bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development and Application of a New Technique for Upscaling Miscible Processes
Authors: Hui Mun-Hong , Zhou Dengen , Wen Xian-Huan , Durlofsky Louis J. 
Published: April 2006

Summary
To better design and manage miscible gas injection, a fast and accurate coarse-scale miscible simulation capability is required. In this paper, we present a new technique for the upscaling of first-contact miscible displacements. The method comprises two components: effective flux boundary conditions (EFBCs) and the extended Todd-Longstaff1 with upscaled relative permeabilities (ETLU) formulation. The former accounts approximately for the effects of the global flow field on the local upscaling problems, while the latter modifies the way that effective fluid properties and upscaled relative permeabilities are computed so that effectively residual oil is properly represented.
For a sequence of partially layered, synthetic 2D permeability fields, the technique is shown to be successful in reproducing reference fine-scale solutions. The method is also shown to outperform other upscaling techniques over a wide range of coarsening factors. The upscaling procedure is then applied to a 3D simulation of a miscible gas-injection field study. A near-well upscaling technique is also incorporated into the methodology. We show that the new approach provides coarse-scale simulation results that match the reference solutions closely. In addition, the technique is shown to be very efficient computationally.
Monte Carlo Simulation of Vertical-Separators Handling in a Network of Intermittent Gas Lift Wells
Authors: Caicedo Sergio , Trujillo Militza , Florez Horacio 
Published: April 2006

Summary
To date, most of the research concerning the separation process has had a deterministic approach because of its orientation to steady-state-flow regimes. However, this assumption is far from true when many artificial intermittent gas lifted (IGL) wells are connected to the same separator. IGL wells have flow/no-flow periodic conditions associated with long accumulation stages and short production stages lasting approximately 20 minutes and 1 minute, respectively. A stochastic algorithm was developed to simulate the separation process and the proper periodicity of each IGL well, along with the unpredictable delay or synchronization between those wells. The simulation couples the dynamic mass-balance equations in the separator and the Monte Carlo method for predicting the gas and liquid rates associated with the superposition of the IGL wells. The input parameters for this simulation include daily gas/oil production and cycle time of each well, the oil properties, separator pressure and temperature, and the control scheme. The simulator output matched with less than 10% of the field data. The results obtained with the approach suggested in this work could be used for new criteria in design, simulation, and evaluation of separation facilities under fluctuating conditions.
Exploring Reservoir Engineering Aspects of Completion in Gas/Condensate Reservoirs: West African Examples
Authors: Kabir C. S. , Chang M. -M. , Taghizadeh O. 
Published: April 2006

SummaryThis paper explores multiple completion options in gas/condensate reservoirs with compositional simulations. Besides intelligent-well completion (IWC), options included commingling two reservoirs of contrasting conductivity (permeability-thickness product) and selectively perforating zones or reservoirs to offset the permeability contrast. At the outset, a value-of-information exercise suggested probing downhole sensing and completion issues in a stacked-reservoir situation. The ultimate objective of this study was to ascertain economic completion strategy so that depletion of reservoirs occurs evenly at the project's termination.Single-well compositional simulations formed the backbone for our evaluation of three completion options. Each reservoir was characterized by history matching drillstem tests (DSTs). Experimental design (ED) reduced the large number of simulation runs to a manageable few for probabilistic forecasting. Comparison of three options suggested that all of them nearly produced the desired results of maximum liquid recovery despite a 10-fold difference in permeability between the two horizons.Results further showed that condensate banking was a nonissue in this high-kh system of reservoirs as far as the gas deliverability is concerned. In other words, although 40 to 60% degradation in the gas productivity index (PI) occurred, gas deliverability remained intact. In contrast, both the liquid PI and rate declined with time owing to phase-behavior and relative permeability issues. Finally, we learned that the net income generated by IWC is no better than the specific-perforation completion (SPC).
Proppant Distribution and Flowback in Off-Balance Hydraulic Fractures
Authors: Daneshy Ali 
Published: April 2006

SummaryThe vast majority of industrial hydraulic fractures propagate in off-balance mode (in which the fracture is not in a single plane), including many shear fractures and branches, and are shorter and narrower than computed by existing models. Proppant transport, deposition, and flowback in these fractures are also substantially different from what occurs in single fractures. Presence of shear fractures leads to the formation of many randomly distributed tight proppant packs. Many of these are inherently unstable and serve as sources for proppant flowback, but they are also the source for fracture conductivity. Gravity causes the formation of proppant beds. These are usually formed at the lower extremities of the fracture. Branches generally trap the proppant and are unlikely sources for flowback. They also add little to the productive capacity of the fracture. Some of the proppant in the fracture is loosely scattered inside and is free to move when sufficient drag is exerted by fluid flow.This paper places special emphasis on proppant flowback and shows that the three requirements for its occurrence are motion initiation, motion maintenance, and infinite conductivity along the return path. Gravity plays a very important role in this process, as does well completion. Tendency for equilibrium between reservoir-fluid velocity and deposited proppant results in a gradual decrease and, eventually, stoppage of proppant return at any given flow rate. This equilibrium can be disrupted by sudden increases in flow rate, which then trigger instability and proppant flowback.Case histories from actual treatments illustrate and reinforce the findings of this paper.
Streamline-Based Production Data Integration in Naturally Fractured Reservoirs
Authors: Al-Harbi Mishal , Cheng Hao , He Zhong , Datta-Gupta Akhil 
Published: April 2006

SummaryStreamline-based models have shown great potential in reconciling high-resolution geologic models to production data. In this paper, we extend the streamline-based production data integration technique to naturally fractured reservoirs. Describing fluid transport in fractured reservoirs poses additional challenges arising from the matrix/fracture interactions. We use a dual-porosity streamline model for fracture-flow simulation by treating the fracture and matrix as separate continua that are connected through a transfer function. Next, we analytically compute the sensitivities that define the relationship between the reservoir properties and the production response in fractured reservoirs. The sensitivities are an integral part of our approach and can be evaluated very efficiently as 1D integrals along streamlines. Finally, the production data integration is carried out by a generalized travel-time inversion that has been shown to be robust because of its quasilinear properties and that uses established techniques from geophysical inverse theory.We also apply the streamline-derived sensitivities in conjunction with a dual-porosity finite-difference simulator to combine the efficiency of the streamline approach with the versatility of the finite-difference approach. This significantly broadens the applicability of the streamline-based approach in terms of incorporating compressibility effects and complex physics. We demonstrate the power and utility of our approach using 2D and 3D synthetic examples designed after actual field conditions. The reference fracture patterns are generated using a discrete fracture network (DFN) model that allows us to include statistical properties of fracture swarms, fracture densities, and network geometries. The DFN is then converted to a continuum model with equivalent gridblock permeabilities. Starting with prior models with varying degrees of fracture information, we match the water-cut history from the reference model. Both dual-porosity streamline and finite-difference simulators are used to model fluid flow in the fractured media. Our results indicate the effectiveness of our approach and the role of prior information and production data in reproducing fracture connectivities and preferential flow paths.
Analysis of Oil/Water-Flow Tests in Horizontal, Hilly Terrain, and Vertical Pipes
Authors: Abduvayt P. , Manabe R. , Watanabe T. , Arihara N. 
Published: April 2006

SummaryFlow pattern, pressure drop, and water holdup were measured for oil/water flow in horizontal, hilly terrain (±0.5 and ±3°), and vertical pipelines at a temperature of approximately 35 (±5) °C and a pressure of approximately 245 kPa using the large-scale multiphase-flow test facility of Japan Oil, Gas and Metals Natl. Corp. (JOGMEC). Test lines of 4.19-in. (106.4-mm) inner diameter (ID) and 120-m total length were used, which included a 40-m horizontal or hilly terrain (near-horizontal) and a 10-m vertical test section sequentially connected. The flow pattern was determined by visual observation with video recordings, and a flow-pattern map was made for each condition.New flow patterns were identified for horizontal and hilly terrain flow such as oil flow in a snake-like shape at top of pipe at high rate of water flow and water flow at bottom of pipe at high rate of oil flow.New holdup and pressure-drop data are presented for each flow condition. Flow rate and inclination angle influence holdup and pressure-drop behaviors. In vertical flow, when the oil superficial velocity exceeds a certain value, the pressure drop decreases exponentially as the superficial oil velocity, vSO, increases.Slippage between the phases was analyzed using the measured water holdup plotted against the input water cut with inlet-oil flow rate as a parameter and slip velocity vs. measured water holdup. It was found that the slippage changed significantly with slight changes in inclination angle.This paper provides new experimental data of flow pattern, water holdup, and pressure drop measured particularly at horizontal, hilly terrain, and vertical conditions, with large-diameter pipes. This is indispensable information for developing reliable prediction models for oil/water two-phase and gas/oil/water three-phase flow in pipelines.
Compositional Modeling by the Combined Discontinuous Galerkin and Mixed Methods
Authors: Hoteit H. , Firoozabadi A. 
Published: April 2006

SummaryIn this work, we present a numerical procedure that combines the mixed finite-element (MFE) and the discontinuous Galerkin (DG) methods. This numerical scheme is used to solve the highly nonlinear coupled equations that describe the flow processes in homogeneous and heterogeneous media with mass transfer between the phases. The MFE method is used to approximate the phase velocity based on the pressure (more precisely average pressure) at the interface between the nodes. This approach conserves the mass locally at the element level and guarantees the continuity of the total flux across the interfaces. The DG method is used to solve the mass-balance equations, which are generally convection-dominated. The DG method associated with suitable slope limiters can capture sharp gradients in the solution without creating spurious oscillations. We present several numerical examples in homogeneous and heterogeneous media that demonstrate the superiority of our method to the finite-difference (FD) approach. Our proposed MFE-DG method becomes orders of magnitude faster than the FD method for a desired accuracy in 2D.
Unified Model of Heat Transfer in Gas/Liquid Pipe Flow
Authors: Zhang H.-Q. , Wang Q. , Sarica C. , Brill J. P. 
Published: April 2006

Summary
A unified model of multiphase heat transfer is developed for different flow patterns of gas/liquid pipe flow at all inclinations −90° to +90° from horizontal. The required local flow parameters are predicted by use of the unified hydrodynamic model for gas/liquid pipe flow recently developed by Zhang et al. (2003a, 2003b). The model prediction of the pipe inside convective-heat-transfer coefficients are compared with experimental measurements for a crude-oil/natural-gas system in horizontal and upward-vertical flows, and good agreement is observed.
Including Nonequilibrium Relaxation in Models for Rapid Multiphase Flow in Wells
Authors: Civan Faruk 
Published: April 2006

Summary
The modeling of rapid flow of multiphase reservoir fluids in wells involving nonequilibrium partial separation of dissolved gases from the metastable oil and water phases is reviewed and formulated. The multiphase-fluid flow is described by means of the differential mass, momentum, and energy-balance equations along the well. The rate of gas transfer from the metastable liquid phases to the gas phase is expressed in terms of the relaxation time determined by the prevailing gas-phase volume fraction and the pressure and temperature conditions. The differential equations are solved numerically under a typical scenario involving the constant gas-, oil-, and water-production rates at the wellhead. It is demonstrated that the nonequilibrium saturation and pressure distributions in wells deviate from the equilibrium results, depending on the variation of the local relaxation time along the well. It is concluded that inclusion of nonequilibrium relaxation effects in models for rapid multiphase flow in wells is required.
Practical Considerations for Pressure-Rate Deconvolution of Well-Test Data
Authors: Levitan Michael M. , Crawford Gary E. , Hardwick Andrew 
Published: April 2006

Summary
Pressure-rate deconvolution provides equivalent representation of variable-rate well-test data in the form of characteristic constant rate drawdown system response. Deconvolution allows one to develop additional insights into pressure transient behavior and extract more information from well-test data than is possible by using conventional analysis methods. In some cases, it is possible to interpret the same test data in terms of larger radius of investigation.
There are a number of specific issues of which one has to be aware when using pressure-rate deconvolution. In this paper, we identify and discuss these issues and provide practical considerations and recommendations on how to produce correct deconvolution results. We also demonstrate reliable use of deconvolution on a number of real test examples.
Lessons From Integrated Analysis of GOM Drilling Performance
Authors: Iyoho A. W. , Meize R. A. , Millheim K. K. , Crumrine M. J. 
Published: April 2006

SummaryOffshore drilling continues to be extremely cost intensive, with U.S. $50 million wells not uncommon. This paper discusses one company's experience and the lessons it learned from a comprehensive analysis of Gulf of Mexico (GOM) historical data for drilling-performance benchmarking and continuous cost reduction. Drilling operations were broken down into discrete activities, and the best times from all the wells—including trouble time—were aggregated to form the "best composite time" (BCT). The BCT, introduced in recent papers,1–3 was applied, along with learning-curve analysis and other investigative tools, to examine drilling problems and the lessons learned to capture the best practices and, there by, challenge well-planning and construction practices.The "best composite cost" (BCC), or the monetary equivalent of the BCT, was also calculated and used for well-cost benchmarking. Correlative analyses of the wells (i.e., crossplots of drilling events along side mud-log data, wireline logs, and geologic data) were used to elucidate major well problems and abnormal flat times that caused deviations from the BCT. Correlative analysis also helped explain why some wells were drilled relatively trouble-free, even in difficult environments.From a more detailed trouble-time analysis of company-operated wells, tool/equipment failure was seen as a significant trouble-time component. Major drilling problems were also found to be mostly well-pressure related (e.g.,well control, lost circulation, and stuck pipe), supporting increased emphasison improved planning and quantification of equivalent circulating density(ECD), deepwater geopressures, and narrow drilling margins, especially in ultradeepwater environments. Overall, the company's 2003 trouble time was 26% of the total drilling time from spud to rig release.The BCT/BCC methodology is actually one element of "The Ten-Step Process" discussed exhaustively in Refs. 1 and 2. Applications to two onshore areas, so far, have shown encouraging results in drilling-costreduction. Applications to more-complicated offshore GOM wellbores, cost components, and narrow geopressure margins are the focus of this paper. The fields investigated are located in different parts of the GOM (Table 1). For brevity, results are shown only for the subsalt area of South Timbalier, the deepwater Green Canyon (GC) area, and the ultradeepwater eastern Gulf of Mexico(EGOM).
Well-Control Analyses on Extended-Reach and Multilateral Trajectories
Authors: Choe Jonggeun , Schubert Jerome J. , Juvkam-Wold Hans C. 
Published: April 2006

SummaryFor economic and technical reasons, the industry has used directional, extended-reach, horizontal, and multilateral wells. Although technologies are well developed for these wells, and there are numerous successes in the last decade, these wells still have high level of risk in drilling and completion. Well control is one of the relatively unanswered, but important, operations because improper well control, followed by a blowout is one of the most expensive and feared operational hazards.To maintain a specified bottomhole pressure (BHP), surface choke pressures highly depend on kick vertical height in the well and well trajectory. As the final hold angle of the well increases from vertical, shut-in casing pressure (SICP) reduces to shut-in drillpipe pressure (SIDPP) and remains the same as long as the kick stays in the horizontal section. For equal vertical depths, the maximum choke pressure is insensitive to hold angles or hold lengths, aslong as the initial pit-volume gain is the same. However, for directional andextended-reach wells, choke pressure can increase, even without kick expansion, because of the gain of kick vertical height in the build section. This may maskchoke-pressure reduction because of larger annular capacity when the kick passes the casing shoe, especially if the kickoff point (KOP) and casing-shoe depth are close.In multilateral wells with more than one kicking wellbore, SIDPP is affected by both formation over pressure and kick size in each wellbore. The maximum value among them will appear at the surface. Therefore, we should be careful in the interpretation of the shut-in pressures. For safe kick circulation, we must consider additional pressure to compensate for hydrostatic-pressure reduction resulting from kick migration and expansion in branch wellbores.
Understanding rural Zambia today: the relevance of the Rhodes-Livingstone Institute
Authors: van Donge Jan Kees 
Published: April 2006

Opening ParagraphIn the colonial period Zambia, then Northern Rhodesia, was a field for brilliant social research. The social scientists who worked at the Rhodes-Livingstone Institute (hereafter abbreviated to RLI) in Lusaka produced studies which can be found in libraries throughout the world. Yet the relevance of this literature for understanding present-day Zambia may not be immediately obvious. Our knowledge of society turns into historical knowledge, especially when great social changes such as decolonization take place. Social scientists inevitably capture one particular historical moment. The work of those connected with the RLI can therefore be treated as part of history; Kuper (1973) has characterised its role in the development of British anthropological thought as a part of the history of ideas, and Brown (1973, 1979) has written evocative accounts of the involvement of its members in the country as an example of the white man's presence in Africa.
One hundred and fifty years of Christianity in a Ghanaian town
Authors: Middleton John 
Published: April 2006

Opening ParagraphThis paper deals with certain aspects of a Christian congregation in a kingdom of southern Ghana, in particular its growth over the past 150 years and the part it plays in the lives of the people of the capital town of the state. Most studies of the development of Christianity in Africa deal with questions of religious ideology (especially that of the conflict between different systems of belief), of conversion, and of the growth of syncretist and separatist movements. Here I am concerned with the development of a Christian congregation that is neither syncretist nor separatist and with its place as one element of a total local religious system which includes other faiths. It is the local congregation of the Presbyterian Church of Ghana in the town of Akuropon, the capital of the eastern Akan kingdom of Akuapem, in the Akuapem Hills that lie some twenty-five miles north of Accra, the national capital. The state has a resident population of about 70,000 and the town one of some 6000. However, the number of people who, wherever they live, regard themselves asAkuroponfo, ‘people of Akuropon’, probably amounts to some 20,000. Those who live elsewhere return to the town when they can at weekends, Christmas, Easter, and the great annual purificatory festival ofOdwira, held in September or October; and most hope finally to return to their ‘home-town’ (as it is known in Ghana) to be buried. Although not a large town, it is known widely as the seat of the main educational facilities of the Presbyterian Church since the arrival of the Basel Mission in the then Gold Coast in 1828. Due largely to this fact it has provided more than its share of political, educational and other leaders of Gold Coast and Ghanian society.
The Loonkidongi prophets and the Maasai: protection racket or incipient state?
Authors: Spencer Paul 
Published: April 2006

AbstractThe Maasai are widely assumed to be a highly egalitarian society whose past success in dominating their neighbours owed much to the advice of their Prophets (loibonok, ‘laibons’). This article examines the practice of divination and prophecy in relation to the reputation of and the beliefs surrounding the principal family of, Maasai Prophets, the Loonkidongi. Undermining the egalitarian ideal, which is shared by the Maasai themselves, the Loonkidongi are shown to have been accepted as an elite. Throughout the twentieth century they have continued to dominate the Maasai in initiating and controlling sorcery, giving protection on the one hand and fostering the belief in Maasai vulnerability on the other. Living apart from other Maasai, with more wives and larger herds, with their own dynasty and dynastic feuding, with their penetrating mystical powers and networks of influence, the Loonkidongi have the symbolic trappings of a superior class of rulers. From this point of view the Maasai are not egalitarian, but are the clients of a protection racket that in pre-colonial times amounted to an incipient state. Today the Prophets continue to wield influence and are accorded more power popularly than elsewhere in eastern Africa, where surviving traditional rulers have been subordinated to the imposed state apparatus of colonial and post-colonial government.