Inverting DAS data using energy conservation principles

2021 ◽  
pp. 1-32 ◽  
Author(s):  
Vladimir Kazei ◽  
Konstantin Osypov
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Energy Conservation ◽  
Energy Balancing ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Conservation Principles ◽  
Distributed Acoustic Sensing ◽  
To Come ◽  
Seismic Wavefield

Distributed acoustic sensing (DAS) technologies are now becoming widespread, in particular in Vertical Seismic Profiling (VSP). Being a spatially densely sampled recording of seismic wavefield, DAS data provides an extended measurement as compared with point geophone VSP. We developed a basic theory that enables intuitive geophysical understanding of DAS data using the concepts of kinetic and potential energy and their fluxes. We start by relating DAS and geophone measurements to potential energy and kinetic energy, correspondingly. We use this relationship and energy balancing along the well to come up with a scheme for inverting DAS and geophone wavefields for density and velocity simultaneously. Then, recognizing that it may be impractical to have both geophones and DAS, we propose a second inversion scheme that eliminates the need for geophones and uses upgoing and downgoing DAS wavefields instead. There is no need for first-break picking windowing the data and full DAS records can be utilized in both inversion schemes. We test the feasibility of these inversion schemes on 2D elastic synthetics.

scholarly journals GRAVITY HEATS THE UNIVERSE

2009 ◽  
Vol 18 (14) ◽  
pp. 2201-2207
Author(s):  
ADAM MOSS ◽  
DOUGLAS SCOTT
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Energy Conservation ◽  
Cosmic Microwave Background ◽  
Initial Conditions ◽  
Gravitational Instability ◽  
Simplified Model ◽  
Microwave Background ◽  
Average Temperature ◽  
The Universe

Structures in the Universe grew through gravitational instability from very smooth initial conditions. Energy conservation requires that the growing negative potential energy of these structures be balanced by an increase in kinetic energy. A fraction of this is converted into heat in the collisional gas of the intergalactic medium. Using a toy model of gravitational heating, we attempt to link the growth of structure in the Universe with the average temperature of this gas. We find that the gas is rapidly heated from collapsing structures at around z ~ 10, reaching a temperature > 106 K today, depending on some assumptions of our simplified model. Before that there was a cold era from z ~ 100 to ~10 in which the matter temperature was below that of the cosmic microwave background.

How to twist and turn a fiber: Performance modeling for optimal DAS acquisitions

2019 ◽  
Vol 38 (3) ◽  
pp. 226-231 ◽  
Author(s):  
Andreas Wuestefeld ◽  
Matt Wilks
Keyword(s):  
Strain Energy ◽  
Performance Modeling ◽  
Design Parameters ◽  
Target Area ◽  
Complex Velocity ◽  
Detection Thresholds ◽  
Seismic Profiling ◽  
Velocity Models ◽  
Vertical Seismic Profiling ◽  
Distributed Acoustic Sensing

The success of a distributed acoustic sensing (DAS) survey depends on strain energy impeding at favorable angles at most sections of the fiber. Although constrained to the path of the wellbore, there are various design parameters that can influence the recorded DAS amplitude. We present here a method to model the performance of DAS installations. We use precise raypath modeling in complex velocity models to determine ray incidence angles and show variations between different wrapping angles and detection thresholds. We then propose a way to evaluate the performance of the DAS acquisition design, and how to optimize processing, based on the percentage of DAS channels above a chosen amplitude threshold. For microseismic studies, the best wrapping angle of the fiber can be determined, which may be defined as covering the target area most homogeneously. For vertical seismic profiling projects, surface shot positions can be evaluated for their predicted recorded energy.

scholarly journals On Fulfillment of Energy Conservation Law in Theory of Elastic Waves V. V. Nevdakh1)

2021 ◽  
Vol 20 (2) ◽  
pp. 161-167
Author(s):  
V. V. Nevdakh
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Energy Conservation ◽  
Elastic Wave ◽  
Total Energy ◽  
Elastic Deformation ◽  
Sound Wave ◽  
Elastic Waves ◽  
Conservation Law ◽  
Energy Conservation Law

In accordance with the energy conservation law, the total energy of a closed physical system must remain constant at any moment of time. The energy of a traveling elastic wave consists of the kinetic energy in the oscillating particles of the medium and the potential energy of  its elastic deformation. In the existing theory of elastic waves, it is believed that the kinetic and potential energy densities of a traveling wave without losses  are the same at any moment of time and vary according to the same law. Accordingly, the total energy density of such wave is different at various moment of time, and only its time-averaged value remains constant. Thus, in the existing theory of elastic waves, the energy conservation law is not fulfilled. The purpose of this work is to give a physically correct description of these waves. A new description of a sound wave in an ideal gas has been proposed and it is based on the use of a wave equation system for perturbing the oscillation velocity of gas particles, which determines their kinetic energy, and for elastic deformation, which determines their potential energy. It has been shown that harmonic solutions describing the oscillations of the gas particles velocity perturbation and their elastic deformation, which are phase shifted by p/2, are considered as physically correct solutions of such equations system for a traveling sound wave. It has been found that the positions of the kinetic and potential energy maxima in the elastic wave, described by such solutions, alternate in space every quarter of the wavelength. It has been established that every quarter of a period in a wave without losses, the kinetic energy is completely converted to potential and vice versa, while at each spatial point of the wave its total energy density is the same at any time, which is consistent with the energy conservation law. The energy flux density of such traveling elastic wave is described by the expression for the Umov vector. It has been concluded that such traveling sound wave without losses  in an ideal gas can be considered as a harmonic oscillator.

Vertical seismic profiling using distributed acoustic sensing in a hydrofrac treatment well

2014 ◽  
Author(s):  
Sudhish K. Bakku* ◽  
Michael Fehler ◽  
Peter Wills ◽  
Jeff Mestayer ◽  
Albena Mateeva ◽  
...  
Keyword(s):  
Acoustic Sensing ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Distributed Acoustic Sensing

Borehole Seismic: Essential Contributions Over the Oilfield Lifecycle

2021 ◽  
Author(s):  
Rajeev Kumar ◽  
Pierre Bettinelli
Keyword(s):  
Hydraulic Fracturing ◽  
Real Time ◽  
Depth Information ◽  
Acoustic Sensing ◽  
Seismic Profiling ◽  
Production Phase ◽  
Vertical Seismic Profiling ◽  
Wide Range ◽  
Distributed Acoustic Sensing ◽  
Borehole Seismic

Abstract During the evolution of the petroleum industry, surface seismic imaging has played a critical role in reservoir characterization. In the early days, borehole seismic (BHS) was developed to complement surface seismic. However, in the last few decades, a wide range of BHS surveys has been introduced to cater to new and unique objectives over the oilfield lifecycle. In the exploration phase, vertical seismic profiling (VSP) provides critical time-depth information to bridge time indexed subsurface images to log/reservoir properties in depth. This information can be obtained using several methods like conventional wireline checkshot or zero-offset vertical seismic profiling (ZVSP), seismic while drilling (SWD) or distributed acoustic sensing (DAS) techniques. SWD is a relatively new technique to record real-time data using tool deployed in the bottomhole assembly without disturbing the drilling. It helps to improve decision making for safer drilling especially in new areas in a cost-effective manner. Recently, a breakthrough technology, distributed acoustic sensing (DAS), has been introduced, where data are recorded using a fiber-optic cable with lots of saving. ZVSP also provides several parameters like, attenuation coefficient (Q), multiples prediction, impedance, reflectivity etc., which helps with characterizing the subsurface and seismic reprocessing. In the appraisal phase, BHS applications vary from velocity model update, anisotropy estimation, well- tie to imaging VSPs. The three-component VSP data is best suited for imaging and amplitude variation with offset (AVO) due to several factors like less noise interference due to quiet downhole environment, higher frequency bandwidth, proximity to the reflector, etc. Different type of VSP surveys (offset, walkaway, walkaround etc.) were designed to fulfill objectives like imaging, AVO, Q, anisotropy, and fracture mapping. In the development phase, high-resolution images (3D VSP, walkaway, or crosswell) from BHS surveys can assist with optimizing the drilling of new wells and, hence reduce costs. it can help with landing point selection, horizontal section placement, and refining interpretation for reserve calculation. BHS offers a wide range of surveys to assist the oilfield lifecycle during the production phase. Microseismic monitoring is an industry-known service to optimize hydraulic fracturing and is the only technique that captures the induced seismicity generated by hydraulic fracturing and estimate the fracture geometry (height, width, and azimuth) and in real time. During enhanced oil recovery (EOR) projects, BHS can be useful to optimize the hydrocarbon drainage strategies by mapping the fluid movement (CO2, water, steam) using time-lapse surveys like walkaway, 3D VSP and/or crosswell. DAS has brought a new dimension to provide vital information on injection or production evaluation, leak detection, flow behind tubing, crossflow diagnosis, and cement evaluation during production phase. This paper highlights the usage of BHS over the lifecycle of the oilfield.

scholarly journals Wireline distributed acoustic sensing allows 4.2 km deep vertical seismic profiling of the Rotliegend 150 °C geothermal reservoir in the North German Basin

Solid Earth ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 521-537
Author(s):  
Jan Henninges ◽  
Evgeniia Martuganova ◽  
Manfred Stiller ◽  
Ben Norden ◽  
Charlotte M. Krawczyk
Keyword(s):  
Elevated Temperatures ◽  
Volcanic Rocks ◽  
Vertical Component ◽  
Geothermal Reservoir ◽  
Fiber Optic Sensor ◽  
Acoustic Sensing ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Recorded Data ◽  
Distributed Acoustic Sensing

Abstract. We performed so-far-unprecedented deep wireline vertical seismic profiling at the Groß Schönebeck site with the novel method of distributed acoustic sensing (DAS) to gain more detailed information on the structural setting and geometry of the geothermal reservoir, which is comprised of volcanic rocks and sediments of Lower Permian age. During the survey of 4 d only, we acquired data for 61 source positions using hybrid wireline fiber-optic sensor cables deployed in two 4.3 km deep, already existing wells. While most of the recorded data have a very good signal-to-noise ratio, individual sections of the profiles are affected by characteristic coherent noise patterns. This ringing noise results from incomplete coupling of the sensor cable to the borehole wall, and it can be suppressed to a large extent using suitable filtering methods. After conversion to strain rate, the DAS data exhibit a high similarity to the vertical component data of a conventional borehole geophone. We derived accurate time–depth relationships, interval velocities, and corridor stacks from the recorded data. Based on integration with other well data and geological information, we show that the top of a porous and permeable sandstone interval of the geothermal reservoir can be identified by a positive reflection event. Overall, the sequence of reflection events shows a different character for both wells explained by lateral changes in lithology. The top of the volcanic rocks has a somewhat different seismic response in both wells, and no clear reflection event is obvious at the postulated base of the volcanic rocks, so that their thickness cannot be inferred from individual reflection events in the seismic data alone. The DAS method enabled measurements at elevated temperatures up to 150 ∘C over extended periods and led to significant time and cost savings compared to deployment of a conventional borehole geophone string. This wireline approach finally suggests significant implications for observation options in old wells for a variety of purposes.

scholarly journals Incorporating the Work Done by Vertical Density Fluxes in Both Kinetic and Thermal Energy Conservation Equations to Satisfy Total Energy Conservation

2019 ◽  
Vol 58 (2) ◽  
pp. 213-230 ◽  
Author(s):  
Jielun Sun
Keyword(s):  
Thermal Expansion ◽  
Energy Balance ◽  
Kinetic Energy ◽  
Potential Energy ◽  
Energy Conservation ◽  
Total Energy ◽  
Thermal Energy ◽  
Temporal Variations ◽  
Vertical Density ◽  
Total Energy Conservation

AbstractConservation of total, kinetic, and thermal energy in the atmosphere is revisited, and the derived thermal energy balance is examined with observations. Total energy conservation (TEC) provides a constraint for the sum of kinetic, thermal, and potential energy changes. In response to air thermal expansion/compression, air density variation leads to vertical density fluxes and potential energy changes, which in turn impact the thermal energy balance as well as the kinetic energy balance due to the constraint of TEC. As vertical density fluxes can propagate through a large vertical domain to where local thermal expansion/compression becomes negligibly small, interactions between kinetic and thermal energy changes in determining atmospheric motions and thermodynamic structures can occur when local diabatic heating/cooling becomes small. The contribution of vertical density fluxes to the kinetic energy balance is sometimes considered but that to the thermal energy balance is traditionally missed. Misinterpretation between air thermal expansion/compression and incompressibility for air volume changes with pressure under a constant temperature would lead to overlooking important impacts of thermal expansion/compression on air motions and atmospheric thermodynamics. Atmospheric boundary layer observations qualitatively confirm the contribution of potential energy changes associated with vertical density fluxes in the thermal energy balance for explaining temporal variations of air temperature.

Vertical Seismic Profiling via Coiled Tubing-Conveyed Distributed Acoustic Sensing

2019 ◽  
Author(s):  
Andreas Ellmauthaler ◽  
William Palacios ◽  
Michel LeBlanc ◽  
Mark Willis ◽  
George Knapo
Keyword(s):  
Acoustic Sensing ◽  
Seismic Profiling ◽  
Vertical Seismic Profiling ◽  
Coiled Tubing ◽  
Distributed Acoustic Sensing
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