Low Volumetric Efficiency Research Articles

Performance improvements in a longer-stroke, spark-ignition gas engine

The engine performance with several stroke/cylinder diameter (S/D) ratios from 1.0 to 2.0 was investigated in a small spark-ignition gas engine by experiments and with computational fluid dynamics (CFD) engine analysis. The experiments were conducted on a specially manufactured, single-cylinder, spark-ignition gas engine with the cylinder head of a commercial diesel engine with a spark plug instead of a fuel injector. The cylinder diameter was fixed at 70 mm, the same as the original engine, and the stroke length was varied at 70 mm (S/D = 1.0), 105 mm (S/D = 1.5), and 140 mm (S/D = 2.0) under the same compression ratio of 12:1 by changing the piston, the cylinder liner, the cylinder block, the crankshaft, and the connecting rod. The engine speed was set at 1200 r/min, and the test fuel was commercial compressed natural gas provided from a bottle. The indicated thermal efficiency improved significantly with S/D ratio, mainly due to the reductions in cooling loss, maintaining the degree of constant-volume heat release at high levels, and also due to improvements in the combustion efficiency. The optimum S/D ratio is about 1.5, as the improvement in indicated thermal efficiency with increase of S/D from 1.0 to 1.5 was more significant than that with S/D increase from 1.5 to 2.0. The indicated mean effective pressure (IMEP) with S/D = 1.5 was the largest among these S/D ratios, and the IMEP with S/D = 2.0 was much smaller due to lower volumetric efficiency. The indicated thermal efficiency improved with longer strokes in the stoichiometric and lean conditions of excess air ratios below 1.5, but the deterioration in thermal efficiency with leaner conditions, above 1.5, was more pronounced with longer strokes. The CFD analysis also showed the improvement in thermal efficiency with longer strokes, and the indicated thermal efficiency improved more in the case of the same cylinder diameter than in the case of the same displacement volume. This is mainly due to the larger reduction in cooling loss in the case with the same cylinder diameter. However, even with the same displacement volume, the reduction in cooling loss and the improvement in indicated thermal efficiency with longer strokes were reliably obtained. The experimental equations for the heat transfer coefficient with mean piston speed, including Woschni’s equation, do not express the change in heat transfer at the higher S/D ratios.

Prediction of Leakage Flow in a Shrouded Centrifugal Blood Pump

This article proposes a phenomenological model to predict the leakage flow in the clearance gap of shrouded centrifugal blood pumps. A good washout in the gap clearance between the rotating impeller surfaces and volute casing is essential to avoid thrombosis. However, excessive leakage flow will result in higher fluid shear stress that may lead to hemolysis. Computational fluid dynamics (CFD) analysis was performed to investigate the leakage flow in a miniaturized shrouded centrifugal blood pump operating at a speed of 2000 rpm. Based on an analytical model derived earlier, a phenomenological model is proposed to predict the leakage flow. The leakage flow rate is found to be proportional to h(α) , where h is the gap size and the exponent α ranges from 2.955 to 3.15 for corresponding gap sizes of 0.2-0.5 mm. In addition, it is observed that α is a linear function of the gap size h. The exponent α compensates for the variation of pressure difference along the circumferential direction as well as inertia effects that are dominant for larger gap clearances. The proposed model displays good agreement with computational results. The CFD analysis also showed that for larger gap sizes, the total leakage flow rate is of the same order of magnitude as the operating flow rate, thus suggesting low volumetric efficiency.

Techbits: Waterflood-Management Strategies Explored in Argentina (February 2010)

Techbits An SPE Applied Technology Workshop (ATW) titled “Keys to Effective Mature Waterflood Management” held in Buenos Aires allowed more than 100 industry professionals to share best practices and lessons learned in waterflood management. Waterflood Case Studies The ATW’s opening session highlighted several case studies in Argentina’s fields. Daniel Biedma and Enrique Muruaga of Tecpetrol reviewed different waterflooding techniques aimed at improving the oil recovery factor by maximizing the volumetric sweep efficiency in the mature El Tordillo field. The techniques included infill drilling, selective-water-injection completions (multiple packers and mandrels), modifying water-injection patterns, and a gel-injection pilot test that was expanded to 14 injection patterns. Alejo Holub and Federico Schamann of Chevron presented a holistic field-performance optimization of the mature El Trapial oil field. They showed how an integrated approach incorporating stochastic models and multidisciplinary teams can result in better decisions. This approach, which also uses Monte Carlo simulation, reservoir simulation, and decision-tree analysis, is especially useful to evaluate and select best scenarios from multiple possibilities during field development and latter stages of maturity. An Apache presentation on a waterflooding project in the Guanaco Centro field, which was discontinued due to operational problems, showed how the project could be revitalized and recovery factors improved by redesigning waterflooding patterns. Engineers performed a single-layer numerical simulation study to evaluate pattern reconfiguration to optimize the recovery factor of the field and keep costs down. Reservoir Characterization and Modeling William Cobb, 2008 SPE president and principal of William Cobb and Associates, presented a method to determine waterflood volumetric sweep efficiency by using oil-production rates. He described how production history and pressure/volume/temperature properties can be used to estimate volumetric sweep efficiency within certain regions of a field. Identifying regions of low volumetric sweep efficiency may show potential areas to improve the recovery factor through different techniques, such as infill drilling, selective completions, or gel injection. Marcelo Crotti of Inlab presented a study highlighting the importance of considering capillary forces as well as viscous and gravity forces in models that simulate the movement of waterfronts in a reservoir. Laboratory experiments indicate that under certain conditions, the influence of capillary forces can cause water to move faster through low-permeability layers. Crotti also discussed the importance of reservoir heterogeneities and how they can affect the response of the waterfront. Improved-Oil-Recovery Techniques An ongoing alkali surfactant polymer pilot test for a field in Neuquén Basin was next reviewed by Pluspetrol’s Raul Puliti. Laboratory testing, including core analysis and the Helle Shaw cell test, was being carried out to select chemical product candidates. The patterns for the pilot test were selected, and Puliti stressed that before commencing the pilot test, it was important to ensure production and injection remain stable for the pattern and neighbor wells.

Nanocomposite Film Dielectrics for High Temperature Power Conditioning Capacitors

Emerging power electronics in a broad range of military, aerospace, hybrid vehicle, renewable energy and down-hole drilling applications rely on advances in dielectric materials for capacitors. Compact capacitors possessing low dielectric loss and high operating temperature capability are needed for power conditioning in advanced converter and inverter designs for these applications. Wound film capacitors represent the preferred capacitor technology but are limited by low operating temperature capabilities, < 150°C, and low volumetric efficiency, capacitance per unit volume less than 1.0 μF/cc. TPL is developing processes and manufacturing techniques for fabrication of advanced capacitor films comprised of high temperature polymers modified with ceramic nanoparticles. The selected polymers enable high temperature operation and the ceramic nanoparticles enhance volumetric efficiency by increasing the dielectric constant. The fabricated films are directly adaptable to conventional wound film capacitor construction methodologies. This paper provides an overview of TPL's experience to-date with a film dielectric material system comprised of fluorenone polyester polymer and titanate nanoparticle filler. The fluorenone polyester polymer was selected to provide a stable operating temperature of at least 300°C, while the addition of the titanate powder increases the dielectric constant and, in turn, the volumetric efficiency of wound film capacitors constructed with this film system. The targeted device for the film is a 500 to 800 V filter capacitor for high temperature power conditioning applications.

Evaluation of the maximum horsepower of vehicles converted for use with natural gas fuel

Tests to measure the maximum horsepower of commercial vehicles converted for use with natural gas fuel indicate a reduction of approximately 20% in horsepower compared with gasoline-driven vehicles. This reduction in horsepower resulting from the use of gas is due basically to the lower thermal efficiency of the cycle of natural gas compared with that of gasoline and to its lower volumetric efficiency, since natural gas is injected into the combustion chamber in gaseous form, unlike gasoline, in which part of the fuel entering the cylinder is in the liquid phase. Natural gas used as a fuel generates lower quantities of air pollutants, particularly unburned hydrocarbons (HCs) and carbon monoxide (CO). Despite the downside of reduced horsepower, the use of natural gas as a fuel for automotive vehicles equipped with Otto-cycle engines is economically viable owing to the wide availability of natural gas.

The hydrogen-fueled internal combustion engine: a technical review

A review is given of contemporary research on the hydrogen-fueled internal combustion engine. The emphasis is on light- to medium-duty engine research. We first describe hydrogen-engine fundamentals by examining the engine-specific properties of hydrogen and surveying the existing literature. Here it will be shown that, due to low volumetric efficiencies and frequent preignition combustion events, the power densities of premixed or port-fuel-injected hydrogen engines are diminished relative to gasoline-fueled engines. Significant progress has been made in the development of advanced hydrogen engines with improved power densities. We discuss several examples and their salient features. Finally, we consider the overall progress made and provide suggestions for future work.

축분을 이용한 바이오가스 엔진 개발 - 기초설계 및 성능분석 -

This is a fundamental study to develop a bio-gas utilization technology using livestock manure. Especially, this study was carried out to develop an engine using bio-gas. A bio-gas engine was designed and manufactured by modification of a diesel engine of 3 cylinders powering 13.31 kW/2800 rpm, changing the fuel supplying system fit for bio-gas. The result showed that, when the Air/Fuel ratio was controlled with fixed spark timing, the power of biogas-fueled engine is about lower then that of LNG-fueled engine because of low volumetric efficiency. The engine output and torque was kW, , respectively at the engine speed of 2600 rpm. Bio-gas consumption rate was 260.20 g/kW/hr, 315.20 g/kW/hr in engine speed or 1000 rpm, 2800 rpm, respectively.

Overview of Short-Distance Oil Displacement Processes

Abstract With the advent of horizontal wells, a distinct change is tacitly taking place in our approach to improved recovery of heavy oil: from displacing mobilized oil in a flood pattern from injector to producer over long distances of the order of hundreds of metres, to short-distance oil displacement (SDOD) processes (typically over a few metres). Due to the high viscosity of oil, its displacement to a producer site located a long distance away is usually inefficient. In these cases, the required pressure drop may be very high, and/or the mobility ratio between injectant and oil exceedingly large. Either gravity override or very intensive channeling may take place, resulting in extremely low volumetric sweep efficiency and hence, generally marginal or poor economics. Using horizontal wells, travel distances for the mobilized oil to reach the producer can be shortened. SDOD processes are aimed at mobilizing oil and producing it immediately, via the shortest path, into a horizontal producer. SDOD processes can utilize horizontal producers and injectors, or combinations of horizontal producers and vertical injectors. Based on the displacement front's position relative to the horizontal section of a producer, SDOD processes could be divided into two categories:Those with a displacement front quasi-parallel to the horizontal producer.Those with a displacement front quasi-perpendicular to the horizontal producer. While the first type of SDOD process uses two parallel horizontal wells (one for injection and the other one for production), the second type uses a vertical injector and a horizontal producer with the toe of the producer located in the proximity of the shoe of the injector. In the first type of process, production occurs throughout the entire horizontal section. In the second type, the swept zone extends and moves from the toe towards the heel, utilizing reduced sections of the horizontal well for production. Steam Assisted Gravity Drainage (SAGD) and Vapour Extraction (VAPEX) processes belong to the first type. Toe-To-Heel (TTH) displacement processes are of the second type. These TTH displacement processes can be applied in a non-thermal mode, such as Toe-To-Heel Waterflooding or a thermal mode such as THAI (Toe-To-Heel Air Injection) along with its variant, CAPRI, aimed at in situ oil upgrading. An analysis of all SDOD processes (SAGD, VAPEX, and TTH displacement processes) was performed, focusing on their relative merits in terms of override or underride due to gravity segregation, injectant channeling due to reservoir heterogeneity, and injectant/oil mobility ratio causing instabilities. These negative factors are very important in defining the efficiency of the long-distance oil recovery techniques, but they are substantially less important during the SDOD processes. Therefore, in many situations, the efficiency of heavy oil exploitation via SDOD IOR/EOR processes is usually better than alternate recovery schemes. Finally, basic concepts behind different TTH displacement processes are examined in light of available laboratory and simulation results. Also, various aspects of SDOD process implementation in the field along with practical considerations are discussed.

High Performance RF Passive Integration on a Si Smart Substrate for Wireless Applications

To achieve cost and size reductions, we developed a low cost manufacturing technology for RF substrates and a high performance passive process technology for RF integrated passive devices (IPDs). The fabricated substrate is a conventional 6' Si wafer with a 25 μm thick Sio 2 surface. This substrate showed a very good insertion loss of 0.03 dB/mm at 4 GfIz, including the conductive metal loss, with a 50 Ω coplanar transmission line (W=50 μm, G=20 μm). Using benzo cyclo butene (BCB) interlayers and a 10 μm Cu plating process, we made high Q rectangular and circular spiral inductors on Si that had record maximum quality factors of more than 100. The fabricated inductor library showed a maximum quality factor range of 30-120, depending on geometrical parameters and inductance values of 035-35 nH. We also fabricated small RF IPDs on a thick oxide Si substrate for use in handheld phone applications, such as antenna switch modules or front end modules, and high-speed wireless LAN applications. The chip sizes of the wafer-level-packaged RF IPDs and wire-bondable RF IPDs were 1.0-1.5 mm 2 and 0.8-1.0 mm 2 , respectively. They showed very good insertion loss and RF performances. These substrate and passive process technologies will be widely utilized in hand-held RF modules and systems requiring low cost solutions and strict volumetric efficiencies.

Use of Air-Liquid Two-Phase Flow in Hydrophobic Microfluidic Channels for Disposable Flow Cytometers

This paper describes a disposable flow cytometer that uses an air-liquid two-phase microfluidic system to produce a focused high-speed liquid sample stream of particles and cells. The susceptibility of thin liquid columns to instabilities may suggest that focusing of sample liquids with streams of air would be difficult. The design of channel geometry, control of flow rates, and use of appropriate surface chemistries on the channel walls, however, enabled the generation of thin (15–100 μm) and partially bounded sample streams that were stable and suitable for rapid cell analysis. Using an inverted epi-fluorescence microscope with a photo-multiplier tube, we demonstrated that the system is capable of counting the number of beads and C2C12 myoblast cells. The effects of different flow rates and surface chemistries of the channel walls on the air-liquid two-phase flows were characterized using optical and confocal microscopy. Use of air instead of liquids as a sheath fluid eliminates the need for large sheath liquid reservoirs, and reduces the volume and weight requirements. The low manufacturing cost and high volumetric efficiency make the air-sheath flow cytometer attractive for use as a stand-alone device or as an integrated component of bio-artificial hybrid microsystems.

An analytical examination of the effects of hydrogen addition on cyclic variations in homogeneously charged compression–ignition engines

The operation of homogeneously charged compression–ignition (HCCI) engines at low loads often suffer from excessive cyclic variations since the homogeneous charge is too fuel-lean to burn completely. These variations can be further exacerbated if natural gas is used due to the relatively narrow operational limits of methane. The paper describes the results of an analytical approach that models in full the reaction rate development when hydrogen is added to a naturally aspirated, methane or propane-fuelled motored HCCI engine. The operating conditions at which these effects are studied are those that are conducive to the onset of cyclic variations, such as fuel-lean conditions and low volumetric efficiencies. It is shown that the addition of hydrogen, which has a relatively wide operating range, to a methane- or propane-fuelled engine can reduce cyclic variations while extending the operating region of the engine.

Controlling Sand Production During Downhole Emulsification

Abstract Experiments were carried out using a physical model to emulate the downhole-emulsification conditions in the presence of produced sand in a well containing a progressive cavity (Moyno) pump. Five commercially available emulsifiers were, tested for their ability to reduce pressure drop in the flowline by forming low-viscosity oil-in-water emulsions and at the same, time retain sand within the oil phase. The chemical concentrations were varied from 100 to 1,711 mg/L and sand and water cuts were maintained at 5% (v/v) and 30% (v/v), respectively. Laboratory experimental results showed that the Rexol 25/10 chemical had strong sand-retention and moderate pressure-reduction characteristics. Addition of polymer material, Flocon 4800C, to the Flothin F2 chemical also showed excellent sandretention and sufficient pressure-reduction capability. The tests indicated that to attain the optimum conditions of pressure reduction and sand retention, one should have an effective emulsion viscosity of about 800 to 900 rnPa.s (dead-oil viscosity is: 8.000 mFa.s) for an 11 ° API oil. Based on the laboratory results, the Rexol 25/10 chemical was field tested in a five-well downhole-emulsification project. The results of the field trial showed an increase in both productivity and surface sand cut. Introduction The high viscosity of heavy oils causes several operational problems, which include low pump volumetric efficiency, slow rod drop rare, rod parting and high flow-line pressure drop. Several methods including the application of bottomhole heaters and light oil diluents(1), water injection2 and downhole emulsification(3–6) (DHE) have been implemented to overcome these problems. Among these methods, DHE proves to be a relatively effective operational technique to produce heavy oil. The DHE process primarily involves injection of an aqueous surfactant solution either into the tubing-casing annulus or through the hollow rod system into rhe bottomhole area to convert high-viscosity oil or W/O emulsion into low-viscosity oil-in-water (o/w) emulsion. The olw emulsion is fanned by the mixing action that occurs as the surfactant solution falls through the oil and water. This mixing may be aided byturbulence caused by gas liberation, and/orthe intermingling of the fluids entering the pump This mixing action causes the continuous oil phase to break into small droplets, which disperse in the water phase. The presence of surfactant reduces the interfacial tension between water and oil and aids in the formation of oil dispersion with a minimum of mechanical energy input. Proper selection can also cause the surfactant to concentrate at the oil-water interface and aid in regarding the coalescence of the oil droplets. Both ionic and non-ionic types of surface-active chemicals form low-viscosity O/W emulsions under downhole conditions. Non-ionics are preferred because of the following Characteristic4their emulsifying action is nor adversely affected by the salinity of the produced water.the emulsions formed generally have a low viscosity,the produced emulsions are easier to separate in conventional oil-water separators, andnon-ionics do not introduce an inorganic residue that will affect the crude oil during refining. Both reciprocating and progressive cavity pumps can be used in the field for the downhole emulsification process.

Performance of a spark-ignition engine fuelled with hydrogen using a high-pressure injector

Abstract The operation of a spark-ignition engine using high-pressure hydrogen injection represents an elegant solution to the problems of pre-ignition, back-firing and low volumetric efficiency often associated with hydrogen fuelling. Further challenges are to develop the high-pressure injection system to eliminate knocking combustion, minimize NOx formation and maximize thermal efficiency. This paper presents the results of testing a Ricardo E6 research engine on hydrogen employing a specially developed solenoid actuated injector. The injector design utilized an elastomeric seat to ensure that the injector did not leak when closed. The engine was operated over a range of compression ratios, engine speeds and mixture strengths. The effects of variation in injection timing were also investigated.

Air-Breathing Hypersonic Cruise: Prospects for Mach 4–7 Waverider Aircraft

There is currently a renewal of world-wide interest in hypersonic flight. Vehicle concepts being considered range from cruise missiles to SSTO and TSTO vehicles. The new characteristics of these vehicles are that they will be powered by air-breathing engines and have long residence times in the air-breathing corridor. In the Mach 4–7 regime, waverider aircraft are being considered as candidates for both long-range and short-range cruise missions, as hypersonic missiles, and as high-L/D highly maneuverable vehicles. This paper will discuss the potential for near-term and far-term application of air-breathing engines to the above-mentioned waverider vehicle concepts and missions. In particular, the cruise mission is discussed in detail and attempts are made to compare and contrast it with the accelerator mission. Past criticisms levied against waveriders alleging low volumetric efficiency, lack of engine/airframe integration studies, poor off-design performance, poor take-off and landing capability, have been shown by ongoing research to be unfounded. A discussion is presented of some of the technical challenges and ongoing research aimed at realizing such vehicles: from turboramjet and scramjet technology development, propulsion-airframe integration effects on vehicle performance, aeroservothermoelastic systems analysis, hypersonic stability and control with aeroservothermoelastic and propulsion effects, etc. A unique and very strong aspect of hypersonic vehicle design is the integration and interaction of the propulsion system, aerodynamics, aerodynamic heating, stability and control, and materials and structures. This first-order multidisciplinary situation demands the ability to integrate highly coupled and interacting elements in a fundamental and optimal fashion to achieve the desired performance. Some crucial technology needs are found in propulsion-airframe integration and its role in configuration definition, hypersonic boundary-layer transition and its impact on vehicle gross-weight and mission success, scramjet combustor mixing length and its impact on engine weight and, CFD (turbulence modeling, transition modeling, etc) as a principal tool for the design of hypersonic vehicles. Key technology implications in thermal management, structures, materials, and flight control systems will also be briefly discussed. It is concluded that most of the technology requirements in the Mach 4–7 regime are relatively conventional, making cited applications near-term, yet offering very significant advancements in aircraft technology.

Improved Sweep Efficiency By Selective Plugging of Highly Watered Out Zones By Alcohol Induced Precipitation

Abstract A new selective plugging process has been developed for improving volumetric sweep efficiency and thus, the enhancement of recovery from oil reservoirs. The new process is based on the theory of "salting out" in which a non-electrolyte is added to water to reduce the solubility of electrolytic substances. In this new process, following a concentrated brine preflush, one or more slugs of a water soluble alcohol (such as ethanol) are injected into a reservoir. The mixing of alcohol with brine will cause salt precipitation. Alcohol and concentrated brine prefer to flow through water flooded zones because of the high relative permeability to these fluids. The formation of solid precipitate can partially or completely block the high-permeability zones and divert subsequent fluid flow into lower permeability zones where oil saturations are greater. A larger volume of the reservoir is thus contacted by the injected fluid, improving the overall volumetric sweep efficiency and the oil recovery. In homogeneous sandpack flow tests, a permeability reduction of up to 70% is obtained. In heterogeneous sandpack flow tests, the permeability is reduced to 50% of original brine permeability. The experimental results show that the new selective plugging process can recover an additional 15% of original oil in place (OOIP). There are advantages to this new method over other selective permeability reduction techniques. The process can be applied to deep and shallow oil reservoirs. In addition, the plugging of more permeable zones is easy to remove by injecting brine with low salt concentration, if required. Introduction A large portion (as much as 65% average) of the original oil in place in oil reservoirs is not recoverable with conventional waterflooding technology(1). This low oil recovery is due to both low displacement efficiency and low volumetric sweep efficiency. The oil industry has been seeking enhanced oil recovery methods to improve displacement efficiency and volumetric sweep efficiency. In oil reservoirs, almost all formations are heterogeneous. Some regions have low permeability while others have high permeability. All injected fluids have the tendency to flow through the least resistant regions (having the highest permeability) bypassing the lower permeability zones. In a waterflooded reservoir, after a substantial amount of oil is recovered from high permeability areas, the recovery process may become uneconomical because the water-oil ratio is high. Therefore, if a selective permeability plugging method could be developed to block off highly water-invaded regions any subsequently injected fluids would have to pass through regions not previously invaded by water. As a result selective permeability plugging would improve volumetric sweep efficiency and increase ultimate oil recovery. Interest in plugging highly water-invaded zones in oil reservoirs for improved sweep efficiency, has increased over the past several decades. Numerous methods have been studied to plug highly water-invaded regions including foams, polymers, surfactants, and microbes(2–8). However, each of these methods has limited application because of some inherent problems. For example, polymers are degraded by shear forces as they are propagated through reservoir rock. In surfactant processes, adsorption of surfactants on minerals is a major cause of surfactant degradation and uneconomic performance.

Simulation of Thermal-Well Sucker-Rod Pumping

Summary A major problem experienced in pumping thermal wells is low volumetric efficiencies resulting from steam and noncondensable gas interference. This paper examines the results of physical simulations performed on a full-scale sucker-rod pump test facility and numerical simulations that used an equation of state (EOS) to predict theoretical volumetric pump efficiencies.

Waterflood Surveillance in the Kuparuk River Unit With Computerized Pattern Analysis

This paper describes the computer-aided waterflood surveillance method used in the Kuparuk River field. The flood is monitored pattern by pattern, with production and injection allocations verified by comparison of measured field pressures with pressures calculated by material balance. The resulting detailed knowledge about waterflood progress has led to operational changes and workovers to optimize waterflood performance.

Down-Hole Emulsification for Improving Viscous Crude Production

Abstract The down-hole emulsification process has been developed to improve productivity and operating efficiency of oil wells that produce viscous crudes. The process involves using surface active chemicals in the wellbore to convert high viscosity oil or water-in-oil (W/O) emulsions to low viscosity oil-in-water (O/W) emulsions. Improved pump efficiency, faster rod drop rate, and lower flow-line pressure-drop result. pressure-drop result. Benefits obtainable from down-hole emulsification have been demonstrated in a series of field tests. The principal test, of 6 months duration, involved three wells, and showed that surfactant injection increased oil production 34 percent for a surfactant cost of $0.08/bbl of incremental oil produced. Introduction The economics of producing viscous crudes from pumped wells are affected by pumping unit limitations. pumped wells are affected by pumping unit limitations. The high viscosity of the crudes or the water-in-oil (W/O; water droplets surrounded by oil as the continuous phase) emulsions produced with the crudes causes low pump volumetric efficiency, slow rod drop rate, and high flowline pressure drop. Various methods, such as the use of bottom-hole heaters and light oil diluents, and water injection, have been used in the past to overcome these limitations. The purpose of this paper is to describe a new and improved method the down-hole emulsification processfor improving the economics of viscous crude production. Down-hole emulsification involves the use of surface active chemicals to convert high viscosity fluids in a wellbore into low viscosity oil-in-water (O/W; oil droplets surrounded by water as the continuous phase) emulsions. These emulsions result in improved pump performance and economical increases in productivity and operating efficiency. Process Description Process DescriptionThe down-hole emulsification process, illustrated in Fig. 1, consists of three primary steps: preparation, production and separation. Preparation of low viscosity O/W emulsions from viscous crude oils and the W/O emulsions produced with the oils is accomplished simply by mixing these fluids with the proper surfactants. The surfactants can be dissolved in water and injected, either continuously or in batches, into the tubing-casing annulus. The O/W emulsion is formed by the mixing action that occurs as the surfactant falls through the oil and water. This mixing may be aided by turbulence caused by gas liberation or the intermingling of the fluids entering the pump and flowing up the tubing. The oil is broken into droplets and the water forms a continuous phase surrounding the droplets. It is the continuous water phase that imparts low viscosity to the O/W emulsions. The surfactants concentrate at the oil-water interface, retarding oil droplet coalescence. At least 10 percent water cut is needed in the wellbore to make the surfactant effective. Details of emulsion preparation and viscosity data are in the Appendix. Production of the O/W emulsions formed in the wellbore is accomplished in the usual manner by pumping up the tubing and through the surface gathering lines. Because the emulsion has a lower viscosity than the crude oil, it is possible to obtain increased pump efficiency and rod drop possible to obtain increased pump efficiency and rod drop rate, and decreased rod loading and gathering-line pressure drop. pressure drop. Successful application of down-hole emulsification requires preparation of O/W emulsions that are stable when flowing; this avoids premature separation or inversion to a high viscosity W/O emulsion. (Conditions required to maintain stability are discussed in the Appendix.) Conversely, in surface equipment, O/W emulsions must separate readily into dry oil and disposable water. Emulsions prepared with nonionic surfactants meet these requirements prepared with nonionic surfactants meet these requirements more easily than those prepared with anionic surfactants. Separation of a variety of crude-oil-in-water emulsions has been accomplished by processing them in conventional horizontal separators (having hold-up times ranging from 1 to 4 hours) at elevated temperatures. Increasing temperature reduces solubility of nonionic surfactants in water, but increases their solubility in oil, thus reducing the coalescence barrier at the oil-water interface. pH control may be desirable in some applications. Data on O/W emulsion separation are in Fig. 6. Field Applications Down-hole emulsification has been successfully field tested in eight oil fields. The results of two tests are reported here. JPT P. 1349

Settling of Activated Sludge in Horizontal Tanks

The settling properties of activated sludge in the aerator effluent from 20 activated-sludge plants were examined in settling tubes. A study of flow conditions and efficiencies of the secondary sedimentation tanks at the plants, all of the horizontal type, was conducted. It was found that density currents caused low volumetric efficiency, but at actual loading conditions all settleable material was removed. The apparent depth of the bottom density current was found in all cases to be about 2 ft. Unsettleable floc in the settled water occurred noticeably when the concentration of sludge in the aeration tanks was low. The investigations indicate that considerable improvements in the design of secondary settling tanks are possible. The design must be made with respect to the highest concentration of activated sludge liquor that will be used in the process.

Late Developments in the Seeligson Zone 20B-07 Enriched - Gas - Drive Project

Abstract An enriched-gas-drive project has been in progress in the Seeligson Zone 20B–07 field over four years. It has been established that recovery approaches 100 per cent in portions of the reservoir actually swept by enriched gas. On the other hand, breakthrough volumetric sweep efficiency is low, on the order of 23 per cent, with the result that recovery at breakthrough is less than expected. Low volumetric sweep efficiency appears to be the result of a combination of causes, including adverse mobility ratio and sand heterogeneity. It is too early in the life of the project to present a final evaluation of the recovery potential of the enriched-gas process. For this reason operations will be continued with no major changes until definite conclusions concerning ultimate performance can be made. It is anticipated that at sometime prior to blowdown the project will be modified in an effort to increase ultimate recovery by improving sweep efficiency. Introduction The relatively new concept of miscible displacement has offered the petroleum industry a method of appreciably increasing its reserve of recoverable oil. As is frequently the case with new techniques or processes, the basic principle is apparently sound; however, the most effective method of application has not yet been demonstrated in actual field operations. Experimental work in the laboratory, under simulated reservoir conditions, has indicated that essentially 100 percent recovery can be achieved from that portion of an oil sand swept by a miscible fluid. In recent years, there has been a concerted effort within the industry to develop an effective method of utilizing the basic concept. Several variations of the process have been proposed. These include:high-pressure gas injection,LPG-slug injection,simultaneous injection of water and enriched gas, andenriched-gas injection. Although all these techniques differ in application, they share the same goal-to significantly increase ultimate oil recovery through miscible displacement. Enriched-gas drive involves the injection of gas enriched at the surface with intermediate-molecular-weight components such as propane. On contact, these intermediates condense into the reservoir oil. The oil swells, its viscosity is lowered and phase boundaries disappear to be replaced by a transition zone in which fluid properties grade from those of the native oil to those of the injected gas. In the region where miscibility is achieved, capillary and interfacial tension forces are not believed to be present. In their absence there is no tendency for oil to remain as residual saturation, and 100 per cent recovery from connected pores is possible. The enriched-gas process is applicable to a wide range of crude oils and to reservoirs in which the operating pressure ranges from about 1,500 to 3,000 psi. Although the results of early laboratory testing of the enriched-gas- drive process were encouraging, it was recognized that selected field tests to substantiate these results would be required. In addition, field tests were required to investigate the effects of various other conditions, the aggregate of which could not be adequately simulated in the laboratory. Among these conditions are the following:VISCOUS FINGERING--Viscous fingering of enriched gas through the reservoir oil is a result of the adverse mobility ratio between the displaced and displacing fluid. In the absence of capillary forces, such intrusions by the displacing fluid are quite unstable and can be expected to grow rapidly.SAND HETEROGENEITY--This condition could lead both to channeling through various sand members and to the formation of viscous fingers.STRUCTURAL DIP--In low-dip reservoirs producing at practical rates, gravity forces are expected to be ineffective in mitigating the growth of viscous fingers.RESERVOIR GEOMETRY AND WELL CONFIGURATION--It is desirable to determine to what extent these two factors can be utilized to offset the inherent restrictions imposed by the other conditions. JPT P. 261^