12999638
Descrição
Quiz por Aiman Zamri, atualizado more than 1 year ago
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Criado por Aiman Zamri
mais de 6 anos atrás
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Questão 1
Questão
Which of the following are valid guidelines, or rules of thumb, for constructing variograms?
Responda
-
a. it is best to start with isotropic variograms before proceeding to investigation of anisotropic variograms
-
b. estimation of variograms should begin with large tolerances, and should be decreased as needed to achieve a clearly defined structure
-
c. use half the maximum possible distance within a region of interest as the maximum lag distance at the which the variogram is calculated
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d. at least 15 to 20 data pairs are needed for a reliable estimate of the variogram for a given lag distance
Questão 2
Questão
Which of the following are true statements about variogram models?
Responda
-
a. the spherical model is probably the most commonly used model
-
b. any linear combination of nugget, exponential, spherical and Gaussian models is a valid variogram model
-
c. the simplest model is the exponential model
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d. the Gaussian model is more robust than the exponential model
Questão 3
Questão
To model the condition of geometric anisotropy, we have to use the same combination of linear models in both directions except with different sills.
Responda
- True
- False
Questão 4
Questão
Which of the following are reasons why we restrict the number of samples to a smaller neighborhood for estimation using kriging?
Responda
-
a. Because kriging requires inverting a matrix, using a large number of data points can require an excessive amount of memory and computation time requirements
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b. If too many sample points are used, there is a possibility the matrix will become close to singular
-
c. If we use data points at large distances, we may have to extrapolate beyond the available data in the variogram model
-
d. Restricting the search to closer samples results in a more representative estimate, because of local variations due to a lack of stationarity in practice
-
e. Use of sample points farther away tend to screen sample points that are closer, reducing the accuracy of the estimation
Questão 5
Questão
The maximum size of the search neighborhood for kriging should be based on the range of the variogram model.
Responda
- True
- False
Questão 6
Questão
Which of the following are true statements about kriging cross validation?
Responda
-
a. Cross validation involves the estimation of values at unsampled locations so they can be compared with values at sampled locations
-
b. Cross validation can identify glaring errors in estimation, but it does not guarantee a successful kriging operation
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c. "Jackknifing" is the most common version of cross validation
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d. Heteroscedasticity of error variance is a desirable outcome of a cross validation exercise
Questão 7
Questão
Which of the following are true statements about kriging?
Responda
-
a. The maximum kriging error variance is the data variance
-
b. Simple kriging is the most popular kriging procedure
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c. Kriging is a weighted average of values at sampled locations
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d. Kriging weights assigned to sample values are directly proportional to the covariances among the sample points
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e. Kriging weights assigned to sample values are directly proportional to the covariances between sample points and the unsampled location
Questão 8
Questão
Ordinary kriging overcomes which of the following problems that can occur with simple kriging?
Responda
-
a. the true global mean is rarely known
-
b. all of the other choices
-
c. the local mean within the search neighborhood may vary over the region of interest
-
d. the assumption of first-order stationarity may not be strictly valid
Questão 9
Questão
In ordinary kriging, the sum of the weights is forced to be zero.
Responda
- True
- False
Questão 10
Questão
Because λ0 is forced to be zero in ordinary kriging, there are only n unknowns to solve for instead of n+1 unknowns as for simple kriging.
Responda
- True
- False
Questão 11
Questão
Weights can be negative in ordinary kriging.
Responda
- True
- False
Questão 12
Questão
The presence of a high nugget effect reduces spatial information, which results in higher error variance.
Responda
- True
- False
Questão 13
Questão
One common application of cross variograms is using high-density seismic data to help estimate permeability at undrilled well locations.
Responda
- True
- False
Questão 14
Questão
Which of the following are true statements about cross variograms?
Responda
-
a. the cross covariance is symmetric.
-
b. the cross variogram is symmetric.
-
c. the cross variogram is always non-negative.
-
d. estimation of the cross variogram requires that both variable values be available at locations ui and ui+L.
Questão 15
Questão
In variogram modeling for two variables, the x variogram, y variogram, and x-y cross variogram must all have the same linear combination of structures and must all have the same sill.
Responda
- True
- False
Questão 16
Questão
In variogram modeling with multiple variables and anisotropy, if all the variograms cannot be modeled well, it is critical to model the cross variograms well while the other models can be sacrificed somewhat.
Responda
- True
- False
Questão 17
Questão
The cross variogram provides a quantitative measure of the spatial relationship between two variables.
Responda
- True
- False
Questão 18
Questão
Additional information from the covariable in cokriging should reduce the error variance as compared to just kriging of the primary variable.
Responda
- True
- False
Questão 19
Questão
Simple cokriging with one secondary variable requires the inversion of a (n+m+2)-size matrix, where n is the number of samples of the primary variable and m is the number of samples of the covariable.
Responda
- True
- False
Questão 20
Questão
Collocated cokriging requires the covariable sample to be available at every location where the primary variable is to be estimated, which increases the matrix size compared to regular (non-collocated) cokriging.
Responda
- True
- False
Questão 21
Questão
Which of the following factors, if favorable, support use of cokriging?
Responda
-
a. there is a physical basis for the relationship between the primary variable and covariable
-
b. the primary variable is considerably undersampled
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c. the relationship between the primary variable and covariable is strong
-
d. the covariable has been used successfully in the past for estimation of the primary variable
-
e. the primary variable and covariable are linearly related
Questão 22
Questão
The kriging error variance is a good measure of the local uncertainty at the unsampled location.
Responda
- True
- False
Questão 23
Questão
The estimated value from kriging is dependent on the values of the surrounding samples, while the error variance is independent.
Responda
- True
- False
Questão 24
Questão
Estimation by kriging does not reproduce extreme values observed in the sample data because the weights associated with individual samples are nearly always less than one, thus reducing the effects of extreme values.
Responda
- True
- False
Questão 25
Questão
Which of the following characterize the differences between conventional estimation and conditional simulation techniques?
Responda
-
a. Conventional estimation does not reproduce extreme values in the sample data, while conditional simulation is able to.
-
b. Conventional estimation does not provide a good estimation of local uncertainty, while conditional simulation is able to.
-
c. Conventional estimation preserves the spatial relationship among the estimated values while conditional simulation does not.
Questão 26
Questão
A variogram based on estimated values from kriging will have higher sill than the variogram based on sample data.
Responda
- True
- False
Questão 27
Questão
One of the advantages of conditional simulation is that if we create multiple equiprobable realizations and these realizations correctly represent the multivariate distribution, they will bound the true realization.
Responda
- True
- False
Questão 28
Questão
A major disadvantage of grid-based simulation methods is that they do not honor the spatial relationships of reservoir properties.
Responda
- True
- False
Questão 29
Questão
A major disadvantage of object-based simulation methods is that it is difficult to condition data at individual well locations.
Responda
- True
- False
Questão 30
Questão
Estimation using conventional kriging techniques is dependent on the order in which unsampled locations are visited, while simulation using sequential conditional simulation methods is independent of the order in which unsampled locations are visited.
Responda
- True
- False
Questão 31
Questão
In the sequential simulation technique, in addition to selecting the sampled points within the search neighborhood, previously simulated points within the search neighborhood are also selected.
Responda
- True
- False
Questão 32
Questão
The ability to closely reproduce the basic univariate statistics of the conditioning data is one of the best properties of sequential Gaussian simulation.
Responda
- True
- False
Questão 33
Questão
The five-step sequential simulation process is as follows: (1) model variograms, (2) transform the original data into a new domain, (3) determine a random path to visit all the unsampled locations, (4) sequentially estimate values at the unsampled locations, and (5) back-transform the values to the original domain.
Responda
- True
- False
Questão 34
Questão
Grid-based conditional simulation methods employ kriging as part of the simulation process.
Responda
- True
- False
Questão 35
Questão
If full cokriging is used in sequential cosimulation, the following variograms are required for modeling:
Responda
-
a. cross-variograms for all pairs of attributes in the original domain
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b. variograms for each attribute in the transformed domain
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c. cross-variograms for all pairs of attributes in the transformed domain
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d. cross-variograms for all pairs of attributes for which there are dependencies in the original domain
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e. cross-variograms for all pairs of attributes for which there are dependencies in the transformed domain
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f. variograms for each attribute in the original domain
Questão 36
Questão
In a typical reservoir characterization involving cosimulation, geological facies are dependent on porosity and permeability while seismic attributes are dependent on facies and porosity.
Responda
- True
- False
Questão 37
Questão
The primary advantage of sequential cosimulation is its ability to honor the local relationships between multiple attributes, as well as the individual spatial relationships of the multiple attributes.
Responda
- True
- False
Questão 38
Questão
In sequential cosimulation of multiple attributes, at each unsampled location, all the unknown attributes are simulated in sequential order from least independent to most independent to preserve their relationships.
Responda
- True
- False
Questão 39
Questão
If cokriging is used in cosimulation, then the local relationships among the attributes must be linear in the transformed domain.
Responda
- True
- False
Questão 40
Questão
Geostatistical estimation, or kriging, is based on minimizing the variance between the estimation point and the available samples.
Responda
- True
- False
Questão 41
Questão
The variability of a regionalized variable is always zero for distance zero.
Responda
- True
- False
Questão 42
Questão
Estimating the values at unsampled points requires knowledge about the relationship between sampled and unsampled locations.
Responda
- True
- False
Questão 43
Questão
Geological features are randomly distributed in a spatial context.
Responda
- True
- False
Questão 44
Questão
Reservoirs are heterogeneous and have directions of continuity because of their specific depositional, structural, and digenetic histories.
Responda
- True
- False
Questão 45
Questão
Two different reservoir models with similar statistics can be very different in geological features.
Responda
- True
- False
Questão 46
Questão
For a given direction, spatial covariance depends only on the distance and not location.
Responda
- True
- False
Questão 47
Questão
By assuming stationarity, we can use observations from one part of the reservoir to construct variograms for other parts.
Responda
- True
- False
Questão 48
Questão
A Variogram is a measure of similarity between two random variables.
Responda
- True
- False
Questão 49
Questão
The range in variogram is the distance at which the variogram value becomes constant with respect to lag.
Responda
- True
- False
Questão 50
Questão
Kriging allows for production uncertainty analysis.
Responda
- True
- False
Questão 51
Questão
Both Kriging and simulation methods can honor hard data.
Responda
- True
- False
Questão 52
Questão
Both Kriging and simulation methods can honor the local variogram model.
Responda
- True
- False
Questão 53
Questão
Relative to Kriging, the sequential Gaussian simulation is locally accurate.
Responda
- True
- False
Questão 54
Questão
If the random path in sequential Gaussian simulation is not changed, the generated realizations will be identical.
Responda
- True
- False
Questão 55
Questão
Similar to variance, covariance is defined in units that depend on the units of x and y but the correlation coefficient is dimensionless, and its value always falls between the limits of 1 and -1.
Responda
- True
- False
Questão 56
Questão
When the square of the correlation coefficient is used to describe the relationship between two variables, whether the two variables are negatively or positively related cannot be exhibited, but it is a common way in describing the "goodness of fit" in a linear regression between two variables.
Responda
- True
- False
Questão 57
Questão
A Q-Q plot is a scattered plot based on ranked pair data, so two samples with equal size are always required.
Responda
- True
- False
Questão 58
Questão
SGEMS Objects are files with numerical information and there are two types, Data and Grid, both of which specify the location in the file.
Responda
- True
- False
Questão 59
Questão
Geostatistics represents a set of mathematical tools which have deterministic or stochastic components, may represent different types of data at different scales, but cannot fill the interwell space properly.
Responda
- True
- False
Questão 60
Questão
The SGEMS grid(s) has to be specified before attempting any processing that will result in the generation of a grid variable such as Kriging.
Responda
- True
- False
Questão 61
Questão
In SGEMS, grids can only be displayed in graphical form and grid values are stored in binary form.
Responda
- True
- False
Questão 62
Questão
The semivariogram is related to the covariance by the difference between the variance and the spatial covariance regardless of the stationarity of the mean.
Responda
- True
- False
Questão 63
Questão
The spatial covariance always starts with a zero value and increases as the lag distance between the two values increases.
Responda
- True
- False
Questão 64
Questão
Kriging is a form of linear regression and works best for estimation inside a convex hull of the data.
Responda
- True
- False
Questão 65
Questão
The most frequently used types of semi-variogram models are Gaussian, Spherical, and Exponential models.
Responda
- True
- False
Questão 66
Questão
A semivariogram model is:
Responda
-
A polynomial expression representing sample variance
-
A mathematical approximation of sample variability
-
A determinate trend in sample values
-
None of the above
Questão 67
Questão
Assume we have two porosity models generated with the same parameters using Gaussian and exponential models. Identify the variogram model for porosity map given in Figure (1).
Image:
1 (binary/octet-stream)
Responda
-
Gaussian Model
-
Exponential Model
Questão 68
Questão
Assume we have two porosity models generated with the same parameters using Gaussian and exponential models. Identify the variogram model for porosity map given in Figure (2).
Image:
1 (binary/octet-stream)
Responda
-
Gaussian Model
-
Exponential Model
Questão 69
Questão
For the following three basic variogram models, which one has the highest growth at the origin? (i.e. the biggest slope at origin)
Image:
2 (binary/octet-stream)
Responda
-
1
-
2
-
3
Questão 70
Questão
For the following three basic variogram models, which one has the lowest growth at the origin? (i.e. the smallest slope at origin)
Image:
2 (binary/octet-stream)
Responda
-
1
-
2
-
3
Questão 71
Questão
Conditional simulation reproduces the value and location of observations.
Responda
- True
- False
Questão 72
Questão
Kriging method accounts for local variations.
Responda
- True
- False
Questão 73
Questão
Kriging estimation method is appropriate for flow simulation.
Responda
- True
- False
Questão 74
Questão
Sequential Gaussian simulation requires transformation of data to normal scores.
Responda
- True
- False
Questão 75
Questão
Geo-statistical simulation method cannot use secondary data.
Responda
- True
- False
Questão 76
Questão
For collocated cokriging method, the secondary data points have to be at the same locations as the primary data points.
Responda
- True
- False
Questão 77
Responda
-
5.87
-
3.14
-
2.73
-
None of the above
Questão 78
Responda
-
3.64
-
2.07
-
2.23
-
3.78
Questão 79
Questão
In the following drawing, we know the attributes at S1, S2, and S3. What is Z(S0)?
As shown, we know the distances in between, e.g. the distance between S1 and S2 is 20. We also know the variogram model.
Image:
5 (binary/octet-stream)
Responda
-
21.69
-
21.83
-
22.83
-
23.34
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