Oil Production Pipelines Research Articles

A correlation to quantify hydrate plugging risk in oil and gas production pipelines based on hydrate transportability parameters

Solid gas hydrate particles may form in oil and gas pipelines in the presence of water at high pressures and low temperatures; typical conditions of subsea hydrocarbon pipelines used in offshore facilities. Gas hydrate particles that form within these pipelines may create blockages following a complex multi-physics phenomenon involving emulsification, hydrate formation and subsequent hydrate particle agglomeration and bedding. Here we present a conceptual model depicting different hydrate plugging risk levels associated with oil-dominated systems, developed based on observations from high-pressure flowloop experiments. Using experimental measurements from these experiments, we develop a mathematical correlation to classify and quantify hydrate plugging risk in oil and gas pipelines. The correlation is based on assessable parameters that govern hydrate transportability in pipelines, such as, liquid loading, mixture velocity, fluid properties, and hydrate amount. A parametric study is performed using the proposed hydrate plugging risk correlation showing the plugging risk increasing with decrease of liquid loading and fluid velocity. The hydrate plugging risk estimation approach using the proposed correlation is illustrated for steady-state and transient operations of a long subsea tieback facility based on numerical transient multiphase flow simulations. The hydrate plugging risk is found to evolve over time as a function of hydrate volume fraction along the pipeline length. The hydrate plugging risk quantification presented, in terms of Hydrate Risk Evaluator, in this study represents an advancement in the area of hydrate risk assessment, as it can be used to assess hydrate plugging risk and consequently operational safety of hydrocarbon transport pipelines from the flow assurance perspective.

Statistical analysis of mechanical test results for samples of pipes from trunk oil pipelines after long-term operation

CONDUCTING ANY SCIENTIFIC RESEARCH includes the process of acquiring, processing, and analysing data which are obtained as a result of one or a series of experiments. Over the prolonged period for which science has existed, a multitude of methods have been created for obtaining experimental data. As part of studying the properties of materials, standard methods are applied for tensile, impact toughness, and hardness tests, as well as fatigue tests. This list of tests can be taken as a base which is used to establish the level and character of loads the given material is capable to sustain during operation. This paper examines approaches to processing experiment results which are obtained using standard (basic) methods when testing pipe steels for trunk oil and oil product pipelines. At the present time, the degree of automation in experimental equipment is fairly high. However, there is still some human participation when preparing samples and setting-up the experiments, which may lead to errors occurring when performing the tests (the human factor). This article presents some approaches which make it possible to perform initial processing and verification of experimental data for errors and reliability, and against hypotheses and distribution laws for the results obtained. Methods are also suggested for determining the minimum quantity of samples to be tested, based on evaluation of the mechanical property variations in pipe steels. Several approaches may be applied to solve the task of identifying links and relationships between the analysed parameters. The first approach is deterministic and requires long-term study. When one takes into account the considerable number of factors being studied, it is also fairly expensive and involves rather complicated experiments. The second approach is probabilistic and statistical, which allows implicit dependences to be established between series of measurements (correlation analysis) and linear (pair regression) and non-linear dependences (multiple regression) to be revealed between the parameters being examined. This study applies the statistical approach to analysing data from mechanical tests of pipe steels in trunk oil and oil product pipelines.

An Examination of the Prediction of Hydrate Formation Conditions in the Presence of Thermodynamic Inhibitors

Abstract Gas hydrates are crystalline compounds, solid structures where water traps small guest molecules, typically light gases, in cages formed by hydrogen bonds. They are notorious for causing problems in oil and gas production, transportation and processing. Gas hydrates may form at pressures and temperatures commonly found in natural gas and oil production pipelines, thus causing partial or complete pipe blockages. In order to inhibit hydrate formation, chemicals such as alcohols (e.g., ethanol, methanol, mono-ethylene glycol) and salts (sodium, magnesium or potassium chloride) are injected into the produced stream. The purpose of this work is to briefly review the literature on hydrate formation in mixtures containing light gases (hydrocarbons and carbon dioxide) and water in the presence of thermodynamic inhibitors. Four calculation methods to predict hydrate formation in those systems were examined and compared. Three commercial packages (Multiflash®, PVTSim® and CSMGem) and a hydrate prediction routine in Fortran90 using the van der Waals and Platteeuw theory and the Peng-Robinson equation of state were tested. Predictions given by the four methods were compared to independent experimental data from the literature. In general, the four methods were found to be reasonably accurate. CSMGem and Multiflash® showed the best results.

A comprehensive study of steel properties in trunk oil and petroleum product pipelines with various service lives

The article examines the approaches of a number of scientific institutions to the degradation of mechanical properties in pipe steels which may occur over long-term service life. It also presents the results of research into the actual mechanical properties and chemical composition characteristics of pipe steels with various service lives. The classification (ranking) of pipe steels of various grades used by PJSC Transneft is presented according to the criteria of length, service life, manufacturer, regulatory documents for supply, etc. The pipe steels are grouped according to their actual mechanical properties: ultimate strength, elongation, impact toughness, and chemical composition characteristics.

Studies on water carrying of diesel oil in upward inclined pipes with different inclination angle

The characteristics of oil-water two phase flow in the case of water initially accumulated at low position in upward inclined pipelines were researched. A large scale experiment loop was conducted to analyse the flow characteristics by using a series of 50 mm transparent acrylic bends with different inclination angle (10° ∼ 45° at the interval of 5°). Five flow patterns were identified and a corresponding flow pattern map was established. The same situation was also simulated by using computational fluid dynamics (CFD) techniques, and the results of simulation were validated by comparing with the experimental results. The impact of oil superficial velocity, inclination angle and initial water volume on flow characteristics was further investigated. The results indicate that the backflow effect in water phase is the major factor that causes water accumulation at the bottom of the pipe. The initial residual water volume has no influence on the oil-water flow pattern and the water-carrying capacity of oil. The lower flow rate and the higher inclination angle cause the decrease of water-carrying capacity of oil, resulting in the water accumulation at the low position and internal corrosion of product oil pipelines.

A self-learning approach for optimal detailed scheduling of multi-product pipeline

Pipeline transportation is cost-optimal in refined product transportation. However, the optimization of multi-product pipeline scheduling is rather complicated due to multi-batch sequent transportation and multi-point delivery. Even though many scholars have conducted researches on the issue, there is hardly a model settling the discontinuous constraints in the model as a result of batch interface migration. Moreover, through investigation, there is no self-learning approach to pipeline scheduling optimization at present. This paper considers batch interface migration and divides the model into time nodes sequencing issue and a mixed-integer linear programming (MILP) model with the known time node sequence. And a self-learning approach is proposed through the combination of fuzzy clustering analysis and ant colony optimization (ACO). This algorithm is capable of self-learning, which greatly improves the calculation speed and efficiency. At last, a real pipeline case in China is presented as an example to illustrate the reliability and practicability of the proposed model. • A self-learning algorithm is proposed for detailed optimal scheduling for product oil pipeline. • Two novel discontinuous process constraints are taken into consideration. • This algorithm can improve calculation speed and efficiency by itself. • A real example with six cases is given to demonstrate the method’s practicality.

Hydrate Formation in Water-in-Crude Oil Emulsions Studied by Broad-Band Permittivity Measurements

To develop more cost-effective and environmentally friendly strategies to prevent the formation of gas hydrate plugs in oil production pipelines, a better understanding of the mechanisms of plug formation is needed. This paper presents broad-band permittivity measurements of hydrate formation in water-in-oil emulsions. The experiments were conducted at atmospheric pressure using dead crude oil and diesel fuel, with cyclopentane as hydrate former. However, the use of dielectric probes employed in this work can be extended to more realistic systems, as they are able to withstand high pressures and harsh chemical environments. The results show that broad-band permittivity measurements can be used to detect hydrate agglomeration and formation of hydrate deposits in oil-dominated systems. By applying existing dielectric mixing models, the fractions of oil, water, and hydrates can be estimated.

Research advances in the influence of temperature on the sequential transportation in product pipeline

Sequential transportation is the main way of long-distance transportation for the oil product, whose essence is a coupling process of flow, mass transfer and heat transfer. Thus, like the pressure gradient and the concentration gradient, the heat gradient is one main power source of the mentioned coupling process as well. The previous related study done by researchers both at home and abroad mainly focus on the aspects including the making scheduling plans for batches in the oil product pipeline, the oil batch interface tracking as well as simulation, the scheme optimization for activating pumps, the mechanism of forming mixed oil and the detection of oil leakage. However, all of these works have failed to take the proper factor of temperature into consideration. As for the researches on experiments, the majority of them concentrate on factors such as the flow patterns, the categories of the oil product, and the parameters of the pipeline and on those factors’ influence upon the total amount of the mixed oil. They all have been irrespective of the effect of temperature and corresponding mechanism. Most of the researches regard the pipeline as an isothermal body, which is a postulated condition in their papers. In the background of digital pipeline system and intelligentized management transportation system, both of a better accuracy and reliability are required for the model to deal with the problem mentioned above. Thus, the classical theory regarding mixed oil, coupling of flow and heat transfer, scheduling plans, separation of mixed oil and leakage detection cannot keep up with the pace the development of the pipeline system. At present, researches of the following aspects are in a fledging period: the smearing phenomenon of mixed oil, the scheduling plans making considering nonlinear factors, the scheduling plan optimization considering coupling of hydraulic and thermal factors, the batch interface tracking regarding the oil quality and the three-dimensional transient flow simulation in long-distance pipeline, which need to make a further study shedding light on the detailed mechanism concerning the temperature’s influence. Thus, firstly in the paper, the correlated researches on mixed oil, scheduling plans, heated oil pipelines and batch interface tracking without taking temperature’s influence into account have been summarized and the corresponding defect has been discussed. Next, current status of researches about the temperature’s influence on the mechanism of mixed oil and on the process of mass transfer as well as heat transfer are analyzed and commented, including the related experimental research. The influences are embodied in the change of transport capacity, the vaporization of oil, the decreasing quality of oil, the low accuracy of batch interface tracking, the high risk of mixed oil cutting and the large pressure drop after pipeline shutdown. Correspondingly, the relevant theoretical and experimental studies are not perfect and sufficient. And the empirical formulae or modified coefficient methods presented in these studies are not suitable enough for the industrial applications. At the end of the paper, it is pointed out that based on the development requirements of the pipeline system, the scheduling plan combined with thermal as well as hydraulic factors, the abnormal diffusion considering temperature between different batches, the three-dimensional simulation of compressible multi-phase turbulence and the batch interface tracking in complex pipelines are the major research directions and key issues in the research field.

Membrane Lipids as Indicators for Viable Bacterial Communities Inhabiting Petroleum Systems.

Microbial activity in petroleum reservoirs has been implicated in a suite of detrimental effects including deterioration of petroleum quality, increases in oil sulfur content, biofouling of steel pipelines and other infrastructures, and well plugging. Here, we present a biogeochemical approach, using phospholipid fatty acids (PLFAs), for detecting viable bacteria in petroleum systems. Variations within the bacterial community along water flow paths (producing well, topside facilities, and injection well) can be elucidated in the field using the same technique, as shown here within oil production plants in the Molasse Basin of Upper Austria. The abundance of PLFAs is compared to total cellular numbers, as detected by qPCR of the 16S rDNA gene, to give an overall comparison between the resolutions of both methods in a true field setting. Additionally, the influence of biocide applications on lipid- and DNA-based quantification was investigated. The first oil field, Trattnach, showed significant PLFA abundances and cell numbers within the reservoir and topside facilities. In contrast, the second field (Engenfeld) showed very low PLFA levels overall, likely due to continuous treatment of the topside facilities with a glutaraldehyde-based antimicrobial. In comparison, Trattnach is dosed once per week in a batch fashion. Changes within PLFA compositions across the flow path, throughout the petroleum production plants, point to cellular adaptation within the system and may be linked to shifts in the dominance of certain bacterial types in oil reservoirs versus topside facilities. Overall, PLFA-based monitoring provides a useful tool to assess the abundance and high-level taxonomic diversity of viable microbial populations in oil production wells, topside infrastructure, pipelines, and other related facilities.

Metabolomic and Metagenomic Analysis of Two Crude Oil Production Pipelines Experiencing Differential Rates of Corrosion.

Corrosion processes in two North Sea oil production pipelines were studied by analyzing pig envelope samples via metagenomic and metabolomic techniques. Both production systems have similar physico-chemical properties and injection waters are treated with nitrate, but one pipeline experiences severe corrosion and the other does not. Early and late pigging material was collected to gain insight into the potential causes for differential corrosion rates. Metabolites were extracted and analyzed via ultra-high performance liquid chromatography/high-resolution mass spectrometry with electrospray ionization (ESI) in both positive and negative ion modes. Metabolites were analyzed by comparison with standards indicative of aerobic and anaerobic hydrocarbon metabolism and by comparison to predicted masses for KEGG metabolites. Microbial community structure was analyzed via 16S rRNA gene qPCR, sequencing of 16S PCR products, and MySeq Illumina shotgun sequencing of community DNA. Metagenomic data were used to reconstruct the full length 16S rRNA genes and genomes of dominant microorganisms. Sequence data were also interrogated via KEGG annotation and for the presence of genes related to terminal electron accepting (TEA) processes as well as aerobic and anaerobic hydrocarbon degradation. Significant and distinct differences were observed when comparing the ‘high corrosion’ (HC) and the ‘low corrosion’ (LC) pipeline systems, especially with respect to the TEA utilization potential. The HC samples were dominated by sulfate-reducing bacteria (SRB) and archaea known for their ability to utilize simple carbon substrates, whereas LC samples were dominated by pseudomonads with the genetic potential for denitrification and aerobic hydrocarbon degradation. The frequency of aerobic hydrocarbon degradation genes was low in the HC system, and anaerobic hydrocarbon degradation genes were not detected in either pipeline. This is in contrast with metabolite analysis, which demonstrated the presence of several succinic acids in HC samples that are diagnostic of anaerobic hydrocarbon metabolism. Identifiable aerobic metabolites were confined to the LC samples, consistent with the metagenomic data. Overall, these data suggest that corrosion management might benefit from a more refined understanding of microbial community resilience in the face of disturbances such as nitrate treatment or pigging, which frequently prove insufficient to alter community structure toward a stable, less-corrosive assemblage.

Short-term operational planning of refined products pipelines

Fil: Cafaro, Diego Carlos. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Desarrollo Tecnologico para la Industria Quimica. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnologico para la Industria Quimica; Argentina

Studies on the impact of fluid flow on the microbial corrosion behavior of product oil pipelines

The effect of fluid flow on the microbial corrosion behavior of API 5L X60 pipeline steel is investigated in product oil pipelines. It is confirmed that there is a small amount of trapped water accumulated at low elevation sections along the pipelines. The trapped water and dissolved oxygen (DO) in pipelines promote the growth of both aerobic and anaerobic bacteria, causing microbiologically influenced corrosion (MIC). MIC has been detected not only in static fluid systems, but also in flow systems. In product oil pipelines, MIC is conventionally attributed to three species of bacteria namely sulfate-reducing bacteria (SRB), iron oxidizing bacteria (IOB) and total general bacteria (TGB) which were influenced by the fluid flow condition. By applying a large flow loop, we conducted the experiment that the above three species of bacteria attached to the coupons were scoured by diesel oil at three different flow velocity (1.3m/s, 1.5m/s and 3m/s). The macroscopic and microcosmic analysis results indicate that after the scouring experiment all the bacterial corrosion behaviors almost remain the same as those before the experiment even at high flow velocity (3m/s), which far exceeds the economic field flow velocity (1–2m/s) of product oil pipelines. Consequently, once there are sessile bacteria on the inner wall of pipelines, serious corrosion will occur. Those bacteria play a key role in the corrosion of product oil pipelines.

Overall reliability analysis on oil/gas pipeline under typical third-party actions based on fragility theory

Based on fragility and internal & external hazard, an overall reliability model can be established as a theoretical basis for quantitative risk assessment on oil and gas pipeline systems.In this paper, overall reliability is regarded as conditional probability, including probability of third-party hazard and pipeline fragility. Third parties refer to all individuals, organizations and mechanical tools that cause unexpected damages to pipelines when they are carrying out operations either relevant or irrelevant to pipelines.By analyzing the propagation, waveform and frequency spectrum of natural seismic waves, the acceleration waveform of an artificial seism is simulated. Also a finite element model of pipeline's seismic response is established. Various pipelines' reactions simulated by ANSYS software are analyzed. Then the fragility probability of pipelines under blasting seismic actions is determined by normal distribution model.The overall reliability model is established and quantitatively evaluates the risks of Petro-China Gang-Zao product oil pipeline. By comparing the calculation results from algorithm software with the actual situation, the confidence interval of this model is [95%, 100%]. This model can precisely calculate the risk probability of certain pipe sections and then decide which section should be preferentially maintained and protected, increasing the efficiency of pipeline management.

Erratum to: Supply-based optimal scheduling of oil product pipelines

Erratum to: Supply-based optimal scheduling of oil product pipelines

Supply-based optimal scheduling of oil product pipelines

Oil product pipelines have features such as transporting multiple materials, ever-changing operating conditions, and synchronism between the oil input plan and the oil offloading plan. In this paper, an optimal model was established for a single-source multi-distribution oil product pipeline, and scheduling plans were made based on supply. In the model, time node constraints, oil offloading plan constraints, and migration of batch constraints were taken into consideration. The minimum deviation between the demanded oil volumes and the actual offloading volumes was chosen as the objective function, and a linear programming model was established on the basis of known time nodes’ sequence. The ant colony optimization algorithm and simplex method were used to solve the model. The model was applied to a real pipeline and it performed well.

Binding pipelines? Oil, armed conflicts, and economic rationales for peace in the two Sudans

The independence referendum of South Sudan in 2011 brought about the birth of a new land-locked and oil export-dependent African country. Despite obvious challenges, there was hope that oil could fund South Sudanese development, and that mutual economic dependence on a thriving oil sector would incentivize peaceful bilateral relations between South Sudan and Sudan. Yet, within six months of independence, tensions escalated, Sudan leveraged its control of oil export infrastructure to demand hefty transit payments and an end to South Sudanese support to rebels in the north, with South Sudan responding by shutting down its oil production and seeking alternative pipeline routes. Domestically, the mismanagement of oil revenues and shutdown of oil production also exacerbated tensions within the South Sudanese Government, contributing to its breaking apart and renewed civil war in December 2013. In contrast to optimistic views of oil-fuelled peace incentives, we point at the challenging political geography of oil in the two Sudans and the tensions undermining economic logics of ‘mutual interests’ and ‘peace dividends’ between, and within, these two countries.

Application of a wax deposition model in oil production pipelines

El objetivo de este trabajo es estudiar el proceso de deposicion de parafinas sobre la superficie interna de las tuberias de produccion de petroleo y la influencia de parametros como la velocidad de flujo y la temperatura de la pared sobre el espesor del deposito para un crudo ligero con alto contenido parafinico considerando tres condiciones de frontera sobre la pared de la tuberia; dos de las cuales suponen un perfil de temperatura en la frontera, hecho que no ha sido considerado en trabajos anteriores, y la tercera un valor constante. El analisis se realizo suponiendo condiciones seudo-estables en la fase fluida. El metodo de diferencias finitas se aplico para resolver el sistema de ecuaciones diferenciales y la solucion se llevo a cabo numericamente utilizando el lenguaje de programacion C++. El modelo fue validado a partir de los resultados experimentales reportados por Singh et al. (2000) y posteriormente utilizados para simular el crecimiento de los depositos de parafina como una funcion de la velocidad de flujo y la temperatura de la tuberia. Los resultados mostraron que el aumento de la velocidad de flujo reduce el maximo espesor del deposito, pero este se extiende sobre una distancia mas larga sobre la tuberia cuando se considera una temperatura de pared constante o cuando se considera el gradiente de temperatura axial con pendiente positiva; mientras que se observa el efecto contrario cuando se considera el gradiente de temperatura axial con pendiente negativa.

First stages of siderite crystallisation during CO2 corrosion of steel evaluated using in situ synchrotron small- and wide-angle X-ray scattering.

We use in situ synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS) to demonstrate that the formation of crystalline siderite (FeCO(3)) during the corrosion of steel in CO(2)-saturated brine - a problem of practical interest relating to the growth of protective scales on the interior surface of oil and gas production pipelines - is preceded by the formation of a colloidal precipitate in the solution and an amorphous surface layer, both assumed to be amorphous ferrous carbonate. Grazing incidence SAXS shows instantaneous film formation upon the application of an anodic potential, followed by development of a separate population of particles at later times, then by the formation of crystalline species, observed by WAXS. These observations can be interpreted in terms of crystal nucleation within the amorphous surface layer. Traces of Cr(3+) in the solution significantly accelerate the precipitation rate of the colloidal precursor and accelerate the appearance of the crystalline scale. We speculate on the significance of these observations for the nucleation, growth and morphology of the corrosion scale and hence its protectiveness.

Evaluating the effects of high liquid viscosity and flow variables on horizontal oil–gas slug flows by gamma radiation method

Hydrodynamic slug fl ow is the commonest fl ow regime observed in high viscosity liquid–gas horizontal pipelines over a wide range of different fl ow conditions. Hydrodynamic slugging tends to generate large vibrations that may impose structural instability or even damage oil production pipelines. For that reason, there is a need to investigate high viscosity slug fl ow regime to understand its complex characteristics. This is pertinent when considering that existing slug fl ow models used in the petroleum industry to design production pipelines are not suitable for predicting the behaviour of high viscosity oil–gas fl ow. In this study, the effects of liquid viscosity and fl ow variables on slug fl ow regime were investigated experimentally through the analysis of two key parameters—slug frequency and slug body liquid holdup, both measured with a gamma densitometer. Comparison of the measured slug parameters to existing correlations revealed that slug body liquid holdup correlations were in close agreement with high viscosity experimental data. However, none of the existing slug frequency correlations used was able to produce accurate predictions. A new empirical correlation for slug frequency was proposed. Compared with existing correlations, the newly proposed correlation performed much better in predicting slug frequency of high viscosity liquid–gas fl ows.

The Analysis Pressure Drop between Initial Station and 1#valve when Lan-Zheng-Chang Product Pipeline Shutdown

Considering the product oil has volume compressibility and volume expansion in different temperature and pressure, calculate the LAN-Zheng- Chang product pipeline in the shutdown during the initial station and 1#valve pressure drop rate, combined with the first station in Lanzhou reservoir area of the oil temperature oil temperature drop analysis is the first station in the main reason of pressure pipeline shutdown early fall, and provides technical support for the other new product oil pipeline.