University of Khartoum

Probability-Based Screening Models for Various Well Stimulation Treatments

Probability-Based Screening Models for Various Well Stimulation Treatments

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Title: Probability-Based Screening Models for Various Well Stimulation Treatments
Author: Babiker, Quosay Awad Ahmed
Abstract: Well stimulation is a well intervention performed on oil or gas well aims to increase production rate by improving the fluid flow from the drainage area into the well bore. The main objective of this research is to identify and to quantify the uncertainty effect of different variables and parameters in the design outcomes of various well stimulation techniques. In this research, Monte Carlo simulation technique is used to develop probability based models for both hydraulic fracturing (in both conventional and shale gas formations) and near wellbore chemical injection. The probabilistic model is based on assigning probability distribution for all variables and parameters used in the designing process. Real cases and hypothetical examples are used to simulate the effect of different variables and designing parameters on the outcomes of hydraulic fracturing process and chemical injection in multi layered reservoir. Variance based sensitivity analysis (VBSA) was performed to quantify the contribution and the correlation between different model’s inputs and outcomes. The outcomes generated from the probability based models can be used to weigh and evaluate the importance of input information needed for any similar well stimulation treatment. According to the results of the VBSA on the hydraulic fracturing probability-based model, it is found that the uncertainty in many variables and parameters are differently affecting the process design outcomes. It is found that reservoir rock properties have insignificant effect on the fracture width compare to fracturing fluid’s effect. Moreover, the VBSA and parametric study showed that Poisson’s ratio and rock density were the major parameters that control fracture half-length, breakdown pressure and fluid’s surface injection pressure. Fracture height has been found to be predominantly controlled by formation thickness. Therefore, it is recommended to perform in-depth analysis for these factors prior conducting any designing process of hydraulic fracturing. On the other hand, computational model, based on analytical equations of flow in porous media, is developed to simulate bullhead injection of water based chemical solutions into well with multi opened zones. Analytical equations are developed to model fluid penetration radius, injected volume and injection rate for every opened zone during the injection process. Equations describe cooling effect by the injected fluid into the hot formation is arranged and simulated to illustrate radial and vertical heat cooled area during the injection process. An equation is developed to simulate dilution of chemical concentration into the formation water. Throughout VBSA, it is found that data accuracy of many variables and parameters used in the model are not of importance as for formation permeability, porosity, layer thickness, pressure and temperature of the injected fluid. This model is very useful when it comes to plan and design of matrix acidizing, chemical water shut off, sand consolidation, microbial fluid placement, injection of mobility control fluids or any treatment involves bullheading of chemical concentrated solutions into multi layered reservoir. It can be also used to design many workover applications especially for comminglely completed wells.
URI: http://khartoumspace.uofk.edu/123456789/25545


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