Hydraulic Effects of Shales in Fluvial-Deltaic Deposits: Ground-Penetrating Radar, Outcrop Observations, Geostatistics, and Three-Dimensional Flow Modeling for the Ferron Sandstone, Utah   总被引：1，自引：0，他引：1  

Djuro Novakovic  Christopher D. White  Rucsandra M. Corbeanu  William S. Hammon III  Janok P. Bhattacharya  George A. McMechan 《Mathematical Geology》2002,34(7):857-893

Ground-penetrating radar (GPR) surveys, outcrop measurements, and cores provide a high-resolution 3D geologic model to investigate the hydraulic effects of shales in marine-influenced lower delta-plain distributary channel deposits within the Cretaceous-age Ferron Sandstone at Corbula Gulch in central Utah, USA. Shale statistics are computed from outcrop observations. Although slight anisotropy was observed in mean length and variogram ranges parallel and perpendicular to pale of low , the anisotropy is not statistically significant and the estimated mean length is 5.4 m. Truncated Gaussian simulation was used to create maps of shales that are placed on variably dipping stratigraphic surfaces interpreted from high-resolution 3D GPR surveys, outcrop interpretations, and boreholes. Sandstone permeability is estimated from radar responses calibrated to permeability measurements from core samples. Experimentally designed flow simulations examine the effects of variogram range, shale coverage fraction, and trends in shale coverage on predicted upscaled permeability, breakthrough time, and sweep efficiency. Approximately 1500 flow simulations examine three different geologic models, flow in the 3 coordinate directions, 16 geostatistical parameter combinations, and 10 realizations for each model. ANOVA and response models computed from the flow simulations demonstrate that shales decrease sweep, recovery, and permeability, especially in the vertical direction. The effect on horizontal flow is smaller. Flow predictions for ideal tracer displacements at Corbula Gulch are sensitive to shale-coverage fraction, but are relatively insensitive to twofold variations in variogram range or to vertical trends in shale coverage. Although the hydraulic effects of shale are statistically significant, the changes in flow responses rarely exceed 20%. As a result, it may be reasonable to use simple models when incorporating analogous shales into models of reservoirs or aquifers.  相似文献   

现代冲积河流的河型空间转化模式探讨   总被引：11，自引：2，他引：9  

倪晋仁  王随继  王光谦 《沉积学报》2000,18(1):1-6

论述了现代冲积河流系统中常见河型的自然分布及转化特征,归纳了河型从上游向下游发生空间转化的 5种主要模式。这些河型转化模式发生的相对频率是不同的,其中从辫状河流向曲流河流转化的发生频率最大。文中通过具体实例总结了这些转化模式分别发生时的主要影响因素。  相似文献   

Spatial and temporal variations in bank erosion on sand‐bed streams in the seasonally wet tropics of northern Australia     

M. J. Saynor  Wayne D. Erskine 《地球表面变化过程与地形》2006,31(9):1080-1099

Bank erosion rates and processes across a range of spatial scales are poorly understood in most environments, especially in the seasonally wet tropics of northern Australia where sediment yields are among global minima. A total of 177 erosion pins was installed at 45 sites on four sand‐bed streams (Tributaries North and Central, East Tributary and Ngarradj) in the Ngarradj catchment in the Alligator Rivers Region. Bank erosion was measured for up to 3·5 years (start of 1998/99 wet season to end of 2001/02 wet season) at three spatial scales, namely a discontinuous gully (0·6 km²) that was initiated by erosion of a grass swale between 1975 and 1981, a small continuous channel (2·5 km²) on an alluvial fan that was formed by incision of a formerly discontinuous channel between 1964 and 1978, and three medium‐sized, continuous channels (8·5–43·6 km²) with riparian vegetation. The bank erosion measurements during a period of average to above‐average rainfall established that substantial bank erosion occurred during the wet season on the two smaller channels by rapid lateral migration (Tributary Central) and by erosion of gully sidewalls due to a combination of within‐gully flows and overland flow plunging over the sidewalls (Tributary North). Minor bank erosion also occurred during the dry season by faunal activity, by desiccation and loss of cohesion of the sandy bank sediments and by dry flow processes. The larger channels with riparian vegetation (East Tributary and Ngarradj) did not generate significant amounts of sediment by bank erosion. Deposition (i.e. negative pin values) was locally significant at all scales. Bank profile form and channel planform exert a strong control on erosion rates during the wet season but not during the dry season. Copyright © 2006 Commonwealth Government of Australia.  相似文献   

A conceptual model of depositional,rather than erosional,tidal channel development in the rapidly prograding Skagit River Delta (Washington,USA)     

W. Gregory Hood 《地球表面变化过程与地形》2006,31(14):1824-1838

The origin and growth of blind tidal channels is generally considered to be an erosional process. This paper describes a contrasting depositional model for blind tidal channel origin and development in the Skagit River delta, Washington, USA. Chronological sequences of historical maps and photos spanning the last century show that as sediments accumulated at the river mouth, vegetation colonization created marsh islands that splintered the river into distributaries. The marsh islands coalesced when intervening distributary channels gradually narrowed and finally closed at the upstream end to form a blind tidal channel, or at mid‐length to form two blind tidal channels. Channel closure was probably often mediated through gradient reduction associated with marsh progradation and channel lengthening, coupled with large woody debris blockages. Blind tidal channel evolution from distributaries was common in the Skagit marshes from 1889 to the present, and it can account for the origin of very small modern blind tidal channels. The smallest observed distributary‐derived modern blind tidal channels have mean widths of 0·3 m, at the resolution limit of the modern orthophotographs. While channel initiation and persistence are similar processes in erosional systems, they are different processes in this depositional model. Once a channel is obstructed and isolated from distributary flow, only tidal flow remains and channel persistence becomes a function of tidal prism and tidal or wind/wave erosion. In rapidly prograding systems like the Skagit, blind tidal channel networks are probably inherited from the antecedent distributary network. Examination of large‐scale channel network geometry of such systems should therefore consider distributaries and blind tidal channels part of a common channel network and not entirely distinct elements of the system. Finally, managers of tidal habitat restoration projects generally assume an erosional model of tidal channel development. However, under circumstances conducive to progradation, depositional channel development may prevail instead. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Bed waves at the basin scale: implications for river management and restoration     

L. Allan James 《地球表面变化过程与地形》2006,31(13):1692-1706

An extensive literature about fluvial sediment waves, slugs or pulses has emerged in the past 20 years. The concept has been useful in many respects, but has been applied to diverse phenomena using a variety of definitions. Moreover, inferred linkages between channel‐bed changes and sediment loads are often not justifiable. This paper reviews concepts of large fluvial sediment waves at scales extending to several tens of kilometres. It points out constraints on the inferences that can be made about sediment loads based on changes in channel‐bed elevation at this scale where channel sediment interacts with storage in floodplain and terrace deposits. The type area of G. K. Gilbert's initial sediment‐wave concept is re‐examined to show that neither wave translation nor dispersion occurred in the simple manner commonly assumed. Channel aggradation and return to graded conditions provide an alternative theory explaining Gilbert's observed bed‐elevation changes. Recognizing the evidence and implications of the former passage of a large‐scale bed wave is essential to the accurate diagnosis of catchment conditions and the adoption of appropriate river restoration goals or methods. Sediment loads, water quality, channel morphologic stability and aquatic ecosystems often reflect changes in sediment storage long after the channel bed has returned to grade. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

The dynamics of a channel-fed lava flow on Pico Partido volcano, Lanzarote     

Duncan Woodcock  Andrew Harris 《Bulletin of Volcanology》2006,69(2):207-215

A short length of channel on Pico Partido volcano, Lanzarote, provides us the opportunity to examine the dynamics of lava flowing in a channel that extends over a sudden break in slope. The 1–2-m-wide, 0.5–2-m-deep channel was built during the 1730–1736 eruptions on Lanzarote and exhibits a sinuous, well-formed channel over a steep (11° slope) 100-m-long proximal section. Over-flow units comprising smooth pahoehoe sheet flow, as well as evidence on the inner channel walls for multiple (at least 11) flow levels, attest to unsteady flow in the channel. In addition, superelevation is apparent at each of the six bends along the proximal channel section. Superelevation results from banking of the lava as it moves around the bend thus causing preferential construction of the outer bank. As a result, the channel profile at each bend is asymmetric with an outer bank that is higher than the inner bank. Analysis of superelevation indicates flow velocities of ~8 m s^–1. Our analysis of the superelevation features is based on an inertia-gravity balance, which we show is appropriate, even though the down-channel flow is in laminar flow. We use a viscosity-gravity balance model, together with the velocities calculated from superelevation, to obtain viscosities in the range 25–60 Pa s (assuming that the lava behaved as a Newtonian liquid). Estimated volume fluxes are in the range 7–12 m³ s^–1. An apparent down-flow increase in derived volume flux may have resulted from variable supply or bulking up of the flow due to vesiculation. Where the channel moves over a sharp break in slope and onto slopes of ~6°, the channel becomes less well defined and widens considerably. At the break of slope, an elongate ridge extends across the channel. We speculate that this ridge was formed as a result of a reduction in velocity immediately below the break of slope to allow deposition of entrained material or accretion of lava to the channel bed as a result of a change in flow regime or depth.  相似文献   

CHANNEL SHRINKAGE AND ITS INSTABILITY IN THE LOWER YELLOW RIVER1     

Jianguo CHEN  Wenhao ZHOU  Anjun DENG 《国际泥沙研究》2006,21(1)

From the mid 1980s through the late 1990s, the channel of the lower Yellow River experienced serious shrinkage, which has decreased the flood conveyance of the channel and the sediment carrying capacity of the flow, raised the water levels of floods, and, thus, severely threatened the safety of flood control along the river. The completion of Xiaolangdi Dam in 1999 could help mitigate the channel shrinkage problem, but the situation has not changed yet. This paper analyses the characteristics, mechanisms, and conditions resulting in channel shrinkage, points out channel instabilities, and puts forward approaches of channel rehabilitation.  相似文献   

台兴油田下第三系阜宁组下亚段储层沉积微相研究     

赵永强  朱建辉  李海华  程晓玲 《江苏地质》2006,30(1):50-53

通过钻井、测井资料分析,建立了台兴油田下第三系阜宁组(Ef3)下亚段测井相与沉积微相的关系,研究了台兴油田的沉积微相类型及主要含油气单元———各砂体沉积微相的平面展布特征。研究表明,Ef3下亚段主要砂体沉积微相类型为水下分流河道、河漫滩、河口砂坝以及席状砂沉积微相。  相似文献   

地质雷达探测工程的几个问题   总被引：1，自引：0，他引：1  

余中明  丁强 《地质找矿论丛》2006,21(Z1):182-184

地质雷达(GPR)探测技术在浅层地质勘探领域广泛应用,并取得较好的应用效果.文章针对消除干扰的方法、关于防空洞探测、关于公路路面检测和隧道衬砌质量检测、地下岩溶探测等内容进行了探讨.  相似文献   

Seismic identification of channel sandbodies in the Fuyang oil layer in North Songliao Basin, China     

刘金平王允清  杨懋新谢春来赵秀红  陈淑梅 《应用地球物理》2007,4(2):127-132

The Fuyang oil-layer in North Songliao Basin is characterized by thin interbedded sands and shales, strong lateral variation, strong reservoir heterogeniety, and so on. The thickness of individual sand layers is generally 3 - 5 m. Identifying the channel sand-bodies of the Fuyang oil layer using seismic techniques is very difficult due to the low seismic resolution. Taking the GTZ area as an example, we discuss the genetic characteristics of the channel sand-bodies and point out the real difficulty in using seismic techniques to predict the channel sand-bodies. Two methods for the identification of channels are presented： frequency spectrum imaging and pre-stack azimuthal anisotropy. Identifying the channel sand-bodies in Fuyu oil-layer using the two seismic methods results in a success rate up to 80% compared with well data.  相似文献