Depletion drive

Solution gas drive (or depletion drive) Gas cap drive Water drive with a large underlying aquifer Undersaturated oil (no gas cap) Saturated oil with a gas cap Saturated or undersaturated oil... 

Once the production potential of the producing wells is insufficient to maintain the plateau rate, the decline periodbegins. For an individual well in depletion drive, this commences as soon as production starts, and a plateau for the field can only be maintained by drilling more wells. Well performance during the decline period can be estimated by decline curve analysis which assumes that the decline can be described by a mathematical formula. Examples of this would be to assume an exponential decline with 10% decline per annum, or a straight line relationship between the cumulative oil production and the logarithm of the water cut. These assumptions become more robust when based on a fit to measured production data. 

Below the bubble-point, pressure gas percolates out of the oil phase, coalesces and displaces the crude oil. The gas phase, which is much less viscous and thus more mobile than the oil phase, fingers through the displaced oil phase. In the absence of external forces, the primary depletion inefficiently produces only 10 to 30 percent of the original oil in place. In the secondary stage of production, water is usually injected to overcome the viscous resistance of the crude at a predetermined economic limit of the primary depletion drive. The low displacement efficiencies, 30 to 50 percent, of secondary waterfloods are usually attributed to vertical and areal sweep inefficiencies associated with reservoir heterogeneities and nonconformance in flood patterns. Most of the oil in petroleum reservoirs is retained as a result of macroscopic reservoir heterogeneities which divert the driving fluid and the microscopically induced capillary forces which restrict viscous displacement of contacted oil. This oil accounts for approximately 70 percent, or 300 x 10 bbl, of the known reserves in the United States. 

Diffusion as referred to here is molecular diffusion in interstitial water. During early diagenesis the chemical transformation in a sediment depends on the reactivity and concentration of the components taking part in the reaction. Chemical transformations deplete the original concentration of these compounds, thereby setting up a gradient in the interstitial water. This gradient drives molecular diffusion. Diffusional transport and the kinetics of the transformation reactions determine the net effectiveness of the chemical reaction. 

Winship IR, Plaa N, Murphy TH (2007) Rapid astrocyte calcium signals correlate with neuronal activity and onset of the hemodynamic response in vivo. J Neurosci 27 6268-6272 Wu MM, Buchanan J, Luik RM, Lewis RS (2006) Ca store depletion causes STIMl to accumulate in ER regions closely associated with the plasma membrane. J Cell Biol 174 803-813 Wyss-Coray T (2006) Inflammation in Alzheimer disease driving force, bystander or beneficial response Nat Med 12 1005-1015... 

Typical results, shown in Fig. 21(a), demonstrate that the rate constant for the reaction between TCNQ and aqueous Fe(CN)g increases with increasing driving force, promoted by decreasing [CIO4 as evidenced by the steeper Fe(CN)g concentration profiles. Moreover, the Tafel plot obtained for ET between Fe(CN)g and TCNQ is linear with an apparent measured a value of 0.31 0.02. In these studies, the concentration of reactant in the droplet phase was always at least 10 times the concentration of the reactant in the receptor phase, to ensure that depletion (and diffusional) effects within the droplet were negligible. 

The complications associated with the presence of nonreacting ions in the diffusion layer are discussed extensively by Selman and Newman (S9a, S9b). In free convection, where the driving force, that is, the density difference, is affected by the accumulation or depletion of nonreacting ions at the electrode, consideration of the concentration profiles of these species assumes special importance (Section IV,B). 

Nonspecific protein binding to the solid phase complicates the method and is a selective pressure driving its evolution. The adaptive response has been the development of intrinsically comparative methods in which specific binding to an immobilized ligand is blocked in one out of two otherwise identical samples. When the respective protein components of the samples are compared, specifically bound proteins are present in one but severely depleted in the other. To allow relative quantitation, the two samples can be made isotopically distinct by a chemical or metabolic process and then mixed for an analytical step that avoids intersample variability [15]. 

In the next sections I will present the main results from these recent Li and Be datasets. In particular, I will address the following questions 1. What are the timescales of Li depletion 2. Is the Sun typical 3. What parameter drives Li depletion at old ages 4. Do stars deplete Be at the same rate as Li Whereas I will mostly focus on stars with masses close to solar, I mention in passing that light element depletion is also strongly dependent on stellar mass. 

The originally proposed hypothesis that there might have been more than an episode of star formation within M 67 and that, accordingly, Li-rich/poor cluster stars might represent the young/old population ([10]) can be excluded, since we now know that Li at old ages is not necessarily low (see Fig. 1). The scatter in M 67 indeed reinforces the conclusion that at least one further parameter besides age and mass drives Li depletion, the possible additional parameters being the presence of planets, chemical composition ([10], [14]) and rotation and/or rotational history ([9]). 

---