Availability analysis of waste-water recovery systems

The objective is to evaluate the energetic and entropic characteristics of the components of waste-water recovery systems that can be used in varying applications such as enclosed life support systems or industrial waste-water treatment processes. Techniques and methods that are used to evaluate these characteristics have been developed to model and analyze these systems;Availability analysis and pinch analysis are used to study the behavior of these systems in order to increase the efficiency of useful energy utilization, and therefore reduce the energy consumption and utilities loads. The availability analysis method, which is a combined first law and second law analysis method, can locate the irreversibility of the system components. The irreversibility of the components may be reduced and entropically optimal systems may be designed using availability analysis. Pinch analysis is an easy and effective method to analyze and optimize heat exchanger networks. The pinch analysis results for the heat exchanger network are used by the availability analysis to evaluate the entire system behavior. The integrated method will be more effective than either of these two methods;A generic model is established for treating waste-water containing solids, organic and inorganic contaminants using vapor compression distillation and gas-phase oxidation reactions. Solids and non-volatile species are removed by vapor compression distillation. Volatile organic and inorganic contaminants are destroyed by chemical oxidation reactions in the vapor phase. Because of the diversity of waste-water, it is unrealistic to list all possible contaminants in the waste-water stream. A simplified waste-water stream containing water, methanol, ammonia and sodium chloride is used in this study. Methanol represents the volatile organic species in waste-water, ammonia represents inorganic contaminants, while sodium chloride represents dissolved solids;Material and energy balances as well as the values of lost work and the second law efficiency of the components of this model under various operating conditions are computed and evaluated. The irreversibility of the components may be reduced and entropically optimal systems may be designed. The limiting relationships between contaminant level and energy consumption are obtained based on the results of the analysis

A Systems Biology Approach in Therapeutic Response Study for Different Dosing Regimens—a Modeling Study of Drug Effects on Tumor Growth using Hybrid Systems

Motivated by the frustration of translation of research advances in the molecular and cellular biology of cancer into treatment, this study calls for cross-disciplinary efforts and proposes a methodology of incorporating drug pharmacology information into drug therapeutic response modeling using a computational systems biology approach. The objectives are two fold. The first one is to involve effective mathematical modeling in the drug development stage to incorporate preclinical and clinical data in order to decrease costs of drug development and increase pipeline productivity, since it is extremely expensive and difficult to get the optimal compromise of dosage and schedule through empirical testing. The second objective is to provide valuable suggestions to adjust individual drug dosing regimens to improve therapeutic effects considering most anticancer agents have wide inter-individual pharmacokinetic variability and a narrow therapeutic index. A dynamic hybrid systems model is proposed to study drug antitumor effect from the perspective of tumor growth dynamics, specifically the dosing and schedule of the periodic drug intake, and a drug’s pharmacokinetics and pharmacodynamics information are linked together in the proposed model using a state-space approach. It is proved analytically that there exists an optimal drug dosage and interval administration point, and demonstrated through simulation study

An iterative algorithm for separation of S and ScS waves of great earthquakes

Teleseismic SH waves are essential for imaging the rupture processes of large earthquakes. However, for great earthquakes (M8+) such as the 2004 Sumatra earthquake, the 2008 Wenchuan earthquake and the recent Tohoku-Oki earthquake, the source duration is very long (>100 s). Thus the direct SH waves are overlapped with ScS waves for epicentral distances larger than 60°, leaving contaminated S waves for source processes modelling. Therefore artefacts in finite fault models of large earthquake could be produced with such contaminated body waves. We propose an iterative algorithm based on the slowness information of S and ScS waves and stacking technique, to separate S and ScS waves with records from a regional seismic network. Tests on various synthetic data sets show that the algorithm is effective in retrieving teleseismic SH waveforms from complicated wave trains containing both S and ScS. Separation of waveforms for the 2008 Wenchuan earthquake with our algorithm clearly demonstrates the influence of ScS energy, suggesting necessity of recovering S waves

Dynamic mechanisms of tight gas accumulation and numerical simulation methods: Narrowing the gap between theory and field application

Despite the significant progress made in tight gas exploration and development in recent years, the understanding of the dynamic mechanisms of tight gas accumulation is still limited, and numerical simulation methods are lacking. In fact, the gap between theory and field application has become an obstacle to the development of tight gas exploration and development. This work sheds light on the dynamic mechanisms of hydrocarbon accumulation in tight formations from the aspect of capillary self-sealing theory by embedding calculation of pressure- and temperature-dependent capillary force in a pore network model. The microscale dynamic mechanisms are scaled up to the reservoir level by geological simulation, and the quantitative evaluation of reserves based on real geological sections is realized. From the results, several considerations are made to assist with resource assessment and sweet spot prediction. Firstly, the self-sealing effect of capillary in the micro-nano pore-throat system is at the core of tight sandstone gas accumulation theory; the hydrocarbon-generated expansion force is the driving force, and capillary force comprises the resistance. Furthermore, microscopic capillary force studies can be embedded into a pore network model and scaled up to a geological model using relative permeability curve and capillary force curve. Field application can be achieved by geological numerical simulations at the reservoir scale. Finally, high temperature and high pressure can reduce capillary pressure, which increases gas saturation and reserves.Cited as: Zhao, W., Jia, C., Song, Y., Li, X., Hou, L., Jiang, L. Dynamic mechanisms of tight gas accumulation and numerical simulation methods: Narrowing the gap between theory and field application. Advances in Geo-Energy Research, 2023, 8(3): 146-158. https://doi.org/10.46690/ager.2023.06.0

Stress arch effect on the productivity of the vertical fractured well

Rock permeability impacts by effective stress. Permeability modulus is used to evaluate the level of permeability reduction due to effective stress change. And the permeability modulus is always obtained by the experiment which assumes that the overburden pressure is constant during production. Actually, the overburden pressure reduces during production due to stress arch effect and it is easy to form a stress arch in the overburden when the reservoir is small and soft compared with surrounding’s rock. Based on the definition of the permeability modulus, we obtain an expression between permeability modulus bγ considering stress arch effect and permeability modulus b0 without stress arch. There lies a linear ship between bγ and b0, which is also proved by the experiment data. Based on the relationship between bγ and b0, a delivery equation for vertical fractured well is established. Compared with the absolute open flow with stress arch ratio of 0, the absolute open flow increases by 2.87 %, 6.79 %, 12.32 %, 20.12 % and 25.44 % for the stress arch ratio of 0.12, 0.28, 0.5, 0.8 and 1, respectively, with permeability modulus b0 of 0.0397 MPa-1. And it increases by 7.31 %, 18.1 %, 34.88 %, 61.02 % and 79.97 % for the stress arch ratio of 0.12, 0.28, 0.5, 0.8 and 1, respectively, when b0= 1. So absolute open flow with high permeability modulus b0 is more sensitive to stress arch ratio. Stress arch also impacts the optimum fracture half-length. Vertical well has the maximum absolute open flow when it has the optimum fracture half-length. The maximum absolute open flow increases with the increasing of stress arch ratio, while optimum fracture half-length decreases with increasing of stress arch ratio for the same permeability modulus b0. Compared with case with no stress arch, the optimum fracture half-length reduces by 2.86 %, 5.7 %, 11.43 %, 17.14 % and 22.86 % for the stress arch ratio of 0.12, 0.28, 0.5, 0.8 and 1 respectively when b0 equals to 0.0397 MPa-1. While the maximum absolute open flow increases by 1.6 %, 3.8 %, 7.16 %, 12.02 % and 15.60 % for the stress arch ratio of 0.12, 0.28, 0.5, 0.8 and 1 respectively. Thus, vertical well considering stress arch needs smaller fracture half-length than that with no stress arch. Meanwhile, the maximum absolute open flow and optimum fracture conductivity both increase as stress arch ratio increases. Compared with the case without stress arch, the optimum fracture conductivity increases by 50 %, while the maximum absolute open flow increases by 21.40 % with stress arch ratio of 0.5 when b0 equals to 0.0397 MPa-1. The stress arch greatly impacts on the stress sensitive permeability, permeability modulus and well performance, which can’t be neglected especially in the low and ultra-low permeability reservoir