Minimize Water Production Research Articles

Optimization of vacuum membrane distillation and advanced design of compact solar water heaters with heat recovery

With the escalating global population, freshwater scarcity has become a pressing challenge. To address this issue, this paper presents a novel compact solar water heater (CSWHT) system incorporating heat recovery and submerged-membrane filtration. The research aims to develop an efficient desalination method that reduces water production costs and maximizes output. The system comprises a feed storage tank, a vacuum membrane distillation (VMD) system positioned atop the submerged CSWHT, a liquid ring vacuum pump (LRVP) utilizing waste heat from the outlet to preheat the feed, and hollow fiber membranes.Three critical parameters, namely the mass of the feed in the storage tank, the number of hollow fiber membrane rows, and the feed volumetric flow rate, were optimized using a multi-objective non-dominated sorting genetic algorithm II (NSGA II) to minimize water production cost (WPC) while maximizing water production. Subsequently, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) was employed to identify the optimal scenario from among the selected best solutions.For Mediterranean seawater and a 6 m2 solar collector area, the multi-objective NSGA II algorithm identified 20 membrane rows per collector, 334.4 kg feed mass in the storage tank, and 0.027 kg.s−1 feed mass flow rate as the optimal system parameters. Under these optimized conditions, the system exhibited a daily production capacity of 92.5 kg water, 4.6 kg chloride, and 0.03 g bromide, while achieving a production cost of 12.2 USD.m−3 and a gain output ratio (GOR) of 1.6. These results highlight the system's remarkable potential for desalination with high efficiency and low cost. Future research should focus on scaling up the system and exploring its applicability in various geographical locations.

Performance of the Petroleum Reservoir Under Waterflooding at the Petrochad Field in Mangara-Chad

The Mangara petroleum field is made up of three superimposed reservoirs (C, D, E) with approximately 2500 m depth. These are unconsolidated sandstone reservoirs with an underlying active aquifer. The petrophysical properties of the reservoirs are relatively good as it’s a self-sourced unconventional reservoir based on its organic richness characteristics unconventional resource opportunity as tight carbonate reservoir. Tank pressure is approximately 2900 psi, for an average temperature of 180°F. Of the 50 wells initially drilled, 23 are currently producing. The pressure is support by 04 injector wells, and daily production is estimated at approximately 12,000 bbl/d. To maximize oil production and minimize water production, the positions of injection wells were moved, which permitted to reduce the number of producing wells from 23 to 18. The result revealed that this scheme can maintained the pressure at desired levels of 2900 psi, until year 2040 and reversed the current trend in water production, which was 14,000 bbl/d. In the predicted scenarios, cumulative production will be maintain at 25,000 bbl/d with a daily production of around 18,000bbl of oil compared to formerly figure of 7000 bbl of water until 2040.

Retrofitted Autonomous Inflow Control Devices Optimize Completions Design

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 31301, “Optimized Completions Design Using Retrofit Autonomous Inflow Control Devices,” by Ezinne A. Nnebocha, Schlumberger; Akinola Akinbola, NPDC; and Omagbemi G. Kayakor, First Hydrocarbon Nigeria, et al. The paper has not been peer reviewed. Copyright 2021 Offshore Technology Conference. Reproduced by permission. _ Discovered in 1964, the Beta Field in the Niger Delta sedimentary basin consists of 25 stacked hydrocarbon-bearing reservoirs between 5,500 and 12,000 ft true vertical depth subsea (TVDSS). Oil production peaked at 8,900 STB/D shortly after field startup and has been on the decline. Two horizontal wells, Beta 7 and Beta 8, were planned in the field, but a production forecast of the planned wells showed potential early water breakthrough and high water cut. Autonomous inflow control devices (AICDs) were deployed successfully in the Beta Field for the purpose of minimizing water production and maximizing oil recovery. Introduction After history matching, the two new horizontal wells were simulated to target the sweet spots in the reservoir using constraints of oil saturation, porosity and permeability limits, and distance to the oil/water contact (OWC). The history-matched model was then used in forecasting the production profile for the new wells using a target liquid production rate of 2,000 STB/D. The production forecast without inflow control showed water breakthrough in the new wells within the first month of production, reaching to 45% within 3 months of production. Cyclonic AICD completions then were simulated for Beta-7 and Beta-8 horizontal wells, which showed improved oil production and delayed water production. AICD Retrofit Design Cyclonic AICDs were selected for application in the Beta Field to improve production performance. However, the short lead time required for the job execution and border closures caused by the COVID-19 pandemic created restrictions in mobilizing personnel and equipment from outside the country. It did not appear that the equipment could arrive in time for the job. The conventional nozzle-based passive ICD joints were available in country. Therefore, leveraging engineering skills and operational knowledge, a solution to retrofit AICD nozzles in existing ICD screen joints was conceived. The engineering team developed a design of machined components that could be quickly manufactured at the facility of the original equipment manufacturer (OEM) and shipped to the location. Failure-mode and effects-analysis assessment, and subsequent risk-management procedures, became useful to manage the process locally with the help of the remote OEM team. A step-by-step procedure on the retrofit was devised. Fig. 1 shows a flow chart used to guide the retrofitting process and the retrofitted AICD joints after modification. Upon completion of the screen retrofit, the joints were quality-checked and inspected to verify their preparedness for well completion.

A review of coal bed methane production techniques and prospects in India

This paper presents a comprehensive analysis of the challenges and opportunities associated with Coalbed Methane (CBM) extraction in the energy industry. It covers various aspects including the extraction process, major challenges faced, water management strategies, and the social and environmental implications of large-scale CBM production. CBM extraction involves the gradual transformation of buried plant materials into coal over millions of years, resulting in the release of methane and other by-product gases. Understanding the adsorption mechanism of CBM molecules onto the coal matrix and the role of the cleat system is crucial for efficient extraction. The cleat system, composed of face cleats and butt cleats, creates interconnected pathways for gas flow within coal seams, facilitating the extraction of CBM. However, water management poses a significant challenge in CBM extraction, as water production within the cleat system needs to be effectively managed to reduce pressure and enable gas desorption. Techniques such as dewatering and gas diffusion are employed to optimize gas production rates while minimizing water production. Large-scale CBM production has social and environmental implications, and it can result in land use changes, community displacement, and conflicts over resource allocation. Additionally, the release of methane during extraction contributes to greenhouse gas emissions and climate change. Mitigation measures and thorough assessment are necessary to minimize these impacts and ensure responsible and sustainable CBM development. India, with its abundant coal reserves and identified CBM producing blocks, holds significant prospects for CBM production. The paper discusses these prospects, considering the country's coal reserves and the current status of CBM exploration and production activities. It informs of future energy planning of CBM development in India. Thus, this comprehensive analysis discusses the multifaceted aspects of CBM production, from extraction challenges to environmental considerations, and details potential of CBM sustainable development in India.

Feasibility of desalination by solar stills for small community scale freshwater demand

Solar stills are conventional desalination systems based on direct solar heating. While their productivity is limited, their simple construction and low maintenance requirements makes them an attractive and feasible option for community-scale desalination. This study shows that low-cost solar stills are capable of producing sufficient freshwater for small disadvantaged communities at costs lower than competing technologies. A variety of solar still materials are investigated showing that the cost of freshwater produced is sensitive to the solar still cost. Inexpensive carbon black particles dispersed in the water are used to increase solar still performance, and a set of low-cost solar still materials are identified from a pool of candidate materials to minimize water production cost by means of optical and energy analyses. In addition, communities with fewer than 10000 residents are identified in the reference region of California to perform an energy analysis to determine freshwater productivity yield and the cost of freshwater production. It is determined that a 10000 m2 solar still could produce freshwater meeting the requirements of small rural communities costing less than $ 7.71 /m3. Attractive investment options are available that could reduce the cost of water produced to less than $ 1.75 /m3. Solar stills were found to be feasible when comparing the cost of freshwater produced with a comparable photovoltaic reverse osmosis system. The proposed methodology can be extrapolated to determine the feasibility of solar still-based desalination systems in other geographical locations. From the results of the analysis, solar stills are proposed for effectively producing low-cost freshwater to increase the accessibility of freshwater in small rural communities.

Hydrophobically modified melamine‐formaldehyde sponge used for conformance control and water shutoff during oil production

AbstractPolymer or polymer gels have been widely used to control excessive water during oil production by homogenizing injection profile and reducing water cut in the produced fluids. However, the gels used are generally unable to selectively minimize water production, and face the challenge of syneresis of gels under high temperature and high salinity environment. In this work, melamine‐formaldehyde sponge was modified with AlCl3 solution, rendering a transition from hydrophilic to hydrophobic state with a water contact angle of 130° on the surface of the modified product. Filtration results show that mineral oil and water can be selectively separated with the hydrophobically modified sponge powders. Simulated water shutoff experiments demonstrated the blockage efficiency against water was 30% higher than that against oil, and the oil production was increased 7.4% after blocking. The parallel profile control tests confirmed that the fraction flow of high permeable channel decreased about 75%, accompanied with 60% rise of oil recovery factor. These results indicated that such hydrophobic materials can significantly reduce excessive water production, and this work provided a new idea to offer a low‐cost hydrophobic material for conformance control and water shutoff during oil production.

Sugarcane bagasse for environmentally friendly super-absorbent polymer: synthesis methods and potential applications in oil industry

Super-absorbent polymer (SAP) is able to absorb water by multiple times more than its own weight. Sugarcane bagasse (SCB) raw material has been excessively produced as a byproduct in sugar factory. The synthesis of SAP from SCB creates a balance between the utilization of industrial by-product and the resulted environmentally friendly material. In oil production water might be a troublesome, thus minimizing water production while extracting oil is essential. Besides, diversion of the flow in heterogeneous reservoir optimizes the oil production. SCB-SAP might have the potential to act as a water absorbing agent and flow diverter by taking the advantage of SAP high swelling ratio characteristic. This study provides the information of SCB-SAP synthesis methods and highlights the current application of SAP in oil industry, including the laboratory studies and field tests.

An analytical investigation on the energy efficiency of integration of natural gas hydrate exploitation with H2 production (by in situ CH4 reforming) and CO2 sequestration

Natural gas hydrate is considered as a new sustainable energy resource with huge potential and the increasing demand for green fuel hydrogen provides an opportunity for adopting alternative routines to produce hydrogen. The novel integrated system: natural gas hydrate exploitation by CO2/H2 replacement integrated with in situ methane reforming, can simultaneously produce H2 and sequestrate CO2. However, there is still a lack of in-depth research on the energy efficiency and economic performance of the novel integrated system. Therefore, we conducted a process design, modeling and simulation, exergy analysis, process integration, and sensitivity analysis of the integrated system for the first time. When the CO2 composition of the injected gas is 72 mol %, that is, the CH4 composition of the produced gas is 48.07 mol %, the exergy ratio of the integrated system after process integration is 1.54. The operating profit is 6.41 MM$/y. The exergy efficiency of the methane reforming subsystem is 0.62. The CO2 emission from methane reforming subsystem can be sequestrated through the natural gas hydrate exploitation by CO2/H2 replacement, achieving CO2 sequestration amount of 3914 kg/h with the CO2 sequestration ratio of 65%. The CO2 sequestration amount, CH4 composition in the produced gas, exergy ratio, and operating profit of the integrated system decrease as the CO2 composition of the injected gas decreases. Finally, sensitivity analysis results reveal that increasing the CH4 composition of the produced gas, minimizing water production, and increasing gas production in the exploitation unit will improve the energy performance of the novel integrated system. This work can guide the evaluation of energy efficiency and economy for the subsequent commercial exploitation of natural gas hydrate.

Economic performance of membrane distillation configurations in optimal solar thermal desalination systems

In this study we provide a comprehensive evaluation of the economic performance and viability of solar membrane distillation (MD). To achieve this goal, process models based on mass and energy balances were used to find the minimum cost of water in MD systems. Three MD configurations: direct contact, sweeping gas, and vacuum MD, were compared in terms of economic cost and energy requirements in optimized, solar-driven desalination systems constrained to produce 10 m3 d−1 of distillate from 3.5% or 15% salinity water. Simulation results were used to calculate the water production cost as a function of 13 decision variables, including equipment size and operational variables. Non-linear optimization was performed using the particle swarm algorithm to minimize water production costs and identify optimal values for all decision variables. Results indicate that vacuum MD outperforms alternative MD configurations both economically and energetically, desalting water at a cost of less than $15 per cubic meter of product water (both initial salt levels). The highest fraction of total cost for all configurations at each salinity level was attributed to the solar thermal collectors—approximately 25% of the total present value cost. Storing energy in any form was economically unfavorable; the optimization scheme selected the smallest battery and hot water tank size allowed. Direct contact MD consumed significantly more energy (primarily thermal) than other MD forms, leading to higher system economic costs as well.

Cost and energy needs of RO-ED-crystallizer systems for zero brine discharge seawater desalination

A zero brine discharge seawater desalination concept integrating reverse osmosis (RO), electrodialysis (ED) and crystallizer into a single system (REC) is presented. Analytical models were used to optimize parameters and minimize water production costs. Parameters varied were: the ratio of seawater to RO brine in the ED diluate channel, ED current density, ED diluate outlet salinity, electricity and salt prices, and RO recovery by adding high pressure RO (HPRO). Using only RO brine instead of only seawater in the ED diluate channel reduced water production costs by 87% from 27 to 3.5 $/m3 while increasing salt production costs 26% from 135 to 170 $/tonne-salt. The former was best for brine minimization, and the latter for salt production. Optimizing ED current density reduced REC costs by another 14% to 3.0 $/m3 while increasing specific energy consumption 26% to 12.7 kWhe/m3, corresponding to a Second Law efficiency of 18%. Adding an HPRO stage was uneconomical as it increased specific costs 21%. A salt price of 104.5 $/tonne-salt will justify the cost of adding an ED-crystallizer. REC systems may be economically feasible in parts of the Middle-East. Producing other products such as Mg(OH)2 or Br2 may further improve economics.

Development of fly ash reinforced nanocomposite preformed particle gel for the control of excessive water production in the mature oil fields

One of the appropriate methods to minimize water production and increase sweep efficiency is the utilization of Preformed Particle Gel (PPG) in the mature oil fields. In this paper, a new fly ash reinforced nanocomposite PPG was developed by the reaction of acrylamide as monomer, N,N′-Methylenebis (acrylamide) as crosslinker and nano fly ash in presence of Potassium Persulfate as initiator and it was compared with a conventional PPG which was designed without nano fly ash. On the incorporation of nano fly ash, swelling performance and thermal stability of PPG had increased significantly. Rheological data revealed that dynamic moduli (G′ and G″) of fly ash reinforced nanocomposite PPG has improved viscoelastic properties with a higher value of critical shear stress as compared to conventional PPG. The single sandpack flow experiment has shown the injectivity of nanocomposite PPG into the sandpack with a maximum resistance factor of 60.57. However, parallel-sandpack flow experiment showed that the newly developed nano fly ash reinforced nanocomposite PPG has a profile improvement rate of 92.98% and 97.83% for the permeability contrast of 2.16 and 4.14 respectively and hence it may be a promising agent in reducing excessive water production in mature oil fields.

Trading the Economic Value of Unsatisfied Municipal Water Demand

Abstract. Modelling and optimization techniques for water resources allocation are proposed to identify the economic value of the unsatisfied municipal water demand against demands emerging from other sectors. While this is always an important step in integrated water resource management perspective, it became crucial for water scarce Countries. In fact, since the competition for the resource is high, they are in crucial need to trade values which will help them in satisfying their policies and needs. In this framework, hydro-economic, social equity and environmental constraints need to be satisfied. In the present study, a hydro-economic decision model based on optimization schemes has been developed for water resources allocation, that enable the evaluation of the economic cost of a deficiency in fulfilling the municipal demand. Moreover, the model enables efficient water resources management, satisfying the demand and proposing additional water resources options. The formulated model is designed to maximize the demand satisfaction and minimize water production cost subject to system priorities, preferences and constraints. The demand priorities are defined based on the effect of demand dissatisfaction, while hydrogeological and physical characteristics of the resources are embedded as constraints in the optimization problem. The application to the City of Amman is presented. Amman is the Capital City of the Hashemite Kingdom of Jordan, a Country located in the south-eastern area of the Mediterranean, on the East Bank of the Jordan River. The main challenge for Jordan, that threat the development and prosperity of all sectors, is the extreme water scarcity. In fact, Jordan is classified as semi-arid to arid region with limited financial resources and unprecedented population growth. While the easy solution directly goes to the simple but expensive approach to cover the demand, case study results show that the proposed model plays a major role in providing directions to decision makers to orient their policies and strategies in order to achieve sustainability of scarce water resources, satisfaction of the minimum required demand as well as financial sustainability. In addition, results map out national needs and priorities that are crucial in understanding and controlling the complexity of Jordan's water sector, mainly for the city of Amman.

Optimal Number of Effects for Multi Effect Evaporation Seawater Desalination Process Using Solar Thermal Energy-Plate Evaporators

Seawater desalination using Multi effect-plate evaporators and solar energy is one of very promising ways to deal with fresh water shortage and pollution in the same time. Indeed, falling film plate evaporators are becoming more used in the desalination applications. This is because of their multiple advantages compared to tubular evaporators such as high heat transfer rate and low investment cost. This study presents the methodology used for sizing and optimization of plate evaporators for seawater desalination unit using multi effect evaporation and solar thermal energy. The pilot plant unit operates with hot water provided by solar vacuum tubes. The unit was designed for a production capacity of 5 to 7 m3/day of fresh water obtained from evaporation of 28 to 30% of feed seawater. The modeling equations are given at steady-state conditions and they are based on mass, heat balance and heat transfer equations, and thermodynamic and physical properties of each stream. MATLAB programming software is used to resolve the developed algorithm. This work focuses more on studying and analyzing the impact of the number of effects on the total required heat transfer area, the required thermal energy and therefore on the specific cost of water. The obtained results show that it is more beneficial to use nine effects, which gives the key solution for minimizing water production cost. The optimal design shows that the total required heat transfer area of evaporators and the last condenser is approximately equal to 42 m2 and the thermal energy needed to drive the pilot unit is about 64 kW.

Production Optimization in Waterfloods: A New Approach to Interwell-Connectivity Modeling

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 182450, “Production Optimization in Waterfloods With a New Approach to Interwell-Connectivity Modeling,” by Xiang Zhai, Tailai Wen, and Sebastien Matringe, Quantum Reservoir Impact, prepared for the 2016 SPE Asia Pacific Oil and Gas Conference and Exhibition, Perth, Australia, 25–27 October. The paper has not been peer reviewed. In the complete paper, the authors present a novel methodology to model interwell connectivity in mature waterfloods and achieve an improved reservoir-energy distribution and sweep pattern to maximize production performance by adjusting injection and production strategy on the well-control level. The method involves a reduced-physics-based fast numerical tracer test on each well, which yields interwell connection strength or well-allocation factors (WAFs), and then a data-driven efficiency model on each interwell connection calibrated automatically from the injection and production history of the reservoir. Introduction The approach combines and balances the advantages of both simulation and data-driven techniques. The approach models interwell connections based on a relatively mature waterflood history and performs fast forecast and waterflood optimization on the basis of the interwell-connection analysis. Injector/producer connections are identified by computing WAFs with a numerical tracer method. Then, a data-driven empirical efficiency model is adopted that de-fines the profile of the oil cut of each interwell connection, and reservoir-production history is used to calibrate the model. Therefore, each interwell connection is quantified with two critical parameters: WAF and connection efficiency. The reservoir model is simplified into a connection-based network model that can be used to predict oil and water production without use of rigorous time-dependent numerical simulation. A production-optimization algorithm is then implemented. The optimization objective is to minimize water production while maintaining oil-production rate, subject to a range of practical constraints. The production optimization is integrated into a numerical-simulation model, and a blind test is run for 6 months. A significant decrease in water production is observed. Methodology Waterflood Surveillance. WAF. In the process of waterflooding, water is injected into injectors to displace remaining oil. In this water/oil communication system, incompressibility is assumed in fluid dynamics and reservoir rock. This assumption is equivalent to assuming that pressure communication between any two points in the reservoir is essentially instantaneous. The WAF quantifies the strength of connection between two wells of different types. WAF is often computed by tracing streamlines and counting the number of streamlines between wells. However, the streamline-based method is incompatible with a dual-porosity system, and in general has poor performance in unstructured grids. The authors adopt a stationary numerical tracer method to compute WAF. The equations used in this process are presented in the complete paper.

A Novel Integrated Approach to Oil Production Optimization and Limiting the Water Cut Using Intelligent Well Concept: Using Case Studies

Intelligent well technology has provided facility for real time production control through use of subsurface instrumentation. Early detection of water production allows for a prompt remedial action. Effective water control requires the appropriate performance of individual devices in wells on maintaining the equilibrium between water and oil production over the entire field life. However, there is still an incomplete understanding of using intelligent well concept to control unwanted fluids and the way this leads to improving hydrocarbon recovery. The present study proposes using intelligent well technology to develop a new integrated methodology for selecting/ranking the candidate wells/fields, interval control valve (ICV) size determination, and ICV setting optimization. Various technical and economical parameters weighted by expert opinions are used for candidate well/field ranking to implement the intelligent technology. A workflow is proposed for ICV size determination based on its effect on a predefined objective function. Inappropriate ICV size selection leads to suboptimum production scenarios. Furthermore, this study proposes an efficient ICV setting optimization in an intelligent well. The objective function can maximize cumulative oil, minimize water production, or conduct both. It was shown that for selecting the optimized cases, the balance between water and oil production under predefined criteria should be practiced. Real case studies were considered to demonstrate the effectiveness and robustness of the proposed methodology. A considerable improvement in the objective function was achieved using the developed methodology.

Multi-objective optimization for rapid and robust optimal oilfield development under geological uncertainty

Optimal well placement is critical to oil and gas field development. Typical workflows involve procedures to place a new well or a group of new wells in a reservoir in order to maximize some pre-defined reservoir performance metric. However, there are two main drawbacks with these traditional optimization approaches: First, the impact of geological uncertainty is often neglected or there may be no framework to include geological uncertainty. Second, traditional optimization techniques normally cannot meet the requirement of optimizing two or more conflicting objectives simultaneously—this may be useful when maximizing oil recovery while also minimizing water production. Consequently, in recent years, multiple objective optimization to obtain robust solutions that minimize the decision risk under geological uncertainty becomes a topic of renewed interest. Therefore, in this work, we develop a new work flow for well placement optimization while considering geological uncertainty in reservoir models. In general, when considering geological uncertainty, the primary goal is to maximize the mean net present value (NPV) over all realizations. However, restricting the search to simply maximizing the mean NPV may be inappropriate or inadequate for decision-making. A more reasonable choice is to maximize the mean NPV while minimizing the spread of the optimal NPV’s obtained for each realization. Therefore, in this work, we apply multi-objective optimization techniques to maximize the mean and minimize the variance of NPV values over all geological realizations to provide robust well placement solutions for decision-makers to select according to their risk attitude towards field development plans.

Recovery Optimization of an Oil Reservoir by Water Flooding under Different Scenarios; a Simulation Approach

Water flooding used in secondary oil recovery to level up reservoir pressure can be enhanced in order to fit the reservoir conditions to optimally recover oil. The main goal consists in maximizing oil recovery while minimizing water production. As the dynamic of two immiscible flows is governed by its flow and rock properties and reservoir condition, the water flood optimization must be appropriately performed for a single reservoir. In this case study, it is shown theoretically and by means of Eclipse 100 that according to the basic elementary reservoir characteristics, certain parameters can be added and changed to obtain an optimum oil recovery for a faster and a slower water case. In each run reservoir characteristics and oil properties were fixed while water flooding parameters were changed. Both homogeneous and heterogeneous reservoirs were tested. Then, the graphs generated at each run are interpreted and the variables are adjusted accordingly. Much care was taken to minimize the cost while achieving high oil cut versus water cut (or water production) for the longest time interval within water flood life if not the whole duration. A single major problem which Eclipse 100 does not take into account is starting injection at an optimum time. As a result, both injection and production were started at the same time. Despite this, the cases were able to be compared with each other as with the initial base case (no injection). Moreover, conclusion and recommendations were drawn based on the results and analysis with regard to the recovery optimization.

Numerical modeling and optimization of vacuum membrane distillation module for low-cost water production

A two-dimensional numerical model, involving energy conservation, momentum transport and continuity equations, was developed to provide the profiles of temperature, velocity and pressure of vacuum membrane distillation (VMD) process using hollow fiber module. The theoretical prediction was in good agreement with the experimental results from literature. Four design and operation variables, including feed temperature, hollow fiber length, feed volume flow rate and vacuum pressure, were optimized to minimize water production cost (WPC) using genetic algorithm (GA). A case study shows that the WPC can be decreased by 38.1% in comparison with the non-optimized VMD process. Meanwhile, a general guidance for reducing the WPC was also provided. The feed temperature should be adopted as high as possible, while the hollow fiber length cannot be too long to result in a decrease in water flux and an increase in pressure drop. The flow rate is recommended to take a lower bound value and the moderate degree of vacuum is preferable. This study indicates the importance of VMD system optimization to minimize water production cost.

Finite Element Simulation of Compression of Elastomeric Seals in Open Hole Liners

Control of water flow in open hole wells is an urgent necessity to minimize water production and maximize oil output. Elastomers provide tight seals as they deform against formation during the expansion process of a solid expandable tubular. A better prediction of behavior of elastomers in compression will achieve an effective sealing mechanism. Due to the inherent nonlinearity of tubular expansion and elastomer compression against open hole formation, a closed form solution is extremely difficult to obtain. Finite element modeling provides a viable alternative, as an approximate simulation tool, to determine the seal pressure without significant compromise on the complexity of the problem. The finite element analysis software is employed to model the tubular expansion resulting in compression of elastomer seal to effectively isolate unwanted water producing zones. The formation is modeled as a rigid body or an elastic or elastic-plastic material. Two different boundary conditions, fixed-free and fixed-fixed, are employed depending on prevailing practices of oil operators in such applications. The effect of seal length and thickness, compression ratio and shear resistance at seal-formation interface are determined on the contact pressure between seal and formation.

Reverse osmosis desalination with high permeability membranes — Cost optimization and research needs

Reverse osmosis (RO) water desalination is now well established as a mature water desalination technology. With the current generation of seawater and brackish-water RO membranes, it is now both economically and technically feasible to desalt brackish water and seawater on a large scale. In order to further expand the applications of RO desalting technologies, optimal process conditions must be selected to minimize water production costs associated with energy consumption, membrane replacement costs, chemical usage, and residual brine concentrate management. In the present review, a multi-pronged process-optimization approach for reverse osmosis desalination is presented. A theoretical framework discussed for optimizing energy consumption with and without energy recovery devices (ERDs), considering the impact of membrane replacement and brine management costs. The approach enables quantification of the optimal water recovery of RO desalting, considering various factors including the use of energy recovery devices, the topological arrangement of membrane modules (e.g., single stage, multi-stage and multi-pass processes), and the costs associated with membrane replacement, brine treatment and brine disposal. Comparative analyses of single vs. two-pass RO desalting operation subject to temporally varying feed salinity were carried out to demonstrate operational approaches for minimizing the specific energy consumption. In addition, the roles of brine treatment and disposal was analyzed to demonstrate the potential for optimizing RO desalting cost while taking into account the constraints imposed by antiscalant effectiveness against membrane scaling and the associated brine management challenge. The present analysis concludes that further reduction to RO desalination cost is less likely to arise from the development of membranes with higher permeability than the current generation, but is more likely to arise from optimal process configuration and control schemes, utilization of low-cost renewable energy sources, improvements in membranes' fouling resistance and rejection with respect to specific contaminants, and developments of less-chemical intensive feed and brine treatment strategies.