scholarly journals Fluid Discrimination in Ultra-Deep Reservoirs Based on a Double Double-Porosity Theory

2021 ◽  
Vol 9 ◽  
Author(s):  
Xinyang Zhou ◽  
Jing Ba ◽  
Juan E. Santos ◽  
José M. Carcione ◽  
Li-Yun Fu ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Wave Attenuation ◽  
Poisson Ratio ◽  
Mass Density ◽  
Rock Physics ◽  
Spectral Ratio ◽  
Double Porosity ◽  
P Wave ◽  
Oil Saturation ◽  
Frequency Bands

We develop a methodology, based on rock-physics templates, to effectively identify reservoir fluids in ultra-deep reservoirs, where the poroelasticity model is based on the double double-porosity theory. P-wave attenuation, the ratio of the first Lamé constant to mass density (λ/ρ) and Poisson ratio are used to build the templates at the ultrasonic and seismic frequency bands to quantitatively predict the total and crack (soft) porosities and oil saturation. Attenuation on these frequency bands is estimated with the spectral-ratio and frequency-shift methods. We apply the methodology to fault-controlled karst reservoirs in the Tarim Basin (China), which contain ultra-deep hydrocarbon resources with a diverse pore-crack system, low porosity/permeability and complex oil-water spatial distributions. The results are consistent with well-log data and actual oil recovery. Crack porosity can be used as an indicator to find regions with high oil saturation, since high values implies a good pore connectivity.

Rock-physics modeling of ultrasonic P- and S-wave attenuation in partially frozen brine and unconsolidated sand systems and comparison with laboratory measurements

Geophysics ◽  
2019 ◽  
Vol 84 (5) ◽  
pp. MR153-MR171 ◽  
Author(s):  
Linsen Zhan ◽  
Jun Matsushima
Keyword(s):  
Ultrasonic Wave ◽  
Wave Attenuation ◽  
Freezing Point ◽  
Rock Physics ◽  
Ultrasonic Waves ◽  
P Wave ◽  
Dominant Factor ◽  
S Wave ◽  
High Attenuation ◽  
Unconsolidated Sand

The nonintuitive observation of the simultaneous high velocity and high attenuation of ultrasonic waves near the freezing point of brine was previously measured in partially frozen systems. However, previous studies could not fully elucidate the attenuation variation of ultrasonic wave propagation in a partially frozen system. We have investigated the potential attenuation mechanisms responsible for previously obtained laboratory results by modeling ultrasonic wave transmission in two different partially frozen systems: partially frozen brine (two phases composed of ice and unfrozen brine) and unconsolidated sand (three phases composed of ice, unfrozen brine, and sand). We adopted two different rock-physics models: an effective medium model for partially frozen brine and a three-phase extension of the Biot model for partially frozen unconsolidated sand. For partially frozen brine, our rock-physics study indicated that squirt flow caused by unfrozen brine inclusions in porous ice could be responsible for high P-wave attenuation around the freezing point. Decreasing P-wave attenuation below the freezing point can be explained by the gradual decrease of squirt flow due to the gradual depletion of unfrozen brine. For partially frozen unconsolidated sand, our rock-physics study implied that squirt flow between ice grains is a dominant factor for P-wave attenuation around the freezing point. With decreasing temperature lower than the freezing point, the friction between ice and sand grains becomes more dominant for P-wave attenuation because the decreasing amount of unfrozen brine reduces squirt flow between ice grains, whereas the generation of ice increases the friction. The increasing friction between ice and sand grains caused by ice formation is possibly responsible for increasing the S-wave attenuation at decreasing temperatures. Then, further generation of ice with further cooling reduces the elastic contrast between ice and sand grains, hindering their relative motion; thus, reducing the P- and S-wave attenuation.

The longitudinal modulus of bitumen: Pressure and temperature dependencies

Geophysics ◽  
2019 ◽  
Vol 84 (4) ◽  
pp. MR139-MR151 ◽  
Author(s):  
Arif Rabbani ◽  
Douglas R. Schmitt
Keyword(s):  
Shear Modulus ◽  
Bulk Modulus ◽  
Wave Attenuation ◽  
Rock Physics ◽  
P Wave ◽  
Complex Shear Modulus ◽  
Temperature Dependent ◽  
Wave Speeds ◽  
Complex Shear ◽  
Longitudinal Modulus

Bitumen retains significant solid-like behavior even in temperatures in excess of 50°C. Traditional ultrasonic wave-propagation studies have, however, largely ignored the existence of the shear modulus in such materials, and they have mostly assumed that the observed longitudinal (P) wave speeds solely depend on the fluid’s bulk modulus. To further study this, we have measured ultrasonic longitudinal (P) wave transmission speeds through viscous bitumen at different pressures (0.1–15 MPa) and temperatures (7–132°C) using an adapted version of the technique that consists of two piezoelectric receivers placed at unequal lengths from the transmitter. As such, we are able to calculate the P-wave attenuation and velocity that is used to derive the material’s complex longitudinal modulus. Using parallel measurements of the bitumen’s complex shear modulus, we find that the bulk modulus differs from the longitudinal modulus particularly at lower (reservoirs) temperatures. The results, together with the realization that bitumen experiences a sequence of various compositional and thermophysical phase that is primarily temperature-dependent, can be implemented to improve the fluid-substitution analyses of rock-physics studies of bitumen-saturated reservoirs.

Enhanced oil recovery monitoring using P‐wave attenuation

1996 ◽  
Author(s):  
Jerry M. Harris ◽  
Feng Yin ◽  
Youli Quan
Keyword(s):  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Wave Attenuation ◽  
P Wave ◽  
Recovery Monitoring

HOW GAS HYDRATE SATURATION AND MORPHOLOGY CONTROL SEISMIC ATTENUATION: A CASE STUDY FROM THE SOUTH HYDRATE RIDGE

2021 ◽  
pp. 1-63
Author(s):  
Aoshuang Ji ◽  
Tieyuan Zhu ◽  
Hector Marin-Moreno ◽  
Xiong Lei
Keyword(s):  
Gas Hydrate ◽  
Wave Attenuation ◽  
Rock Physics ◽  
Seismic Profile ◽  
Seismic Attenuation ◽  
P Wave ◽  
Frequency Range ◽  
The South ◽  
Hydrate Ridge ◽  
Hydrate Saturation

Prior studies have shown an ambiguous relationship between gas hydrate saturation and seismic attenuation in different regions, but the effect of gas hydrate morphology on seismic attenuation of hydrate-bearing sediments was often overlooked. Here we combine seismic data with rock physics modeling to elucidate how gas hydrate saturation and morphology may control seismic attenuation. To extract P-wave attenuation, we process both the vertical seismic profile (VSP) data within a frequency range of 30 – 150 Hz and sonic logging data within 10 – 15 kHz from three wells in the south Hydrate Ridge, offshore of Oregon (USA), collected during Ocean Drilling Program (ODP) Leg 204 in 2000. We calculate P-wave attenuation using spectral matching and centroid frequency shift methods, and use Archie's relationship to derive gas hydrate saturation from the resistivity data above the bottom simulating reflection (BSR) at the same wells. To interpret observed seismic attenuation in terms of the effects of both gas hydrate saturation and morphology, we employ the Hydrate-Bearing Effective Sediment (HBES) rock physics model. By comparing the observed and model-predicted attenuation values, we infer that: (1) seismic attenuation appears to not be dominated by any single factor, instead, its variation is likely governed by both gas hydrate saturation and morphology; (2) the relationship between seismic attenuation and gas hydrate saturation varies with different hydrate morphologies; (3) the squirt flow, occurring at different compliances of adjacent pores driven by pressure gradients, may be responsible for the significantly large or small attenuation over a broad frequency range.

Estimation of microfracture porosity in deep carbonate reservoirs based on 3D rock-physics templates

2020 ◽  
Vol 8 (4) ◽  
pp. SP43-SP52
Author(s):  
Mengqiang Pang ◽  
Jing Ba ◽  
Li-Yun Fu ◽  
José M. Carcione ◽  
Uti I. Markus ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Velocity Ratio ◽  
Rock Physics ◽  
Total Porosity ◽  
Spectral Ratio ◽  
Wave Impedance ◽  
Seismic Attenuation ◽  
Carbonate Reservoirs ◽  
P Wave ◽  
Ratio Method

Carbonate reservoirs in the S area of the Tarim Basin (China) are ultradeep hydrocarbon resources, with low porosity, complex fracture systems, and dissolved pores. Microfracturing is a key factor of reservoir connectivity and storage space. We have performed measurements on limestone samples, under different confining pressures, and we used the self-consistent approximation model and the Biot-Rayleigh theory of double porosity to study the microfractures. We have computed the fluid properties (mainly oil) as a function of temperature and pressure. Using the dependence of seismic [Formula: see text] on the microfractures, a multiscale 3D rock-physics template (RPT) is built, based on the attenuation, P-wave impedance, and phase velocity ratio. We estimate the ultrasonic and seismic attenuation with the spectral-ratio method and the improved frequency-shift method, respectively. Then, calibration of the RPTs is performed at ultrasonic and seismic frequencies. We use the RPTs to estimate the total and microfracture porosities. The results indicate that the total porosity is low and the microfracture porosity is relatively high, which is consistent with the well log data and actual oil production reports. This work presents a method for identification of deep carbonate reservoirs by using the microfracture porosity estimated from the 3D RPT, which could be exploited in oil and gas exploration.

Viscoelasticity of Ells River bitumen sand and 4D monitoring of thermal enhanced oil recovery processes

Geophysics ◽  
2013 ◽  
Vol 78 (6) ◽  
pp. D419-D428 ◽  
Author(s):  
James W. Spencer
Keyword(s):  
Bulk Modulus ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Pore Space ◽  
Rock Physics ◽  
Steam Injection ◽  
P Wave ◽  
Low Frequencies ◽  
Recovery Processes ◽  
Seismic Frequencies

Samples of Ells River bitumen sand from Alberta, Canada were measured at low frequencies (0.2–205 Hz) to determine the temperature and frequency dependence of velocities and attenuations. The samples were first measured “as received” where the pore space is mostly filled with bitumen but also contains small amounts of air and water. With residual air in the pores, at 5°C, there is strong dispersion in the P-wave modulus and a peak in attenuation at seismic frequencies. The frequency-dependent moduli and attenuations shift by three orders of magnitude in frequency as temperature is increased from 5°C to 48°C, consistent with the bitumen viscosity. Samples were then saturated so any empty pore space is filled with water. After saturation, at 1 Hz, increasing temperature from 5°C to 49°C causes a 30% reduction in the saturated P-wave modulus, a 34% reduction in the saturated bulk modulus, and a 6% reduction in the shear modulus. This behavior can only be explained by the temperature-dependent bulk modulus of bitumen. The results enable predictions regarding the P-velocities that can be expected during seismic monitoring of thermal enhanced oil recovery processes. Velocities for cold bitumen sand are near [Formula: see text] at reservoir pressure and temperature. Following steam injection, velocities should be very low (near [Formula: see text]) in heated zones more than 50°C with a free gas phase, which could be steam or gas. There will be a progressive reduction in velocities, i.e., [Formula: see text] at 25°C and [Formula: see text] at 49°C, in areas of formation heating, but without steam or gas in the pores. Albeit smaller than the effect of steam, the effect of formation heating alone is large enough to be easily detected by today’s 4D surveys. With local rock physics calibration, it should be possible to map the areal extent of formation heating using 4D seismic data.

scholarly journals Seismic wave attenuation in the uppermost glacier ice of Storglaciären, Sweden

2010 ◽  
Vol 56 (196) ◽  
pp. 249-256 ◽  
Author(s):  
Alessio Gusmeroli ◽  
Roger A. Clark ◽  
Tavi Murray ◽  
Adam D. Booth ◽  
Bernd Kulessa ◽  
...  
Keyword(s):  
Seismic Wave ◽  
Wave Attenuation ◽  
Seismic Refraction ◽  
Spectral Ratio ◽  
P Wave ◽  
Ratio Method ◽  
Polar Ice ◽  
Seismic Line ◽  
Seismic Wave Attenuation ◽  
Glacier Ice

AbstractWe conducted seismic refraction surveys in the upper ablation area of Storglaciären, a small valley glacier located in Swedish Lapland. We estimated seismic-wave attenuation using the spectral-ratio method on the energy travelling in the uppermost ice with an average temperature of approximately −1 °C. Attenuation values were derived between 100 and 300 Hz using the P-wave quality factor, QP, the inverse of the internal friction. By assuming constant attenuation along the seismic line we obtained mean QP = 6 ± 1. We also observed that QP varies from 8 ± 1 to 5 ± 1 from the near-offset to the far-offset region of the line, respectively. Since the wave propagates deeper at far offsets, this variation is interpreted by considering the temperature profile of the study area; far-offset arrivals sampled warmer and thus more-attenuative ice. Our estimates are considerably lower than those reported for field studies in polar ice (∼500–1700 at −28°C and 50–160 at −10°C) and, hence, are supportive of laboratory experiments that show attenuation increases with rising ice temperature. Our results provide new in situ estimates of QP for glacier ice and demonstrate a valuable method for future investigations in both alpine and polar ice.

A rock-physics investigation of unconsolidated saline permafrost: P-wave properties from laboratory ultrasonic measurements

Geophysics ◽  
2016 ◽  
Vol 81 (1) ◽  
pp. WA233-WA245 ◽  
Author(s):  
Shan Dou ◽  
Seiji Nakagawa ◽  
Douglas Dreger ◽  
Jonathan Ajo-Franklin
Keyword(s):  
Wave Attenuation ◽  
Rock Physics ◽  
P Wave ◽  
Data Sets ◽  
Pore Scale ◽  
Seismic Properties ◽  
Rock Physics Modeling ◽  
Physics Modeling ◽  
Ice Content ◽  
Wave Properties

Saline permafrost is sensitive to thermal disturbances and is prone to subsidence, which renders it a major source of geohazard in Arctic coastal environments. Seismic methods could be used to map and monitor saline permafrost at scales of geotechnical interests because of the ice-content dependencies of seismic properties. We have developed a comprehensive study of the ultrasonic P-wave properties (i.e., velocity and attenuation) of synthetic saline permafrost samples for a range of salinities and temperatures, and measurements conducted on a fine-grained permafrost core obtained from Barrow, Alaska. The resulting data consist of P-wave properties presented as functions of temperature and salinity. Notable observations include the following: P-wave velocities showed marked reductions in the presence of dissolved salts and complex variations resulting from the water-to-ice phase transitions; strong P-wave attenuation was present in the temperature intervals in which the samples were partially frozen. When presented as functions of ice saturation, the data sets lead us to two key findings: (1) neither a purely cementing nor a purely pore-filling model of the pore-scale distributions of ice could adequately fit the observed velocity data and (2) although the velocities increase monotonically with increasing ice saturations, P-wave attenuation reaches a maximum at intermediate ice saturations—contrary to the ordinary expectation of decreasing attenuation with increasing velocities. The observed ice-content dependencies of P-wave properties, along with the implications on the probable pore-scale distributions of ice, provide a valuable basis for rock-physics modeling, which in turn could facilitate seismic characterizations of saline permafrost.

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