An integrated approach to lithologic inversion—Part I: Theory

For the complex problem of lithologic inversion a new formalism is proposed, using a spatial distribution of seismic velocities ([Formula: see text]) and densities (ρ) as input. At each subsurface grid point, the inversion result consists of the most likely lithotype (gas, sand, shale, etc.) together with its related litho parameters (frame strength, porosity, etc.). The inversion method is based on the Bayesian theory of parameter estimation, allowing specification of inaccuracies in the input and the incorporation of geological knowledge. An important advantage of the proposed inversion method is that for each practical situation the necessary accuracy of [Formula: see text], [Formula: see text] and ρ can be predetermined to distinguish between specific lithotypes or to estimate a specific litho parameter with a prespecified accuracy. For instance, inversion results show that water saturation can only be estimated for an unrealistic accurate input. On the other hand, for the estimation of porosities it is generally sufficient to have compressional velocities available with a realistic accuracy.

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Safety of medical activities as an integrated problem

Vestnik Roszdravnadzora ◽

10.35576/2070-7940-2019-2019-6-30-35 ◽

2019 ◽

Vol 2019 (6) ◽

pp. 30-35

Author(s):

Алан Карсанов ◽

Alan Karsanov ◽

Наталья Полунина ◽

Natal'ya Polunina

Keyword(s):

Integrated Approach ◽

Complex Problem ◽

Healthcare Organization ◽

Structural Components ◽

Medical Activity ◽

Staff Motivation ◽

Medical Technologies ◽

Systemic Nature ◽

Clinical Risks

The combined nature of the factors that threaten the patient and the complex subordination of many clinical risks are the basis of the authors' perception of the safety of medical activity (SMA) as a complex problem, the solution of which should be sought in improving managerial measures of a systemic nature. As structural components of an integrated approach to providing SMA, measures should be implemented aimed at increasing staff motivation, at increasing the level of medical communications, at introducing modern diagnostic and medical technologies, at improving the control and administrative component based on the industrial model of healthcare organization.

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Direct elastic properties to resistivity transforms

Geophysics ◽

10.1190/geo2015-0388.1 ◽

2016 ◽

Vol 81 (5) ◽

pp. IM109-IM118

Author(s):

Dimitrios Economou ◽

Behzad Alaei

Keyword(s):

Water Saturation ◽

Data Sets ◽

Seismic Velocities ◽

Even Start ◽

Novel Approach ◽

Multivariate Nonlinear Regression ◽

Subsurface Resistivity ◽

Relationship Of ◽

Norwegian Continental Shelf ◽

Good Agreement

Numerous publications have dealt with estimations of resistivity from elastic parameters and vice versa. Attempts have been made in the cross-property relationship of elastic and electric properties, in particular, velocity to resistivity using different parameters, such as porosity and water saturation. These types of transforms are currently used to predict background seismic velocities and resistivities, or even start models for seismic or controlled source electromagnetic (CSEM) inversions. However, they are not reliable predictors because they depict the regional elastic or electric variations with limited accuracy. We present a novel approach for the development of models capable of estimating the regional subsurface resistivity based on information from regional wells and seismic inversions. We apply multivariate nonlinear regression on data derived from regional wells and seismic inversions and subsequently produced an estimation of subsurface horizontal resistivity that could be either used as a direct hydrocarbon indicator or provide a constraint on the horizontal resistivity in anisotropic CSEM inversions. We have verified the validity of the approach using two data sets from the Norwegian continental shelf. We found very good agreement between the borehole-measured and predicted resistivity.

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An Accurate Jacobian Matrix with Exact Zoeppritz for Elastic Moduli of Dry Rock

Applied Sciences ◽

10.3390/app9245485 ◽

2019 ◽

Vol 9 (24) ◽

pp. 5485

Author(s):

Xiaobo Liu ◽

Jingyi Chen ◽

Fuping Liu ◽

Zhencong Zhao

Keyword(s):

Jacobian Matrix ◽

Incidence Angle ◽

Inversion Method ◽

Seismic Velocities ◽

Amplitude Variation ◽

Amplitude Variation With Offset ◽

Shear Moduli ◽

Partial Derivatives ◽

Solid Matrices ◽

Derivatives Of

Seismic velocities are related to the solid matrices and the pore fluids. The bulk and shear moduli of dry rock are the primary parameters to characterize solid matrices. Amplitude variation with offset (AVO) or amplitude variation with incidence angle (AVA) is the most used inversion method to discriminate lithology in hydrocarbon reservoirs. The bulk and shear moduli of dry rock, however, cannot be inverted directly using seismic data and the conventional AVO/AVA inversions. The most important step to accurately invert these dry rock parameters is to derive the Jacobian matrix. The combination of exact Zoeppritz and Biot–Gassmann equations makes it possible to directly calculate the partial derivatives of seismic reflectivities (PP-and PS-waves) with respect to dry rock moduli. During this research, we successfully derive the accurate partial derivatives of the exact Zoeppritz equations with respect to bulk and shear moduli of dry rock. The characteristics of these partial derivatives are investigated in the numerical examples. Additionally, we compare the partial derivatives using this proposed algorithm with the classical Shuey and Aki–Richards approximations. The results show that this derived Jacobian matrix is more accurate and versatile. It can be used further in the conventional AVO/AVA inversions to invert bulk and shear moduli of dry rock directly.

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Bayesian inversion of CSEM and magnetotelluric data

Geophysics ◽

10.1190/geo2010-0298.1 ◽

2012 ◽

Vol 77 (1) ◽

pp. E33-E42 ◽

Cited By ~ 37

Author(s):

Arild Buland ◽

Odd Kolbjørnsen

Keyword(s):

Prior Knowledge ◽

Inversion Method ◽

Earth Model ◽

Magnetotelluric Data ◽

Inversion Result ◽

Electromagnetic Data ◽

Magnetic Components ◽

Resistivity Model ◽

Frequency Components ◽

Inversion Procedure

We have developed a Bayesian methodology for inversion of controlled source electromagnetic (CSEM) data and magnetotelluric (MT) data. The inversion method provided optimal solutions and also the associated uncertainty for any sets of electric and magnetic components and frequencies from CSEM and MT data. The method is based on a 1D forward modeling method for the electromagnetic (EM) response for a plane-layered anisotropic earth model. The inversion method was also designed to invert common midpoint (CMP)-sorted data along a 2D earth profile assuming locally horizontal models in each CMP position. The inversion procedure simulates from the posterior distribution using a Markov chain Monte Carlo (McMC) approach based on the Metropolis-Hastings algorithm. The method that we use integrates available geologic prior knowledge with the information in the electromagnetic data such that the prior model stabilizes and constrains the inversion according to the described knowledge. The synthetic examples demonstrated that inclusion of more data generally improves the inversion results. Compared to inversion of the inline electric component only, inclusion of broadside and magnetic components and an extended set of frequency components moderately decreased the uncertainty of the inversion. The results were strongly dependent on the prior knowledge imposed by the prior distribution. The prior knowledge about the background resistivity model surrounding the target was highly important for a successful and reliable inversion result.

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Pressure‐dependent seismic response of fractured rock

Geophysics ◽

10.1190/1.1778232 ◽

2004 ◽

Vol 69 (4) ◽

pp. 885-897 ◽

Cited By ~ 17

Author(s):

Evgenii A. Kozlov

Keyword(s):

Pore Pressure ◽

Effective Stress ◽

Water Saturation ◽

Fractured Rock ◽

Gas Production ◽

Fluid Replacement ◽

Seismic Velocities ◽

Amplitude Versus Offset ◽

Model Predictions ◽

Avo Attributes

Effects of external stress and pore pressure variations on the seismic signature of fractured rocks remain of interest to geoscientists and practicing geophysicists. Commonly, the effects are modeled theoretically, assuming fracture faces to be rough surfaces contacting each other via the surface asperities. The model proposed here differs from other models of this kind in that (1) fracture roughness is described by a single parameter and (2) a controlled degree of hydraulic connectivity between fractures and equant pores is introduced. This adds to the model's convenience and makes it applicable to a wide variety of reservoirs. The model predictions of seismic velocities in fractured rock at variable stress are consistent with experimental data. For fixed effective stress, the model predictions coincide with those obtained using the model with ellipsoidal fractures of certain average aspect ratio and the same fracture porosity. Apart from known effects, the model introduced predicts an amplification of the stress variation influence on fracturing‐induced anisotropy with an increase of connected equant porosity, a decrease of VP/VS with effective stress, and implicit frequency dependence of the VP/VS relation. It is also shown that amplitude versus offset (AVO) anomalies caused by fluid replacement can be seriously distorted if the fluid replacement is accompanied by significant variations of pore pressure, as, for example, at intense gas production. Neglecting these effects can lead to erroneous conclusions on shear modulus dependence on the pore fluid type. Qualitatively, in rocks with azimuthally aligned fracturing, the increase of effective stress affects AVO gradient in about the same way as the increase of water saturation parameter Vw. In contrast, the AVO intercept is not affected by variations of effective stress, while fluid replacement effect on the intercept is significant. Potentially, this can help distinguish the effects of pore pressure variations and fluid replacement on the AVO attributes.

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AN INTEGRATED PETROPHYSICAL WORKFLOW TO GENERATING FLUID SUBSTITUTED LOGS FOR AVO CHARACTERISATION—GIPSY AND NORTH GIPSY FIELDS CASE STUDY, NORTH WEST SHELF, AUSTRALIA

The APPEA Journal ◽

10.1071/aj01026 ◽

2002 ◽

Vol 42 (1) ◽

pp. 477

Author(s):

D.L Clarke ◽

A.P Clare

Keyword(s):

Field Study ◽

Water Saturation ◽

Integrated Approach ◽

Rock Properties ◽

Intrinsic Permeability ◽

North West ◽

Consistent Model ◽

Original Field ◽

Elastic Rock

As part of a multi-well field study an integrated petrophysical workflow was developed to include the generation of fluid substituted logs for AVO characterisation.The workflow relied upon the construction of a multimineral model that best approximated the actual mineral content of the reservoir. Any limitations or assumptions were noted and taken into account when creating the multi-mineral model. Other petrophysical results were derived from the same model to validate its consistency such as intrinsic permeability, porosity, water saturation, etc. Iteration between the model and the results was required until a consistent model was achieved.The estimation of an intrinsic permeability log was based upon the k-Lambda method that uses the multimineral model and porosities.The estimation of a shear slowness log and the fluid substituted logs was based upon elastic rock properties derived from the multi-mineral model and the acquired compressional slowness log and bulk density log. This integrated approach provides a higher confidence in the derived results, which are then used as input into the reservoir model, thereby improving the reserve calculations.The interdependence of each derived result on the same input multi-mineral model ensures consistency and predictability in a complex geological environment, which captures all available information.The method is demonstrated with the Gipsy–1 and North Gipsy–1 wells, which were part of the original field study.

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Investigation of fluid effects on seismic responses through a physical modeling experiment

Interpretation ◽

10.1190/int-2020-0116.1 ◽

2020 ◽

pp. 1-38

Author(s):

Chao Xu ◽

Pinbo Ding ◽

Bangrang Di ◽

Jianxin Wei

Keyword(s):

Seismic Data ◽

Physical Modeling ◽

Seismic Velocity ◽

Water Saturation ◽

P Wave ◽

Seismic Velocities ◽

Seismic Responses ◽

Modeling Experiment ◽

Seismic Reflections ◽

Tight Rocks

We investigated fluid effects on seismic responses using seismic data from a physical modeling experiment. Eight cubic samples with cavities quantitatively filled with air, oil, and water and sixteen non-fluid samples were set within a physical model. Both pre-stack and post-stack seismic responses of the samples were analyzed to quantitatively investigate the fluid effect on the seismic response. It was indicated that fluids could cause detectable changes in both pre-stack and post-stack seismic responses for tight rocks. At first, fluids filled within samples caused changes in pre-stack seismic responses. Visible differences could be detected between angle gathers of the samples filled with air, oil, and water. For the base reflections, the amplitudes at large angles of the air-filled and oil-filed samples are obviously stronger than those of the water-filled sample. In addition, the presence of fluids within samples led to significant changes in post-stack seismic reflections. For samples with similar P-wave impedances to the background, we found strong seismic reflections for the fluid samples and weak or even no reflections for the non-fluid samples. There was notable interference between the top and base reflections for the fluid samples while there was none for the non-fluid samples. Seismic velocities were estimated using the two-way travel times between the top and base reflections. The estimated seismic velocity gently declined with increasing water saturation until 90%. When the water saturation was more than 90%, the seismic velocity showed a steep increase.

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Poststack Seismic Inversion Using A Patch-based Gaussian Mixture Model

Geophysics ◽

10.1190/geo2020-0185.1 ◽

2021 ◽

pp. 1-102

Author(s):

Lingqian Wang ◽

Hui Zhou ◽

Hengchang Dai ◽

Bo Yu ◽

Wenling Liu ◽

...

Keyword(s):

Gaussian Mixture Model ◽

Mixture Model ◽

Acoustic Impedance ◽

Structural Information ◽

Gaussian Mixture ◽

Seismic Inversion ◽

Inversion Method ◽

Borehole Data ◽

Inversion Result ◽

Band Limited

Seismic inversion is a severely ill-posed problem, because of noise in the observed record, band-limited seismic wavelets, and the discretization of a continuous medium. Regularization techniques can impose certain characteristics on inversion results based on prior information in order to obtain a stable and unique solution. However, it is difficult to find an appropriate regularization to describe the actual subsurface geology. We propose a new acoustic impedance inversion method via a patch-based Gaussian mixture model (GMM), which is designed using available well logs. In this method, firstly, the non-local means (NLM) method estimates acoustic impedance around wells in terms of the similarity of local seismic records. The extrapolated multichannel impedance are then decomposed into impedance patches. Using patched data rather than a window or single trace for training samples to obtain the GMM parameters, which contain local lateral structural information, can provide more impedance structure details and enhance the stability of the inversion result. Next, the expectation maximization (EM) algorithm is used to obtain the GMM parameters from the patched data. Finally, we apply the alternating direction method of multipliers (ADMM) to solve the conventional Bayesian inference illustrating the role of regularization, and construct the objective function using the GMM parameters. Therefore, the inversion results are compliant with the local structural features extracted from the borehole data. Both synthetic and field data tests validate the performance of our proposed method. Compared with other conventional inversion methods, our method shows promise in providing a more accurate and stable inversion result.

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Seismic velocities and electrical resistivity of recent volcanics and their dependence on porosity, temperature, and water saturation

Geophysics ◽

10.1190/1.1441148 ◽

1981 ◽

Vol 46 (10) ◽

pp. 1415-1422 ◽

Cited By ~ 3

Author(s):

A. W. Ibrahim ◽

George V. Keller

Keyword(s):

Water Saturation ◽

Strong Dependence ◽

Electric Resistivity ◽

P Wave ◽

Seismic Velocities ◽

Fine Grained ◽

Wave Velocities ◽

Electrical Resistivities ◽

P Wave Velocities ◽

Water Saturated

Variation of P‐wave velocities and electrical resistivities of several suites of water‐saturated recent volcanics was investigated. Both P‐velocities and resistivities exhibited strong dependence on porosity. Resistivity was also dependent upon degree of water saturation and temperature. P‐wave velocities, while showing a strong dependence on porosity, appear to be independent of water saturation and temperature. Volcanics, in general, exhibit higher resistivities compared to other igneous rocks and sediments. Electric resistivity of fine‐grained basalts is anomalously low, probably due to higher content of disseminated iron. Pyroclastics and volcanic breccia, on the other hand, exhibit higher resistivities in relation to fine‐grained basalts.

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Emission rate and chemical state estimation by 4-dimensional variational inversion

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-3749-2007 ◽

2007 ◽

Vol 7 (14) ◽

pp. 3749-3769 ◽

Cited By ~ 182

Author(s):

H. Elbern ◽

A. Strunk ◽

H. Schmidt ◽

O. Talagrand

Keyword(s):

Data Assimilation ◽

Sulphur Dioxide ◽

Emission Rate ◽

Grid Point ◽

Chemical State ◽

Inversion Method ◽

Initial Value ◽

The University ◽

Skill Evaluation ◽

Data Assimilation Technique

Abstract. This study aims to assess the potential and limits of an advanced inversion method to estimate pollutant precursor sources mainly from observations. Ozone, sulphur dioxide, and partly nitrogen oxides observations are taken to infer source strength estimates. As methodology, the four-dimensional variational data assimilation technique has been generalised and employed to include emission rate optimisation, in addition to chemical state estimates as usual objective of data assimilation. To this end, the optimisation space of the variational assimilation system has been complemented by emission rate correction factors of 19 emitted species at each emitting grid point, involving the University of Cologne mesoscale EURAD model. For validation, predictive skills were assessed for an August 1997 ozone episode, comparing forecast performances of pure initial value optimisation, pure emission rate optimisation, and joint emission rate/initial value optimisation. Validation procedures rest on both measurements withheld from data assimilation and prediction skill evaluation of forecasts after the inversion procedures. Results show that excellent improvements can be claimed for sulphur dioxide forecasts, after emission rate optimisation. Significant improvements can be claimed for ozone forecasts after initial value and joint emission rate/initial value optimisation of precursor constituents. The additional benefits applying joint emission rate/initial value optimisation are moderate, and very useful in typical cases, where upwind emission rate optimisation is essential. In consequence of the coarse horizontal model grid resolution of 54 km, applied in this study, comparisons indicate that the inversion improvements can rest on assimilating ozone observations only, as the inclusion of NOx observations does not provide additional forecast skill. Emission estimates were found to be largely independent from initial guesses from emission inventories, demonstrating the potential of the 4D-var method to infer emission rate improvements. The study also points to the need for improved horizontal model resolution to more efficient use of NOx observations.

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