Haitham M.S. Lababidi

Development of an expert system for underbalanced drilling using fuzzy logic

Abstract This paper documents the development of an expert system for screening wells that could be drilled underbalanced, and for aiding in the preliminary selection of appropriate underbalanced drilling fluids for a given range of wellbore and reservoir conditions. This approach combines a qualitative rule-based analysis for assessing formation damage and lost circulation potentials with quantitative analysis for assessing wellbore stability using geomechanical and petrophysical data. To make the analysis complete, a variety of other factors such as pipe sticking potential, wellbore geometry, type of fluid influx anticipated, pore pressure value, and cost benefit are also included in the expert-system decision trees. The main advantage of the expert system, developed in this study, is the use of fuzzy logic for handling cases that lend themselves to partial truth. This feature makes the system a powerful tool for analyzing ambiguous drilling scenarios. Results of compared field cases are encouraging and conformal to field practices. Allowing for human input, when essential data are lacking, makes the system a useful tool that can help less experienced individuals function near the level of proficient drilling engineers.

Optimization of module configuration in membrane gas separation

Mathematical models have been developed to optimize three configurations for membrane gas separation modules. The three systems include the single stage, the two stage, and the continuous membrane column (CMC). Analysis of the three systems is carried out for the case of enriching a binary mixture of methane and carbon dioxide, where the reject stream is the desired product. The cost optimization function includes the capital cost for compressors and membranes as well as the energy operating cost. The cost function is solved subject to a set of equality and inequality constraints. The equality constraints include the module balance equations and the permeation fluxes across the membrane. The inequality equations include constraints on mole fractions in permeate and reject streams, operating pressure, membrane area, and the amount of methane recovered in reject stream. Model equations for the three systems are solved using GINO, a program for nonlinear optimization. A quasi-Newton search method is selected and found quite efficient for solution of the equations. Over the range of parameters considered in the analysis, results show that the two stage configuration has a lower production cost than the other two systems. In addition, the operating cost for the CMC and the single stage systems are found to be comparable. Irrespective of this, the optimum amount of methane recovered is the highest for the CMC system. Although the optimum operating costs for the CMC and the single stage systems are higher than the two stage system, comparison should consider other factors including higher methane recoveries generated by the CMC system and the simplicity of design and operation for the single stage system.

Web-based expert system for food dryer selection

Abstract This paper describes an integrated web-based fuzzy expert system for food dryer selection. A modular approach to designing the system was employed. It consists of a number of knowledge sources controlled by a scheduler, which communicate through a common blackboard. The system has been fully implemented to run on the web and provides an excellent example of how a number of heterogeneous tools and applications can be integrated on the www. Java was used as the main programming language, and a new server-side technology, Java servlets, was utilised and found to be very effective in integrating different applications on the web. Rule-based knowledge sources and the inference mechanisms were implemented using ReSolver. The system, which also includes ‘foreign’ programs coded in Fortran, clearly demonstrated the integration of the various tools in a seamless user-friendly environment. The structure of the developed system is presented together with example runs to demonstrate its main functionality.

Energy retrofit study of an ammonia plant

Detailed energy integration study of the front-end of an existing ammonia plant has been performed, using recent advances in Pinch technology. Utility loads demanded by the existing process were found to be very close to the calculated minimum targets. This indicated that the selected ammonia plant is well integrated, and not much saving is expected through process-to-process energy integration. Alternatively, the retrofit study concentrated on better placement of available utilities. Two promising options have been investigated. The first one studied the flue gas temperature in the convection section of the primary reformer, and proposed new arrangements of the heating coils. Boiler feed water heating for high-pressure steam generation has been also considered as a possible source for reduction in energy consumption. Total benefit claimed amounted to 17.6% reduction in combustion fuel consumption. The overall results of this case study are promising. However, economical evaluation of the proposed modifications is essential. Additional possible reduction in energy consumption is also possible in energy and power integration of the back-end section.

Refinery advanced process control planning system

Abstract The process of enhancing a refinerys performance through advanced control usually requires extensive analysis on the plant to determine factors that are constraining the plant from reaching optimum production conditions. An advanced control planning environment (APCO) was developed using mixed integer-programming methodology. It was supported by a friendly graphical user interface (GUI), to make it easy and accessible to refinery planning engineers. Advanced process control benefits programmed into advanced process control optimizer (APCO) are based on benefits already computed for a major refinery in Kuwait. In here, APCO has been customized to adapt a simplified flowsheet model for a 60 000-barrel per day refinery. A number of case studies are included to demonstrate the capabilities of APCO. The case studies reflect situations encountered by decision-makers in refineries. These include single and multiyear plans, as well as self-funded and unit capacity limiting plans. APCO facilitates developing and evaluating different economical scenarios. Results show that analysis of APC benefits and their interaction among units would uncover APC implementations that are otherwise not considered by simplified payback period analysis.

Automating sandstone acidizing using a rule-based system

An expert system for automating sandstone acidizing has been developed in this study. The system consists of six stages, which were built following an acidizing logic structure that is presented in the form of decision trees. The six stages consist of formation oil displacement, formation water displacement, acetic acid, HCl pre-flush, main acid, and over-flush stage. The acid blends recommended by the system are damage-type specific, and account for the compatibility between the injected acid and the in situ crude in order to avoid formation of asphaltene sludge, or emulsions. The acidizing expert system has been implemented as an online web-based application. Applicability of this expert system to acidizing design has been illustrated using three documented actual field cases spanning the Niger Delta region, Algyo Oil field in Hungary, and the Dulang oil field in Malaysia. For Niger Delta field and the Algyo field cases the expert system produced an optimal main acid job design with recommended pre- and post-flushes that are in perfect agreement with successful field treatment. For the Dulang oil field, in actual practice, an organic clay acid was injected for removing problems of fines migration in a reservoir that has a high calcite content, with a moderate amount of feldspar and chlorite clay. The acidizing expert system recommended a chelant-based acid, which is a recent innovation that is considered a more cost-effective acid solution for dissolving fines in presence of calcite and other sensitive clay minerals.

An expert system for dryer selection using fuzzy logic

Abstract Dryer selection can have a major impact on product quality, particularly in the case of thermally sensitive materials such as foodstuffs. This paper discusses some of the principal factors that influence this process. The use of a fuzzy expert system as an aid in the preliminary selection of a batch dryer is described. This incorporates a novel ‘multiple goal’ approach in which different facets, such as dryer type, single or multiple dryers, and atmospheric or vacuum operation, are determined independently.

Non‐Isothermal Non‐Adiabatic Dehydrogenation of Cyclohexane in Catalytic Membrane Reactors

Abstract This study focuses on modeling and analysis of the non‐isothermal, non‐adiabatic, dehydrogenation of cyclohexane in membrane catalytic reactors. The dehydrogenation reaction is endothermic with a low equilibrium conversion of 0.06 at a temperature of 473 K and pressure of 101 kPa. The membrane reactor removes hydrogen from the reaction mixture and results in increase of the reaction conversion. The analysis is made as a function of feed flow rate, feed temperature, feed composition, inert flow rate in the feed stream, flow rate of sweep gas, pressures of the tube side and shell side, permeability constant of hydrogen, and tube diameter. The analysis also includes a study of the co‐current and the counter‐current flow modes. The results show lower conversion for the counter‐current flow mode, because of the decrease in the driving force for permeation. A comparison of model predictions against previous literature studies shows good agreement.

Environmental ranking of desalination plants: the case of the Arabian Gulf

ABSTRACT Performance indicators and ranking methods are effective tools for assessing the environmental impact of emerging technologies and comparing the operational efficiencies of different processes. Desalination of seawater, which is vital for solving the water shortage in the Arabian Gulf region, should be assessed due to its adverse environmental impacts on the shallow and closed Gulf basin. The main objective of the current work is to develop and implement an environmental assessment methodology capable of ranking alternative desalination processes and technologies based on their environmental performance. The proposed methodology starts with identification of relevant indicators and uses the relative ranking of desalination plants together with an aggregated environmental index. The assessment approach was tested on selected desalination plants in the Arabian Gulf region. The results showed that the ranking methods are effective in aggregating the influence of individual indicators to produce a numerical value that indicates the rank of studied desalination plants with respect to their environmental impact.

Application of controllability analysis tools during the conceptual design stage

Abstract This paper presents an extension to KBDS (Banares-Alcantara and Lababidi, 1995), a prototype design support system for process engineering, that will enable the application of controllability and dynamics studies at the early stages of design. The underlying object-oriented knowledge representation structure of KBDS is flexible enough to accommodate such extension. The proposed extension focuses on design models creation and representation, and means of evaluating these models. This includes the addition of steady-state and dynamic modeling capabilities and the provision of communication to external packages to support the analysis and evaluation of design alternatives. Two systems were considered for integration with KBDS: MATLAB (Math Works, Inc., 1993a) and Omola (Andersson, 1995). Communication with these external tools is provided in the first instance through object-oriented message passing; we are planning to use e p e e (Ballinger et al. , 1994) in the future. The integrated tools have been tested on the controllability of multiple CSTRs in series and effects of recycle streams. The control analysis sessions are found vital in supporting the evolution of design alternatives. They also highlight some features of KBDS in the support of the design process itself, i.e. the identification of design versions with the output generated by the control tools and the maintenance of decisions made during their application.