Showing papers in "Journal of Energy Resources Technology-transactions of The Asme in 2008"

Numerical Studies of Gas Hydrate Formation and Decomposition in a Geological Reservoir

Abstract: Numerical modeling of gas hydrates can provide an integrated understanding of the various process mechanisms controlling methane (CH4) production from hydrates and carbon dioxide (CO2) sequestration as a gas hydrate in geologic reservoirs. This work describes a new unified kinetic model which, when coupled with a compositional thermal reservoir simulator, can simulate the dynamics of CH4 and CO2 hydrate formation and decomposition in a geological formation. The kinetic model contains two mass transfer equations: one equation converts gas and water into hydrate and the other equation decomposes hydrate into gas and water. The model structure and parameters were investigated in comparison with a previously published model. The proposed kinetic model was evaluated in two case studies. Case 1 considers a single well within a natural hydrate reservoir for studying the kinetics of CH4 and CO2 hydrate decomposition and formation. A close agreement was achieved between the present numerical simulations and results reported by Hong and Pooladi-Darvish (2003, “A Numerical Study on Gas Production From Formations Containing Gas Hydrates ,” Petroleum Society’s Canadian International Petroleum Conference, Calgary, AB, Jun. 10–12, Paper No. 2003-060). Case 2 considers multiple wells within a natural hydrate reservoir for studying the unified kinetic model to demonstrate the feasibility of CO2 sequestration in a natural hydrate reservoir with potential enhancement of CH4 recovery. The model will be applied in future field-scale simulations to predict the dynamics of gas hydrate formation and decomposition processes in actual geological reservoirs.

Wet Gas Separation in Gas-Liquid Cylindrical Cyclone Separator

Abstract: A novel gas-liquid cylindrical cyclone (GLCC © , ©The University of Tulsa, 1994), equipped with an annular film extractor (AFE), for wet gas applications has been developed and studied experimentally and theoretically. Detailed experimental investigation of the modified GLCC has been carried out for low and high pressure conditions. The results show expansion of the operational envelope for liquid carry-over and improved performance of the modified GLCC. For low pressures, the modified GLCC can remove all the liquid from the gas stream, resulting in zero liquid carry-over (separation efficiency100%). For high pressure conditions, the GLCC with a single AFE has separation efficiency 80% for gas velocity ratio, vsg/vann3. A mechanistic model and an aspect ratio design model for the modified GLCC have been developed, including the analysis of the AFE. The model predictions agree with the experimental data within 15% for low pressure and 25% for high pressure conditions. DOI: 10.1115/1.3000101

An Experimental Study on Wax Removal in Pipes With Oil Flow

Abstract: Pigging is recognized as one of the most used techniques for removing wax deposits in pipelines. In an earlier paper, the mechanics of the wax removal was studied using an experimental setup under dry conditions, i.e., no oil presence. In this study, the pigging experiments are conducted for both regular disc and by-pass disc pigs under flowing conditions. A new test facility was designed and constructed. The test section is 6.1 m (20-ft) long Schedule 40 steel pipe with an inner diameter of 0.0762 m (3-in.). A mixture of a commercial wax and a mineral oil is cast inside the spool pieces for different wax thicknesses and wax oil contents. The wax breaking and plug transportation forces are investigated separately. The results indicated that the wax breaking force increases as wax thickness increases, and the wax plug transportation force gradient is independent of the wax plug length. In comparison to previous test results, presence of oil reduced the wax plug transportation force. Experimental results also showed that the wax transport behavior of the by-pass pig is significantly different than that of the regular pig. The by-pass pig allows the oil to flow through the by-pass holes and mobilizes the removed wax in front of the pig resulting in no discernible wax accumulation in front of the pig. Therefore, no measurable transportation force was observed for the by-pass pig tests.Copyright © 2007 by ASME

Effect of Flue-Gas Impurities on the Process of Injection and Storage of CO2 in Depleted Gas Reservoirs

Abstract: Our previous coreflood experiments—injecting pure CO2 into carbonate cores—showed that the process is a win-win technology, sequestrating CO2 while recovering a significant amount of hitherto unrecoverable natural gas that could help defray the cost of CO2 sequestration. In this paper, we report our findings on the effect of “impurities” in flue gas—N2, O2, H2O, SO2, NO2, and CO—on the displacement of natural gas during CO2 sequestration. Results show that injection of CO2 with approximately less than 1mole% impurities would result in practically the same volume of CO2 being sequestered as injecting pure CO2. This gas would have the advantage of being a cheaper separation process compared to pure CO2 as not all the impurities are removed. Although separation of CO2 out of flue gas is a costly process, it appears that this is necessary to maximize CO2 sequestration volume, reduce compression costs of N2 (approximately 80% of the stream), and improve sweep efficiency and gas recovery in the reservoir.

Improving the Efficiency of the Advanced Injection Low Pilot Ignited Natural Gas Engine Using Organic Rankine Cycles

Abstract: Intense energy security debates amidst the ever increasing demand for energy in the country have provided sufficient impetus to investigate alternative and sustainable energy sources to the current fossil fuel driven economy. This paper presents the Advanced injection Low Pilot Ignition Natural Gas (ALPING) engine as a viable, efficient and low emissions alternative to conventional diesel engines, and discusses further efficiency improvements to the base ALPING engine using Organic Rankine Cycles (ORC) as bottoming cycles. The ALPING engine uses very small diesel pilots, injected early in the compression stroke to compression-ignite a premixed natural gas–air mixture. It is believed that the advanced injection of the higher cetane diesel fuel leads to longer incylinder residence times for the diesel droplets, thereby resulting in distributed ignition at multiple spatial locations, followed by lean combustion of the higher octane natural gas fuel via localized flame propagation. The multiple ignition centers result in faster combustion rates and higher fuel conversion efficiencies. The lean combustion of natural gas leads to reduction in local temperatures and oxides of nitrogen (NOx) emissions, since NOx emissions scale with local temperatures. In addition, the lean combustion of natural gas is expected to produce very little particulate matter (PM) emissions (not measured). Representative baseline ALPING (60° BTDC pilot injection timing) (without the ORC) half load (1700 rev/min, 21 kW) operation efficiencies reported in this study are about 35 percent while the corresponding NOx emissions is about 0.02 g/kWh, which is much lower than EPA 2007 tier 4 heavy duty diesel engine statutes of 0.2 g/kWh. Furthermore, the possibility of improving fuel conversion efficiency at half load operation with Organic Rankine Cycles using “dry fluids” are discussed. Dry organic fluids, due to their lower critical points, make excellent choices for bottoming Rankine cycles. Moreover, previous studies indicate that “dry fluids” are more preferable compared to wet fluids because the need to superheat the fluid to extract work from the turbine is eliminated. It is estimated that ORC–turbocompounding results in fuel conversion efficiency improvements of the order of 10 percent while maintaining the essential low NOx characteristics of ALPING combustion.Copyright © 2007 by ASME

Laboratory Simulation of Drill Bit Dynamics Using a Model-Based Servohydraulic Controller

Abstract: Drilling costs are significantly influenced by bit performance when drilling in offshore formations. Retrieving and replacing damaged downhole tools is an extraordinarily expensive and time-intensive process, easily costing several hundred thousand dollars of offshore rig time plus the cost of damaged components. Dynamic behavior of the drill string can be particularly problematic when drilling high strength rock, where the risk of bit failure increases dramatically. Many of these dysfunctions arise due to the interaction between the forces developed at the bit-rock interface and the modes of vibration of the drill string. Although existing testing facilities are adequate for characterizing bit performance in various formations and operating conditions, they lack the necessary drill string attributes to characterize the interaction between the bit and the bottom hole assembly (BHA). A facility that includes drill string compliance and yet allows real-rock/bit interaction would provide an advanced practical understanding of the influence of drill string dynamics on bit life and performance. Such a facility can be used to develop new bit designs and cutter materials, qualify downhole component reliability, and thus mitigate the harmful effects of vibration. It can also serve as a platform for investigating process-related parameters, which influence drilling performance and bit-induced vibration to develop improved practices for drilling operators. The development of an advanced laboratory simulation capability is being pursued to allow the dynamic properties of a BHA to be reproduced in the laboratory. This simulated BHA is used to support an actual drill bit while conducting drilling tests in representative rocks in the laboratory. The advanced system can be used to model the response of more complex representations of a drill string with multiple modes of vibration. Application of the system to field drilling data is also addressed.

NETL Extreme Drilling Laboratory Studies High Pressure High Temperature Drilling Phenomena

Abstract: The U.S. Department of Energy's National Energy Technology Laboratory (NETL) established the Extreme Drilling Laboratory to engineer effective and efficient drilling technologies viable at depths greater than 20,000 ft. This paper details the challenges of ultradeep drilling, documents reports of decreased drilling rates as a result of increasing fluid pressure and temperature, and describes NETL's research and development activities. NETL is invested in laboratory-scale physical simulation. Its physical simulator will have capability of circulating drilling fluids at 30,000 psi and 480°F around a single drill cutter. This simulator is not yet operational; therefore, the results will be limited to the identification of leading hypotheses of drilling phenomena and NETL's test plans to validate or refute such theories. Of particular interest to the Extreme Drilling Laboratory's studies are the combinatorial effects of drilling fluid pressure, drilling fluid properties, rock properties, pore pressure, and drilling parameters, such as cutter rotational speed, weight on bit, and hydraulics associated with drilling fluid introduction to the rock-cutter interface. A detailed discussion of how each variable is controlled in a laboratory setting will be part of the conference paper and presentation.

Basin Analog Investigations Answer Characterization Challenges of Unconventional Gas Potential in Frontier Basins

Abstract: To meet the global energy demand of the coming decades, the energy industry will need creative thinking that leads to the development of new energy sources. Unconventional gas resources, especially those in frontier basins, will play an important role in fulfilling future world energy needs. To develop unconventional gas resources, we must first identify their occurrences and quantify their potential. Basin analog assessment is a technique that can be used to rapidly and inexpensively identify and quantify potential unconventional gas resources. We have developed a basin analog methodology that is useful for rapidly and consistently evaluating the unconventional hydrocarbon resource potential in exploratory basins. The center of this approach is computer software, Basin Analog Systems Investigation (BASIN), which is used to identify analog basins. This software is linked to a database that includes geologic and petroleum systems information from intensely studied North America basins that contain well characterized conventional and unconventional hydrocarbon resources. To test BASIN, we selected 25 basins in North America that have a history of producing unconventional gas resources and began populating the database with critical data from these basins. These North American basins are “reference” basins that will be used to predict resources in other North American or international “target” or exploratory basins. The software identifies and numerically ranks reference basins that are most analogous to the target basin for the primary purpose of evaluating the potential unconventional resources in the target basin. We validated the software to demonstrate that it functions correctly, and we tested the validity of the process and the database. Accuracy of the results depends on the level of detail in the descriptions of geologic and petroleum systems. Finding a reference basin that is analogous to a frontier basin may provide critical insights into the frontier basin. Our method will help predict the unconventional hydrocarbon resource potential of frontier basins, guide exploration strategies, provide insights to reservoir characteristics, and help engineers make preliminary decisions concerning the best practices for drilling, completion, stimulation and production.Copyright © 2007 by ASME

Quantification of Uncertainty in Reserve Estimation From Decline Curve Analysis of Production Data for Unconventional Reservoirs

Abstract: Decline curve analysis is the most commonly used technique to estimate reserves from historical production data for the evaluation of unconventional resources. Quantifying the uncertainty of reserve estimates is an important issue in decline curve analysis, particularly for unconventional resources since forecasting future performance is particularly difficult in the analysis of unconventional oil or gas wells. Probabilistic approaches are sometimes used to provide a distribution of reserve estimates with three confidence levels (P10, P50, and P90) and a corresponding 80% confidence interval to quantify uncertainties. Our investigation indicates that uncertainty is commonly underestimated in practice when using traditional statistical analyses. The challenge in probabilistic reserve estimation is not only how to appropriately characterize probabilistic properties of complex production data sets, but also how to determine and then improve the reliability of the uncertainty quantifications. In this paper, we present an advanced technique for the probabilistic quantification of reserve estimates using decline curve analysis. We examine the reliability of the uncertainty quantification of reserve estimates by analyzing actual oil and gas wells that have produced to near-abandonment conditions, and also show how uncertainty in reserve estimates changes with time as more data become available. We demonstrate that our method provides a more reliable probabilistic reserve estimation than other methods proposed in the literature. These results have important impacts on economic risk analysis and on reservoir management.

A Study to Prevent Bottom Water From Coning in Heavy-Oil Reservoirs: Design and Simulation Approaches

Abstract: The coning problems for vertical wells and the ridging problems for horizontal wells are very difficult to solve by conventional methods during oil production from reservoirs with bottom water drives. If oil in a reservoir is too heavy to follow Darcy’s law, the problems may become more complicated for the non-Newtonian properties of heavy oil and its rheology. To solve these problems, an innovative completion design with downhole water sink was presented by dual-completion in oil and water columns with a packer separating the two completions for vertical wells or dual-horizontal wells. The design made it feasible that oil is produced from the formation above the oil water contact (OWC) and water is produced from the formation below the OWC, respectively. To predict quantitatively the production performances of production well using the completion design, a new improved mathematical model considering non-Newtonian properties of oil was presented and a numerical simulator was developed. A series of runs of an oil well was employed to find out the best perforation segment and the fittest production rates from the formations above and below OWC. The study shows that the design is effective for heavy oil reservoir with bottom water though it cannot completely eliminate the water cone formed before using the design. It is a discovery that the design is more favorable for new wells and the best perforation site for water sink (Sink 2) is located at the upper 1/3 of the formation below OWC. DOI: 10.1115/1.2955560

Thermoelectric Model of a Tubular SOFC for Dynamic Simulation

Abstract: A one-dimensional transient model of a tubular solid oxide fuel cell stack is proposed in this paper. The model developed in the virtual test bed (VTB ) computational environment is capable of dynamic system simulation. This model is based on the electrochemical and thermal modeling, accounting for the voltage losses and temperature dynamics. The single cell is discretized using a finite volume method where all the governing equations are solved for each finite volume. The temperature, the current density, and the gas concentration distribution along the axial direction of the cell are presented. The dynamic behavior of electrical characteristics and temperature under the variable load is simulated and analyzed. For easy implementation in the VTB platform, the nonlinear governing equations are discretized in resistive companion form. The developed model is validated with experimental results and can be used for dynamic performance evaluation and design optimization of the cell under variable operating conditions and geometric condition.

Monitoring of Energetic and Exergetic Performance Analysis of Salihli Geothermal District Heating System

Abstract: This study deals with a monitoring and assessment of energetic and exergetic analysis of Salihli Geothermal District Heating System (SGDHS) in Manisa, Turkey. In the analysis, actual system yearly average data of latest heating season are used to assess the district heating system exergetic performance. New exergetic model is improved and compared with old exergetic model results throughout the SGDHS. The new exergy losses occur particularly due to the fluid flow, taking place in the reinjection of thermal water (e.g., geothermal fluid), pumps, and the heat exchanger, as well as the natural direct discharge of the system.

Distributed Generation (DG) and the American Electric Utility System: What is Stopping It?

Abstract: Despite the immense environmental, technical, and financial promise of distributed generation (DG) technologies, they still constitute a very small percentage of electricity capacity in the United States. This manuscript answers the apparently paradoxical question: Why do technologies that offer such impressive benefits also find the least use? Going beyond technical explanations of problems related to system control, higher capital costs, and environmental compliance, this paper focuses on sociotechnical barriers related to utility preferences, business practices, regulatory bias, and consumer values. The approach helps us understand the glossing over of DG technologies, and identifies the impediments that policymakers must overcome if they are to find wider use.

Hydrodynamic Modeling of Three-Phase Flow in Production and Gathering Pipelines

Abstract: The transport of unprocessed gas streams in production and gathering pipelines is becoming more attractive for new developments, particularly those in less friendly environments such as deep offshore locations. Transporting gas, oil, and water together from wells in satellite fields to existing processing facilities reduces the investments required for expanding production. However, engineers often face several problems when designing these systems. These problems include reduced flow capacity, corrosion, emulsion, asphaltene or wax deposition, and hydrate formation. Engineers need a tool to understand how the fluids travel together, to quantify the flow reduction in the pipe, and to determine where, how much, and what type of liquid that would form in a pipe. The present work provides a fundamental understanding of the thermodynamics and hydrodynamic mechanisms of this type of flow. We present a model that couples complex hydrodynamic and thermodynamic models for describing the behavior of fluids traveling in near-horizontal pipes. The model presented herein focuses on gas transmission exhibiting low-liquid loading conditions. The model incorporates a hydrodynamic formulation for three-phase flow in pipes, a thermodynamic model capable of performing two-phase and three-phase flash calculations in an accurate, fast, and reliable manner, and a theoretical approach for determining flow pattern transitions in three-phase (gas-oil-water) flow and closure models that effectively handle different three-phase flow patterns and their transitions. The unified two-fluid model developed herein is demonstrated to be capable of handling three-phase systems exhibiting low-liquid loading. Model predictions were compared against field data with good agreement. The hydrodynamic model allows (1) the determination of flow reduction due to the condensation of liquid(s) in the pipe, (2) the assessment of the potential for forming substances that might affect the integrity of the pipe, and (3) the evaluation of the possible measures for improving the deliverability of the pipeline.

Effects of Cooled EGR on a Small Displacement Diesel Engine: A Reduced-Order Dynamic Model and Experimental Study

Abstract: Diesel engines are critical in fulfilling transportation and mechanical/electrical power generation needs throughout the world. The engine’s combustion by-products spawn health and environmental concerns, so there is a responsibility to develop emission reduction strategies. However, difficulties arise since the minimization of one pollutant often bears undesirable side effects. Although legislated standards have promoted successful emission reduction strategies for larger engines, developments in smaller displacement engines has not progressed in a similar fashion. In this paper, a reduced-order dynamic model is presented and experimentally validated to demonstrate the use of cooled exhaust gas recirculation (EGR) to alleviate the tradeoff between oxides of nitrogen reduction and performance preservation in a small displacement diesel engine. EGR is an effective method for internal combustion engine oxides of nitrogen (NOx) reduction, but its thermal throttling diminishes power efficiency. The capacity to cool exhaust gases prior to merging with intake air may achieve the desired pollutant effect while minimizing engine performance losses. Representative numerical results were validated with experimental data for a variety of speed, load, and EGR testing scenarios using a 0.697l three-cylinder diesel engine equipped with cooled EGR. Simulation and experimental results showed a 16% drop in NOx emissions using EGR, but experienced a 7% loss in engine torque. However, the use of cooled EGR realized a 23% NOx reduction while maintaining a smaller performance compromise. The concurrence between simulated and experimental trends establishes the simplified model as a predictive tool for diesel engine performance and emission studies. Further, the presented model may be considered in future control algorithms to optimize engine performance and thermal and emission characteristics.

Evaluation of “Marching Algorithms” in the Analysis of Multiphase Flow in Natural Gas Pipelines

Abstract: Marching algorithms are the rule rather than the exception in the determination of pressure distribution in long multiphase-flow pipes, both for the case of pipelines and wellbores. This type of computational protocol is the basis for most two-phase-flow software and it is presented by textbooks as the standard technique used in steady state two-phase analysis. Marching algorithms acknowledge the fact that the rate of change of common fluid flow parameters (such as pressure, temperature, and phase velocities) is not constant but varies along the pipe axis while performing the integration of the governing equations by dividing the entire length into small pipe segments. In the marching algorithm, governing equations are solved for small single sections of pipe, one section at a time. Calculated outlet conditions for a particular segment are then propagated to the next segment as its prescribed inlet condition. Calculation continues in a “marching” fashion until the entire length of the pipe has been integrated. In this work, several examples are shown where this procedure might no longer accurately represent the physics of the flow for the case of natural gas flows with retrograde condensation. The implications related to the use of this common technique are studied, highlighting its potential lack of compliance with the actual physics of the flow for selected examples. This paper concludes by suggesting remedies to these problems, supported by results, showing considerable improvement in fulfilling the actual constraints imposed by the set of simultaneous fluid dynamic continuum equations governing the flow.

Experimental Studies on Galling Onset in OCTG Connections: A Review

Abstract: With today’s high prices for natural gas and oil, the demand for oil and country tubular goods (OCTGs) with superior performance properties is very high. Failures in OCTG can be attributed to numerous sources, for example, makeup torque, corrosion, and galling. Thread galling is the most common mode of failure. This failure often leads to leakage, corrosion of the material, and loss of mechanical integrity. The failure of OCTG eventually amounts to excessive operational costs for the gas and oil industry. Numerous approaches have been taken to improve the galling resistance of OCTG connections. The advocacy of these approaches is often achieved through experimental studies using galling testers. There is a need to design and use effective galling testers to understand and improve the performance of OCTG connections. Thus, the objective of this paper is to present a concise review of literature related to the galling testers that may have applications to OCTG.

Capacity Mapping for Optimum Utilization of Pulverizers for Coal Fired Boilers

Abstract: Capacity mapping is a process of comparison of standard inputs with actual fired inputs to assess the available standard output capacity of a pulverizer. The base capacity is a function of grindability; fineness requirement may vary depending on the volatile matter (VM) content of the coal and the input coal size. The quantity and the inlet will change depending on the quality of raw coal and output requirement. It should be sufficient to dry pulverized coal (PC). Drying capacity is also limited by utmost PA fan power to supply air. The PA temperature is limited by air preheater (APH) inlet flue gas temperature; an increase in this will result in efficiency loss of the boiler. The higher PA inlet temperature can be attained through the economizer gas bypass, the steam coiled APH, and the partial flue gas recirculation. The PS/coal ratioincreases with a decrease in grindability or pulverizer output and decreases with a decrease in VM. The flammability of mixture has to be monitored on explosion limit. Through calibration, the PA flow and efficiency of conveyance can be verified. The velocities of coal/air mixture to prevent fallout or to avoid erosion in the coal carrier pipe are dependent on themore » PC particle size distribution. Metal loss of grinding elements inversely depends on the YGP index of coal. Variations of dynamic loading and wearing of grinding elements affect the available milling capacity and percentage rejects. Therefore, capacity mapping in necessary to ensure the available pulverizer capacity to avoid overcapacity or undercapacity running of the pulverizing system, optimizing auxiliary power consumption. This will provide a guideline on the distribution of raw coal feeding in different pulverizers of a boiler to maximize system efficiency and control, resulting in a more cost effective heat rate.« less

Using Transient Inflow Performance Relationships to Model the Dynamic Interaction Between Reservoir and Wellbore During Pressure Testing

Abstract: The fundamental understanding of the dynamic interactions between multiphase flow in the reservoir and that in the wellbore remains surprisingly weak. The classical way of dealing with these interactions is via inflow performance relationships (IPRs), where the inflow from the reservoir is related to the pressure at the bottom of the well, which is a function of the multiphase flow behavior in the well. A steady-state IPRs are normally adopted, but their use may be erroneous when transient multiphase flow conditions occur. The transient multiphase flow in the wellbore causes problems in well test interpretation when the well is shut-in at the surface and the bottomhole pressure is measured. The pressure buildup (PBU) data recorded during a test can be dominated by transient wellbore effects (e.g., phase change, flow reversal, and re-entry of the denser phase into the producing zone), making it difficult to distinguish between true reservoir features and transient wellbore artifacts. This paper introduces a method to derive the transient IPRs at bottomhole conditions in order to link the wellbore to the reservoir during PBU. A commercial numerical simulator was used to build a simplified reservoir model (single well, radial coordinates, homogeneous rock properties) using published data from a gas condensate field in the North Sea. In order to exclude wellbore effects from the investigation of the transient inflow from the reservoir, the simulation of the wellbore was omitted from the model. Rather than the traditional flow rate at surface conditions, bottomhole pressure was imposed to constrain the simulation. This procedure allowed the flow rate at the sand face to be different from zero during the early times of the PBU, even if the surface flow rate is equal to zero. As a result, a transient IPR at bottomhole conditions was obtained for the given field case and for a specific set of time intervals, time steps, and bottomhole pressure. In order to validate the above simulation approach, a preliminary evaluation of the required experimental setup was carried out. The setup would allow the investigation of the dynamic interaction between the reservoir, the near-wellbore region, and the well, represented by a pressured vessel, a cylindrical porous medium, and a vertical pipe, respectively.

Design and Performance of Slug Damper

Abstract: This study investigates theoretically and experimentally the slug damper as a novel flow conditioning device, which can be used upstream of compact separation systems. In the experimental part, a 3 in. ID slug damper facility has been installed in an existing 2 in. diameter two-phase flow loop. This flow loop includes an upstream slug generator, a gas-liquid cylindrical cyclone (GLCC, ©The University of Tulsa, 1994) attached to the slug damper downstream and a set of conductance probes for measuring the propagation of the dissipated slug along the damper. Over 200 experimental runs were conducted with artificially generated inlet slugs of 50 ft length Ls /d 300 that were dumped into the loop upstream of the slug damper, varying the superficial liquid velocity between 0.5 ft/s and 2.5 ft/s and superficial gas velocity between 10 ft/s and 40 ft/s (in the 2 in. inlet pipe) and utilizing segmented orifice opening heights of 1 in., 1.5 in., 2 in., and 3 in. For each experimental run, the measured data included propagation of the liquid slug front in the damper, differential pressure across the segmented orifice, GLCC liquid level, GLCC outlet liquid flow, and static pressure in the GLCC. The data show that the slug damper/ GLCC system is capable of dissipating long slugs, narrowing the range of liquid flow rate from the downstream GLCC. Also, the damper capacity to process large slugs is a strong function of the superficial gas velocity (and mixture velocity). The theoretical part includes the development of a mechanistic model for the prediction of the hydrodynamic flow behavior in the slug damper. The model enables the predictions of the outlet liquid flow rate and the available damping time, and in turn the prediction of the slug damper capacity. Comparison between the model predictions and the acquired data reveals an accuracy of 30% with respect to the available damping time and outlet liquid flow rate. The developed model can be used for design of slug damper units. DOI: 10.1115/1.3000137

Implementation of a Bottom-Hole Assembly Program

Abstract: A state of the art graphical user interface program has been developed to predict and design the bottom-hole assembly (BHA) performance for drilling. The techniques and algorithms developed in the program are based on those developed by Lubinski and Williamson. The BHA program facilitates conducting parametric studies and making field decisions for optimal BHA performance. The input parameters may include formation class, dip angle, hole size, drill collar size, number of stabilizers, and stabilizer spacing. The program takes into consideration bit-formation characteristics and interaction, drilling fluid weight, drill collar sizes, square collars, shock absorbers, measurement while drilling tools, reamer tools, directional tools, rotary steerable systems, etc. The output may consist of hole curvature (buildup or drop rate), hole angle, and weight on bit and is presented in drilling semantics. Additionally, the program can perform mechanical analyses and can solve for the bending moments and reaction forces. Moreover, the program has the capability to predict the wellpath using a drill ahead algorithm. The program consists of a mathematical model that makes assumptions of 2D, static, and constant hole curvature, resulting in a robust computationally efficient tool that produces rapid reliable results.