bluuebunny/crossref_metadata_2025_split huggingface dataset:
Benchmarking the Formation Damage of Drilling Fluids
Authors: Zwaag C. H. van der 
Published: April 2006

SummaryThe unified test protocol for laboratory formation-damage assessments consists of functional procedures that attempt to standardize formation-damage service projects. Setting functional requirements was preferred above comprehensive equipment specifications and detailed instructions on laboratory work processes.To assess the formation-damage potential of a fluid for drilling or well operations, three sections of the protocol need to be accomplished: Information, Simulation, and Analysis.This paper presents the three sections and discusses the effect of the functional approach. Special emphasis is put on a distinction between well fluids that experience dynamic- and static-filtration regimes, because these require different ways of simulating fluid applications to the rock sample. To provide engineering parameters relevant to field scale and to identify the full range of potential formation-damage mechanisms that may affect the reservoir, analyses on cm, mm, and μm scales are suggested.Minimum requirements to scaleup formation-damage measurements to field scale are presented. Also, an option for full-scope diagnostic formation-damage assessments is demonstrated.Applications of numerical models that have been suggested in earlier research yield return permeability, filtrate-invasion depth, laboratory skin, efficiency of flow, and loss of revenue as parameters to benchmark the formation damage of well fluids.
Production Improvement for Horizontal Wells in Sumatra
Authors: Gunarto Ronny , Tran Thanh B. , Widyantoro Barkah , Kritzler Torsten 
Published: April 2006

SummarySeveral horizontal wells have been drilled in different sandstone formations in Sumatra. These formations have a typical permeability of 100 to 500 md, a low bottomhole pressure (BHP) of 450 to 750 psi, and a bottomhole temperature (BHT) of approximately 200°F. The wells are completed with a perforated liner. The objective of the horizontal-drilling program was to increase oil recovery in low-permeability estuarine reservoirs. Some of the drilled horizontal wells did not perform to expectations, and an intensive study was undertaken to identify completion and stimulation opportunities to increase production.During this study, all aspects of the initial completions were examined and redesigned.The drill-in mud was reformulated to reduce the amount of polymer and increase the use of fine calcium carbonate to decrease lost circulation during drilling and to simplify the removal of filter cake during initial completion.Core tests were performed to identify the optimum fluid formulation, which dissolves the remaining filter cake but does not destroy the formation's natural permeability.A new way of removing the filter cake after completing the well was introduced using oxidizer technology.A new, true-fluidic oscillator (TFO) was used to remove near-wellbore skin (in conjunction with an improved acid system) for wells that have been producing for several months or years.The paper presents several case histories to discuss how completion and stimulation problems were systematically evaluated resulting in increased horizontal-well production.
A Simple Model for Predicting Heat Loss and Temperature Profiles in Insulated Pipelines
Authors: Guo Boyun , Duan Shengkai , Ghalambor Ali 
Published: April 2006

Summary
Accurate predictions of heat loss and temperature profile in oil-and gas-production pipelines are essential to designing and evaluating pipeline operations. Although some sophisticated computer packages are available for such purposes, their accuracies suffer from numerical treatments and model-building skills of inexperienced users. A simple and accurate analytical heat-transfer model is highly desirable.
This paper presents three analytical heat-transfer solutions for predicting heat loss and temperature profiles in pipelines transporting petroleum fluids. The three solutions consist of one steadystate-flow solution and two transient-flow solutions. The two transient-flow solutions are for startup mode and flow-rate-change mode (shutting down is a special mode in which the flow rate changes to zero). An application example is presented to illustrate how the models can be used in insulation design of an offshore pipeline.
Framework for Field Optimization To Maximize Asset Value
Authors: Bailey William J. , Couët Benoît , Wilkinson David 
Published: April 2006

SummaryIn this paper, we propose an optimization framework for maximizing asset value, both with and without uncertainty. We first present the methodology to treat a general control optimization in the presence of uncertainty, followed by a brief section on the optimization algorithms used. We then describe the field model example used to illustrate the application of the methodology. Through a systematic analysis of various deterministic and stochastic cases, we address the various objectives sought. Using net present value (NPV) as a measure, we also explore the valuation of advanced completions along with the returns gained from expanding surface gas-handling facilities. The method also generates an efficient frontier that can be used for risk and decision analysis. The results clearly demonstrate the value of such a framework for value maximization in planning both near- and long-term time horizons as well as providing the necessary foundation for maximizing asset value.
Measurement of Total Alkalinity and Carboxylic Acid and Their Relation to Scaling and Corrosion
Authors: Tomson Mason B. , Kan Amy T. , Fu Gongmin , Cong Lili 
Published: April 2006

Summary
Alkalinity is needed in many water-treatment calculations such as scale, corrosion, precipitation, and oxidation, yet the concept is often misunderstood. In natural waters, alkalinity often is not equal to bicarbonate concentration, because natural waters contain base-contributing anions that can significantly affect alkalinity. However, alkalinity is commonly assumed to be equal to the bicarbonate concentration in many scale- and corrosion-prediction algorithms. When other anions (e.g., carboxylates) are present, bicarbonate concentration in production tubing is not a conservative quantity; it varies with CO2 partial pressure, temperature, and carboxylate concentrations in a complicated manner up and down a well.
Reliable methods to accurately measure true alkalinity are scarce, especially when multiple weak acids are present and the effects of TDS on electrode and color endpoint are significant. Oilfield brines contain aliphatic carboxylic acids of one to six carbons (e.g., acetate) up to 5000 mg/L. The highest concentrations of carboxylates tend to be in waters from reservoirs at temperatures of 80 to 100°C. In this paper, a new analytical procedure and computation routine to determine alkalinity and carboxylic acids simultaneously will be discussed. The procedure was recently debugged and simplified by the Rice U. Brine Chemistry Consortium (Rice BCC). The new titration method is based upon simultaneous analysis of the titration curve determined at fixed PCO2 and emphasizes the titration shape (profile) instead of the endpoint inflection as is done presently.
A wide range of natural and synthetic waters has been tested. Excellent agreement was observed between the true and calculated carboxylic acid concentration with a correlation coefficient squared of 0.9986. Once the total alkalinity and acetic acid concentrations are determined, the theoretically correct bicarbonate concentration and/or pH at any given operation temperature or pressure can be calculated. The intricate interrelationship of total alkalinity, carboxylic acids, and pH on scale and corrosion will be discussed by using case studies.
Reaction Kinetics of the Uptake of Chromium(III) Acetate by Polyacrylamide
Authors: Jain R. , McCool C. S. , Green D. W. , Willhite G. P. , Michnick M. J. 
Published: April 2006

Summary
Gelled polymer treatments applied in injection and production wells are used to alter fluid flow in oil reservoirs so that oil production is increased and water production is decreased. A common gel used in field treatments is made by crosslinking partially hydrolyzed polyacrylamide (HPAM) with chromium acetate. The initial step of the crosslink is the uptake of chromium acetate by a carboxyl group on the HPAM. The kinetics of the uptake reaction was studied as functions of the concentrations of chromium, HPAM, and hydrogen ions. The data were regressed to derive a rate expression for the disappearance of unreacted Cr(III) in the gelant.
Composition Routes for Three-Phase Partially Miscible Flow in Ternary Systems
Authors: LaForce Tara , Johns Russell T. 
Published: April 2006

SummaryThree-phase flow often occurs in reservoirs, particularly for secondary or tertiary oil recovery methods such as miscible gas or chemical flooding. In these cases, there is often significant mutual solubility of components in the phases. Unfortunately, there is insufficient understanding of how three partially miscible phases can affect flow. Furthermore, there are currently no benchmark analytical solutions available to validate numerical simulations for this complex flow regime.In this research, compositional solution routes are developed by the method of characteristics (MOC) for 1D, dispersion-free flow wherein up to three partially miscible flowing phases may be present. The method is applied to a water/alcohol/oil system that exhibits a large three-phase region in laboratory experiments. Unique solutions are found based on continuity arguments, shock-jump conditions, entropy constraints, and velocity constraints. The analytical solutions are compared to fine-grid finite-difference simulations to verify that they converge to the same dispersionfree limit.The results show that composition routes within the three-phase region often exhibit one phase below its residual saturation so that only two phases are flowing. As miscibility is approached, cumulative oil recovery initially declines because of the development of constant states in the solution, which cause the leading shock to speed up. We show that multicontact miscibility is developed at the critical point of one two-phase region and along the boundary of the three-phase region where all shocks and waves flow at a dimensionless velocity of one. Last, we show that injectivity changes by a factor of two for the specific relative permeabilities and injection compositions used.
Drift-Flux Parameters for Three-Phase Steady-State Flow in Wellbores
Authors: Shi H. , Holmes J. A. , Diaz L. R. , Durlofsky L. J. , Aziz K. 
Published: April 2006

Summary
Drift-flux models represent multiphase flow in wellbores or pipes in terms of a number of empirically determined parameters. Because of the lack of data for two- and three-phase flow in large-diameter inclined pipes, existing parameters are commonly based on small-diameter pipe experiments, which can lead to significant errors when the models are applied to wellbore flows. In this work, we use recent large-diameter experimental data for the determination of drift-flux parameters for oil/water/gas flow. The parameters are computed through application of an optimization procedure. It is shown that in-situ gas volume fraction in three-phase systems can be estimated using a two-phase flow model by viewing the system as an effective gas/liquid system, with oil and water constituting the "liquid" phase. This approach is, however, generally inaccurate for the determination of oil and water holdups, in which case the effect of gas must be taken into account. Specifically, for pipe inclinations away from horizontal, even small amounts of gas can act to eliminate the slip between oil and water. As the pipe deviation approaches horizontal, however, oil/water slip persists, even in the presence of gas. We develop and apply a unified two-and three-phase flow model to capture this gas effect. The new model is shown to provide much more accurate predictions for oil and water holdups in three-phase systems than were achievable with previous models.
Well-Test Analysis of Horizontal Wells in Gas/Condensate Reservoirs
Authors: Hashemi A. , Nicolas L. M. , Gringarten A. C. 
Published: April 2006

Summary
Gas/condensate reservoirs usually exhibit complex flow behaviors owing to the buildup of condensate banks around the wells when the bottomhole pressure drops below the dewpoint pressure. The formation of this liquid saturation can lead to a severe loss of well productivity and, therefore, lower gas recovery. Several studies have examined various ways to minimize the pressure drop in order to reduce liquid dropout and related problems. One solution implemented over the past decade is the use of horizontal wells.
There is a lack of published knowledge on the flow behavior of horizontal wells in gas/condensate reservoirs. The limited studies in this area (Muladi and Pinczewski 1999; Dehane et al. 2000; Harisch et al. 2001) focused on well performance rather than on well-test behavior. There has been no evidence of condensate dropout effects in published horizontal-well-test data.
This paper presents preliminary results from a study aimed at establishing an understanding of the near-wellbore well-test behavior in horizontal wells in gas/condensate reservoirs, with a focus on the existence of different mobility zones caused by condensate dropout.
We used a 3D fully compositional model to develop derivative shapes to be expected from horizontal-well-test data in gas/ condensate reservoirs below the dewpoint under various conditions. We then analyzed actual well-test data that exhibit such derivative characteristics, using a uniform flux horizontal well with wellbore storage and skin model and appropriate reservoir boundaries. The condensate drop effects in the production tests have been accounted for through changes in the values of the total skin effect. Finally, we used a compositional model to verify the results obtained from conventional well-test analysis.
It was found that condensate deposit near the wellbore yields a well-test composite behavior similar to what is found in vertical wells, but superimposed on horizontal-well behavior, which makes it much more complex.
An Improved Implementation of the LBFGS Algorithm for Automatic History Matching
Authors: Gao Guohua , Reynolds Albert C. 
Published: April 2006

Summary
For large scale history matching problems, where it is not feasible to compute individual sensitivity coefficients, the limited memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS)is an efficient optimization algorithm, (Zhang and Reynolds, 2002; Zhang, 2002). However, computational experiments reveal that application of the original implementation of LBFGS may encounter the following problems: (i) converge to a model which gives an unacceptable match of production data; (ii) generate a bad search direction that either leads to false convergence or a restart with the steepest descent direction which radically reduces the convergence rate; (iii) exhibit overshooting and undershooting, i.e., converge to a vector of model parameters which contains some abnormally high or low values of model parameters which are physically unreasonable. Overshooting and undershooting can occur even though all history matching problems are formulated in a Bayesian framework with a prior model providing regularization.
We show that the rate of convergence and the robustness of the algorithm can be significantly improved by: (1) a more robust line search algorithm motivated by the theoretical result that the Wolfe conditions should be satisfied; (2) an application of a data damping procedure at early iterations or (3) enforcing constraints on the model parameters. Computational experiments also indicate that (4) a simple rescaling of model parameters prior to application of the optimization algorithm can improve the convergence properties of the algorithm although the scaling procedure used can not be theoretically validated.
Improved Drilling Performance in a Troublesome Environment
Authors: Russell K. A. , Jolley S. J. , Koster M. , Crawford A. , Davison M. , Kazi M. , McGrath B. , Cockburn C. , MacLure R. 
Published: April 2006

SummaryThis paper describes an example of drilling-hazard mitigation. It demonstrates how a completely fresh approach, involving geomechanical analysis, planning of a new revised well trajectory, and real-time well monitoring, can reduce nonproductive time and cost and mitigate against unplanned terminal events.Recent drilling operations in a mature field in the North Sea were severely disrupted by wellbore deterioration, stuck pipe, and lost-circulation incidents. A complex geological sequence of tilted fault blocks and partially depleted reservoir sands made well-trajectory and wellbore-stability planning difficult. After two unsuccessful sidetrack attempts, an integrated operator/contractor team performed a detailed audit of the drilling problems and built a geomechanical Earth model to evaluate drilling hazards and develop strategies to mitigate any further wellbore instability. Well objectives were re-evaluated, and a new approach to the drilling process was developed. The keywas simplification of the well path. The operational solution featured management of drilling hazards through a real-time risk-mitigation process. Additional engineers at the well site managed drilling parameters; continuously monitored cavings, cuttings, and drill fluids; and analyzed drilling mechanics and logging-while-drilling (LWD) log data for indications of impending problems. A Web-based real-time data-transfer system was used to deliver data to the onshore drilling and subsurface teams. These methods, combined with advanced communication techniques, enabled tight control of drilling parameters and trajectory and enhanced collaborative understanding within the multidisciplinary team. The third sidetrack was completed without incident, within time, and under budget.
A Systematic Approach to Predicting Liquid Loading in Gas Wells
Authors: Guo Boyun , Ghalambor Ali , Xu Chengcai 
Published: April 2006

Summary
Loading up of liquids in wellbore has been recognized as one of the severe problems in gas production for many years. Accurate prediction of the problem is vitally important for taking timely measures to solve the problem. Although previous investigators have suggested several methods to predict the problem, results from these methods often show discrepancies. Also, these methods are not easy to use because of the difficulties with prediction of bottomhole pressure in multiphase flow. An accurate and easy-to-use method is highly desirable. This paper fills the gap.
Starting from Turner's analysis for prediction of the minimum gas velocity for liquid removal, the minimum kinetic energy of gas that is required to lift liquid droplets was determined in this study. In order to compare gas kinetic energy with the minimum required kinetic energy, a four-phase (gas, oil, water, and solid particles) flow model was developed for mist flow. Applying the minimum kinetic energy criterion to the four-phase flow model resulted in a closed-form analytical equation for predicting the minimum gas-flow rate.
The kinetic energy theory indicates that the controlling conditions for liquid drop removal in gas wells are bottomhole conditions rather than tophole conditions. Our case studies show that Turner's method with 20% adjustment still underestimates the minimum gas velocity for liquid removal, and the newly developed equation is more accurate than Turner's method. The new method is easier to use than other existing methods. This paper provides production engineers with a systematic approach to predicting the minimum gas-production rate for the continuous removal of water and oil from gas wells. Engineering charts are provided for two typical tubing sizes and wellhead pressures.
Chiefs, subchiefs and local control: negotiations over land, struggles over meaning
Authors: Goheen Mitzi 
Published: April 2006

AbstractControl over and access to land in Nso, Cameroon, has always depended on social identity. Control over land is a central symbol of leadership, both historically and today. Since the mid-1970s the Cameroonian state has instituted land ordinances and stressed privatisation and land titling, while Nso ideology has continued to emphasise access to land as a right of Nso citizenship. The contradictions set up by these two differing views are exacerbated by disputes between the Fon Nso and his sub-chiefs, in this case the Fon Nseh, over the right to control access to land. This prerogative, represented by the licence to collect taxes for the people farming on the land, is further complicated by the relationship of the two rulers and their constituents to the national state. Each Fon reinvents tradition by reinterpreting a series of historical events to buttress his claim, the Fon Nso stressing rights in people and the Fon Nseh stressing rights in territory by virtue of his ritual obligation to the ancestors residing there. This article examines the complex relationships and the distribution of power among these traditional rulers, the new elites and the national state.RésuméLe contrôle et l'accession à la terre à Nso, au Cameroun, a toujours dépendu de l'identité sociale. Le controle de la terre symbolise l'idée de chef, à la fois dans le passé et encore de nos jours. Depuis le milieu des années 1970, l'état camerounais a établi des arrêtes fonciers et renforce la privatisation et le droit foncier, alors que l'idéologie Nso a continué à accentuer l'accession à la terre comme un droit de citoyenneté Nso. Les contradictions produites par ces deux points de vues différents sont encore plus exacerbées par les désaccords entre le Fon Nso et ses sous-chefs, dans ce cas le Fon Nseh, sur le droit de controler l'accession à la terre. Ce privilege, representé par le droit de percevoir les impôts payables par les fermiers travaillant sur la terre, se complique encore davantage quant au rapport des deux chefs et de leurs partisans à l'état moderne. Chaque Fon réinvente la tradition en dormant une nouvelle interpretation à certains événement historiques pour étayer sa revendication: le Fon Nso met en valeur les droits du point de vue des gens, alors que le Fon Nseh renforce les droits dans la perspective du territoire en vertue de l'engagement rituel qu'il porte envers les ancêtres qui y résident. Cet article analyse les rélations complexes et la repartition du pouvoir parmi ces chefs traditionnels, les nouvelles élites et l'état moderne.
L'Apport de la teledetection dans l'etude des systemes agraires d'Afrique: l'exemple du Burkina Faso
Authors: Lambin Eric 
Published: April 2006

IntroductionL'anthropologue, tout comme le géographe, a besoin, pour ses analyses, de collecter des informations sur les sociétés qu'il étudie. En particulier lorsqu'on étudie les sociétés rurales d'Afrique, la collecte de ces informations présente des difficultés. En effet, de nombreux obstacles physiques (l'inaccessibilité, l'inconfort) s'interposent entre l'observateur et l'objet de son étude. Par ailleurs, il existe une forte interaction entre l'observateur et son objet d'étude de telle sorte que ce dernier ne se dévoile pas dans toute son authenticité. Les nouvelles technologies de l'information offrent un outil nouveau et utile pour l'anthropologue à cet égard. Il s'agit des satellites d'observation des ressources terrestres. Ceux-ci permettent d'appréhender avec une grande clarté le milieu rural aménagé par les sociétés agraires. Un outil nouveau signifie également une information nouvelle: la télédétection permet une vision spatiale synoptique (qui embrasse en même temps un vaste territoire) et répétitive d'une région. De nouvelles méthodes d'analyse soumises à une approche écologique et systèmique des civilisations agraires doivent être recherchées pour l'utilisation optimale de cet outil.