Engineering Literature

Crude oil is one actively traded commodity globally. Its demand has been growing steadily over the decades, from 60 million barrels per day to 84 million barrels per day (Hasan et al , 2010). In Nigeria, crude oil production has grown from a little above 1000 barrels per day in 1970 to over 3000 barrels per day in 2010 (Fig. 1.1). The world production was conservatively 73 million barrels per day in the year 2005 and within the range of 72 and 75 million barrel per day between 2005 and 2010. Fig. 1.1. Nigerian crude oil production.

In this study, we evaluate the characteristics of four reservoir fluids sampled from two offshore fields in the Gulf of Mexico as well as their propensities towards paraffins deposition due to temperature and/or pressure variations. State-of-the-art techniques, namely a cross polarized microscopy and a laser based solids detection system, have been used to measure the onsets of paraffin crystallization temperatures, also known as wax appearance temperatures ͑WAT͒ and/or cloud points. The results are presented, discussed and compared to reported field data. Explanations for the observed differences and/or similarities between laboratory and field WAT are proposed.

Pipeline transportation of heavy oils as oil-in-water emulsions has been proposed as an alternative to blending the crude oil with natural gas condensate or other diluent. An 18 m long, 0.02 m I.D. closed loop was constructed to investigate the behaviour of an emulsified Cold Lake crude oil under pipeline flow. Pressure drop was measured as a function of flow rate for freshly produced emulsions to establish correlations of friction factor versus Reynolds number. Stability was observed for long term pipeline flow. The time at which the emulsion breakdown occurred was found to be a function of oil concentration and shear rate. The breakdown of the emulsion was clearly indicated by a simultaneous change in the system variables of pressure drop, temperamre and power required to turn the pump at constant speed. Le transport par gazoduc des huiles lourdes sous forme d'Cmulsions d'huile dans I'eau a CtC suggCrC comme alternative au mCIange de brut avec un condensat de gaz nature1 ou un autre diluant. On a construit un circuit en boucle de 18 m de long et 0.02 m de diametre intkrieur pour Ctudier le comportement h I'tcoulement dans un pipeline d'un brut de Cold Lake CmulsifiC. On a mesure la perte de charge en fonction du dCbit pour des Cmulsions fraichement produites. afin d'ttablir des corrCIations du facteur de friction en fonction du nombre de Reynolds. La stabilitC a CtC observCe pour un Ccoulement en pipeline de longue durke. Le temps auquel se produit la rupture de I'tmulsion s'avere &tre une fonction de la concentration de I'huile et du gradient de vitesse. Cette rupture se manifeste clairement par un changement simultanC dans le systeme de la perte de charge, de la temp6rature et de la puissance requise pour faire tourner la pompe a vitesse constante.

This study looked to improve reproducibility in the procedure to determine the yield stress of water-in-oil (W/O) emulsions prepared with waxy crude oil. The influence of various experimental variables was studied: measurement geometry, emulsion cooling rate, shear stress during the cooling step, gap reduction (parallel plates), final gap (parallel plates), and conditioning steps. The measured yield stress varied significantly depending upon the measuring geometry used (from 100 to 500 Pa). The geometries cross-hatched parallel plate (D = 60 mm) and grooved coaxial cylinder measured the highest yield stress, and it was observed that the shear stress during cooling was the most important measurement variable in the emulsion yield stress.

The deposition of paraffin wax from crude oil at low temperatures due to wax deposition, high pour point, high viscosity, and weak flow capability is among the critical and persisting challenges faced by the petroleum industry. In this study, a new para-decyloxy allyl benzoate (I10) was prepared, polymerized into HI10, and copolymerized with dioctadecyl maleate into MHI10 via the freeradical polymerization method employing azobisisobutyronitrile and toluene as the initiator and solvent, respectively. The prepared monomer was characterized by spectroscopic analyses (Fourier-transform infrared (FT-IR)) and proton nuclear magnetic resonance. Further, the polymers were characterized by FT-IR, and their average molecular weights were determined by gel permeation chromatography. The prepared compounds were taken in different concentrations and then tested as flow improvers of Qarun waxy crude oil using pour point depression and rheological parameters. The results of this test indicated th...

Chemical methods are the most convenient and economical for wax precipitation and deposition prevention. The chemical additives so far in use have varied limitations, ranging from high cost to limited spread of crude oil that a particular additive can handle. The influence of cheaper natural chemicals, obtained from plant seeds (jatropha -JSO, rubber -RSO and castor -CSO) on the rheological properties and wax deposition tendencies of Nigerian waxy crude oil were investigated. Previously tested synthetic chemical additives (triethanolamine -TEA and xylene) were simultaneously examined too on the crude oils for comparative study. Four different crude oil samples obtained from Niger Delta region of Nigeria used for the study were characterized to obtain their hydrocarbon composition, wax content, pour points, viscosities, specific gravity and APIg using standard methods. The rheological properties such as apparent viscosity, plastic viscosity, yield stress were determined for the crude oils doped and undoped with the chemical additives using Fann V-G Standard Viscometer. The results obtained revealed that oils from the three seeds could be used as flow improvers and pour depressants for Nigerian waxy crude oil. Jatropha and castor seed oils depressed the pour point than the previously investigated triethanolamine. They are capable of depressing the pour point up to about 17 • C, and they can also reduce the viscosity of the waxy crude oil appreciably within 0.1-0.3% (v/v) dosage concentration. Also, CSO could exhibit as high as 77.7% paraffin inhibition efficiency (PIE) and JSO 73.5% at low concentration of doping.

Pig in pipelines performs operations for cleaning the pipe interior and internal inspection. In the past few years many 1D models have been developed to simulate the process because of their reduced computational cost; however, they rely on simplifications which are not always valid. In this paper, the results of a three-dimensional (3D) numerical investigation of the interaction between a waxy-oil and a dynamic sealing pig in a pipeline are presented. The results are obtained at a reduced computational cost by using a moving frame of reference, and an "injection" boundary condition for the wax deposited on the wall. The effect of the temperature and the wax particles' size has been investigated. The 3D results show the structure assumed by the debris field in front of the pig. In particular, a lubrication region at the bottom of the pipe, whose dimensions are temperature dependent, is shown. This information cannot be deduced from 1D modeling. The influence of the oil on the mixture viscosity and the internal bed dynamics are discussed. This work provides insights into the interaction between the debris field in front of the pig and pipeline hydraulics.

The deposition of paraffin wax from crude oil at low temperatures due to wax deposition, high pour point, high viscosity, and weak flow capability is among the critical and persisting challenges faced by the petroleum industry. In this study, a new para-decyloxy allyl benzoate (I10) was prepared, polymerized into HI10, and copolymerized with dioctadecyl maleate into MHI10 via the freeradical polymerization method employing azobisisobutyronitrile and toluene as the initiator and solvent, respectively. The prepared monomer was characterized by spectroscopic analyses (Fourier-transform infrared (FT-IR)) and proton nuclear magnetic resonance. Further, the polymers were characterized by FT-IR, and their average molecular weights were determined by gel permeation chromatography. The prepared compounds were taken in different concentrations and then tested as flow improvers of Qarun waxy crude oil using pour point depression and rheological parameters. The results of this test indicated th...

Crude oil is one actively traded commodity globally. Its demand has been growing steadily over the decades, from 60 million barrels per day to 84 million barrels per day (Hasan et al , 2010). In Nigeria, crude oil production has grown from a little above 1000 barrels per day in 1970 to over 3000 barrels per day in 2010 (Fig. 1.1). The world production was conservatively 73 million barrels per day in the year 2005 and within the range of 72 and 75 million barrel per day between 2005 and 2010. Fig. 1.1. Nigerian crude oil production.

The gelling of waxy crudes and the deposition of wax on the inner walls of subsea crude oil pipelines present a costly problem in the production and transportation of oil. The timely removal of deposited wax is required to address the reduction in flow rate that it causes, as well as to avoid the eventual loss of a pipeline in the event that it becomes completely clogged. In order to understand this problem and address it, significant research has been done on the mechanisms governing wax deposition in pipelines in order to model the process. Furthermore, methods of inhibiting the formation of wax on pipeline walls and of removing accumulated wax have been studied to find the most efficient and cost-effective means of maintaining pipelines prone to wax deposition. This paper seeks to review the current state of research into these areas, highlighting what is so far understood about the mechanisms guiding this wax deposition, and how this knowledge can be applied to modelling and providing solutions to this problem.

This paper presents the results of a sensitivity study carried out to investigate the performances of two commercial codes, OLGA and LedaFlow, used to model the wax deposition process in pipelines under multiphase flow. Reliable simulations of the phenomenon are essential to properly design pipelines and to adopt cost-effective strategies for prevention and removal of wax deposits, reducing the risks of blockage. The main limit of the available models is that their predictions depend on a number of parameters which are usually adjusted to fit the experimental data obtained from laboratory deposition tests. Since a reliable upscale criterion has not been developed yet, model predictions have been more suitably validated using real field data, reported in literature. The performances of the commercial codes in modelling wax precipitation and deposition have been compared to each other.

Crude oil is one actively traded commodity globally. Its demand has been growing steadily over the decades, from 60 million barrels per day to 84 million barrels per day (Hasan et al, 2010). In Nigeria, crude oil production has grown from a little above 1000 barrels per day in 1970 to over 3000 barrels per day in 2010 (Fig. 1.1). The world production was

The gelling of waxy crudes and the deposition of wax on the inner walls of subsea crude oil pipelines present a costly problem in the production and transportation of oil. The timely removal of deposited wax is required to address the reduction in flow rate that it causes, as well as to avoid the eventual loss of a pipeline in the event that it becomes completely clogged. In order to understand this problem and address it, significant research has been done on the mechanisms governing wax deposition in pipelines in order to model the process. Furthermore, methods of inhibiting the formation of wax on pipeline walls and of removing accumulated wax have been studied to find the most efficient and cost-effective means of maintaining pipelines prone to wax deposition. This paper seeks to review the current state of research into these areas, highlighting what is so far understood about the mechanisms guiding this wax deposition, and how this knowledge can be applied to modelling and providing solutions to this problem.

As part of a wider study probing the molecular-scale factors important in controlling wax crystallisation processes, the effect of additives on the surface and bulk nucleation of wax crystals from hydrocarbon solution phases was examined. Bulk nucleation data obtained in the absence and presence of two growth inhibiting additives indicated an increase in the meta-stable zone width (MSZW) on addition of both inhibitors, and differences in their kinetics of inhibition. Complementary studies of surface nucleation using a pipe blocking apparatus revealed a lowering in the temperature at which blockage occurred on addition of inhibitor to the model oil, and existence of fractional crystallisation observed in the bulk phase was confirmed. The hydrodynamic dependence of the nucleation process provided added information on how the inhibitors and wax would perform in a field situation, with a strong dependence on shear rate.

The gelling of waxy crudes and the deposition of wax on the inner walls of subsea crude oil pipelines present a costly problem in the production and transportation of oil. The timely removal of deposited wax is required to address the reduction in flow rate that it causes, as well as to avoid the eventual loss of a pipeline in the event that it becomes completely clogged. In order to understand this problem and address it, significant research has been done on the mechanisms governing wax deposition in pipelines in order to model the process. Furthermore, methods of inhibiting the formation of wax on pipeline walls and of removing accumulated wax have been studied to find the most efficient and cost-effective means of maintaining pipelines prone to wax deposition. This paper seeks to review the current state of research into these areas, highlighting what is so far understood about the mechanisms guiding this wax deposition, and how this knowledge can be applied to modelling and providing solutions to this problem.

In this study, the cloud and pour point of the Nigerian Niger Delta Crude oil were determined so as to ascertain the temperature at which wax crystallizes and precipitates during crude transportation. Four (4) crude samples were collected and analysed in the laboratory and the results showed that each of the samples had varying cloud points; Sample A-23 0 C, Sample B-14 0 C, Sample C-23 0 C and Sample D-20 0 C with a mean value of 20 0 C. Same trend was also exhibited by the pour points; Sample A-11 0 C, Sample B-2 0 C, Sample C-14 0 C and Sample D-8 0 C with a mean value of 8.75 0 C. It was then concluded that wax deposition during crude transportation in the region can be prevented especially in onshore pipelines if efficient preventive measures are put in place being that the region in the tropics with a minimum ambient temperature of 18 0 C. Factors that affect cloud and pour point of crude oil were also highlighted and recommendations that will help prevent crude oil from wax crystallization and precipitations were given.