Principles of Unitization

In 1920, H. L. Doherty proposed the term unitization for the cooperative operation of an oil pool as though it were owned and operated by one party. The main methods of unitization are: (1) voluntary, (2) cooperative with divided interests, (3) complete with undivided interests, (4) compulsory. The petroleum geologist determines the outlines of the unit by correlating the assembled well data of each operator. After engineering studies have determined the reservoir characteristics, negotiations begin with royalty owners, many of which, not realizing the benefits of unit operations, refuse to permit consolidation of their interests. The state is a party to the formation of a unit and its conservation laws must be strictly obeyed. The participation formula divides income and expenses among the members of the unit. It should be as simple as possible and yet cover all aspects which will determine future production of the reservoir. The “split” formula takes into account that oil fields have a primary and a secondary production; hence by use of this formula the economic adjustment is lessened by maintaining income at a stable level during the transition from primary to secondary recovery. The unit operator is appointed by fellow operators and carries out the orders of the operating committee. The advantages of unitization are chiefly economic, through avoidance of competitive drilling, economic employment of personnel and marketing advantages. Engineering benefits include control of water incursion and reservoir energy, scientific well spacing, and coordination of drilling programs. Unitization tends to have a stagnating effect on the industry, cause restraint of trade, promote unequal distribution of royalty and be monopolistic. Amerada Petroleum Corporation along with twenty other operators are nearly ready to begin secondary recovery operations in Beaver Lodge and Tioga fields in North Dakota. Water flooding, which is expected to produce an additional 125 million barrels of oil, cannot be initiated until eighty-five percent of the royalty owners agree to the program. From past experience, the benefits of unitization of these two fields should exceed any which could be gained by competitive secondary recovery programs

The surficial geology of north-central Kidder County, North Dakota

Kidder County is situated in central North Dakota within the glaciated Missouri Plateau. Rocks underlying the drift range from Cretaceous (Pierre formation) through Palocene (Tongue River formation) in age. The Pierre and Fox Hills formations constitute the majority of the pre-Pleistocene surface. Ice-shove deformation, apparently during Cary time, tilted blocks of Fox Hills in the Sibley Buttes into northeastward-dipping positions. Cary and Mankato subages of Wisconsin age are represented at the surface. Ages are difficult to assign to drift sheets on the basis of lithology or degree of weathering of included tills; but by correlation from South Dakota and crosscutting relationships of moraines, age assignments are suggested. The Sibley Buttes moraine marks a readvance during probable 1st Cary time as indicated by its transection of the Long Lake loop. Small recessional moraines mark positions of stillstand during eastward retreat of 1st Cary ice. Second Cary drift occurs north of Tuttle and Robinson, and outwash to its south indicates melting was the dominant process. Local stagnation formed pitted outwash, especially along the borders of the stagnating ice. First Mankato deposits are not exposed in the area. Second Mankato deposits are represented in part by the massive, lobe-shaped McPhail Buttes moraine. Glaciofluvial material of the 2nd Mankato subage derived from the northeast has partially buried parts of the 2nd Mankato drift in the northeast part of the area. Recent sediment consists of alluvium and reworked outwash sand. Preglacial drainage was southeastward into the preglacial Cannonball River which flowed northeastward across the center of the County

Health care resource use by patients before and after a diagnosis of chronic fatigue syndrome (CFS/ME): a clinical practice research datalink study

BACKGROUND: Our aim was to investigate patterns of health care resource use by patients before and after a diagnosis of CFS/ME, as recorded by Clinical Practice Research Datalink (CPRD) GP practices in the UK. METHODS: We used a case–control study design in which patients who had a first recorded diagnosis of CFS/ME during the period 01/01/2001 to 31/12/2013 were matched 1:1 with controls by age, sex, and GP practice. We compared rates of GP consultations, diagnostic tests, prescriptions, referrals, and symptoms between the two groups from 15 years (in adults) or 10 years (in children) before diagnosis to 10 years after diagnosis. RESULTS: Data were available for 6710 adult and 916 child (age <18 years) matched case–control pairs. Rates of GP consultations, diagnostic tests, prescriptions, referrals, and symptoms spiked dramatically in the year when a CFS/ME diagnosis was recorded. GP consultation rates were 50% higher in adult cases compared to controls 11–15 years before diagnosis (rate ratio (RR) 1.49 (95% CI 1.46, 1.52)) and 56% higher 6–10 years after diagnosis (RR 1.56 (1.54, 1.57)). In children, consultation rates in cases were 45% higher 6–10 years before diagnosis (RR 1.45 (1.40, 1.51)) and 62% higher 6–10 years after diagnosis (RR 1.62 (1.54, 1.70)). For adults and children, rates of tests, prescriptions, referrals, and symptoms were higher in cases compared to controls for up to 10 years before and after diagnosis. CONCLUSIONS: Adults and children with CFS/ME have greater health care needs than the rest of the population for at least ten years before their diagnosis, and these higher levels of health care resource use continue for at least ten years after diagnosis

Hummingbirds arrest their kidneys at night: diel variation in glomerular filtration rate in Selasphorus platycercus

© The Company of Biologists Ltd 2004Small nectarivorous vertebrates face a quandary. When feeding, they must eliminate prodigious quantities of water; however, when they are not feeding, they are susceptible to dehydration. We examined the role of the kidney in the resolution of this osmoregulatory dilemma. Broad-tailed hummingbirds (Selasphorus platycercus) displayed diurnal variation in glomerular filtration rate (GFR). During the morning, midday and evening, GFRs were 0.9±0.6, 1.8±0.4 and 2.3±0.5 ml h–1, respectively. At midday, GFR increased linearly with increased water intake. During the evening, hummingbirds decreased renal fractional water reabsorption linearly with increased water intake. Broad-tailed hummingbirds appeared to cease GFR at night (–0.1±0.2 ml h–1) and decreased GFR in response to short-term (~1.5 h) water deprivation. GFR seems to be very responsive to water deprivation in hummingbirds. Although hummingbirds and other nectarivorous birds can consume astounding amounts of water, a phylogenetically explicit allometric analysis revealed that their diurnal GFRs are not different from the expectation based on body mass.Bradley Hartman Bakken, Todd J. McWhorter, Ella Tsahar and Carlos Martínez del Ri

Understorey diversity in southern boreal forests is regulated by productivity and its indirect impacts on resource availability and heterogeneity

Understanding the relationship between species diversity and productivity is central to linking compositional and functional aspects of terrestrial ecosystems, and little is known about such issues in boreal forests. We used structural equation modelling (SEM) to test several hypotheses about direct and indirect influences of productivity, its correlate basal area, and resources on understorey vascular plant diversity on 2025 plots in 81 southern boreal forests in Minnesota, USA. We first examined the hypothesis that increasing basal area reduces plot-scale species richness due to competitive exclusion from the most limiting resource, light. As expected, light pre-emption increased with total basal area, which directly reduced understorey species richness. However, complex relations between basal area, dominant understorey species, and resource supply to the understorey can also influence understorey communities. Hence, we addressed whether plots with low light availability in the understorey were associated with low abundance of dominant understorey species and alleviation of competitive exclusion of other understorey species. SEM results showed that low light decreased total understorey cover, alleviating resource competition from this stratum and thus increasing understorey species richness. Furthermore, the cover of four dominant understorey species was positively correlated with light availability and negatively correlated with plot-scale species richness. Aggregating data for the 25 plots at each stand, SEM showed that stand-scale species richness was positively influenced by light heterogeneity, which in turn increased with annual above-ground productivity. Species richness was positively influenced by litter %N, considered an index of nitrogen availability at the plot and stand scale. Synthesis. These results suggest that understorey species richness in boreal forests is regulated by productivity, but is primarily mediated by the indirect effects of productivity of the dominant producers on resource availability and heterogeneity. © 2011 The Authors. Journal of Ecology © 2011 British Ecological Society

Evolutionary stasis and lability in thermal physiology in a group of tropical lizards

Understanding how quickly physiological traits evolve is a topic of great interest, particularly in the context of how organisms can adapt in response to climate warming. Adjustment to novel thermal habitats may occur either through behavioural adjustments, physiological adaptation, or both. Here we test whether rates of evolution differ among physiological traits in the cybotoids, a clade of tropical Anolis lizards distributed in markedly different thermal environments on the Caribbean island of Hispaniola. We find that cold tolerance evolves considerably faster than heat tolerance, a difference that results because behavioural thermoregulation more effectively shields these organisms from selection on upper than lower temperature tolerances. Specifically, because lizards in very different environments behaviourally thermoregulate during the day to similar body temperatures, divergent selection on body temperature and heat tolerance is precluded, whereas night-time temperatures can only be partially buffered by behaviour, thereby exposing organisms to selection on cold tolerance. We discuss how exposure to selection on physiology influences divergence among tropical organisms and its implications for adaptive evolutionary response to climate warming

Spatiotemporal dynamics of the postnatal developing primate brain transcriptome.

Developmental changes in the temporal and spatial regulation of gene expression drive the emergence of normal mature brain function, while disruptions in these processes underlie many neurodevelopmental abnormalities. To solidify our foundational knowledge of such changes in a primate brain with an extended period of postnatal maturation like in human, we investigated the whole-genome transcriptional profiles of rhesus monkey brains from birth to adulthood. We found that gene expression dynamics are largest from birth through infancy, after which gene expression profiles transition to a relatively stable state by young adulthood. Biological pathway enrichment analysis revealed that genes more highly expressed at birth are associated with cell adhesion and neuron differentiation, while genes more highly expressed in juveniles and adults are associated with cell death. Neocortex showed significantly greater differential expression over time than subcortical structures, and this trend likely reflects the protracted postnatal development of the cortex. Using network analysis, we identified 27 co-expression modules containing genes with highly correlated expression patterns that are associated with specific brain regions, ages or both. In particular, one module with high expression in neonatal cortex and striatum that decreases during infancy and juvenile development was significantly enriched for autism spectrum disorder (ASD)-related genes. This network was enriched for genes associated with axon guidance and interneuron differentiation, consistent with a disruption in the formation of functional cortical circuitry in ASD