Numerical simulation of individual wells in a field simulation model

Conventional numerical simulation of hydrocarbon reservoirs is inadequate for the prediction of bottom-hole pressures at production wells. This problem can be overcome by using a special mathematical model which combines individual well simulation with reservoir simulation. Severe computational instability is commonly encountered in the radial models due to the relatively small grid-blocks and high fluid velocities in the vicinity of the well bore. This instability is found to be more pronounced during depletion of the reservoir when the pressure near the well bore is below bubble-point pressure. A new technique is introduced here for saturation calculations in the critical region near the well. This technique is found to be stable for computing saturations in the small inner elements of the radial grid. Stability is maintained even for the simulation of reservoir behavior within a few inches of the producing sand face. The mathematical model developed in this study was used to predict performance of a hypothetical oil field, and these predictions were com- , pared to the performance predicted by an areal model. It is suggested that this type of model be used for reservoirs where pressure drawdown at producing wells is large, and bottom-hole pressure is less than bubble-point pressure --Abstract, pages ii-iii

Numerical simulation of one-dimensional three-phase fluid flow in a stratified petroleum reservoir with no cross-flow

A numerical model for linear, three-phase fluid flow in a stratified petroleum reservoir has been developed for the purpose of studying water-flooding performance characteristics. Gravity forces, capillary pressure and cross-flow were neglected, but the fluids were considered compressible and evaluations of dissolved gas concentrations have been accounted for. The model was used in evaluating the performance of a water flood project for a hypothetical reservoir which contained the three phases of oil, gas, and water. The results were then compared with those obtained using the Dykstra-Parsons technique. The model produces results which were found to be similar to those obtained by the Dykstra-Parsons method for the displacement of oil by water with no gas present, but poor agreement resulted when free gas saturations were formed. The results obtained using the numerical model are considered to be more realistic than those obtained by the Dykstra-Parsons method in depleted oil sands with a substantial gas saturation since the Dykstra-Parsons model was built on the assumption that only one phase flows at a point and water displace oil in a piston-like manner. When a free gas saturation is formed at the production well, the oil mobility is reduced substantially resulting in a lower oil recovery at water breakthrough than can be predicted by the Dykstra-Parsons technique --Abstract, Page ii

Cost-Effective Management of Sea Water Intrusion in Shallow Unconfined Aquifers

The cost efficiency aspects of different hydraulic barriers to control seawater intrusion (SWI) in shallow unconfined aquifer are investigated using the direct integration of simulation model with multi objective optimization tool. Positive barrier by recharging the water into aquifer using subsurface pond, negative barrier by abstraction of saline water and combination of these two are the three scenarios that are optimally assessed in this study. In the descriptive case study considered, the results indicate that application of treated waste water (TWW) as source of recharge increases the efficiency and the practical value of combined management scenario to control SWI

Variants of Meir-Keeler Fixed Point Theorem And Applications of Soft Set-Valued Maps

In this paper, we prove a Meir-Keeler type common fixed point theorem for two mappings for which the range set of the first one is a family of soft sets, called soft set-valued map and the second is a point-to-point mapping. In addition, it is also shown that under some suitable conditions, a soft set-valued map admits a selection having a unique fixed point. In support of the obtained result, nontrivial examples are provided. The novelty of the presented idea herein is that it extends the Meir-Keeler fixed point theorem and the theory of selections for multivalued mappings from the case of crisp mappings to the frame of soft set-valued maps. Finally, an application of soft setvalued maps in decision making problems is considered

Numerical modelling of the impacts of sea level rise on seawater intrusion in unconfined coastal aquifers

Copyright © 2014 the University of Exeter.This study presents the application of a density-dependent finite element model to simulate the transient effects of sea level rise (SLR) on seawater intrusion (SWI) in a conceptual case of unconfined aquifer. The model considers both the unsaturated and saturated flow conditions. To model the natural process of SLR, a time-dependent boundary condition is used to define the hydrostatic head imposed by seawater at the coastal boundary where the effect of the gradual rise in the sea level with time is considered. The specified values of SLR are chosen, in the range of that predicted by IPCC (Intergovernmental Panel on Climate Change), for five different periods of time in the current century (from 2014 to 2100). The results indicate that a considerable advance in SWI can be expected in the coastal aquifers until the end of century. The rising of sea level is followed by the lifting of the groundwater table, especially near the shoreline, which gradually declines towards the inland boundary. The effects of spatial variations of the shoreline slope on SWI under SLR condition are also investigated. The results highlight that the flatter slopes of the shoreline intensify the landward process of seawater intrusion

Optimal control of seawater intrusion in coastal aquifers

Seawater intrusion is one of the most serious environmental problems in many coastal regions all over the world. This is because mixing a small quantity of seawater with groundwater makes it unsuitable for use and can result in abandonment of aquifers. Therefore, seawater intrusion should be prevented or at least controlled to protect groundwater resources. This paper presents a new method for optimal control of seawater intrusion. The proposed method is based on a combination of abstraction of saline water near shoreline and recharge of aquifer using surface ponds. The source of water for the surface pond could be treated waste water or excess of desalinated brackish water (if any), etc. The variable density flow and solute transport model, SUTRA, is integrated with a Genetic Algorithm optimization tool in order to investigate the efficacy of different scenarios of the seawater intrusion control in an unconfined costal aquifer. The locations of the pond and the abstraction well in relation to the shoreline, depth of abstraction well and the rates of abstraction and recharge are considered as the main decision variables of the optimization model, which aims to minimize the costs of construction and operation of the abstraction wells and recharge ponds as well as the salt concentrations in the aquifer. Comparison is made between the results of the proposed method and other methods of seawater intrusion control. The results indicate that the proposed method is efficient in controlling seawater intrusion. This proposed strategy can be considered as a powerful tool for cost-effective management of seawater intrusion in coastal aquifers

Effect of some heavy metals on the biochemical parameters of the freshwater shrimp, Macrobrachium nipponense (De Haan, 1849)

The current study aimed to determine the biochemical parameters, including glucose, total protein, cholesterol, and enzymes of AST and ALT, in freshwater shrimp Macrobrachium. nipponense after exposure to different sub-lethal concentrations of heavy metals, including iron, copper, lead, and cadmium. Samples of M. nipponense were collected from Shatt Al-Arab, Southern Iraq. The experiment was carried out in a recycling aquaculture system (RAS) consisting of plastic containers, each of 60 liters. Four different treatments were used, each treatment representing three concentrations of Iron (1.5, 2, and 2.5 ppm), Copper (0.25, 0.35, and 9.45 ppm), Lead (0.05, 0.125, and 0.175 ppm), and Cadmium (0.05, 0.1, and 0.17 ppm), in addition to the control group. The results showed a significant decrease in all biochemical parameters compared to the control one. According to the study results, AST and ALT were significantly increased compared to the control. In addition, liver enzymes and biochemical parameters are significantly impacted by heavy metals. This confirms that liver enzymes and biochemical parameters may be biomarkers to monitor heavy metal pollution

Computational Modelling of Braided Fibre for Concrete Reinforcement

This paper presents numerical modelling of braided fibre, to be used as concrete reinforcement. Ultimately, a corrosive and fire resistant concrete will be produced. A Cubit script (geometry and mesh software) was created to mesh braided yarns under dierent geometric parameters. Fibres were represented using elastic transversely isotropic materials, for which the fibre directions for every yarn were precisely determined from the gradients of the resultant stream functions of potential flow problems. Applying an elastic interfaces between yarns to preventing penetration and having free sliding, convergence studies were conducted on a coarse and fine mesh, using hierarchical higher order approximation [1] for uniform p- and hp-refinement