共查询到20条相似文献，搜索用时 546 毫秒
1.
In situ stress is not only a vital indicator for selecting explorative regions of coalbed methane (CBM), but also a pivotal factor affecting CBM production. The present study explored whether in situ stress affected the development potential of CBM in western Guizhou, China. To this end, we collected injection/falloff well test data and gas content data from 70 coal seams in 28 wells. The study found that from top to bottom, strike slip fault stress fields (<?500 m), normal fault stress fields (500–1000 m) and strike slip fault stress fields (>?1000 m) were successively developed in western Guizhou. The distribution features of vertical permeability in western Guizhou are consistent with the stress fields' transformation location. The coal permeability in the western part in Guizhou presents a tendency of increase followed by decrease as a result of increased burial depth. The vertical development characteristics of coal seam gas content are controlled mainly by reservoir pressure, and the relationship between reservoir pressure and buried depth shows a linear increase. The CBM in western Guizhou is divided vertically into three development potential regions dependent on the characteristics of burial depth, permeability and gas content of coal seams. The most favorable vertical development potential region in western Guizhou is 500–1000 m. This region exhibits high gas content, high permeability and moderate burial depth, which are favorable for the production of CBM. These research results can provide basis for geological selection and engineering implementation of CBM in western Guizhou. 相似文献
2.
Pseudo-reservoir stimulation in horizontal well is an effective technique for indirectly extracting coalbed methane (CBM) in soft coal from the surrounding rocks (pseudo-reservoir). However, systematic studies of the theory and on-site application of this technique are still lacking, which severely hinders its application. In this paper, the technical principles of pseudo-reservoir stimulation are analyzed firstly, and then, the technical advantages are demonstrated by experimental tests and theoretical analysis. The results show that the pseudo-reservoir generally possesses considerable gas adsorption capacity, with the gas content of 1.56–4.22 cm3/g (avg. 2.51 cm3/g) in Well XC-01, which can be extracted as supplementary resources. The fracability of the pseudo-reservoirs is 0.73–0.92, which is much higher than that of the coal seam, i.e., 0.03–0.43. Meanwhile, the compressive and tensile strength and cohesion of the pseudo-reservoir are higher than those of the coal seam, indicating pseudo-reservoir stimulation is more conducive to forming fracture network, and maintaining wellbore stability and fracture conductivity. The technical feasibility of pseudo-reservoir stimulation is determined by the regional geological conditions, showing simple tectonic conditions and well-developed surrounding rocks with high fracability and mechanical strength but low permeability, water sensitivity and water content are beneficial for the technique application. Note that the fracture conductivity in pseudo-reservoir is more stable and higher than that in coal seam, pseudo-reservoir stimulation is beneficial for the CBM extraction from both hard and soft coal seams. By minimizing the gas diffusion distance, this technique overcomes the technical obstacles to the CBM commercialized production in soft coal. 相似文献
3.
The distribution of fractures and its dependence on lithology and petrophysical properties of rock in the Asmari Formation were examined using three wells data of one of the largest oil fields of southwestern Iran. Fractures were measured on cut cores. Mineral content and petrophysical data were obtained through thin section study and core plug measurement respectively. Influence of mineral composition and petrophysical property of rocks on fracture density was explored statistically. Increasing quartz (sand) and anhydrite content of rocks decrease and dolomite increases the threshold of fracture densities, however no significant relation was observed between calcite content of rock and fracture density. Increasing porosity and permeability of rock decrease the threshold of fracture density in some of the defined lithology groups. There are significant differences between the lithology groups in terms of fracture density, although the results in the three wells are not the same. In whole data, the highest fracture density can be observed in dolostone. Limestone and impure carbonates hold broader spaced fractures and sandstones display the least fracture density. The average fracture densities in the wells are strictly different. These differences are the result of the structural position of the wells and also the trend of the well and fractures. The distribution of fractures in most lithology groups can be explained by the function: , where F is relative frequency, D is fracture density and a, b, and c are constants. 相似文献
4.
Since most coalfields in China are commonly characterized by high gas content and low permeability, there is an urgent need to improve coal seam permeability and further enhance coal bed methane (CBM) extraction efficiency. As an emerging fracturing technology, the CO2 gas fracturing (CGF) technology has been widely used because of its advantages of low cost, environmental protection and high fragmentation efficiency. In order to improve the fracturing ability of CGF technique and optimize the release orifices of discharge head, computational fluid dynamics model was used in this paper to simulate the flow fields of dynamic pressure of gas jet released from the orifices with different structures and other geometrical parameters. The results show that the orifice structure has a great influence on the flow field of gas jet, but little influence on the magnitude of the dynamic pressure. Besides, the maximum dynamic pressure of gas jet linearly decreases with the increase in the number of release orifices. Based on a series of simulation results, the discharge head which has single group of orifices with structure c, diameter of 24 mm can be identified as the best choice for fieldwork. Then, two field experiments were conducted in Pingdingshan and Changping coal mines to evaluate the enhanced CBM extraction efficiency by CGF. The results indicate that the CGF can effectively create a large number of cracks in a large range around the fracturing borehole in the coal seam and further significantly improve the permeability. And the CBM extraction efficiency can be improved to a higher level from a lower level and maintained for a long time. Besides, the effective influence radii caused by CGF in Pingdingshan and Changping coal mines are 15.19 m and 12.5 m, respectively. Compared with other fracturing techniques, the CGF technique has a promising application prospect. 相似文献
5.
The permeability of a coal seam is an important index for coal mine gas control and coalbed methane development, and its magnitude determines the degree of difficulty of gas drainage. To obtain the permeability value, a dimensionless mathematical model for dual-porosity borehole gas-coupled flow in a coal seam was established and adopted using a simulator developed by our group. A new method of inversion was developed to determine the fracture permeability coefficient λf and the matrix micro-channel diffusion coefficient Km by fitting the simulated results with onsite measured data. A range of simulations quantified the effects of different dimensionless parameters on gas migration. The results verified the feasibility of the inversion method based on the high matching degree of the fitted results, and the dimensionless mathematical model was accurate. The desorption and release of adsorbed gas from the center to the surface in coal matrices were heterogeneous, and unsteady states and gas migration times in coal matrices cannot be neglected. The new method can be introduced to analyze the problem of gas migration in different coal reservoirs, simplify the corresponding calculation and computational processes, and provide guidance in determining the permeability of coal seams. 相似文献
6.
This article contains a brief summary of some of the 2006 annual committee reports presented to the Energy Minerals Division
(EMD) of the American Association of Petroleum Geologists. The purpose of the reports is to advise EMD leadership and members
of the current status of research and developments of energy resources (other than conventional oil and natural gas that typically
occur in sandstone and carbonate rocks), energy economics, and geospatial information. This summary presented here by the
EMD is a service to the general geologic community. Included in this summary are reviews of the current research and activities
related to coal, coalbed methane, gas hydrates, gas shales, geospatial information technology related to energy resources,
geothermal resources, oil sands, and uranium resources.
相似文献
7.
An equation for correcting log-derived temperatures measured at well depths between 1200 and 5400 m has been derived by comparing log-derived temperatures from wells in the Danish Central Graben (North Sea) with DST temperatures, from the same wells, that are believed to represent true formation temperatures. Equations developed previously using data over different depth ranges from Malaysia and Mexico yield fair results when applied to the North Sea. However, a better fit to the Danish data was obtained using new equations that are similar to those published in the earlier studies. The correction method here is based principally on time since end of circulation (TSC), but it also includes a small dependence on depth. In this study the true subsurface temperature ( Ttrue) (°C) is given by
where the correction factor f = 3.07·TSC (–0.09)/(0.47· Z(0.175)), Tsurf is the seafloor temperature in °C, Tmeas is the measured log temperature in °C, TSC is in hours, and Z is the depth below seafloor in meters. When TSC is not known, maximum probable, minimum probable, and most likely values can be estimated from the observed trend of TSC with depth.An estimate of the uncertainty in the corrected temperature can be obtained from the equation
where is the standard deviation of the error in the correction factor f. This approach can be modified to include the additional uncertainty associated with unspecified TSC. 相似文献
8.
The purpose of this project was to develop and test a methodology for determining the likelihood that mineral resource location
records from two nationwide mineral resource information databases represent the same site. The long-term goal is to create
a comprehensive database by merging the Mineral Resource Data System (MRDS) of the U.S. Geological Survey, and the Mineral
Availability System/Mineral Industry Location System (MAS/MILS) of the U.S. Bureau of Mines (now part of the Geological Survey).
Part of that process involves linking records for the same site from each database. Match probabilities were estimated using
a logistic regression of mineral resource location attributes, derived from known matched (cross-referenced) and known unmatched
randomly sampled mineral site pairs from within the conterminous United States ( n=10,000). Model accuracy was assessed using a randomly sampled test dataset, not used in logistic model development ( n=4,000). Probability distributions were similar between the development and test datasets. The overall agreement beyond chance
was good for the test data set
using the kappa statistic. Classification accuracy was 89.6% for known matched site pairs and 84.0% for known unmatched site
pairs based on a probability threshold of 0.50 for a match. Distributions of attributes were similar between the development
and test datasets. This classification method is a viable approach for estimating match probabilities between database records. 相似文献
9.
A small dataset comprising all temperature available data from reliable Horner plots from the Danish Central Graben was examined. Temperatures obtained by extrapolation using standard Horner plots were determined to be lower than true formation temperatures, as interpreted from DST data. Excellent agreement between true formation temperatures and Horner plot temperatures was achieved when the Horner plot temperatures ( THP) were corrected upward by an amount proportional to the slope ( A) of the Horner plot using the equation
where the temperatures and the slope are in degrees Celsius. The standard deviation of the error in the corrected Horner plot temperatures was 2.1°C, indicating that this method is consistent. Further studies using larger numbers of Horner plots from a variety of geographic areas should be carried out to test and refine the hypotheses presented here. Efforts also should be made to understand the causes of variability in slopes of Horner plots. 相似文献
11.
To evaluate the comparability of neo- and paleo-limnology, we made year-to-year as well as seasonal comparisons of contemporary zooplankton data and cladoceran remains in thick (9–42 mm) annual laminations in sediment of Lake Vesijärvi, southern Finland. We calculated the expected annual exuviae production of nine planktonic taxa in the water column using contemporary zooplankton records, and compared the value to the observed net accumulation of their remains in deep sediment for 7 years. Although all of the species studied occur commonly in the lake pelagic zone, deposition of remains differed significantly among taxa. The observed accumulation of three Bosmina species and Chydorus sphaericus was similar to or exceeded expected values, suggesting good preservation of their remains as well as focusing of sediment into the deepest part of the lake. The accumulation of Limnosida and Leptodora remains exceeded expected values several fold, suggesting under-representation of these species in pelagic plankton samples, as well as efficient transportation and spatial averaging of their remains in the sediment. Daphnia, Diaphanosoma, and Ceriodaphnia were clearly under-represented in the sediment due to poor preservation of their remains and use of a 50-μm sieve in sediment processing. Thus, sieving should be taken into account as a possible source of bias. Correlation between relative abundances of all species in the sediment and in the plankton was weak ( r s = 0.54, P < 0.001), but for well-preserved species, the correlation was strong ( r s = 0.91, P < 0.001). Inter-annual variation in the deposition of remains suggested that resuspension and sediment focusing may vary between years, thus making it difficult to interpret absolute abundances, even though the deepest part of the basin shows clear varve formation and seasonality is well recorded. Detailed study of the uppermost lamination showed the seasonal succession of a cladoceran community within an annual varve as well as differences in the seasonality and intensity of ephippia production among the species. We recommend that results of cladoceran analyses be expressed in several ways (relative abundances, per unit dry weight, per unit organic matter, and as net accumulation values) before drawing final conclusions, as each approach may reveal a different aspect of the deposition process. In addition, sedimentation differences between epilimnetic and hypolimnetic species should be considered in stratified lakes. 相似文献
12.
This paper analyzes energy efficiency of the industrial corn-ethanol cycle. In particular, it critically evaluates earlier
publications by DOE, USDA, and UC Berkeley Energy Resources Group. It is demonstrated that most of the current First Law net-energy
models of the industrial corn-ethanol cycle are based on nonphysical assumptions and should be viewed with caution. In particular,
these models do not (i) define the system boundaries, (ii) conserve mass, and (iii) conserve energy. The energy cost of producing
and refining carbon fuels in real time, for example, corn and ethanol, is high relative to that of fossil fuels deposited
and concentrated over geological time. Proper mass and energy balances of corn fields and ethanol refineries that account
for the photosynthetic energy, part of the environment restoration work, and the coproduct energy have been formulated. These
balances show that energetically production of ethanol from corn is 2–4 times less favorable than production of gasoline from
petroleum. From thermodynamics it also follows that ecological damage wrought by industrial biofuel production must be severe.
With the DDGS coproduct energy credit, 3.9 gallons of ethanol displace on average the energy in 1 gallon of gasoline. Without
the DDGS energy credit, this average number is 6.2 gallons of ethanol. Equivalent CO 2 emissions from corn ethanol are some 50% higher than those from gasoline, and become 100% higher if methane emissions from
cows fed with DDGS are accounted for. From the mass balance of soil it follows that ethanol coproducts should be returned
to the fields.
相似文献
13.
Freshwater lakes are important sources of methane (CH 4) emissions, by organic matter degradation under anaerobic conditions (methanogenesis). Previous studies suggest that lakes contribute up to 16 % of natural emissions. About 60 % of the CH 4 produced is used as an energy source by methane-oxidizing bacteria (MOB—methanotrophs), which could support higher trophic levels, especially Chironomidae (Diptera). Because biogenic methane has a very low stable carbon isotope value, evidence of methane-derived organic-matter assimilation can be tracked by stable carbon isotope analysis in consumers such as chironomids. In some cases, however, chironomid δ 13C values are not low enough to unambiguously demonstrate methanotroph assimilation and an alternative line of evidence is required. Analysis of ancient DNA ( aDNA) from the methanotroph community preserved in lake sediment provides reliable information about past methane oxidation in freshwater lakes. A combination of these two approaches was used to study a sediment core from the deepest zone of Lake Narlay (Jura, France), which covers the last 1,500 years of sediment accumulation. Results show a significant change ca. AD 1600, with an increase in the proportion of MOB in the total bacteria community, and a decrease in chironomid head-capsule δ 13C. These trends suggest assimilation of MOB by chironomid larvae, and account for up to 36 % of the chironomid biomass. The data also provide information about the feeding behavior of chironomids, with evidence for preferential assimilation of methanotroph type I and the NC10 phylum. The combination of aDNA analysis and carbon stable isotopes strengthens the reliability of inferences about carbon sources incorporated into chironomid biomass. 相似文献
14.
Estimates of postglacial rebound in central North America from Laurentide deglaciation to the present time are uncertain as a result of lack of data from the continental interior. A more precise knowledge of postglacial tilt history will assist studies of the evolution of the major lakes in Manitoba and will facilitate the engineering and environmental management of the present-day hydrological system. This paper explores the benefits of combining geomorphological data with high-precision, real-time geodetic data (GPS positioning and absolute gravity) and lake-gauge tilt data now being collected for postglacial rebound studies in Manitoba and adjacent regions in the US. Presently-available data sets representing these data types are (1) tilting of the 9.5 kyr B.P. Campbell strand line south and west of Lake Winnipeg, (2) the rate of decrease in absolute gravity values measured from 1987 to 1995 at Churchill, Manitoba, and (3) the present-day regional tilt rate derived from water-level gauges in southern Manitoba lakes. These data are compared to theoretical predictions based on the published ICE-3G loading history and on a model of Earth rheology characterized by a 1066B density and elastic structure, an upper-mantle viscosity of 10 21Pa s, a lower-mantle viscosity of 2 × 10 21Pa s, and a lithosphere thickness of 120 km (Tushingham & Peltier, 1991). All three data types show disagreement in Manitoba with ICE-3G and the standard Earth model. ICE-4G does better but could not be investigated in any detail. The constraints on model parameters provided by the different data types were investigated by varying, one at a time, three key parameters, (1) the thickness of the lithosphere in excess of 120 km, (2) the lower mantle viscosity, and (3) the thickness of Laurentide ice over the Prairies, to obtain better fits to the data. The present data do not appear to constrain lithosphere thickness in excess of 120 km very well. While both the Campbell strand line data and the Churchill absolute gravity data are consistent with an increase in lower-mantle viscosity, the present-day, lake-gauge data are not. All three data types are consistent with a thinning of the Laurentide ice-sheet over the Prairies relative to the ICE-3G model. Simultaneous adjustment of model parameters with the advantage of anticipated new data in Manitoba and adjacent regions in the US will lead to better understanding of the trade-offs between Earth rheology and ice sheet history and hence to an improved Laurentide postglacial rebound model. 相似文献
15.
通过野外考察和室内自然模型试验,本文探讨边界条件在水库下游再造床过程中的作用。从土壤物理力学性质与水流作用力的对比关系出发,建立了河床边界抗冲性的定量指标;采用多元回归分析的方法,建立了调整之后的河床形态与边界条件、水动力条件之间的经验方程;还运用判别分析的方法,得到了区分水库下游河床演变趋势的判别函数。 相似文献
16.
Based on data on taxed-cropland area and on the number of households in historical documents, a probabilistic model of cropland distribution and a cropland area allocation model were designed and validated. Cropland areas for the years AD976, 997, 1066, and 1078 were estimated at the level of Lu (an administrative region of the Northern Song Dynasty). The results indicated that (1) the cropland area of the whole study region for AD976, 997, 1066, and 1078 was about 468.27 million mu (a Chinese unit of area, with1 mu=666.7m 2), 495.53 million mu, 697.65 million mu, and 731.94 million mu, respectively. The fractional cropland area (FCA) increased from 10.7% to 16.8%, and the per capita cropland area decreased from 15.7 mu to 8.4 mu. (2) With regard to the cropland spatial pattern, the FCA of the southeast, north, and southwest regions of the Northern Song territory increased by 12.0%, 5.2%, and 1.2%, respectively. The FCA of some regions in the Yangtze River Plain increased to greater than 40%, and the FCA of the North China Plain increased to greater than 20%. However, the FCA of the southwest region (except for the Chengdu Plain) in the Northern Song territory was less than 6%. (3) There were 84.2% Lus whose absolute relative error was smaller than 20% in the mid Northern Song Dynasty. The validation results indicate that our models are reasonable and that the results of reconstruction are credible. 相似文献
17.
区域城市间旅游竞争力空间结构体系是一个由不同等级、不同空间区位、不同旅游发展阶段的城市通过旅游资源、旅游交通等生产力要素以及客流有机耦合而形成的。本文在深入分析旅游竞争力含义及其空间结构的基础上,采用城市旅游竞争力的多维评价和综合分析的方法,将珠江三角洲城市旅游目的地划分为不同的3个等级,并总结出珠江三角洲城市旅游竞争力具有以广深为轴线的“哑铃”型双极放射状空间形态模式,提出了凭借城市自身比较优势,承担不同层次旅游竞争与合作角色的空间组织模式,旨在通过研究梳理各城市旅游影响要素的优劣差异,认识区域内旅游竞争力的空间结构特征,为进一步探讨形成互利共赢的城市旅游竞争与合作机制奠定基础,促进珠江三角洲城市旅游经济的和谐发展。 相似文献
19.
环境问题已经成为辽宁省经济发展的瓶颈。基于随机前沿分析SFA与非期望产出的数据包络SBM的研究方法,选取2005年到2011年为研究时间,对辽宁省14个地级市环境效率进行测算,并利用聚类分析、基尼系数与β趋同等研究方法对环境效率进行时空分析。在此基础上,利用Tobit模型建立多元回归,以分析辽宁省环境效率的影响因素。结果表明：大连、沈阳、鞍山的环境绝对效率水平较高,朝阳市绝对效率水平最低;大连、盘锦、沈阳处于生产有效单元,朝阳相对效率属强无效单元;在空间与时间的分析上大连、沈阳等是效率水平高的地区,朝阳为最低地区,空间呈“山脊状”分布;绝对效率值差距在不断缩小,相对效率差距在拉大后趋于稳定;回归结果显示产业结构与经济发展水平对环境经济效率及企业资本深化与生产技术水平起正向作用;财政支持与外商直接投资没有通过模型检验,未对环境效率起作用。 相似文献
|
