The Petrophysical Characteristics of Jurassic Reservoirs of the Coastal Mississippi Counties and Adjacent State Waters

The purpose of this study is the determination of petrophysical characteristics observable for Jurassic reservoirs in the study area; these characteristics are important for hydrocarbon production from those reservoirs. The study area consists of the three Mississippi coastal counties, Hancock, Harrison, and Jackson, and Mississippi's state waters offshore. The section of importance to this study is the Upper Jurassic, which is made up of, from oldest to youngest, the Norphlet Formation, Smackover Formation, Haynesville Formation (including a Frisco City-equivalent granite wash and the Buckner Anhydrite), and Cotton Valley Group. Within the study area only one Upper Jurassic gas field has been discovered. The Catahoula Creek field is located onshore in Hancock County in the western portion of the study area and is productive of gas from Cotton Valley sands below 19,000 ft. Well log and core data from dry exploratory holes in the study area were used to supplement the limited reservoir data at Catahoula Creek. Nine wildcat wells have penetrated the Jurassic in the study area, so the Jurassic wildcat drilling density is approximately one wildcat well per 290 mi2. Because of this lack of data in the study area, published information on the following Upper Jurassic fields in southwestern Alabama, both onshore and offshore, is included: Chunchula field (Smackover), Hatter's Pond field (Smackover), Hatter's Pond field (Norphlet), and Lower Mobile Bay Mary Ann field (Norphlet). Structurally, the three coastal counties and offshore state waters of Mississippi occupy the southern flank of the Wiggins Arch, an area of positive Paleozoic basement features, and the related Hancock Ridge. The Jurassic strati graphic section in the study area consists of more than 5,000 ft of clastics, evaporites, and carbonates at depths below 17,000 ft to 24,000 ft.     

A parsimonious crop-water productivity index: an application to Brazil

Reducing poverty in rural areas of developing countries requires sustained and sustainable increases in agricultural water productivity. However, aside from traditional measures of precipitation, little is known about water available to farmers or how productively they use it. We present a crop-water productivity index (a ratio of the value of annual crop production to a dimensionless potential water availability index) for large water basins using readily available low-resolution data. The index is transferable, permits direct inter-basin comparisons, and is simple to calculate. We calculate the index for each municipality in the São Francisco river basin in Brazil. No clear patterns linking water availability and value of agricultural output are evident, even though clusters of municípios with high- and low-crop-water productivity emerge, and the former may be useful in guiding policies aimed at increasing water productivity. Finally, analyses of the effects of information uncertainty on the crop-water productivity index suggest that the returns to agricultural investments in certain places in the São Francisco river basin are more risky than others. Improvements in data quality and quantity can help refine estimates of the index and reduce their uncertainty.     

NMR Imaging of Fluid Exchange between Macropores and Matrix in Eogenetic Karst

Sequential time-step images acquired using nuclear magnetic resonance (NMR) show the displacement of deuterated water (D₂O) by fresh water within two limestone samples characterized by a porous and permeable limestone matrix of peloids and ooids. These samples were selected because they have a macropore system representative of some parts of the eogenetic karst limestone of the Biscayne Aquifer in southeastern Florida. The macroporosity, created by the trace fossil Ophiomorpha , is principally well connected and of centimeter scale. These macropores occur in broadly continuous stratiform zones that create preferential flow layers within the hydrogeologic units of the Biscayne. This arrangement of porosity is important because in coastal areas, it could produce a preferential pathway for salt water intrusion. Two experiments were conducted in which samples saturated with D₂O were placed in acrylic chambers filled with fresh water and examined with NMR. Results reveal a substantial flux of fresh water into the matrix porosity with a simultaneous loss of D₂O. Specifically, we measured rates upward of 0.001 mL/h/g of sample in static conditions, and perhaps as great as 0.07 mL/h/g of sample when fresh water continuously flows past a sample at velocities less than those found within stressed areas of the Biscayne. These experiments illustrate how fresh water and D₂O, with different chemical properties, migrate within one type of matrix porosity found in the Biscayne. Furthermore, these experiments are a comparative exercise in the displacement of sea water by fresh water in the matrix of a coastal, karst aquifer since D₂O has a greater density than fresh water.     

A methodology for historical assessment of compliance with environmental water allocations: lessons from the Crocodile (East) River,South Africa

Abstract

Environmental flow provisions are a legal obligation under South Africa’s National Water Act (1998) where they are known as the “ecological reserve”, which is now being realized in river operations. This article presents a semi-quantitative method, based on flow–duration curve (FDC) analysis, used to assess the compliance of the Crocodile (East) River with the reserve in an historical context. Using both monthly and daily average flow data, we determine the extent and magnitude of non-compliant flows against environmental water requirements (EWRs) for three periods (1960–1983, 1983–2000, and 2000–2010). The results suggest a high degree of non-compliance, with the reserve increasing with each of these periods (14%, 35%, and 39% of the time), respectively, where effects were most pronounced in the low-flow season. The results also suggest that, whilst the magnitudes of reserve infringements for the latter period are relatively high, there appears to have been some improvement since the implementation of the river’s operating rules.

Editor Z.W. Kundzewicz; Guest editor M. Acreman

Citation Riddell, E., Pollard, S., Mallory, S., and Sawunyama, T., 2014. A methodology for historical assessment of compliance with environmental water allocations: lessons from the Crocodile (East) River, South Africa. Hydrological Sciences Journal, 59 (3–4), 831–843.     

Development of risk matrices for evaluating climatic change responses of forested habitats

We present an approach to assess and compare risk from climate change among multiple species through a risk matrix, in which managers can quickly prioritize for species that need to have strategies developed, evaluated further, or watched. We base the matrix upon earlier work towards the National Climate Assessment for potential damage to infrastructures from climate change. Risk is defined here as the product of the likelihood of an event occurring and the consequences or impact of that event. In the context of species habitats, the likelihood component is related to the potential changes in suitable habitat modeled at various times during this century. Consequences are related to the adaptability of the species to cope with the changes, especially the increasing intensity and/or frequency of disturbance events that are projected. We derived consequence scores from nine biological and 12 disturbance characteristics that were pulled from literature for each species. All data were generated from an atlas of climate change for 134 trees of the eastern United States (www.nrs.fs.fed.us/atlas). We show examples which depict a wide range of risk for tree species of northern Wisconsin, including species that may gain substantial habitat as well as lose substantial habitat, both of which will require the development of strategies to help the ecosystems adapt to such changes.     

Time scales and length scales in magma ?ow pathways and the origin ofmagmatic Ni-Cu-PGE ore deposits

Ore forming processes involve the redistribution of heat, mass and momentum by a wide range of processes operating at different time and length scales. The fastest process at any given length scale tends to be the dominant control. Applying this principle to the array of physical processes that operate within magma flow pathways leads to some key insights into the origins of magmatic Ni-Cu-PGE sulfide ore deposits. A high proportion of mineralised systems, including those in the super-giant Noril'sk-Talnakh camp, are formed in small conduit intrusions where assimilation of country rock has played a major role. Evidence of this process is reflected in the common association of sulfides with varitextured contaminated host rocks containing xenoliths in varying stages of assimilation. Direct incorporation of S-bearing country rock xenoliths is likely to be the dominant mechanism for generating sulfide liquids in this setting. However, the processes of melting or dissolving these xenoliths is relatively slow compared with magma flow rates and, depending on xenolith lithology and the composition of the carrier magma, slow compared with settling and accumulation rates. Chemical equilibration between sulfide droplets and silicate magma is slower still, as is the process of dissolving sulfide liquid into initially undersaturated silicate magmas. Much of the transport and deposition of sulfide in the carrier magmas may occur while sulfide is still incorporated in the xenoliths, accounting for the common association of magmatic sulfide-matrix ore breccias and contaminated "taxitic" host rocks. Effective upgrading of so-formed sulfide liquids would require repetitive recycling by processes such as reentrainment, back flow or gravity flow operating over the lifetime of the magma transport system as a whole. In contrast to mafic-hosted systems, komatiite-hosted ores only rarely show an association with externally-derived xenoliths, an observation which is partially due to the predominant formation of ores in lava flows rather than deep-seated intrusions, but also to the much shorter timescales of key component systems in hotter, less viscous magmas. Nonetheless, multiple cycles of deposition and entrainment are necessary to account for the metal contents of komatiite-hosted sulfides. More generally, the time and length scale approach introduced here may be of value in understanding other igneous processes as well as non-magmatic mineral systems.     

Preservation of a heavily bored belemnite rostrum from the upper Maastrichtian of north-east Belgium

The robust calcite rostra (or guards) of belemnites were attractive substrates for some boring organisms in the Mesozoic. The rostra of belemnitellid coleoids are common at certain levels within the Gulpen and Maastricht formations of the extended type area of the Maastrichtian Stage (Upper Cretaceous) in the south-east Netherlands and north-east Belgium. A range of episkeletozoans have been reported from these substrates hitherto. A new specimen preserved as a natural mould in flint from the province of Liège, north-east Belgium, is distinctive, preserving a dense three-dimensional infestation of long, slender, unbranched and unsculptured borings of constant diameter, Trypanites? isp. These may be the spoor of polychaetes. Variations in diameter between borings suggests that the traces in this specimen may represent four separate infestations.