log based Vp and Vs relations in unconventional formations. They present plots of laboratory data from the Bakken, Bazhenov, Barnett, Eagle Ford, Haynesville, Monterey, and Niobrara organic shales.…”

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confidence: 99%

Meramec Velocity Systematics

Fu¹,

Sondergeld²,

Rai³

2020

Proceedings of the 8th Unconventional Resources Technology Conference

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Experimental Evaluation of Ultrasonic Velocities and Anisotropy in the Tuscaloosa Marine Shale Formation

Ahmadov

Mokhtari

2020

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Tuscaloosa Marine Shale (TMS) formation is a clay- and organic-rich emerging shale play with a considerable amount of hydrocarbon resources. Despite the substantial potential, there have been only a few wells drilled and produced in the formation over the recent years. The analyzed TMS samples contain an average of 50 wt% total clay, 27 wt% quartz and 14 wt% calcite and the mineralogy varies considerably over the small intervals. The high amount of clay leads to pronounced anisotropy and the frequent changes in mineralogy result in the heterogeneity of the formation. We studied the compressional (VP) and shear-wave (VS) velocities to evaluate the degree of anisotropy and heterogeneity, which impact hydraulic fracture growth, borehole instabilities, and subsurface imaging. The ultrasonic measurements of P- and S-wave velocities from five TMS wells are the best fit to the linear relationship with R2 = 0.84 in the least-squares criteria. We observed that TMS S-wave velocities are relatively lower when compared to the established velocity relationships. Most of the velocity data in bedding-normal direction lie outside constant VP/VS lines of 1.6–1.8, a region typical of most organic-rich shale plays. For all of the studied TMS samples, the S-wave velocity anisotropy exhibits higher values than P-wave velocity anisotropy. In the samples in which the composition is dominated by either calcite or quartz minerals, mineralogy controls the velocities and VP/VS ratios to a great extent. Additionally, the organic content and maturity account for the velocity behavior in the samples in which the mineralogical composition fails to do so. The results provide further insights into TMS Formation evaluation and contribute to a better understanding of the heterogeneity and anisotropy of the play.

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Rock Physics Relationships between Compressional, Shear, and Density Logs in Unconventional Formations, Including Deviated Wells

Cited by 3 publications

References 14 publications

Experiments on acoustic measurement of fractured rocks and application of acoustic logging data to evaluation of fractures

Experiments on acoustic measurement of fractured rocks and application of acoustic logging data to evaluation of fractures

Meramec Velocity Systematics

Experimental Evaluation of Ultrasonic Velocities and Anisotropy in the Tuscaloosa Marine Shale Formation

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