bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Simplified Method to Predict and Prevent Asphaltene Deposition in Oilwell Tubings: Field Case
Authors: Al-Kafeef Saad F. , Al-Medhadi Fahed , Al-Shammari Ali D. 
Published: April 2006

Summary
The natural state of asphaltenes in petroleum fluids is described as a colloidal system stabilized, to some extent, by the resins that act as peptizing agents. Destabilization of colloidal asphaltenes appears to happen as a result of changes in temperature, pressure, and composition. This can significantly affect the production efficiency of a reservoir during oil recovery.
The phenomenon of asphaltene flocculation and deposition in well tubing appears to be influenced by two mechanisms: the fluid-phase (gas/liquid/solid) separation and the well-flow regime. Predictions of the onset of asphaltene flocculation determined by fluid-phase laboratory studies do not necessarily imply that asphaltene deposition will occur during flow conditions. This paper presents a method for predicting the onset of asphaltene deposition under well-flow conditions. This method will allow us to take preventive actions before asphaltenes problems occur by keeping the asphaltenes dispersed in the oil phase.
A well-monitoring technique was used in west Kuwait Marrat (Jurassic) deep wells to monitor the well-flow pressure by use of a programmable data logger. The data gathered from the logger predicted the onset of the flow-regime mechanism that influenced asphaltene deposition in well tubing. The deposition thickness of asphaltenes in well tubing was estimated by the data and was found to agree with the results obtained by the caliper test.
The Value of Cement Innovation: Reduced Cycle Time Saves Money
Authors: Myers Roger , Mack David J. , Kendrick Daniel , Woo George , Matz David , Hina Derek 
Published: April 2006

Summary
Lightweight, low-compressive-strength cement slurries save Appalachian basin operators thousands of U.S. dollars per well when compared with two-stage cement jobs using a packer-collar tool. The average amount of annular fill-up that is required in the typical southern West Virginia Devonian shale well is 3,000 ft. Because the shale is naturally fractured and has a low fracture gradient of 0.3-0.4 psi/ft, many operators opt to cement the air-drilled, unconventional gas wells with a 12-ppg lightweight silicate cement.
Over the past 5 years, more than 800 wells have been cemented with water-extended cement slurry, pumped at 12 ppg. Interestingly, the cement's compressive strength in 72 hours measures only 500-700 psi, not nearly enough to be "seen" with the cement-bond logging tools most commonly employed. In fact, at least one operator waits a full 7 days before running a variable-density log because that is about the time needed for the cement to develop enough compressive strength and acoustical impedance to be seen.
While solving one problem related to cutting authorized-for-expenditures well costs, the lightweight cement caused another problem: lost production days because of waiting on cement (WOC). Using knowledge of available Portland cements and a proprietary compressive-strength enhancing agent, a new cement blend was developed that could get higher strengths and better acoustical impedance. This paper will document how one large northeast operator successfully solved the problem of cycle-time reduction while maintaining the cement density at 12 ppg. Key aspects related to the solution, including laboratory testing of the cement and cement additives and examples of post-solution cement-bond logs, will be shown. Economics related to lost days of production over a 100-well drilling program will also be discussed.
Silica-Scale Inhibition for Steam Generation in OTSG Boiler
Authors: Pedenaud Pierre , Goulay Caroline , Pottier Fabien , Garnier Olivier , Gauthier Bernard 
Published: April 2006

Summary
The production of extra-heavy oil or bitumen using the steam-assisted gravity-drainage (SAGD) method entails the generation and injection of a large quantity of steam into the reservoir. A similar quantity of hot water is produced together with the oil. Taking into consideration environmental regulations, it is probable that partial, or even total, recycling of the produced water into steam will be required.
After circulating in the ground, production water may contain high concentrations of silica (up to 400 mg/L). Silica removal is very expensive in terms of investment and operating costs. The risk of silica-salt deposition in the boiler tubes becomes significant when the silica content in the feedwater exceeds 100 mg/L [oncethrough-steam-generation (OTSG) boiler-supplier specifications]. Deposition of silica increases local thermal resistance and can lead to tube failure. The silica-removal process is also an environmental issue owing to the production of sludge.
This paper demonstrates that silica-scale inhibitors can be used in steam generation in an OTSG boiler. The original laboratory test program and results obtained are presented. Test results were corroborated on an industrial OTSG boiler in operating conditions. Results show that use of silica-scale inhibitors instead of silica removal could generate substantial savings in cost. The use of silica scale for steam generation in heavy oil exploitation has been incorporated into French patent 2,858,314-A1 (Gauthier et al. 2003).
Characterization of Partially Formed Polymer Gels for Application to Fractured Production Wells for Water-Shutoff Purposes
Authors: Sydansk R. D. , Xiong Y. , Al-Dhafeeri A. M. , Schrader R. J. , Seright R. S. 
Published: April 2006

Summary
A laboratory study characterized partially formed chromium(III)-carboxylate/acrylamide-polymer (CC/AP) gels for water shutoff in fractures. These partially formed gels showed much lower effective viscosities during placement than comparable fully formed gels. During placement, leakoff rates through fracture faces were low for gelants and partially formed gels. During the first brine injection after gel placement, the pressure gradient required to breach the gel increased with the increasing polymer concentration. Most gel remained in the fracture and did not wash out. During brine flow through "wormholes" in the gel, stabilized residual-resistance factors (Frr) were large and increased with increasing polymer concentration.
Effect of Drainage Height and Grain Size on Production Rates in the Vapex Process: Experimental Study
Authors: Yazdani Ali J. , Maini Brij B. 
Published: April 2006

Summary
Interest in the vapor-extraction (Vapex) process for heavy-oil and bitumen recovery has grown considerably as a viable and environmentally friendly alternative to the currently used thermal methods. The potential for the success of the Vapex process is even more attractive in some scenarios that preclude the thermal methods. The presence of an overlying gas cap and/or bottomwater aquifer, thin pay zones, low thermal conductivity, high water saturation, and unacceptable heat losses to overburden and underbur-den formations are some of the limitations with the thermal techniques, which potentially can be overcome by Vapex implementation. However, predicted low production rates by previous researchers for field application of the Vapex technique remain a serious barrier to commercial applications of the process. The scaleup methods that have been used by previous workers for translating the laboratory results to field predictions were based primarily on the reservoir transmissibility. An analytical model developed by Butler and Mokrys1 showed that the oil rate should be proportional to the square root of reservoir transmissibility. The effect of convective dispersion between solvent and virgin heavy oil in porous media was ignored in developing this model.
The main objective of this work is to develop an improved scaleup method for the Vapex process using physical-model experiments carried out in models of different sizes. In this paper, we report the results of a new series of experiments that extend the previously reported results of Karmaker and Maini2 to a significantly wider range of model heights. These new experiments used a new design of slice-type physical models that places the sandpack in the annulus formed by two cylindrical pipes. Combining the new results with the previous data of Karmaker and Maini,2 we show that the transmissibility-based scaling-up method seriously underpredicts the results at larger scales. This observation suggests that much higher rates can be expected in the field implementation of the Vapex process.
A new correlation also has been proposed for scaling up the experimental data to the real field cases. It indicates the height dependency of the convective-dispersion contribution, which can be the dominant mass-transfer mechanism for the process, to be a higher order than previously postulated. Experimental results from this work show that the stabilized rate is a function of drainage height to the power of 1.1 to 1.3, instead of the square-root functionality of the Butler and Mokrys1 model.
Development of Associative Polymer Technology for Acid Diversion in Sandstone and Carbonate Lithology
Authors: Eoff Larry , Dalrymple Dwyann , Reddy B. R. 
Published: April 2006

Summary
This article describes the use of associative polymer technology (APT) to achieve fluid diversion during an acid stimulation treatment. APT involves the use of a very-low-viscosity aqueous-polymer solution. It reacts immediately with the formation surface to significantly reduce the ability of subsequent aqueous fluids to flow into high-permeability portions of the rock. The first stage containing the APT predominately will enter the most permeable area, diverting the following acid stage(s) to less-permeable sections of the rock. APT has little or no effect on the flow of subsequent hydrocarbon production. Furthermore, in rock containing significant proportions of sandstone-type lithology, the water permeability of the treated zone is decreased permanently, resulting in post-treatment reduced water production from the treated zone.
A general description of associating polymers and their properties, as well as a detailed description of the laboratory development of the current system, are both discussed. Laboratory data will show the effectiveness of APT in reducing the ability of aqueous fluids to flow through porous media. Parallel flow studies using water-saturated and oil-saturated cores are presented that show the ability of APT to divert acid in both sandstone and carbonate cores. These tests also show the ability of APT to decrease water permeability in the water-saturated core while the diverted acid increases the oil permeability of the oil-saturated core.
Simplified Wellbore-Flow Modeling in Gas/Condensate Systems
Authors: Kabir C. S. , Hasan A. R. 
Published: April 2006

Summary
Predicting long-term reservoir performance with realistic wellbore models is fraught with uncertainty owing to the complexity of two-phase flow. That is because even a calibrated two-phase-flow model departs from its expected performance trend when changes in flow conditions occur. These inevitable changes include gas/liquid ratio, wellhead pressure, and flowline pressure with time, among others. Influx of water further exacerbates the prediction problem.
This study explores the possibility of using simplified approaches to compute bottomhole pressure (BHP) from wellhead pressure (WHP), measured rates, gravity of producing fluids, and tubular dimensions. BHP computations on three independent data sets comprising 167 gas/condensate-well tests suggest that the no-slip homogeneous model applies quite well. Statistical results show the homogeneous model compares quite favorably with mechanistic two-phase-flow models. However, the main advantage of the simplified model is that its recalibration with field data is not required because the gas/oil ratio increases with time, thereby making the model increasingly reliable.
Most field data sets suggest random error in BHP calculations; uncertainty in rate measurements appears to be the most probable cause. High gas/liquid ratio (GLR) systems can tolerate large errors in rate measurements, but low-GLR wells demand greater accuracy because of increasing importance of the hydrostatic head.
Uncertainties in Standard Analyses of Boundary Effects in Buildup Data
Authors: Larsen Leif 
Published: April 2006

Summary
Boundary effects are often observed in buildup data—or at least that is the conclusion frequently drawn from an observed increase in derivative on a log-log plot or an increase in slope on a semilog plot. Furthermore, if (for instance) it is concluded that the effects of a sealing fault are seen in a given data set, then simple line methods or direct analytical-modeling efforts are normally used to determine the distance to the boundary. A sealing fault is the normal choice of boundary model if a doubling is observed in derivative or semilog slope. If a four-fold increase in derivative is observed, then a model with the well placed somewhere between two sealing faults forming a right angle would be a normal choice. But what if the two faults are not sealing? If the flow capacity on the other side of the faults is only one-third of the value on the well side, what will be the derivative characteristics?
Problems like these are addressed in detail in this paper, with a series of simple rules given for possible combinations that will generate buildup data of a specific type (i.e., with specific "familiar characteristics"). The rules can be used to list alternative interpretations without running separate analyses. For instance, it is shown that the derivative characteristics of any sector model bounded by sealing faults correspond to an infinite number of two-zone sector models with an angle between the boundaries and permeability contrast satisfying a single equation. Other pairs of models with similar characteristics are models with partially sealing faults and specific three-zone sector models, and either of these types of models and radial composite models. This clearly complicates analyses.
Also addressed are problems related to possible differences in the boundary effects observed in drawdown and buildup data for certain models. As one example, U-shaped and sector models can have identical buildup characteristics over a wide time range, although drawdown data from the models have distinctly different boundary characteristics. Radial composite and composite sector models are also of this type, with potentially significant differences between drawdown and buildup data. The reason for bringing up such cases is to emphasize the importance of attempting to collect high-quality drawdown data in addition to buildup data to limit the range of possible interpretation models.
For completeness, effects of uncertainties in basic input parameters on the final analyses are also covered in the paper.
Cattle and class? Rights to grazing land, family organization and class formation in Msengezi
Authors: Cheater A. P. 
Published: April 2006

Opening ParagraphIn studying class formation in rural Africa, many subtleties of this process are initially elusive, even when the process itself appears to be quite straightforward. The elusiveness of reality frequently results, at least in part, from the assumptions made by the researcher. So, for example, in studying one area of freehold tenure in Zimbabwe, in which ‘squatting’ is officially disapproved and where the land is legally inherited by a single heir, the informal allocation to others of rights to arable land for cultivation has obvious importance in the process of class formation. Less obvious, however (at least to me at the time), was the significance of grazing usufruct.
From equal to better: investing the chief among the northern Yaka of Zaïre
Authors: Devisch René 
Published: April 2006

IntroductionAmong the Northern Yaka of Zaïre the office and function of the chief is thought of as prior to and as the source of all things: the chief represents and surpasses his subordinates by his twofold function. First, he is asovereign rulerwho alone personifies unity, perpetuity and high authority. But the chief fails to live up to these chiefly ideals since his physical body ages and he cannot escape death or transcend the succession of generations and political scenes and factions. This failure seems to be remedied, however, not so much by concealing the chiefs bodily transitoriness through a mystifying cult, but by identifying the chief in his body with the origin of the political institutions. Embodying the founding ancestors, the chief ‘re-presents’ or makes present ‘the primal space–time order’ (yitsi khulu). The ruler thus personifies the legitimate political order: he re-presents and imposes the perennial hierarchical social organisation, territorial unity and moral order. In his enthronement and rule, he must re-enact the founding dramas of conquest and life transmission to renew cultural time by linking it to the ‘primal and permanent space–time order’. Sacrificial death, mortuary ritual, rebirth, purification, etc., re-enact the founding dramas and provide transformative metaphors, linking men and women, life and death, inside and outside, ascendant and descendant, before and after, the local territory and Yaka society.
The sudden death of a millionaire: conversion and consensus in a Ghanaian kingdom
Authors: Gilbert Michelle 
Published: April 2006

Opening ParagraphThe unexpected death of a citizen in 1977 triggered a series of events in one small Ghanaian kingdom, pointing to confusion in the locally accepted criteria for Christian conversion and to contradictions in the avenues to status and power. Since the deceased was a millionaire businessman, something of a huckster, and a person who was at the centre of an unusually complex constellation of social ties, his death forced the people of his local community to re-examine the relationships between traditional religion and Christianity, and between wealth, religious adherence and the display of status and prestige. There was long and bitter hostility between the two towns to which this man was affiliated by descent. Each town competed for the glory of ; claiming him as a member, and while once he too would have desired that, logically it could not be. There was also perennial conflict between the factions within the kingdom's capital. This enhanced the drama and helped explain the urgency of the respective townspeople's attempts to resolve the underlying structural contradictions which became manifest in the events following the death to their own advantage. At the same time this is the story of a self-made man, unusual largely because of his extreme wealth, who understood conflict and ambiguity, and who manipulated the social structure in which he found himself to his own advantage. The funeral of this one man, who simultaneously entertained contradictory belief systems and juggled opposing attributes of leadership, mobilised the attention of the entire population of both towns. It did so precisely because the ritual of his funeral was used to ‘describe in advance a desired but uncertain state of affairs. It [ritual] is about power and is itself more or less political’ (MacGaffey, 1986: 11, emphasis added).
Warfare, oracles and iron: a case study of production among the pre-colonial Klowe, in the light of some recent Marxist analyses
Authors: Brown David 
Published: April 2006

Opening ParagraphIt is perhaps surprising that the recent resurgence of interest in the application of Marxist theory to the study of the historically non-capitalist societies of the Third World should have focused, at least in part, upon the stateless societies of Africa. To some extent, this interest in some of the least differentiated and least class-stratified of societies can be related to the fundamental problematic of Marxist sociology: the characterization of the stage of advanced communism, which remains so obscure in Marx's own theoretical work. An understanding of the dynamics of ‘primitive’ communism might be seen, therefore, as an essential precursor to this underlying concern. Certainly, the often highly tendentious views of Marxist writers on such issues as the definition of the state and the extent of exploitation in the primitive communist mode can be related to this need. However, the rise of Marxist anthropology has not only been presented as a problem of general evolutionary theory. Other influences have been offered to account for the new concern, the most widely cited being the supposed crisis of functionalism, and the resulting necessity for a complete reorientation of the whole discipline of anthropology. Stateless societies, having long occupied a central place in the field of anthropological enquiry, and yet outwardly presenting such simplicity of form, offer a particular challenge to the radical, and in several recent works have been interpreted in what is claimed to be a novel and distinctive way.
Come vero Prencipe Catolico: the Capuchins and the rulers of Soyo in the late seventeenth century
Authors: Gray Richard 
Published: April 2006

Opening ParagraphStudents of Europe's contact with Africa have long regarded the Christian missions in the ancient kingdom of Kongo as a peculiarly potent symbol. For some the conversion and subsequent reign of Afonso I in the first half of the sixteenth century were a momentary aberration, a false dawn quickly to be obscured by the realities of the exploitation associated with mercantile capitalism and the horrors of the Atlantic slave trade. For others, the story of these missions has merely served to illustrate the continuing inviolability of indigenous traditions. Kongo society, it is argued, accepted only a thin veneer of Christianity, while its basic cosmology, practices and beliefs remained unchanged.
Comment on the ‘leopard’ killings
Authors: McCall J. A. G. 
Published: April 2006

Opening ParagraphDr Nwaka, in writing his paper on the ‘man-leopard’ killings of southern Annang, Nigeria, 1943–48, has performed a good public service for Nigeria. During the past few years a number of Nigerians have expressed to me the view that the killings should be written up. Now Dr Nwaka has done just this, and only after a very considerable amount of research, as his extensive references indicate. The fact that I do not accept his main conclusion is not the point. His paper forms the basis for a comprehensive discussion of the circumstances surrounding the killings from 1943 to 1948, and for this we owe him a real debt of gratitude.
W. R. Bascom and the Ife bronzes
Authors: Tignor Robert L. 
Published: April 2006

Opening ParagraphIn 1938 an African building a house in the city of Ife, the cultural capital of the Yorubas and the mythical cradle of Yoruba civilisation, came upon an extraordinary cache of ancient Nigerian bronzes. In all, at least fifteen bronzes were uncovered in 1938 in a compound only 100 yards from the palace of the Oni of Ife. These bronzes were to prove of great historical and artistic significance. Until that time only two other bronzes had been unearthed in the Yoruba area, and one of those had disappeared, leaving Nigeria only a single original and a replica. In the disposition of the priceless new finds there ensued a tale of intrigue, prevarication, outraged nationalism, and narrow-minded ethnocentricism that drew into its maelstrom the British colonial government of Nigeria, the US Consulate in Lagos, and the USA's Department of State. Although the Ife bronzes, which today reside in a handsome if small museum in the city of Ife, are not so well known as, for example, the Elgin marbles or certain other antiquities taken from the Third World, the controversy surrounding their removal from Nigeria and their eventual return was filled with the same emotion and employed the same arguments heard today over the rightful location of national cultural treasures. The Nigerian dispute is made all the more poignant in that one of the major protagonists was not a money-seeking antiquities dealer, but a young American anthropologist destined to be one of the most astute and sympathetic interpreters of Yoruba culture.