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1.
In mineral resource evaluation a careful analysis and assessment of the geology, assay data and structural data is required. One important question is where to position the exploration boreholes, another is what method to use when analyzing the grade in the collected material. Here, a challenge of this type is whether one should analyze the collected core samples with accurate and expensive lab equipment or a simpler hand-held meter. A dataset of about 2000 oxide observations is available, along with relevant explanatory variables, from a deposit in Norway. A Gaussian geostatistical model is used to predict the grade parameter on block support. To improve the predictions, several new boreholes are planned, giving 265 additional samples. The associated uncertainty reduction is evaluated, and a resource evaluation is performed with and without the planned data. Then the value of information of the planned data is computed, using assumed costs, recovery rates and revenues. The data acquired with the hand-held meter has almost the same value as the more expensive acquisition strategy, given that the already established correlation between the two datasets is valid. 相似文献
2.
Karl J. Eidsvik 《Boundary-Layer Meteorology》2008,127(1):153-172
Numerical simulations of geophysical flows have to be done on very sparse grids. Nevertheless, flows over moderately sloped
hills can be predicted quite accurately as long as the near ground vertical resolution is reasonably dense. Recirculation
flows behind steeper hills are associated with slow convergence towards grid independent integrations, but even then moderately
stratified flows of this type can be predicted usefully accurately. For better horizontal grids than about half the hill-height Δx
1/H ≈ 0.5 or so, separation and recirculating domains are predicted with an error factor comparable to 0.3. The characteristic
wavelength of lee waves is predicted more accurately while the lee wave amplitude and the maximum turbulence intensity in
recirculating domains are underestimated by factors comparable to 0.3. Strongly stratified flows may be associated with hydraulic
transitions and even this is predicted on quite coarse grids, up to say Δx
1/H ≈ 0.5. However, the details of such flows turn out to be predicted with considerable errors also on high-resolution grids.
Inaccurate modelling of stratified turbulence is a main contributor to this error. 相似文献
3.
A numerical model based upon fundamental principles, a standard (k, ) turbulence closure and a finite element integration technique, is applied to separated flows over hills. Predictions are compared to experimental data from a wind tunnel. Although few-equation turbulence closures have been shown to have obvious deficiencies with respect to comparable flows, the model predicts remarkably accurately, without coefficient adjustments of any kind. Even the turbulent intensity is predicted quite realistically. 相似文献
4.
State estimation in high dimensional systems remains a challenging part of real time analysis. The ensemble Kalman filter addresses this challenge by using Gaussian approximations constructed from a number of samples. This method has been a large success in many applications. Unfortunately, for some cases, Gaussian approximations are no longer valid, and the filter does not work so well. In this paper, we use the idea of the ensemble Kalman filter together with the more theoretically valid particle filter. We outline a Gaussian mixture approach based on shrinking the predicted samples to overcome sample degeneracy, while maintaining non-Gaussian nature. A tuning parameter determines the degree of shrinkage. The computational cost is similar to the ensemble Kalman filter. We compare several filtering methods on three different cases: a target tracking model, the Lorenz 40 model, and a reservoir simulation example conditional on seismic and electromagnetic data. 相似文献
5.
Jo Eidsvik Geetartha Dutta Tapan Mukerji Debarun Bhattacharjya 《Mathematical Geosciences》2017,49(4):467-491
Value of information analysis is useful for helping a decision maker evaluate the benefits of acquiring or processing additional data. Such analysis is particularly beneficial in the petroleum industry, where information gathering is costly and time-consuming. Furthermore, there are often abundant opportunities for discovering creative information gathering schemes, involving the type and location of geophysical measurements. A consistent evaluation of such data requires spatial modeling that realistically captures the various aspects of the decision situation: the uncertain reservoir variables, the alternatives and the geophysical data under consideration. The computational tasks of value of information analysis can be daunting in such spatial decision situations; in this paper, a regression-based approximation approach is presented. The approach involves Monte Carlo simulation of data followed by linear regression to fit the conditional expectation expression that is needed for value of information analysis. Efficient approximations allow practical value of information analysis for the spatial decision situations that are typically encountered in petroleum reservoir evaluation. Applications are presented for seismic amplitude data and electromagnetic resistivity data, where one example includes multi-phase fluid flow simulations. 相似文献
6.
The Value of Information in Spatial Decision Making 总被引：1，自引：1，他引：0
Experiments performed over spatially correlated domains, if poorly chosen, may not be worth their cost of acquisition. In
this paper, we integrate the decision-analytic notion of value of information with spatial statistical models. We formulate
methods to evaluate monetary values associated with experiments performed in the spatial decision making context, including
the prior value, the value of perfect information, and the value of the experiment, providing imperfect information. The prior
for the spatial distinction of interest is assumed to be a categorical Markov random field whereas the likelihood distribution
can take any form depending on the experiment under consideration. We demonstrate how to efficiently compute the value of
an experiment for Markov random fields of moderate size, with the aid of two examples. The first is a motivating example with
presence-absence data, while the second application is inspired by seismic exploration in the petroleum industry. We discuss
insights from the two examples, relating the value of an experiment with its accuracy, the cost and revenue from downstream
decisions, and the design of the experiment. 相似文献
7.
Data on the acceleration of an oscillating cylinder in water are analysed by a Kalman extended filter. A hydrodynamical forcing model based upon Morison's equation appears to be reasonable and drag estimation appears simple using simulated data. Estimation based upon real data gives an average drag coefficient decreasing with the oscillation amplitude. An assymetric drag coefficient variation over the oscillation period is estimated. 相似文献
8.
Local and Spatial Joint Frequency Uncertainty and its Application to Rock Mass Characterisation 总被引：1，自引：1，他引：0
Stability is a key issue in any mining or tunnelling activity. Joint frequency constitutes an important input into stability
analyses. Three techniques are used herein to quantify the local and spatial joint frequency uncertainty, or possible joint
frequencies given joint frequency data, at unsampled locations. Rock quality designation is estimated from the predicted joint
frequencies. The first method is based on kriging with subsequent Poisson sampling. The second method transforms the data
to near-Gaussian variables and uses the turning band method to generate a range of possible joint frequencies. The third method
assumes that the data are Poisson distributed and models the log-intensity of these data with a spatially smooth Gaussian
prior distribution. Intensities are obtained and Poisson variables are generated to examine the expected joint frequency and
associated variability. The joint frequency data is from an iron ore in the northern part of Norway. The methods are tested
at unsampled locations and validated at sampled locations. All three methods perform quite well when predicting sampled points.
The probability that the joint frequency exceeds 5 joints per metre is also estimated to illustrate a more realistic utilisation.
The obtained probability map highlights zones in the ore where stability problems have occurred. It is therefore concluded
that the methods work and that more emphasis should have been placed on these kinds of analyses when the mine was planned.
By using simulation instead of estimation, it is possible to obtain a clear picture of possible joint frequency values or
ranges, i.e. the uncertainty. 相似文献
9.
10.
Karl J. Eidsvik 《Boundary-Layer Meteorology》1985,32(2):103-132
The best quality wind data from the Norwegian sector of the North Sea, consisting of 3662 20-min time series measured at the top of the Statfjord A drilling derrick, are analyzed. Identification of Autoregressive wind models with Akaike's AIC and Achwarz's BIC measures appears to give rather arbitrary results. Spectral estimation with FFT- and AIC-identified AR-methods give almost identical results in the mean. At the higher frequencies (% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaaaa!36D7!\[f\] > 10–2 s–1) the spectrum is estimated to follow the usual inertial subrange law with little variability. The small-scale turbulent intensity is estimated to be very low, even in hurricane conditions. Comparatively, the low-frequency (% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOzaaaa!36D7!\[f\] ~ 10–3 s–1) fluctuations are more energetic than expected. None of the chosen low-frequency characteristica appear to be significantly linearly correlated to the available mean weather variables. However, some nonlinear relations appear to exist. 相似文献