Márcia Peixoto Vega

Multi-objective dynamic optimization of fixed bed dryers: simulation and experiments

Abstract It is very important a thorough understanding of the drying operation (confident mathematical model) for solving the problems related to the optimization of a dehydration plant, which basic objective is the removal of water up to a certain desired level. Pareto optimization, which improves the performance of dryers for being appropriate to work with conflicting objectives, was implemented through simulation and experimental studies, using a fixed bed alumina drying unit.

Mathematical modeling of single cell protein and ethanol production by Kluyveromyces cicerisporus fermentation on whey

Abstract Phenomenological and empirical nonlinear models were built for describing experimental data of Kluyveromyces cicerisporus batch fermentation on whey, at different temperature and pH levels. The phenomenological model is based on cell death; substrate consumption due to product formation, cell growth and maintenance; substrate/product inhibition and growth-associated/nongrowth-associated product formation. The parameters estimation of the phenomenological model was carried out using the maximum likelihood estimation method. The empirical nonlinear neural network model identification employed traditional and the dynamic simulation analysis as the validation procedures.

Optimization of Performance Qualifiers during Oil Well Drilling

Abstract An optimization analysis of the drilling process constitutes a powerful tool for operating under desired pressure levels (inside operational window) and, simultaneously, maximizing the rate of penetration, which must be harmonized with the conflicting objective of minimizing the specific energy. The drilling efficiency is improved as the rate of penetration is increased, however, there are conflicts with performance qualifiers, such as down hole tool life, footage, vibrations control, directional effectiveness and hydraulic scenarios. Concerning hydraulic effects, the minimization of the specific energy must be constrained by annulus bottom hole pressure safe region, using the operational window, placed above porous pressure and below fracture pressure. Under a conventional oil well drilling task, the pore pressure (minimum limit) and the fracture pressure (maximum limit) define mud density range and pressure operational window. During oil well drilling, several disturbances affect bottom hole pressure; for example, as the length of the well increases, the bottom hole pressure varies for growing hydrostatic pressure levels. In addition, the pipe connection procedure, performed at equal time intervals, stopping the drill rotation and mud injection, mounting a new pipe segment, restarting the drill fluid pump and rotation, causes severe fluctuations in well fluids flow, changing well pressure. Permeability and porous reservoir pressure governs native reservoir fluid well influx, affecting flow patterns inside the well and well pressure. The objective being tracked is operating under desired pressure levels, which assures process safety, also reducing costs. In this scenario, optimization techniques are important tools for narrow operational windows, commonly observed at deepwater and pre-salt layer environments. The major objective of this paper is developing an optimization methodology for minimizing the specific energy, also assuring safe operation (inside operational window), despite the inherent process disturbances, under a scenario that maximization of ROP (rate of penetration) is a target.

MIMO Control during Oil Well Drilling

Abstract A drilling system consists of a rotating drill string, which is placed into the well. The drill fluid is pumped through the drill string and exits through the choke valve. An important scope of the drill fluid is to maintain a certain pressure gradient along the length of the well. Well construction is a complex job in which annular pressures must be kept inside the operational window (limited by fracture and pore pressure). Monitoring bottom hole pressure to avoid fluctuations out of operational window limits is an extremely important job, in order to guarantee safe conditions during drilling. Under a conventional oil well drilling task, the pore pressure (minimum limit) and the fracture pressure (maximum limit) define mud density range and pressure operational window. During oil well drilling, several disturbances affect bottom hole pressure; for example, as the length of the well increases, the bottom hole pressure varies for growing hydrostatic pressure levels. In addition, the pipe connection procedure, performed at equal time intervals, stopping the drill rotation and mud injection, mounting a new pipe segment, restarting the drill fluid pump and rotation, causes severe fluctuations in well fluids flow, changing well pressure. Permeability and porous reservoir pressure governs native reservoir fluid well influx, affecting flow patterns inside the well and well pressure. In this work, a non linear mathematical model (gas-liquid-solid), representing an oil well drilling system, was developed, based on mass and momentum balances. Besides, for implementing classic control (PI), alternative control schemes were analyzed using mud pump flow rate, choke opening index and weight on bit as manipulated variables in order to control annulus bottomhole pressure and rate of penetration. Classic controller tuning was performed for servo and regulatory control studies, under MIMO frameworks.

Experimental Control of Annulus Pressure While Drilling Oil Wells

Abstract Under a conventional oil well drilling task, the pore pressure (minimum limit) and the fracture pressure (maximum limit) define mud density range and pressure operational window. During oil well drilling, several disturbances affect bottom hole pressure; for example, as the length of the well increases, the annulus bottom hole pressure varies for growing hydrostatic pressure levels. In addition, the pipe connection procedure produces disturbances in well fluids flow, changing well pressure. The objective being tracked is operating under desired pressure levels, which assures process safety, also reducing costs, as drilling operation demands around U

Oil Well Drilling Inside Operational Window – Simulation and Experimental Control Studies

500,000.00/day. In this scenario, control techniques are important tools for narrow operational windows, commonly observed at deepwater and pre-salt layer environments. The major objective of this paper is controlling annulus bottom hole pressure of a drilling experimental unit, using the choke opening index as the manipulated variable, in order to guarantee safe operation (target annulus bottom hole pressure), despite the inherent process disturbances and under a scenario that maximization of ROP (rate of penetration) is a target.

Oil Well Drilling Process - Simulation and Experimental Multi-Objective Studies

Abstract Under a conventional oil well drilling task, the pore pressure (minimum limit) and the fracture pressure (maximum limit) define mud density range and pressure operational window. During oil well drilling, several disturbances affect bottom hole pressure; for example, as the length of the well increases, the bottom hole pressure varies for growing hydrostatic pressure levels. In addition, the pipe connection procedure, performed at equal time intervals, stopping the drill rotation and mud injection, mounting a new pipe segment, restarting the drill fluid pump and rotation, causes severe fluctuations in well fluids flow, changing well pressure. Permeability and porous reservoir pressure governs native reservoir fluid well influx, affecting flow patterns inside the well and well pressure. The objective being tracked is operating under desired pressure levels, which assures process safety, also reducing costs, as oil derrick operation demands around U

Optimization Studies of an Oil Well Drilling Process

500,000.00/day. In this scenario, control techniques are important tools for narrow operational windows, commonly observed at deepwater and pre-salt layer environments. The major objective of this paper is controlling annulus bottom hole pressure, through simulation and experimental studies, using mud pump flow as the manipulated variable, in order to guarantee safe operation (target annulus bottom hole pressure), despite the inherent process disturbances and under a scenario that maximization of ROP (rate of penetration) is a target.

Open/closed loop bifurcation analysis for identification and model based control of fluidized catalytic crackers

Abstract The pressure balance between the well section and the reservoir is important. If the pressure in the well is higher than the reservoir pore pressure (over-balanced drilling), the circulation fluids penetrate into the reservoir formation. On the other hand, if the pressure in the well is lower than the reservoir pore pressure (under-balanced drilling), the reservoir fluids migrate into the well annulus. Over-balanced drilling is the most used method for drilling oil wells. The reason for this is that it nearly eliminates the risk of blow-out, where the pressure in the reservoir causes large amounts of the reservoir fluids to penetrate into the well and follow the well to the surface. During drilling, disturbances that produce fluctuations in the well pressure might occur. As the well is drilled, the hydrostatic pressure increases because of the well length grow. In addition, the reservoir fluid influx changes the well flow rate and density of the well fluid mixture. Finally, the pipe connection procedure, which requires stopping and starting of the drill fluid, produce severe fluctuations in the well flow rates. At deepwater environments, complex situations frequently occur, such as narrow operational window between pore and fracture pressures, mainly when lower collapse is higher than pore pressures and/or upper collapse is lower than fracture pressures. Solving optimization problems concerning the drilling process constitutes a powerful tool for operating under desired pressure levels and simultaneously maximizing the penetration rate, which reduces costs, as oil derrick operation demands around U

Open/closed loop bifurcation analysis and dynamic simulation for identification and model based control of polymerization reactors

220,000.00/day. The major objective of this paper is applying optimization strategies to an oil well drilling process, in order to guarantee safe operation (target annulus bottom hole pressure) also maximizing drilling rate.