Oil Recovery Experiments Research Articles

Surfactant oil recovery in fractured carbonates: Experiments and modeling of different matrix dimensions

Abstract Oil recovery from fractured carbonate reservoirs by water flooding is often inefficient due to the commonly oil-wet nature of these rocks and the lack of sufficient spontaneous capillary imbibition driving force to push oil out from the matrix to the fracture network. Chemical processes such as surfactant/alkali-induced wettability alteration and interfacial tension (IFT) reduction have shown great potential to reduce the residual oil saturation in matrix blocks, leading to significant incremental oil recovery (IOR). However, the time required to achieve a significant amount of oil recovery is the most crucial deciding factor in field projects. The magnitude of recovery and response time of any chemical process depends on the degree of wettability alteration and IFT reduction, the nature and density of fracture network, and the matrix block size. Oil recovery experiments were performed for the same matrix rock and chemical formulation, but for different sized cores to gain a better understanding of the time dependence of the recovery process. The measured oil recoveries were history-matched. The simulation models were then used to predict the recovery response times for larger cores. The controlled and systematic laboratory measurements for several core sizes helped in developing dimensionless scaling groups to aid in understanding the time dependence and the upscaling of laboratory results to field-scale applications. This finding is significant as it illustrates the extent of wettability alteration and IFT reduction needed in fractured reservoirs. Laboratory measurements and simulation work substantiate the validity and the range of applicability of upscaled procedures and indicate the importance of viscous and buoyancy forces in larger field cases. The results of this work will be useful for the design of future field projects.

Effect of PEO-PPO-ph-PPO-PEO and PPO-PEO-ph-PEO-PPO on the Rheological and EOR Properties of Polymer Solutions

The rheological properties of partially hydrolyzed polyacrylamide (HPAM) and PEO-PPO-ph-PPO-PEO (BPE) or PPO-PEO-ph-PEO-PPO (BEP) block polyether solutions are investigated here. Another hydrophobically associating polymer (HMPAM) is chosen as a contrast. The rheological results show that the elastic modulus (G′) and viscous modulus (G″) of HPAM/BPE and HPAM/BEP solutions first increase then decrease, while the viscosities of HMPAM/BPE and HMPAM/BEP solutions decrease with the increase of block polyether concentration. The HPAM/BPE solution has a larger viscosity than HPAM/BEP, while the HMPAM/BPE solution has a lower viscosity than HMPAM/BEP. The polymer solutions containing BEP have larger G′ and G″ values than the solutions with BPE. Furthermore, the block polyethers reduce the sensitivity of viscosity to temperature. BEP is more effective to stabilize the viscoelastic property and improve the temperature resistance than BPE in HMPAM system. BEP has a better property to enhance the salt tolerance of the polymer solution than BPE. Moreover, the enhanced oil recovery (EOR) experiments show that HPAM/block polyether mixed solution has a larger oil recovery than HPAM, and HPAM/BEP system has a larger enhanced effect than HPAM/BPE solution.

Mapping oil saturation distribution in a limestone plug with low-field magnetic resonance

Abstract Magnetic resonance imaging (MRI) is used to quantify in situ the recovery of crude oil from a strongly oil-wet microporous limestone core-plug. We demonstrate the capability of low-field MRI to continuously monitor oil saturation distribution by obtaining a series of spatially resolved transverse relaxation time ( T 2 ) distributions using the robust spin echo single point image (SESPI) profiling method to obtain T2 maps with a temporal resolution of 45 min. These T2 maps are shown to provide comparable data to nuclear magnetic resonance (NMR) well-logs. The low injection rate of 1.4 × 10 − 3 cm 3 s − 1 (equivalent to an interstitial velocity of 1 ft day−1 in the formation) allowed a large number of T2 maps to be acquired during the flood. Fluid-phase discrimination is achieved here in the T2 dimension; the brine relaxation time is reduced by addition of paramagnetic manganese. Some manganese is lost through adsorption on the limestone surface, but sufficient relaxation contrast is obtained to position an unambiguous oil/brine T2 cut-off. The spatial distributions of both the brine and oil are therefore determined simultaneously and independently. Capillary end effects are observed in the short core-plug due to the difference in wettability and permeability between the plug faces and the core-holder end-caps. The inclusion of the spatial dimension in the experiment allows a region of the plug, unaffected by end effects, to be considered representative of behavior in the reservoir. Overall, we highlight the importance of spatial resolution in laboratory-scale core analysis and demonstrate the capability of low-field MRI spectrometers to continuously monitor oil recovery experiments.

Enterobacter cloacae as biosurfactant producing bacterium: Differentiating its effects on interfacial tension and wettability alteration Mechanisms for oil recovery during MEOR process

Microbial enhanced oil recovery (MEOR) process utilizes microorganisms or their metabolites to mobilize the trapped oil in the oil formation after primary and secondary oil recovery stages. MEOR technique is considered as more environmentally friendly and low cost process. There are several identified mechanisms for more oil recovery using MEOR processes however; wettability alteration and interfacial tension (IFT) reduction are the important ones. Enterobacter Cloacae, a facultative bio-surfactant producer bacterium, was selected as a bacterial formulation due to its known performance on IFT reduction and wettability alteration. To quantify the effects of these two mechanisms, different tests including oil spreading, in situ and ex situ core flooding, wettability measurement (Amott), IFT, viscosity and pH measurements were performed. The obtained results revealed that the experimental procedure used in this study was able to quantitatively identify the individual effects of both mechanisms on the ultimate microbial oil recovery. The results demonstrated considerable effects of both mechanisms on the tertiary oil recovery; however after a proper shut in time period, more tertiary oil was recovered because of wettability alteration mechanism. Finally, SEM images taken from the treated cores showed biofilm formation on the rock pore surfaces, which is responsible for rock surface wettability alteration.

Comparative study of biosurfactant produced by microorganisms isolated from formation water of petroleum reservoir

Biosurfactant produced by Pseudomonas aeruginosa, Bacillus subtilis and Rhodococcus erythropolis that isolated from the formation water of Chinese petroleum reservoir has been compared in surface abilities and oil recovery. Maximum biosurfactant production reached to about 2.66 g/l and the surface tension of liquid decreased from 71.2 to 22.56 mN/m using P. aeruginosa. Three strains exhibited a good ability to emulsify the crude oil, and biosurfactant of P. aeruginosa attained an emulsion index of 80% for crude oil which was greater than other strains. Stability studies were carried out under the extreme environmental conditions, such as high temperature, pH, salinity and metal ions. Results showed an excellent resistance of all biosurfactants to retain their surface-active properties at extreme conditions. It was found that the biosurfactants from three isolated bacteria showed a good stability above pH of 5, but at lower pH (from 1 to 5) they will harmfully be affected. They were able to support the condition up to 20 g/l salinity. P. aeruginosa biosurfactant was even stable at the higher salinity. Regarding temperature, all produced biosurfactants demonstrated a good stability in the temperature up to 120 °C. But stability of three biosurfactants was affected by monovalent and trivalent ions. Oil recovery experiments in physical simulation showed 7.2–14.3% recovery of residual oil after water flooding when the biosurfactant of three strains was added. These results suggest that biosurfactants of these indigenous isolated strains are appropriate candidates for enhanced oil recovery with a preference to biosurfactant of P. aeruginosa.

Alkyl Polyglycoside/1-Naphthol Formulations: A Case Study of Surfactant Enhanced Oil Recovery

Abstract We present a case study of surfactant enhanced oil recovery using Alkyl polyglucoside/1-naphthol formulations. Alkyl polyglucosides are a green, non-toxic and renewable surfactant class synthesized out of agricultural raw materials. We measured interfacial tensions versus n-octane and viscosities of these formulations and conducted one coreflood enhanced oil recovery (EOR) experiment where we recovered 82.6 % of initial oil in place demonstrating that these formulations are efficient EOR agents.

Investigation by ICP-MS of trace element levels in vegetable edible oils produced in Spain

The content of trace elements (Ag, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Ti, Tl and V) in edible oils (virgin olive, olive, pomace-olive, sunflower, soybean and corn) from Spain was determined, using inductively-coupled plasma-mass spectrometry (ICP-MS) after microwave digestion, employing only nitric acid in this step. The method has been validated by using both an oil reference material and recovery experiments over different oil samples, obtaining satisfactory results in all cases. Inter-day repeatabilities lower than 10% were observed for all of the analysed elements in the different kinds of oil samples. Studying the content of trace elements, in order to detect tendencies in the samples of the same type of oil, principal components analysis was used. Promising groupings were observed using a model with two principal components and retaining 75.3% of the variance.

Using the value of the crosscorrelation coefficient to locate microseismic events

A procedure to locate seismic events uses the value of the crosscorrelation coefficient between waveforms of different events. First, an empirical relation between spatial event separation and maximum crosscorrelation coefficient is established for a subset of a priori located reference events. Then this relation is used to determine the hypocenters of an increasing number of events by a grid-search strategy. Measured arrival-time differences between S- and P-waves also constrain the location. Although the reference events are located by a standard method using the arrival-time measurements at three or more receivers, the correlation-based location requires only one receiver. The method has been applied to microseismic data recorded at a single borehole sensor during the 2004/05 injection experiment at the Continental Deep Drilling Site (KTB) in Germany. With the approach, significantly more weak seismic events were located, compared to the number of events recorded by a near-surface receiver array and by inversion of arrival times. The proposed location method is particularly well suited to locate small-magnitude earthquakes within dense event clouds when too few arrival-time observations for part of the events are available and standard location methods fail. These conditions are frequently met in the case of microseismic monitoring of geothermal or enhanced oil recovery experiments.

Fluorosurfactants in Enhanced Oil Recovery

Fluorosurfactants are effective in a variety of Enhanced Oil Recovery (EOR) techniques including (i) improv- ing subterranean wetting, (ii) increasing foam stability, and (iii) modifying the surface properties of the reservoir forma- tion. While fluorosurfactants have been used in gas and oil exploration for four decades, the increased demand for petro- leum and the greater understanding of the benefits of fluorosurfactants have led to growing acceptance for fluorosurfac- tants throughout the petroleum industry. This mini-review summarizes the published research for fluorosurfactants in EOR from 1977 to 2007. The references in this mini-review are mostly patents (vs peer reviewed articles) and laboratory models of the benefits of fluorosurfactants in EOR (vs actual oil and gas recovery experiments). This summary of the pub- lished reports on fluorosurfactants in EOR provides petroleum scientists and engineers an overview of this emerging tech- nology.

D305 ヘリコプター搭載型蛍光イメージングライダーによる流出油のリモートセンシング

A tanker accident is a potential crisis leading to severe ocean pollution. The operation for recovering oil spill needs precise information of position, scale and type of oil. A new oil spill monitoring system is required in full-time and all-weather wide area coverage. National, Maritime Research Institute (NMRI) developed a new helicopter-based fluorescence imaging lidar (laser radar) system for remote sensing of oil spill. It consists of a 355nm UV pulsed laser, four-wavelength optical systems, and a gated ICCD imaging camera. Since this system discriminates the oil from seawater by the presence of laser induced fluorescence light, it is possible to visualize the oil spill in all weather, day or night. Not only diesel, fuel or crude oil, but also some petroleum chemicals on the ocean, normally hard to identify with the naked eye, can be targeted.The first oil spill observation was conducted on May 2004 on the French coast in collaboration with DEPOL04, the international oil spill observation and recovery experiment. We succeeded in observing the 2-D images of the fluorescent light from artificially-spilled oil, and the water Raman scattering light from sea water. The discrimination of oil and water was examined by the signal ratio of the three wavelength signals to the 405nm signal, which is water Raman dominant.

The potential of Bacillus licheniformis strains for in situ enhanced oil recovery

The ability of microorganisms isolated from oil reservoirs to increase oil recovery by in situ growth and metabolism following the injection of laboratory grown microbial cells and nutrients were studied. Four strains isolated from Northern German oil reservoirs at depths of 866 to 1520 m, and identified as Bacillus licheniformis, were characterized taxonomically and physiologically. All strains grew on a variety of substrates at temperatures of up to 55°C and at salinities of up to 12% NaCl. Extracellular polymer production occurred both aerobically and anaerobically over a wide range of temperatures, pressures and salinities, though it was optimal at temperatures around 50°C and at salinities between 5 and 10% NaCl. Strain BNP29 was able to produce significant amounts of biomass, polymer, fermentation alcohols and acids in batch culture experiments under simulated reservoir conditions. Oil recovery (core flooding) experiments with strain BNP29 and a sucrose-based nutrient were performed with lime-free and lime-containing, oil-bearing sandstone cores. Oil recovery efficiencies varied from 9.3 to 22.1% of the water flood residual oil saturation. Biogenic acid production that accompanied oil production, along with selective plugging, are important mechanisms leading to increased oil recovery, presumably through resulting changes in rock porosity and alteration of wettability. These data show that strain BNP29 exhibits potential for the development of enhanced oil recovery processes.

A New Variation of Chemical EOR and its Economic Potential: The ASP Process

Abstract Current world oil prices have forced a revaluation of many enhanced oil recovery processes. One very promising approach is the use of low-cost alkaline chemicals combined with surfactants and polymers. It has been determined from the testing of hundreds of oils that acid number and API gravity are simplistic screening criteria and are of very little value in many cases. Oil recovery experiments in the laboratory have resulted in residual oil saturations as low as with the micellar-polymer technology for as little as 10% of the chemical costs. At this time, field applications are still in their early stages, but indications are that this technology has the potential for producing incremental oil for less than $3 per barrel.

Flow of emulsions in porous media, and potential for enhanced oil recovery

Oil-in-water and water-in-oil emulsions offer considerable promise as oil recovery agents. They can provide mobility control in certain situations, and may even serve as blocking agents. This paper examines selected aspects of emulsion characteristics, and flow in porous media, in the context of laboratory experiments. Oil-in-water and water-in-oil emulsions were prepared using surfactants, acid, an basic solutions. The emulsions were characterized by rheology, quality, and drop size distributions. These properties were measured before and after passage through a porous medium of known pore size distribution. The results show that the drop size retained - hence mobility control - is rate-dependent and related to pore size distribution. A number of emulsions were used in oil recovery experiments, and the results were compared with similar floods using caustic solutions. It is concluded that emulsions can be effective oil recovery agents.

Mobilization of Residual Oil Under Equilibrium and Nonequilibrium Conditions

AbstractA microvisual study of residual oil mobilization that uses a relatively simple chemical system consisting of water, n-propanol, and cyclohexane is presented. Two different classes of experiments were performed to determine the sensitivity of the capillary number required to displace a particular residual oil globule from chemical equilibrium. It was found that under certain circumstances the capillary number required to mobilize the oil drop could be reduced greatly if the displacing phase contained more alcohol than it would in equilibrium with the trapped phase.Experiments clearly demonstrated that spontaneous emulsification by a diffusion and stranding mechanism could not account for the differences between equilibrium and nonequilibrium capillary numbers. Experimental observations did correlate well with the development of interfacial turbulence (Marangoni effect). Variations that, according to theory, tended to enhance the level of interfacial turbulence between the equilibrium and nonequilibrium capillary numbers were observed. The importance of the Marangoni effect relative to laboratory oil recovery experiments is discussed.A second class of experiments consisted of observing the displacement of residual oil globules that had been increased in volume (swollen) by mass transfer from a continuous phase flowing too slowly to displace the drop. Once the residual oil globule attained equilibrium with the continuous phase, the flooding velocity was increased until the swollen globule was displaced. Surprisingly, slightly swollen globules required a larger capillary number for mobilization than the original drop. Thus, the capillary number for swollen residual oil globules goes through a maximum as a function of the degree of volume increase. The precise position of the maximum varies for each globule since mobilization is a complex function of geometry.

Firefood Microseismic Monitoring: Results And Potential For Process Control

Abstract A pilot fireflood in a 750m deep high permeability unconsolidated channel sand in eastern Alberta was instrumented for microseismic emission to evaluate the technique for in-situ process monitoring. The pilot consists of a central air injection well, eight surrounding production wells on artificial lift, and two internally placed observation wells. Three surface geophones and a downhole 12-hydrophone string in a single well were deployed. Data were collected for 22 hours. Event detectors and cassette recorders were used for data collection. The recorders are triggered by a preset signal-to-noise ratio, allow pre- and post-event buffer recording, and can record 200 samples per second. The devices are self-triggering so that one large signal automatically causes recording on other channels. Monitoring during twelve hours of steady air injection at 625m3/s yielded a clear event frequency of about 50 events/h. The events are mostly clear compressional wave arrivals, each consisting of 1 to 2 cycles with a repeat signal, in-phase with the first, occurring shortly afterwards (0.2–0.3 sec later). Stopping air injection caused a gradual drop in event frequency, and the rate was re-established when air injection was continued. The surface geophone yielded no useful data associated with in-situ processes. Spectral frequency analysis and knowledge of material properties indicated that the events are shears of a stick-slip nature associated with the strain weakening behavior of the over-compacted reservoir sands. The recording accuracy implies a capability to locate events to within 10m in space, and signal analysis indicates that some discrimination between events as a function of processes may be achieved. The system is therefore directly applicable to mapping of firefloods and can thus be used as an aid to process control. Other in-situ recovery technologies may also produce useful signals for process control. In particular, steam flooding, hydraulic fracturing, and high-pressure injection operations likely generate mappable microseismic events which can be applied directly to production/injection strategy. Introduction As part of an ongoing program of studies relating to the process of fireflood recovery of heavy oil. Noreen Energy Resources Ltd. and the University of Alberta have monitored a fireflood with a vertical string of Mark Products T27 hydrophones in an observation well very close to the burn zone. An enhanced oil recovery experiment is being carried out in the Bodo pool at a depth of 750m in east-central Alberta. A fireflood scheme is active using a central air injection well and eight peripheral wells in a square pattern on pump. The air injection rate is 625m3 /h and the pattern contains two observation wells monitored for temperature changes. The project (Fig. 1) was monitored for microseismic activity for a 22-hour period in the spring of 1981 using a string of hydrophones in one observation well and a set of three surface geophones. The purpose of the microseismic experiment was to find out if seismic energy was being emitted as the result of the process, and to assess whether this energy could be used to clarify in-situ processes and ultimately be applied to aid process control by delineating fire flood fronts and velocities.

Geologic Controls of In-Situ Processing of Tar Sands, N.W. Asphalt Ridge, Utah: ABSTRACT

End_Page 630------------------------------The Laramie Energy Technology Center completed three in-situ oil-recovery experiments from tar sands at N.W. Asphalt Ridge, Utah. The 10-acre (4 ha.) tract is part of the Sohio Shale Oil Co. D tract located west of Vernal, in Uintah County. Asphalt Ridge, lying on the northern boundary of the Uinta basin, is a northwest-southeast-trending ridge. The area on the northwest is structurally a monocline dipping southwest. The 3.28 to 14.75 m thick experimental tar-sand zones are in the Rim Rock Sandstone Member of the Mesaverde Formation of Cretaceous age. The beds dip 28°SW, and overburden thicknesses range from 89 to 164 m. Two known faults, with throws up to 66 m, bound the tract. Three experiments were performed at the tract on varying partial acreages from 1975 to 1980. Two combustion tests using reverse combustion and a combination reverse and forward combustion were completed in a tar-sand bed 3.28 to 3.93 m thick. Recovered oil and water for the experiments ranged from 65 to 580 bbl and 167 to 600 bbl, respectively. The third test used steam injection on a 14.75 m thick bed. Production was 1,150 bbl of oil and 6,250 bbl of water. Tar-sand analyses yielded the following range of data for the three tests: extracted porosity, 26.1 to 31.1%; absolute air permeability, 651 to 2,175 md; oil saturation, 62 to 75% pore volume; water saturation, 2.4 to 7.9% pore volume. Various geologic controls can determine the effectiveness of the extraction process. These inclu e the dip of the beds, reservoir thickness, water and oil saturation, porosity, permeability, vertical and horizontal continuity of section, confinement of zone, and potential fractures and faulting in area. End_of_Article - Last_Page 631------------

A Porous, Permeable Carbonate for Use in Oil Recovery Experiments

Introduction Previous research in the use of surfactants and polymers Previous researchin the use of surfactants and polymers in tertiary oil recovery concentrated onsandstone reservoirs, with most laboratory work for the design using Bereasandstone and with a final check on the system being made in reservoir corematerial. With increased understanding of how surfactants act to recover oilcarbonate reservoirs are being considered for surfactant flooding. However, aporous permeable, carbonate mineral is needed to permit numerous tests ofvarious compositions in carbonate rock during the design of an oil recoverysystem for carbonate reservoirs. An appropriate core material was found aftersearching for quarried, consolidated, fine-grained, carbonate minerals with 20%or more porosity and 100 md or more intergranular permeability. Only a rockmeeting these criteria will permit reproducible laboratory tests to beconducted under representative field conditions - a frontal advance rate of upto 0.6 ft/D and a pressure gradient of less than 1 psig/ft. A rock meetingthese criteria is described here. Porous Permeable Carbonate Porous Permeable Carbonate The most appropriatecombination of rock properties for core tests was found in a dolomite quarriedby J. E. Baker Co.* Baker dolomite quarried in Millersville, Sandusky County, OH, is a primary, sedimentary dolomite formed in a warm. shallow marineenvironment. This rock is from the Niagara group, Guelph formation, UpperSilurian epoch, Paleozic era and is considered 400 to 425 million years old.The dolomite is highly crystalline, generally massive and varies from nearlywhite to light TABLE 1-DATA FOR BAKER DOLOMITE Porosity, Permeability, and Grain Density Porosity, Permeability, and GrainDensity Porosity Permeability Grain Density Plug (vol%) (md) (g/cm3) Plug(vol%) (md) (g/cm3) 1 22.5 65.7 2.86 2 26.8 126.0 2.86 3 28.2 187.2 2.86 4 23.376.2 2.86 Chemical Composition Weight Percent Element Composition Ca* Mg** Fe Mn Si Cr Upper limit 0.1 0.030.01 0.01 22.6 12.7 Lower limit 0.01 0.003 0.001 0.001 Relative Displacement Index Relative Plug Displacement Index 1 +0.414 2+0.689 JPT P. 1632

Cosurfactants in Micellar Systems Used for Tertiary Oil Recovery

Abstract The influence of alcohols used as cosurfactants on several micellar systems was investigated. These alcohols modify phase behavior and control the amount of brine or hydrocarbon that a microemulsion can "solubilize." Also, viscosity can be adjusted using the right cosurfactant for mobility control. Relationships between cosurfactant concentration and electrolyte concentration, hydrocarbon type, or temperature are presented. Introduction Micellar slugs used as oil-displacing agents in extra-oil recovery projects are usually composed of surfactant(s), hydrocarbon, water, electrolyte, and one or more alcohols that serve as cosurfactants. Physicochemical properties of these systems have Physicochemical properties of these systems have been presented by several authors; phase behavior has received special attention. Such emphasis is justified because of displacement-mechanism considerations and micellar-slug deterioration by reservoir rock and fluids. Other work has been concerned with defining the role of particular sulfonates in oil displacement and loss of surfactant to reservoir rock. Healy et al. presented detailed analyses of a single surfactant/cosurfactant combination in micellar systems and laboratory oil recovery experiments. Papers have presented qualitative information on the role of cosurfactants. Gogarty and Tosch found that the amount of 2-propanol (IPA) required to produce phase-stable systems depended on produce phase-stable systems depended on hydrocarbon type. They and others reported that IPA makes a micellar slug more compatible with reservoir brines, whereas oil-soluble alcohols enhance compatibility with crude oils. Cosurfactants have various effects on viscosity; IPA usually causes a reduction. Healy and Reed noted a decrease in viscosity upon addition of tertiary amyl alcohol (TAA). For the system examined, TAA increases the size of the water-external region in the ternary phase diagram. Others have reported that cosurfactants increase water solubility of sulfonates and reduce adsorption on reservoir rock. Although cosurfactants have been shown to perform a variety of functions, no systematic quantitative study of their effect on physicochemical properties of micellar systems has appeared in the petroleum literature. This paper will show how cosurfactants affect phase behavior, control hydrocarbon and brine solubility, interact with electrolyte concentration, and change viscosity and electrical conductivity. Systems examined include a low-water-concentration, oil-external microemulsion; a water-external microemulsion; and "intermediate" systems for which the continuous phase is not clearly defined. Each type of micellar system has been tested in field applications of the Maraflood oil recovery process. process. MATERIALS AND METHODS Compositions of the six micellar systems studied are shown in Table 1, which also indicates the source and equivalent weight of the petroleum sulfonate surfactants used. Table 2 lists information about the alcohols used as cosurfactants. Viscosities were measured at 72 deg. F and at 3 or 6 rpm with a Brookfield Model LVT viscometer equipped with a UL adaptor. Shear rates at this speed are about 5 to 10 sec-1. All phase-behavior experiments were performed at 72 deg. F, with the exception of the relationships shown in Fig. 11. Systems were observed for a minimum of 24 hours. PHASE BEHAVIOR WITH ALCOHOL PHASE BEHAVIOR WITH ALCOHOL Alcohols as cosurfactants modify the phase behavior of a brine-hydrocarbon-surfactant micellar system. For example, Composition A in Table 1, composed of an oleophilic surfactant (470-equivalent-weight petroleum sulfonate), 28-weight-percent water, petroleum sulfonate), 28-weight-percent water, and hydrocarbon (light, straight run gasoline), separates into an aqueous phase in equilibrium with a microemulsion phase. SPEJ P. 161

Shale Oil Recovery by In-Situ Retorting-A Pilot Study

Results of this in-situ combustion experiment, conducted by the U. S. Bureau of Mines near Rock Springs, Wyoming, to produce shale oil from oil shale, indicate that a combustion zone can be established in a fractured oil shale body by using air injection and a propane burner. During the six-week period that combustion was maintained, 8,000 gallons of oil was produced. produced. Introduction This paper describes an in-situ combustion experiment conducted by the U. S. Bureau of Mines in the Green River oil shale formation near Rock Springs, Wyo. The experiment was designed to study the engineering problems associated with the establishment, maintenance, and control of a self-sustaining combustion zone in the oil shale and the use of this process to produce shale oil. A 20-ft-thick section of the oil shale located from 68 to 88 ft below the surface of the ground was ignited by use of a propane burner in the central well of an expanded five-spot development pattern. A combustion zone was established in the formation and maintained with little difficulty for a 6-week period, at the end of which time air injection and the combustion phase of the project weld terminated. Several thousand phase of the project weld terminated. Several thousand gallons of shale oil were recovered and stored for analysis. Permeability loss at the injection well and high viscosity of shale oil were problems experienced by other investigators during oil shale retorting, but were not encountered during this test. Geology The combustion experiment was performed in the Tipton member of the Green River oil shale formation near Rock Springs, Wyo. The Tipton member in the area of the test-site has a 2-percent dip to the west and a general geologic strike to the north, Green River oil shale is a dolomitic marlstone with a finely laminated structure consisting of an intimate mixture of organic and inorganic materials. The mineral portion ranges from 92 weight percent of shales having an oil yield (as determined by Fischer assay) of 10 gal/ton to 60 weight percent of those having a yield of 75 gal/ton. It consists largely of dolomite, calcite, feldspars, quartz, and illite clay. In the leaner shales cementation is primarily inorganic; however in rich strata it appears that the organic material is the principal cementing agent principal cementing agent Both the porosity and the permeability of oil shale are extremely low because the solid, essentially insoluble organic material serving as a cementing agent blocks the major portion of any pores that might be present. present. Site Preparation Since the success of any in-situ combustion oil recovery experiment in oil shale depends directly on the ability of air, combustion gases, and produced oil to move through the shale formation, produced oil to move through the shale formation, the first part of the site preparation consisted of an intensive fracturing program. Fracturing techniques that were investigated included electrolinking, hydraulic fracturing, and explosive fracturing. P. 1520

The Oil Industry of Germany

Abstract The German oil industry began shortly after oil was discovered in the United States, but the development of oil production was at a much slower rate because the early wells produced in small quantity. During World War II the existing fields were produced to their maximum capacity, but it was not until after the Federal Republic of Germany was formed, when the oil industry received the benefits of substantial protective tariffs, that extensive exploration for new fields was commenced. This work resulted in the discovery of new reserves of substantial size, and at the present time Germany has the largest domestic production of oil in Free Europe. Under the terms of the European Economic Community Treaty, the system of protective tariffs on imported crude oil, under which the German oil industry has flourished, were to be discontinued gradually and were to be eliminated by 1970. As it was faced with this prospect, the German oil industry appealed to its government form assistance, which was granted by a recent act of Parliament which provides for the payment of subsidies on domestic oil production in decreasing amount for six years. Also, low interest loans are to be made to German companies to enable them to prospect for oil in foreign lands. Introduction The recent discovery of large gas reserves in The Netherlands and the commencement of the application of the European Economic Community Treaty relating to oil on Jan. 1, 1964, have had a profound effect on the oil industry of Germany. Germany is the most important oil country in Free Europe, so, because of the significance of these events, it is believed that a discussion of the petroleum geology of Germany, a description of the way that oil fields have been found, developed and produced, and a consideration of the impending changes in the fuel economy of the nation should be of interest to the United States engineers. History The German oil industry had its beginning at approximately the same time as in the United States, but development was at a much slower rate than in this country because the early wells produced oil in small quantity. Drilling was undertaken, just as was the case in northwestern Pennsylvania, because of surface seeps in the County of Celle, particularly in the vicinity of the Village of Wietze. Starting in 1876 in this area. heavy oil was produced from numerous shallow wells. Subsurface mining operations were commenced in the shallow Wietze field in 1920. In the beginning of this mining operation, oil was produced by seepage from the reservoir rock into the tunnels which had been excavated away from the central shaft. Subsequently the oil sand was excavated and brought to the surface where i was washed and the oil extracted by this process. A great mound of washed sand near the mine shaft indicates the magnitude of these underground operations. It is estimated that recovery was increased from about 15 per cent of oil in place by the production obtained from wells to about 38 per cent by the mining operation. In recent years expansion of the Wietze mine was discontinued largely for economic reasons, but it has been used for several interesting oil recovery experiments. It was concluded as a result of these experiments that as much oil could be produced by various recovery processes using wells drilled into the oil reservoirs from the surface, so the mining operation was shut down in the summer of 1963. This operation was notable in that it provided the unique opportunity of direct inspection underground of a producing oil reservoir, and of direct observation of the effects of various recovery processes. Petroleum was of such insignificant importance at the time the General Mining Law of Germany was adopted in 1865 that it was not included with other minerals. Thus, up until 1934, when the first Petroleum Law was enacted and which vested title to all undiscovered oil and gas fields in the state, development of the oil fields and the production of oil was carried on by lease agreements between land owners and oil companies similar to the manner in which land is leased, wells are drilled and oil is produced in the U.S. The Petroleum Act of 1934 did not invalidate existing lease agreements and some oil, chiefly from the shallow fields of early discovery, is still produced under such agreements. JPT P. 589ˆ