Pipelining of heavy crudes can be facilitated by preparing oil-in-water (O/W) emulsions of the crude, but separation of the oil from the water after pipelining is problematic if conventional surfactants are used. Long-chain acetamidines are CO 2 -triggered switchable surfactants, being surface-active when CO 2 is present but not when CO 2 is absent. Unfortunately, in the presence of CO 2 , they stabilize water-in-oil (W/O) emulsions of heavy crude rather than the desired O/W emulsions. However, in the absence of added CO 2 , several compounds (Na 2 CO 3 , three of the long-chain acetamidines, and two other amidines) stabilize O/W emulsions. These low-viscosity emulsions can later be broken by the addition of CO 2 . The residual oil content in the recovered water is lowest if the compound used to stabilize the original emulsion was a long-chain acetamidine.
Wax inhibitors are sometimes used to reduce the rate of wax deposition in pipelines. The efficiency of the inhibitors depends on several factors such as the right chemistry, injection or introduction at the correct location, targeting the right operating conditions and testing appropriately. It is known that bench top tests such as cold finger tests, while useful to qualitatively gauge chemical performance, are not useful to quantitatively predict the performance of a chemical under field operating conditions. This is because the operating parameters such as the temperature difference, heat flux, and shear rates experienced in the field cannot be reproduced in such bench top devices simultaneously.In this study, we discuss the use of a "cold disk" apparatus for screening chemicals to reduce wax deposition rates of a relatively waxy offshore crude oil. Several chemicals were screened by choosing temperature differentials similar to those expected in the field where maximum deposition was predicted to occur. The best chemical was then chosen for larger scale flow loop study. Flow loop deposition experiments were performed with the chosen chemical after appropriately choosing the flow rate and heat flux to drive the deposition. The results showed quantitatively good agreement with the cold disk experiment.Testing and agreement at such different scales provided a greater degree of confidence in the efficiency of the wax inhibitor, although it is understood that field performance may still vary depending on various other factors some of which relate to operating conditions, fluid composition, wax content, pipeline size and shear. Modeling deposition in the flow loop also improved the confidence in these results.
Performance of compact separators depends on implementation of stable and robust control strategies that are suited for specific applications. In this investigation, an intelligent control system has been developed for Compact Multiphase Separation System (CMSS©) which consists of integrated configurations of three compact separators, namely, Gas-Liquid Cylindrical Cyclone (GLCC©), Liquid-Liquid Cylindrical Cyclone (LLCC©) and Liquid-Liquid Hydrocyclone (LLHC). This is a two-part paper, the first part (current paper) deals with the Modeling and Simulation of the CMSS© and the second part deals with Experimental Investigation. The specific objective of this CMSS© configuration is to knock out free water from the upstream fluids. In mature oil fields, water handling poses a huge problem. Thus water knock out at the earliest stage helps in significant cost savings. A novel fuzzy logic control system has been designed and tested for change in set-point of differential pressure ratio in LLHC. Dynamic models have been developed for each of the above mentioned control systems for design of stable PID parameters. A dynamic simulation platform (DSP) has been developed based on these models in Matlab/Simulink™ for predicting the transient performance of the integrated system. Steady state mechanistic models of individual devices are integrated to the Matlab/Simulink™ platform using look up tables to predict the overall response of the CMSS© for different scenarios.
In this investigation, an intelligent control system has been developed for Compact Multiphase Separation System (CMSS©) which consists of integrated configurations of three compact separators, namely, Gas-Liquid Cylindrical Cyclone (GLCC©), Liquid-Liquid Cylindrical Cyclone (LLCC©) and Liquid-Liquid Hydrocyclone (LLHC). This is a two-part paper, the first part deals with the Modeling and Simulation of the CMSS© and the second part (current paper) deals with Experimental Investigation. A new dual differential pressure sensor system has been implemented and tested for GLCC©, to eliminate the error in liquid level measurement due to change in watercut. A new watercut based control system using downstream pump speed control has been designed and tested for the LLCC© system. A new cascaded control strategy for change in set-point of differential pressure ratio using underflow quality from hydrocyclone has been designed and developed. Comparison of CMSS© performance simulator and experimental results shows that the control system simulator is capable of representing the real physical system and can be used to validate the controller design. Fuzzy logic controller has been successfully implemented and tested. Experimental results show a similar trend as the dynamic simulator results for the various input conditions and scenarios. The results from theoretical and experimental studies have shown that Free Water Knock Out (FWKO) CMSS© system can be readily deployed in the field using the control system strategies designed, implemented and tested in this study. Reliability analysis for FWKO CMSS© system has been conducted. System reliability has been calculated from reliability of components and performance reliability of the system. A new protocol has been introduced to calculate performance reliability based on performance failure of the system from simulation data. This protocol has been proven to predict performance reliability of a new system which does not have prior information on failure of components or devices.
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