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121.
122.
岩石介质中多裂纹扩展相互作用及其贯通机制的数值模拟 总被引:14,自引:0,他引:14
运用岩石破裂过程分析RFPA^2D系统,通过对岩石试样中预置的一组右行右阶雁列式裂纹扩展过程的数值模拟,研究了非均匀岩石介中多裂纹扩展的相互作用模式及其贯通机制。数植模拟再现的受压混合型裂纹扩展过程中逐步演变的全场变形过程,以及与细观非均匀性有关的声发射和断续扩展模式的“岩桥”现象,清晰地揭示出多裂纹扩展的相互作用及其贯通机制。模拟结果说明,对于岩石这种地质介质而言,忽略其非均匀性影响,可能会掩盖岩石变形与破裂过程中的许多与非均匀性有关的特殊现象,包括声发射或微震模式、岩桥或雁行断裂等。 相似文献
123.
In many areas of the world, the presence of shallow high velocity, highly heterogeneous layers complicate seismic imaging of deeper reflectors. Of particular economic interest are areas where potentially hydrocarbon-bearing strata are obscured by layers of basalt. Basalt layers are highly reflective and heterogeneous. Using reflection seismic, top basalt is typified by a high-amplitude, coherent reflector with poor resolution of reflectors below the basalt, and even bottom basalt. Here, we present a new approach to the imaging problem using the pattern recognition abilities of a back-propagation Artificial Neural Network (ANN). ANNs are computational systems that attempt to mimic natural biological neural networks. They have the ability to recognize patterns and develop their own generalizations about a given data set. Back-propagation neural networks are trained on data sets for which the solution is known and tested on the data that are not previously presented to the ANN in order to validate the network result. We show that Artificial Neural Networks, due to their pattern recognition capabilities, can invert the medium statistics based on the seismic character. We produce statistically defined models involving a basalt analogous layer, and calculate full wavefield finite difference synthetic seismograms. We vary basalt layer thickness and source frequency to generate a synthetic model that produces seismic that is similar to real sub-basalt seismic, i.e. high amplitude top basalt reflector and the absence of base basalt and sub-basalt events. Using synthetic shot gathers, generated in a synthetic representation of the sub-basalt case, we can invert the velocity medium standard deviation by using an ANN. By inverting the velocity medium standard deviation, we successfully identified the transition from basalt to sub-basalt on the synthetic shot gathers. We also show that ANNs are capable of identifying the basalt to sub-basalt transition in the presence of incoherent noise. This is important for any future applications of this technique to the real-world seismic data, as this data is never completely noise-free. There is always a certain level of residual (noise remaining after initial noise filtering) environmental/ambient noise present on the recorded seismics, hence, neural network training with noise-free synthetic seismic is less than optimal. 相似文献
124.
Robert Corthsy Maria Helena Leite Denis E. Gill Bernard Gaudin 《Engineering Geology》2003,69(3-4):381-397
The objective of this paper is to demonstrate that accurate and reliable in situ stress measurements can be performed in soft rocks. A quick overview of the mechanical behaviour of soft rocks is presented. After reviewing stress measurement techniques that have been used in soft rocks, the modified doorstopper technique is presented and the advantages it has over other techniques in soft rocks are underlined. Results from laboratory simulations in controlled conditions show that the technique is reliable and accurate. It is then shown, through field applications in a potash mine in Brazil, in an underwater tunnel in shales in Canada and in an exploratory drift in molassic rocks of the French Alps, how the technique yields results that can sometimes be confirmed by field observations. 相似文献
125.
采用秩相关系数分析等方法,在层序地层等时框架内,定量研究体系域内砂、砾岩储层的纵向变化特征,建立体系域内5种储层非均质定量模式.由于沉积环境,沉积物供给,所经历的构造、成岩演化等方面的差异,储层在空间上表现出不同程度的非均质性.工区内沙3段自下而上划分为5个层序,其中,1层序中高水位体系域,主要发育弱非均质性储层,Ⅴ、Ⅱ层序中水进体系域,主要发育中等非均质储层,其余各层序体系域储层主要具强非均质性.总的来说,河流作用相对较强的高水位体系域,储层较水进体系域,储层的物性非均质性要强,最大洪泛面也是物性、非均质性转换面。 相似文献
126.
127.
Sedimentary deposits are often characterized by various distinct facies, with facies structure relating to the depositional
and post-depositional environments. Permeability (k) varies within each facies, and mean values in one facies may be several
orders of magnitude larger or smaller than those in another facies. Empirical probability density functions (PDFs) of log(k)
increments from multi-facies structures often exhibit properties well modeled by the Levy PDF, which appears unrealistic physically.
It is probable that the statistical properties of log(k) variations within a facies are very different from those between
facies. Thus, it may not make sense to perform a single statistical analysis on permeability values taken from a mix of distinct
facies. As an alternative, we employed an indicator simulation approach to generate large-scale facies distributions, and
a mono-fractal model, fractional Brownian motion (fBm), to generate the log(k) increments within facies. Analyses show that
the simulated log(k) distributions for the entire multi-facies domain produce apparent non-Gaussian log(k) increment distributions
similar to those observed in field measurements. An important implication is that Levy-like behavior is not real in a statistical
sense and that rigorous statistical measures of the log(k) increments will have to be extracted from within each individual
facies.
Electronic Publication 相似文献
128.
R. L. Dann M. E. Close L. Pang M. J. Flintoft R. P. Hector 《Hydrogeology Journal》2008,16(6):1177-1191
The combined use of pumping and tracer test data enabled the derivation of equivalent average hydraulic conductivities (Kavg) for each test in a heterogeneous channelized alluvial aquifer, whereas K values of the preferential flow paths were two orders of magnitude higher. Greater and earlier drawdown was generally observed along preferential flow lines in a pumping test, within an array of 21 wells. The study aim was to characterize hydraulic properties of a channelized aquifer system in New Zealand by combining tracer and pumping test data. Estimates were able to be made of the percentage of highly permeable channels within the profile (~1.2%), effective porosity that reflected the maximum fraction of highly permeable channels within the aquifer (?eff–pc ~0.0038), and flows through highly permeable channels (~98%) and the sandy gravel matrix material (~2%). Using ?eff–pc, a tracer test Kavg value (~93 m/day) was estimated that was equivalent to pumping test values (~100 m/day), but two orders of magnitude smaller than K calculated solely from transport through permeable channels (Kpc ~8,400 m/day). Derived K values of permeable and matrix material were similar to values derived from grain size distribution using the Kozeny-Carman equation. 相似文献
129.
Subsurface flows are affected by geological variability over a range of length scales. The modeling of well singularity in
heterogeneous formations is important for simulating flow in aquifers and petroleum reservoirs. In this paper, two approaches
in calculating the upscaled well index to capture the effects of fine scale heterogeneity in near-well regions are presented
and applied. We first develop a flow-based near-well upscaling procedure for geometrically flexible grids. This approach entails
solving local well-driven flows and requires the treatment of geometric effects due to the nonalignment between fine and coarse
scale grids. An approximate coarse scale well model based on a well singularity analysis is also proposed. This model, referred
to as near-well arithmetic averaging, uses only the fine scale permeabilities at well locations to compute the coarse scale
well index; it does not require solving any flow problems. These two methods are systematically tested on three-dimensional
models with a variety of permeability distributions. It is shown that both approaches provide considerable improvement over
a simple (arithmetic) averaging approach to compute the coarse scale well index. The flow-based approach shows close agreement
to the fine scale reference model, and the near-well arithmetic averaging also offers accuracy for an appropriate range of
parameters. The interaction between global flow and near-well upscaling is also investigated through the use of global fine
scale solutions in near-well scale-up calculations. 相似文献
130.
Regional evaluation of hydraulic properties in variably fractured rock using a hydrostructural domain approach 总被引:1,自引:1,他引:0
A hydrostructural domain approach was tested and validated in fractured bedrock aquifers of the Gulf Islands, British Columbia (BC), Canada. Relative potential hydraulic properties for three hydrostructural domains in folded and faulted sedimentary rocks were derived using stochastically generated fracture data and hybrid discrete fracture network-equivalent porous media (DFN-EPM) modelling. Model-derived relative potential transmissivity values show good spatial agreement with transmissivity values obtained from pumping tests at selected sites. A spatial pattern of increasing transmissivity towards the southeast along the island chain is consistent between both datasets. Cluster analysis on relative potential permeability values obtained from a larger dataset for the region identified four clusters with geometric means of 9?×?10?13, 4?×?10?13, 2?×?10–13, and 3?×?10–14 m2. The general trend is an increase in relative potential permeability toward the southeast, emulating the trends identified in the site-specific analyses. Relative potential permeability values increase with proximity to the hinge line of a regional northwest-trending asymmetric fault propagation fold structure, and with proximity to superimposed high-angle north- and northeast-trending brittle faults. The results are consistent with documented patterns of structurally controlled fluid flow and show promise for use in regional characterization of fractured bedrock aquifers. 相似文献