Acoustic signature of fluid substitution in reservoir rocks

2020 ◽  
Author(s):  
Christian David ◽  
Joël Sarout ◽  
Christophe Barnes ◽  
Jérémie Dautriat ◽  
Lucas Pimienta
Keyword(s):  
Wave Velocity ◽  
Water Injection ◽  
P Wave ◽  
Rock Properties ◽  
Fluid Distribution ◽  
Fluid Substitution ◽  
Ultrasonic Monitoring ◽  
Reservoir Rocks ◽  
Water Imbibition ◽  
P Wave Velocity

<p>During the production of hydrocarbon reservoirs, EOR operations, storage of CO2 underground or geothermal fluid exchanges at depth, fluid substitution processes can lead to significant changes in rock properties which can be captured from the variations in seismic waves attributes. In the laboratory, fluid substitution processes can be investigated using ultrasonic monitoring. </p><p>The motivation of our study was to identify the seismic attributes of fluid substitution in reservoir rocks through a direct comparison between the variation in amplitude, velocity, spectral content, energy, and the actual fluid distribution in the rocks. Different arrays of ultrasonic P-wave sensors were used to record at constant time steps the waveforms during fluid substitution experiments. Two different kinds of experiments are presented: (i) water injection experiments in oil-saturated samples under stress in a triaxial setup mimicking EOR operations, (ii) spontaneous water imbibition experiments at room conditions.</p><p>In the water injection tests on a poorly consolidated sandstone saturated with oil and loaded at high deviatoric stresses, water weakening triggers mechanical instabilities leading to the rock failure. The onset of such instabilities can be followed with ultrasonic monitoring either in the passive mode (acoustic emissions recording) or in the active mode (P wave velocity survey).</p><p>In the water imbibition experiments, a methodology based on the analytical signal and instantaneous phase was designed to decompose each waveform into discrete wavelets associated with direct or reflected waves. The energy carried by the wavelets is very sensitive to the fluid substitution process: the coda wavelets are impacted as soon as imbibition starts and can be used as a precursor for remote fluid substitution. It is also shown that the amplitude of the first P-wave arrival is impacted by the upward moving fluid front before the P-wave velocity is. Several scenarios are discussed to explain the decoupling between P wave amplitude and velocity variations during fluid substitution processes.</p>

Studying the correlation of rock properties with P-wave velocity index in dry and saturated conditions

2019 ◽  
Vol 169 ◽  
pp. 49-57 ◽  
Author(s):  
Mohammad Rezaei ◽  
Pouya Koureh Davoodi ◽  
Iraj Najmoddini
Keyword(s):  
Wave Velocity ◽  
P Wave ◽  
Rock Properties ◽  
P Wave Velocity

Fluid substitution: Estimating changes in VP without knowing VS

Geophysics ◽  
1995 ◽  
Vol 60 (6) ◽  
pp. 1750-1755 ◽  
Author(s):  
Gary Mavko ◽  
Christina Chan ◽  
Tapan Mukerji
Keyword(s):  
Wave Velocity ◽  
P Wave ◽  
Large Set ◽  
Fluid Substitution ◽  
S Wave ◽  
Shear Moduli ◽  
P Wave Velocity ◽  
The Common ◽  
Common Situation ◽  
Rock Bulk

Two methods are presented for estimating the change of seismic P‐wave velocity that accompanies pore fluid changes in a rock in the common situation when S‐wave velocity is unknown. In contrast, Gassmann’s relation operates on the rock bulk modulus, which can only be calculated when both [Formula: see text] and [Formula: see text] are measured. The first method operates directly on the P‐wave modulus and is equivalent to replacing the bulk moduli of the rock and mineral in Gassmann’s relation with the corresponding P‐wave moduli. The second method uses a graphical construction to estimate the decomposition of the measured P‐wave modulus into bulk and shear moduli, which then allows the conventional Gassmann’s formula to be used. When applied to a large set of sandstone data, the predictions of both methods, computed with [Formula: see text] only, are within a few percent of the Gassmann’s relation, using both [Formula: see text] and [Formula: see text].

AN ROCK-PHYSICS-BASED COMPLEX PORE-FLUID-DISTRIBUTION MODEL TO SEISMIC DYNAMICAL RESPONSE

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1437-1442
Author(s):  
CHENGYUAN ZHANG ◽  
XIAOYAN LIU ◽  
DAOYING XI ◽  
QUANSHENG LIU
Keyword(s):  
Wave Velocity ◽  
Seismic Reflection ◽  
Rock Physics ◽  
Pore Fluid ◽  
P Wave ◽  
Reservoir Rock ◽  
Fluid Distribution ◽  
Dynamical Response ◽  
Distribution Models ◽  
P Wave Velocity

It is very important to know how the reservoir rock and its fluid properties are linked to seismic dynamic response. Literatures show that there are a variety of rock-physics models such as the most famous Biot-Gassmann equation aimed at the relationship between seismic velocity and liquid saturation. Most of these models make a fundamental assumption of one fluid phase or homogeneous phase within the pore volume. In this paper, we discuss possible seismic velocities change in a two immiscible pore fluids (i.e. water-gas) saturated reservoir with patchy saturation distribution. It is found that P-wave velocity of a reservoir rock with the same saturation but different pore fluid distribution exhibits noticeable variation and deviate overall from Gassmann's results. We use DEM theory to explain this phenomenon. It belongs to hybrid approach in rock-physics modeling and can handle complex pore-fluid-distribution cases. Based on the modeling study, we found that various fluid-distribution models may significantly affect the modulus and P-wave velocity. The seismic reflection time, amplitude and phase characteristics may change with the choice of pore-fluid-distribution models. Relevant rock mechanical experiments indicate the same trend of seismic responses. It also be proven by seismic reservoir monitoring experiment (time lapse study) that incorrect conclusion may be drawn about the strong seismic reflection in pure Utsira Sand if the microscopic pore-fluid-distribution effects are not taken into account.

Impact of change in pore-fill material on P-wave velocity

Geophysics ◽  
2014 ◽  
Vol 79 (6) ◽  
pp. D399-D407 ◽  
Author(s):  
Nishank Saxena ◽  
Gary Mavko
Keyword(s):  
Shear Modulus ◽  
Wave Velocity ◽  
P Wave ◽  
Exact Equation ◽  
Fluid Substitution ◽  
Seismic Velocities ◽  
S Wave ◽  
Wave Velocities ◽  
Fill Material ◽  
P Wave Velocity

The problem of predicting the change in seismic velocities (P-wave and S-wave) upon the change in pore-fill material properties is commonly known as substitution. For isotropic rocks, P- and S-wave velocities are fundamentally linked to the effective P-wave and shear moduli. The change in the S-wave velocity or shear modulus upon fluid substitution can be predicted with Gassmann’s equations starting only with the initial S-wave velocity. However, predicting changes in P-wave velocity or the P-wave modulus requires knowledge of the initial P- and S-wave velocities. We initiated a rigorous derivation of the P-wave modulus for fluid and solid substitution in monomineralic isotropic rocks for cases in which an estimate of the S-wave velocity or shear modulus is not available. For the general case of solid substitution, the exact equation for the P-wave modulus depends on parameters that are usually unknown. However, for fluid substitution, fewer parameters are required. As Poisson’s ratio increases for the mineral in the rock frame, the dependence of exact substitution on these unknown parameters decreases. As a result, in the absence of shear velocity, P-wave modulus fluid substitution can, for example, be performed with higher confidence for rocks with a calcite or dolomite frame than it can for rocks with quartz frame. We evaluated a recipe for applying the new P-wave modulus fluid substitution. This improves on existing work and is recommended for practice.

scholarly journals Experimental Investigation of the Relationship between the P-Wave Velocity and the Mechanical Properties of Damaged Sandstone

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Qi-Le Ding ◽  
Shuai-Bing Song
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Young’S Modulus ◽  
Wave Velocity ◽  
Young's Modulus ◽  
P Wave ◽  
Rock Properties ◽  
High Temperature Treatment ◽  
P Wave Velocity ◽  
The Relationship

To obtain an improved and more accurate understanding of the relationship between the P-wave velocity and the mechanical properties of damaged sandstone, uniaxial compression tests were performed on sandstone subjected to different high-temperature treatments or freeze-thaw (F-T) cycles. After high-temperature treatment, the tests showed a generally positive relationship between the P-wave velocity and mechanical characteristics, although there were many exceptions. The mechanical properties showed significant differences for a given P-wave velocity. Based on the mechanical tests after the F-T cycles, the mechanical properties and P-wave velocities exhibited different trends. The UCS and Young’s modulus values slightly decreased after 30, 40, and 50 cycles, whereas both an increase and a decrease occurred in the P-wave velocity. The UCS, Young’s modulus, and P-wave velocity represent different macrobehaviors of rock properties. A statistical relationship exists between the P-wave velocity and mechanical properties, such as the UCS and Young’s modulus, but no mechanical relationship exists. Further attention should be given to using the P-wave velocity to estimate and predict the mechanical properties of rock.

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