碳酸盐岩缝洞体宽度估算方法

定量估算缝洞体宽度是碳酸盐岩缝洞型油气藏勘探开发过程中的一个实际问题.在根据空间子波理论推导横向地质体HTA(水平道振幅)函数的基础上,定量分析了偏移成像确定地质体宽度的能力并发展了一种估算碳酸盐岩缝洞体宽度的方法.将此方法应用于物理正演模拟数据,获得了理想的结果.     

A tracer dilution method for fracture characterization in bedrock wells

This investigation was undertaken to develop an integrated method of downhole fracture characterization using a tracer. The method presented can be used to locate water-bearing fractures that intersect the well, to determine the ambient fracture flow rate and hydraulic head, and to calculate fracture transmissivity. The method was tested in two fractured crystalline bedrock wells located at the University of Connecticut in Storrs. The method entails injecting a tracer (uranine dye) into the well, while at the same time water is pumped out of the well. After steady-state conditions are reached, a borehole tracer concentration profile is developed. The dilution of the tracer is used to locate the inflowing fractures and to determine their flow rate. The fracture flow rate, plus the drawdown in the well, is then used to determine the fracture hydraulic head, transmissivity, and ambient flow rate.     

A method for estimating specimen tangent stiffness for hybrid simulation

Researchers have long recognized the importance and potential benefits of utilizing the tangent stiffness matrix of a test specimen in hybrid simulations employing implicit and mixed‐integration schemes. However, the computation of the tangent stiffness matrix during testing has proved to be challenging, particularly for test specimens with more than one degree of freedom (dof). This paper presents a new methodology that is more straightforward and simpler than existing techniques for computing the tangent stiffness matrix of a multi‐dof test specimen. The proposed method is combined with the operator‐splitting method (OSM), and the capabilities, advantages and limitations of the new formulation are demonstrated through several examples. The accuracy, stability, and error propagation characteristics of the modified OSM are also studied theoretically as well as numerically. The research results show that the proposed algorithm provides results that are better than those produced via the regular OSM alone, especially for damped structures undergoing highly inelastic behavior during testing. Copyright © 2008 John Wiley & Sons, Ltd.     

A method for the interpolation of nonnegative functions with an application to contaminant load estimation

The objective of this work is to extend kriging, a geostatistical interpolation method, to honor parameter nonnegativity. The new method uses a prior probability distribution based on reflected Brownian motion that enforces this constraint. The work presented in this paper focuses on interpolation problems where the unknown is a function of a single variable (e.g. time), and is developed both for the case with and without measurement error in the available data. The algorithms presented for conditional simulations are computationally efficient, particularly in the case with no measurement error. We present an application to the interpolation of dissolved arsenic concentration data from the North Fork of the Humboldt River, Nevada.     

一种基于有限动态源的烈度估计方法

首先,基于地震烈度与震级和震中距或震源距的经验关系,考虑实际地震断层的有限性以及几何学和运动学特性,提出了一种基于有限动态源模型的烈度预估方法.然后,利用数值实验讨论了体现几何学和运动学特性的参数的作用以及断层的倾角和破裂速度的影响;最后,将这种方法应用于近年来发生的两次破坏性地震,讨论了这种方法的实用性与不足之处.在实时获取破裂过程图像成为可能的今天,用这种方法预估烈度对于震后救援十分重要.     

估计和比较地震动潜在破坏势的综合评述

如何估计和比较地震动对结构的破坏作用，一直是国内外抗震研究中的一个至关重要的问题。本主要篇幅用于介绍这一领域迄今所取得的成果并作了简单的评述，并在此基础上，提出了一种可用来比较地震动潜在破坏势的综合评估法，提出该方法的目的并不在意去确定什么量更能代表地震动在潜在破坏势，而只是在考察现有的各种被认为能代表地震动的潜在破坏势的各种参数基础上，考虑采用什么方法才能更合理地判定和比较地震动的破坏势，为此本将通常作为地震动潜在破坏势的地震动参数分成两类：一类为直接由地震动本身得到的参数，另一类为地震动通过结构反应得到的参数，并分别对此进行了讨论和分析，在此基础上得出了一种在目前可认为是研究地震动潜在破坏势押送为合理的方法-地震动潜在破坏势综合评价法。     

A method of estimating the stress exponent in the flow law for rocks using fold shape

On the basis of experiment and theory, we expect rocks to deform in a linear fashion when diffusive processes control deformation, and nonlinearly in most other situations. The geometric characteristics of buckle folds in layered materials are dependent on rheological parameters, and in particular depend strongly on the stress exponent,n _L , of the stiff layers involved. Thus, information about the deformation rocks have undergone and their rheological state during deformation can be obtained by studying fold shapes and strain distributions. This is important because there is uncertainty in extrapolating laboratory-derived flow laws to the very slow natural strain rates and large strains found in nature.We have studied the development of buckle folds in linear and nonlinear materials using finite-element modeling, and interpolated the numerical results to construct plots relating several geometric parameters to variations in power-law exponent,n _L , and viscosity ratio,m, of layer to matrix. Such plots allow for a comparison of the results of numerical models with data for many natural and experimentally-produced folds, and there is consistency among the data for folds produced in physical models, using both linear and nonlinear materials and the numerical simulations. data for folds from the Appalachian Mountains, the Alps and elsewhere, however, suggest high values ofn _L in the flow laws for a number of rock types. The unexpectedly high estimates ofn _L suggest that other factors, such as strain softening or anisotropy, may influence fold shape, and thus complicate the estimation of the rheological properties of rocks.     

A time-domain induced-polarization method for estimating permeability in a shaly sand reservoir

It is known that the time‐domain induced‐polarization decay curve for a shaly sand reservoir depends on the pore structure of the reservoir, and this curve can be used to estimate permeability, which is a determining factor in making production decisions in the petroleum industry. Compared with NMR logging tools, induced polarization has several advantages, such as a deep depth of investigation and a high signal‐to‐noise ratio. The purpose of this paper is to establish an appropriate model using induced polarization to estimate the permeability. The curve can be modelled as a weighted superposition of exponential relaxations. The plot of weight versus the relaxation time constant is defined as the relaxation time spectrum. Induced‐polarization decay‐curve measurements were performed on 123 samples from the Daqing oilfield using a four‐electrode technique. A singular‐value decomposition method was used to transform the induced‐polarization decay data into a spectrum. Different models to estimate the permeability were discussed. The results of the research indicate that the induced‐polarization measurements greatly improve the statistical significance of permeability correlations. Compared with the traditional forms, Aφ^C and AF^C, the forms, AT^Bφ^C and AT^BF^C, have lower error factors, where T, Φ and F are the geometric mean time constant of the induced‐polarization relaxation time spectrum, the porosity and the resistivity formation factor, respectively, and A, B and C are constants. The mean time constant is the decisive parameter in the permeability estimation and it is not completely independent of the resistivity formation factor. The additional use of the porosity and the resistivity formation factor leads to an appreciable improvement. It is concluded that this new model will make it possible to estimate the permeability of a shaly sand reservoir downhole.     

A method for estimating sediment budgets of washover deposits using digital terrain models

Washover fans are located on small barriers in fetch-limited micro-tidal coastal environments in Denmark. These washover fans are formed during high-energy storm events and we present a method to quantify their volumes and to estimate sediment exchanges between washover fans and their adjacent morphologies. We use high resolution digital terrain models (DTMs) based on light detection and ranging (LiDAR) data. We have delineated landforms using known methods of scale analysis and geomorphometric classification. We quantified volumes of the delineated landforms and estimated the related sediment budgets. These computed volumes were compared using different pre-depositional surfaces. Finally, we assessed the sediment exchange and associated sources of sediments of the washover fans. We applied a scale analysis to determine suitable DTM resolution and focal statistics window size as input to a geomorphometric classification analysis. Landform areas and landforms were delineated using morphometric threshold values, and volumes and sediment budgets of the delineated landforms were computed using different assumptions to define the pre-depositional surface. Resulting washover fan volumes were validated against digital elevation model (DEM) of difference (DoD) derived volumes. Sediment budgets were derived from representative volumes of the washover fans and adjacent berms. We show that quantification of washover features derived from DTMs, using geomorphometric analysis is feasible and that the presented approach provides estimates of washover deposit volumes with an accuracy between 1% and 28% compared to control volumes. © 2021 John Wiley & Sons, Ltd.     

Characterization of groundwater contaminant source using Bayesian method

Contaminant source identification in groundwater system is critical for remediation strategy implementation, including gathering further samples and analysis, as well as implementing and evaluating different remediation plans. Such problem is usually solved with the aid of groundwater modeling with lots of uncertainty, e.g. existing uncertainty in hydraulic conductivity, measurement variance and the model structure error. Monte Carlo simulation of flow model allows the input uncertainty onto the model predictions of concentration measurements at monitoring sites. Bayesian approach provides the advantage to update estimation. This paper presents an application of a dynamic framework coupling with a three dimensional groundwater modeling scheme in contamination source identification of groundwater. Markov Chain Monte Carlo (MCMC) is being applied to infer the possible location and magnitude of contamination source. Uncertainty existing in heterogonous hydraulic conductivity field is explicitly considered in evaluating the likelihood function. Unlike other inverse-problem approaches to provide single but maybe untrue solution, the MCMC algorithm provides probability distributions over estimated parameters. Results from this algorithm offer a probabilistic inference of the location and concentration of released contamination. The convergence analysis of MCMC reveals the effectiveness of the proposed algorithm. Further investigation to extend this study is also discussed.     

基于轴向位移的钢支撑疲劳损伤评估方法

在罕遇地震下,框架-中心支撑结构中的钢支撑常因局部屈曲位置的低周疲劳开裂而过早退出工作。本文在焊接工字形钢支撑低周疲劳试验研究基础上,提出了一种可用于框架-中心支撑体系非线性动力时程分析中钢支撑疲劳损伤评估的经验方法,并给出了相关步骤的算法流程。研究结果表明:本文方法以钢支撑轴向位移为损伤参量,能实时估算在随机位移荷载下钢支撑的低周疲劳累积损伤发展,并与试验结果吻合较好。     

A new method for determining weathering rates in weathering pits

Determining the rates of rock weathering is difficult because, firstly, the weathering rate of rocks is usually so slow that it is difficult to measure; secondly, it is also difficult to determine the start time and duration of weathering. The Shanxi River Valley in Fujian, China dried up after a reservoir was built upstream in 1959, and became a stone quarry site. Quarrying ceased in 1977, so a large amount of quarry wastes with artificially excavated surfaces were left in the valley. The concave-upward curved rocky surface, broken by manual excavation, easily contains rainwater in its central part, which was easily weathered into a more concave surface. Plaster mould casting was performed in situ on such a concave surface of an excavated stone rock in the valley and scanned with a high-precision 3D scanner to obtain 3D data of the concave-upward rock surface and its more concave middle part, which was considered as an initial weathering pit. The 3D model provided an in-depth understanding of the initial formation process of weathering pits, indicating that: (1) the average weathering rate of a weathering pit is 10.8 ± 0.49 cm ka⁻¹; (2) weathering pits are generally formed by standing water in depressions on a flat near-horizontal rock surface due to weathering actions involving water; (3) the deepening rate of a weathering pit is about four times greater than that of the surrounding area; (4) the growth of a weathering pit can begin in some small concavities on the flat rock surface without pre-existing depressions and gradually expands; (5) a weathering pit is generally wider than deep or with a flat bottom due to expansion with a lateral weathering rate that is greater than that of the vertical, and the lamination of the host rock is not necessary for the formation of flat-floored weathering pits. © 2020 John Wiley & Sons, Ltd.     

Evaluation of the Glugla method for estimating evapotranspiration and groundwater recharge

Abstract

Estimates of groundwater recharge are often needed for a variety of groundwater resource evaluation purposes. A method for estimating long-term groundwater recharge and actual evapotranspiration not known in the English literature is presented. The method uses long-term average annual precipitation, runoff, potential evaporation, and crop-yield information, and uses empirical parameter curves that depend on soil and crop types to determine long-term average annual groundwater recharge (GWR). The method is tested using historic lysimeter records from 10 lysimeters at Coshocton, Ohio, USA. Considering the coarse information required, the method provides good estimates of groundwater recharge and actual evapotranspiration, and is sensitive to a range of cropping and land-use conditions. Problems with practical application of the technique are mentioned, including the need for further testing using given parameter curves, and for incorporating parameters that describe current farming practices and other land uses. The method can be used for urban conditions, and can be incorporated into a GIS framework for rapid, large-area, spatially-distributed estimations of GWR. An example application of the method is given.     

A simple method for calculating growth rates of petroleum hydrocarbon plumes

Consumption of aquifer Fe(III) during biodegradation of ground water contaminants may result in expansion of a contaminant plume, changing the outlook for monitored natural attenuation. Data from two research sites contaminated with petroleum hydrocarbons show that toluene and xylenes degrade under methanogenic conditions, but the benzene and ethylbenzene plumes grow as aquifer Fe(III) supplies are depleted. By considering a one-dimensional reaction front in a constant unidirectional flow field, it is possible to derive a simple expression for the growth rate of a benzene plume. The method balances the mass flux of benzene with the Fe(III) content of the aquifer, assuming that the biodegradation reaction is instantaneous. The resulting expression shows that the benzene front migration is retarded relative to the ground water velocity by a factor that depends on the concentrations of hydrocarbon and bioavailable Fe(III). The method provides good agreement with benzene plumes at a crude oil study site in Minnesota and a gasoline site in South Carolina. Compared to the South Carolina site, the Minnesota site has 25% higher benzene flux but eight times the Fe(III), leading to about one-sixth the expansion rate. Although it was developed for benzene, toluene, ethylbenzene, and xylenes, the growth-rate estimation method may have applications to contaminant plumes from other persistent contaminant sources.     

基于统计学的地震显著平静阈值估计

提出具有统计学意义的地震显著平静阈值估算方法,用于中国大陆及川滇、新疆和华北地区中强震活动分析,在不同区域得到不同起始震级的显著平静阈值范围。结果显示:(1)中国大陆7级、6级和5级地震显著平静的阈值范围分别为3.9—6.2年、7.9—9.6个月和62—70天;(2)川滇地区6级和5级地震显著平静的阈值范围分别为2.1—2.9年和7.0—8.5个月;(3)新疆地区6级和5级地震显著平静的阈值范围分别为2.6—4.0年和8.5—10.5个月;(4)华北地区6级和5级地震显著平静的阈值范围分别为11.7—23.4年和5.2—7.7年。     

Evidence of distinct contaminant transport patterns in rivers using tracer tests and a multiple domain retention model

Solute transport in rivers is controlled by surface hydrodynamics and by mass exchanges with distinct retention zones. Surface and hyporheic retention processes can be accounted for separately in solute transport models with multiple storage compartments. In the simplest two component model, short term storage can be associated to in-channel transient retention, e.g. produced by riparian vegetation or surface dead zones, and the long-term storage can be associated to hyporheic exchange. The STIR (Solute Transport In Rivers) multiple domain transport model is applied here to tracer test data from three very different Mediterranean streams with distinctive characteristics in terms of flow discharge, vegetation and substrate material. The model is used with an exponential residence time distribution (RTD) to represent surface storage processes and two distinct modeling closures are tested to simulate hyporheic retention: a second exponential RTD and a power-law distribution approximating a known solution for bedform-induced hyporheic exchange. Each stream shows distinct retention patterns characterized by different timescales of the storage time distribution. Both modeling closures lead to very good approximations of the observed breakthrough curves in the two rivers with permeable bed exposed to the flow, where hyporheic flows are expected to occur. In the one case where the occurrence of hyporheic flows is inhibited by bottom vegetation, only the two exponential RTD model is acceptable and the time scales of the two components are of the same magnitude. The significant finding of this work is the recognition of a strong signature of the river properties on tracer data and the evidence of the ability of multiple-component models to describe individual stream responses. This evidence may open a new perspective in river contamination studies, where rivers could possibly be classified based on their ability to trap and release pollutants.     

A new method for estimating BOD and the rate of biochemical oxidation based on modified Streeter-Phelps equations

An analytical solution of a modified system of Streeter-Phelps equations in the absence of aeration of the water body is given. Such solution is of interest in calculating the dynamics of biochemical oxidation of organic matter in a water body or a river channel covered by ice. The same solution can be used to describe processes taking place in a sealed flask in the determination of biochemical demand of the examined water sample over some period. The analytical solution of the modified system of Streeter-Phelps equations was used to derive formulas for calculating biochemical oxygen demand and the rate of biochemical oxidation.     

Inverse model method for estimating assimilation by aquatic invertebrates

Physiological data indicate that a 3-compartment model appropriately represents ingestion, assimilation, and accumulation of somatic and reproductive tissue by an aquatic invertebrate predator. A secondary production model calibrated to growth and respiration data is used to constrain the model equations. Inverse solution methods are used to estimate rate constants for digestion and for net accrual of tissue by growing animals at different temperatures. Predicted time to 50% maximum digestion matches well with the empirical rate of digestion of prey enzymes in the predator gut. Model-derived digestion rates are consistent with the assimilation rate constant obtained by independent radiotracer methods, and with experimental detection time for prey enzymes. The model approach permits parameter estimation within a complex system of equations so that results can be compared with experimental data.     

A modified stochastic finite-fault method for estimating strong ground motion:Validation and application

We developed a modified stochastic finite-fault method for estimating strong ground motions. An adjustment to the dynamic corner frequency was introduced, which accounted for the effect of the location of the subfault relative to the hypocenter and rupture propagation direction, to account for the influence of the rupture propagation direction on the subfault dynamic corner frequency. By comparing the peak ground acceleration(PGA), pseudo-absolute response spectra acceleration(PSA, damping ratio...     

An efficient method for estimating the collapse risk of structures in seismic regions

Assessing the probability of collapse is a computationally demanding component of performance‐based earthquake engineering. This paper examines various aspects involved in the computation of the mean annual frequency of collapse (λ_c) and proposes an efficient method for estimating the sidesway collapse risk of structures in seismic regions. By deaggregating the mean annual frequency of collapse, it is shown that the mean annual frequency of collapse is typically dominated by earthquake ground motion intensities corresponding to the lower half of the collapse fragility curve. Uncertainty in the collapse fragility curve and mean annual frequency of collapse as a function of the number of ground motions used in calculations is also quantified, and it is shown that using a small number of ground motions can lead to unreliable estimates of a structure's collapse risk. The proposed method is shown to significantly reduce the computational effort and uncertainty in the estimate. Copyright © 2012 John Wiley & Sons, Ltd.