Papers by Musa Maharramov
Proceedings, May 23, 2011
ABSTRACT
68th EAGE Conference and Exhibition incorporating SPE EUROPEC 2006, 2006
We describe a methodology for updating velocity models for depth imaging based on one-way wavefie... more We describe a methodology for updating velocity models for depth imaging based on one-way wavefield extrapolation. The method uses an objective function that optimizes focusing in the offset domain, or equivalently, gather flatness in the angle domain. We illustrate various aspects of the method with 2D synthetic and 3D data examples from an area exhibiting strong velocity contrasts due to thin carbonate layering in sediment.
The leading edge, May 1, 2018
Temperature and pressure changes associated with the cyclic steam stimulation (CSS) used in heavy... more Temperature and pressure changes associated with the cyclic steam stimulation (CSS) used in heavy oil production from sands are accompanied by significant deformation. Inversion of induced reservoir pore-pressure changes from deformation measurements may provide a potentially powerful reservoir-monitoring tool if the issues of measurement noise, uncertainty in model parameterization, and numerical accuracy and stability can be resolved. We discuss inverting injection-induced reservoir pressure changes from observable surface deformations using a linear poroelastostatic model of a heavy oil reservoir. We also present results of inversion from surface tilt measurements taken at a production site undergoing CSS. We demonstrate that a stable inversion of the reservoir pore-pressure change can be achieved from sparse and noisy surface tilt measurements using constrained regularized optimization. The results provide an insight into the heterogeneity of reservoir stimulation and could help with optimizing well locations and stimulation protocols.
Proceedings, Mar 6, 2017
Fluid movement in the subsurface and the associated changes in saturation translate into changes ... more Fluid movement in the subsurface and the associated changes in saturation translate into changes of the subsurface elastic parameters. Stress changes, whether due to fluid extraction/injection or deformation such as slips on preexisting faults, affect the elastic parameters as well. Detecting and inverting the imprint of changing subsurface elastic parameters on seismic data lies at the heart of time-lapse seismic imaging for reservoir monitoring. In this work we demonstrate that the recently proposed technique of simultaneous time-lapse full-waveform inversion with a model-difference regularization can be used to extract high-resolution information on magnitude and location of subsurface velocity and stress anomalies, potentially providing valuable input for reservoir monitoring and assessment of geohazards.
Geophysics, Nov 1, 2016
Compaction in the reservoir overburden can impact production facilities and lead to a significant... more Compaction in the reservoir overburden can impact production facilities and lead to a significant risk of well-bore failures. Prevalent practices of time-lapse seismic processing of 4D data above compacting reservoirs rely on picking time displacements and converting them into estimated velocity changes and subsurface deformation. This approach relies on prior data equalization and requires a significant amount of manual interpretation and quality control. We have developed methods for automatic detection of production-induced subsurface velocity changes from seismic data. We have evaluated a time-lapse inversion technique based on a simultaneous regularized full-waveform inversion (FWI) of multiple surveys. In our approach, baseline and monitor surveys are inverted simultaneously with a model-difference regularization penalizing nonphysical differences in the inverted models that are due to survey or computational repeatability issues. The primary focus of our work was the inversion of long-wavelength “blocky” changes in the subsurface model, and this was achieved using a phase-only FWI with a total-variation model-difference regularization. However, we have developed a multiscale extension of our method for recovering long- and short-wavelength production effects. We have developed a theoretical foundation of our method and analyzed its sensitivity to a realistic 1%–2% velocity deformation. The method was applied in a study of overburden dilation above the Gulf of Mexico Genesis field and recovered blocky negative-velocity anomalies above compacting reservoirs.
The leading edge, Dec 1, 2019
We demonstrate that a workflow combining emergent timelapse full-waveform inversion (FWI) and mac... more We demonstrate that a workflow combining emergent timelapse full-waveform inversion (FWI) and machine learning technologies can address the demand for faster time-lapse processing and analysis. During the first stage of our proposed workflow, we invert long-wavelength velocity changes using a tomographically enhanced version of multiparameter simultaneous reflection FWI with model-difference regularization. Short-wavelength changes are inverted during the second stage of the workflow by a specialized high-resolution image-difference tomography algorithm using a neural network. We discuss application areas for each component of the workflow and show the results of a West Africa case study.
Current wave-equation tomography techniques based on migrated image differences, such as those ob... more Current wave-equation tomography techniques based on migrated image differences, such as those observed in 4D data sets, use the image difference as a measure of velocity misfit. Computation of the objective function gradient is accomplished by the adjoint application of the derivative of the imaging operator to this image difference. In all techniques developed to date this process is carried out by computing the gradient over a relatively large number of depth steps, and then optimizing the objective function globally over the entire range. In this abstract, we extend this concept to compute the gradient and objective function locally, within several or even one depth step at a time. In principle, for objective functions that are sharply peaked around the global minimum, and have other minima elsewhere, this localization should reduce the possibility of falling into a false minimum, and significantly reduce the number of iterations required in the optimization. In addition, since the velocity is optimized in depth as the extrapolation proceeds, the method is significantly more immune to cycle-skipping at higher frequencies than global methods.
AGU Fall Meeting Abstracts, Dec 17, 2015
AVO is an important tool in the interpretation of seismic data. Azimuthal AVO models (AVAZ) have ... more AVO is an important tool in the interpretation of seismic data. Azimuthal AVO models (AVAZ) have been used to characterize fracture distributions and directions in HTI (Horizontal Transverse Isotropy) media. The main subject of this paper is a method for the stabilization of AVAZ parameters. We present an extension of the technique of Whitcombe, Dyce, McKenzie and Hoeber (2004) for gradient stabilization in the standard 2-term AVO model given by the Shuey equation to the case of Ruger and Tsvankin's (1997) azimuthal AVO analysis. We also investigate the estimated errors in the AVAZ model parameters with varying HTI isotropy plane direction for a selection of offset-azimuth distributions, including azimuthal sectors and Common Offset Vector (COV) classes. The application of the technique to WAZ land data from Algeria illustrates the use of the techniques. Azimuthal AVO: models and uncertainties Ruger and Tsvankin (1997) proposed a model for the dependence of the amplitude of a reflection event, R, on the shot-receiver azimuth, φ, and narrow angles of incidence, θ, for an isotropic half space over a HTI anisotropic half space, given by:
arXiv (Cornell University), May 19, 2012
We propose a computationally efficient technique for extrapolating seismic waves in an arbitrary ... more We propose a computationally efficient technique for extrapolating seismic waves in an arbitrary isotropic elastic medium. The method is based on factorizing the full elastic wave equation into a product of pseudo-differential operators. The method extrapolates displacement fields, hence can be used for modeling both pressure and shear waves. The proposed method can achieve a significant reduction in the cost of elastic modeling compared to the currently prevalent time-and frequency-domain numeric modeling methods and can contribute to making multicomponent elastic modeling part of the standard seismic processing work flow.
arXiv (Cornell University), Apr 30, 2013
This paper has evolved out of our previous work on static stress transfer, where we used the full... more This paper has evolved out of our previous work on static stress transfer, where we used the full-space elastostatic Green's tensor to compute the Coulomb stress transfer impact of the Landers earthquake on the Hector Mine event. In this work, we use the elastostatic Green's tensor for an arbitrary layered Earth model with free-surface boundary conditions to study the impact of elastic heterogeneity as well as source-fault slip and geometry on the stress transfer mechanism. Slip distribution and fault geometry of the source have a significant impact on the stress transfer, especially in case of spatially extended triggered events. Maximization of the Coulomb stress transfer function for known aftershocks provides a mechanism for inverting for the source event slip. Heterogeneity of the elastic earth parameters is shown to have a sizeable, but lower-magnitude, impact on the static stress transfer in 3D. The analysis is applied to Landers/Hector Mine and 100 small "aftershocks" of the Landers event. A computational toolkit is provided for the study of static stress transfer for arbitrary source and receiver faults in layered Earth.
arXiv (Cornell University), Feb 19, 2016
We present a powerful and easy-to-implement iterative algorithm for solving large-scale optimizat... more We present a powerful and easy-to-implement iterative algorithm for solving large-scale optimization problems that involve L1/total-variation (TV) regularization. The method is based on combining the Alternating Directions Method of Multipliers (ADMM) with a Conjugate Directions technique in a way that allows reusing conjugate search directions constructed by the algorithm across multiple iterations of the ADMM. The new method achieves fast convergence by trading off multiple applications of the modeling operator for the increased memory requirement of storing previous conjugate directions. We illustrate the new method with a series of imaging and inversion applications.
arXiv (Cornell University), Oct 26, 2014
arXiv (Cornell University), May 21, 2015
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Papers by Musa Maharramov