Interferometric Synthetic Aperture Radar (InSAR) data, gathered over the In Salah CO2 storage project in Algeria, provide an early indication that satellite‐based geodetic methods can be effective in monitoring the geological storage of carbon dioxide. An injected mass of 3 million tons of carbon dioxide from one of the first large‐scale carbon sequestration efforts, produces a measurable surface displacement of approximately 5 mm/year. Using geophysical inverse techniques, we are able to infer flow within the reservoir layer and within a seismically detected fracture/fault zone intersecting the reservoir. We find that, if we use the best available elastic Earth model, the fluid flow need only occur in the vicinity of the reservoir layer. However, flow associated with the injection of the carbon dioxide does appear to extend several kilometers laterally within the reservoir, following the fracture/fault zone.

The plasma equation for a warm collisionless plasma with a Maxwellian particle source is solved in plane parallel geometry. The generalized Bohm criterion is used to identify the plasma–sheath boundary. This kinetic treatment, in common with fluid and cold-ion kinetic models, results in an infinite electric field at the sheath edge. This is in sharp contrast to results from a previous warm-ion kinetic model, by Emmert et al. [Phys. Fluids 23, 803 (1980)], which gave a finite electric field at the sheath edge. Also, the presheath potential given by the present model is greater than that given by Emmert and is in better agreement with fluid results.

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Four models of collisionless one-dimensional plasma flow to a boundary are compared with regard to their predictions of particle and heat fluxes to the boundary for a given plasma density and temperature far from the boundary. The models include two kinetic treatments, that of Emmert et al. [Phys. Fluids 23, 803 (1980)], and that of Bissell and Johnson [Phys. Fluids 30, 779 (1987)], an isothermal fluid model, Self and Ewald [Phys. Fluids 9, 2486 (1966) and Stangeby, [Phys. Fluids 27, 2699 (1984)], and an adiabatic fluid model, Zawaideh, Najmabadi, and Conn [Phys. Fluids 29, 463 (1986)]. The fluid models do not explicitly include collisions; however, the adiabatic closure condition employed, namely, neglect of ion heat conduction, implies a degree of ion self-collisionality. It is found that the particle and heat fluxes to the boundary differ very little among the four models—spanning a range of about ±10%. It is therefore concluded that, with regard to modeling of such important practical quantities as outfluxes, a simple and convenient formulation, such as the isothermal fluid model, is adequate. Substantial differences among the models are found for certain other predicted quantities, namely, the spatial variation of ion temperature along the flow and the magnitude of the electric field near the boundary.

Summary This paper investigates the recovery mechanisms for steam injection intonaturally fractured, carbonate, heavy-oil reservoirs. Interim ideas and resultsof laboratory and simulation studies are presented and topics for furtherinvestigation are suggested. Results presented and topics for furtherinvestigation are suggested. Results so far indicate that both imbibition andinternal gasdrive are effective at driving oil into the fracture network. Introduction Heavy oil contained in carbonate reservoirs worldwide is estimated to be 1.6x 10(12) bbl in place. So far, this major resource has attracted littleattention from the petroleum industry and little has been produced. Thisprobably stems from the conceptually difficult task of recovering viscous oilfrom naturally fractured carbonate formations. Clearly, a means of reducing oilviscosity, such as a thermal recovery technique, is needed to allow flow toproducing wells. Steam injection is currently the most successful thermalrecovery technique available. However, steam might be expected to travelpreferentially through the fracture system and to recover little oilpreferentially through the fracture system and to recover little oil from thematrix; The chemical reactivity of the formation to the steam injectant alsomight be expected to cause problems in the forms of formation damage and scaleproduction. This paper describes recent research in identifyingpressure-cycling steam recovery strategies that could unlock this largeworld-wide resource. Mechanisms thought to offer potential include imbibition, viscosity reduction (from increased temperature and CO2 dissolution), oilswelling (from increased temperature and CO2 dissolution), gravity drainage, and internal depletion gasdrive (from flashing of solution gas, steamcondensate, and dissolved CO2). Initial experimental research studies have beenboth mechanistic and fundamental in nature. High-temperature/high-pressure(HTHP) mechanistic studies are identifying the contribution to recovery fromthe individual mechanisms listed above. The quantitative parameters needed tomodel the most significant processes mathematically are being determined atappropriate temperature and pressure conditions. Fundamental studies aredirected toward identifying scaling rules for modeling imbibition processes. The effects of viscosity ratio, temperature, and matrix/fracture geometry arebeing studied. To advance experimental research, special HTHP facilities havebeen constructed. These have been designed to match reservoir conditions duringcyclic steam processes. Further experiments are planned to study thetemperature dependence of these processes as the matrix heats and wettabilityand rock/fluid interaction contours traverse the rock matrix. An apparatus wasdeveloped to determine the modeling parameters, such as relative permeabilityand capillary pressure, under representative conditions. Effects of increasingtemperature on PV, PV compressibility, and matrix permeability are also beingstudied. PV compressibility, and matrix permeability are also being studied. Anapparatus also was developed to investigate displacement and depletionprocesses by use of X-ray computerized tomography (CT). Novel low-density coreholders with optical fiber temperature sensors are used. Concurrently, mathematical models are being developed to capture the essentialcharacteristics of the recovery processes for sensitivity studies, historymatching, multicycle prediction, and economic optimization. The simulationapproach to the field process that has been developed allows the main recoverymechanisms process that has been developed allows the main recovery mechanismsto be interlinked. At this point, we have used the simulator to investigaterecovery strategies for heavy oil recovery from fractured carbonatereservoirs. Results From Laboratory Program HTHP Mechanistic Studies. Initial HTHP mechanistic studies ere performedwith plugs cut from an outcrop block of Permian performed with plugs cut froman outcrop block of Permian magnesian limestone (dolomite). Table 1 gives themineralogical composition of the sample obtained from X-ray diffraction (xRD), and Table 2 gives the physical characteristics. Table 3 presents the propertiesof the live crude oil used for the studies. The experimental properties of thelive crude oil used for the studies. The experimental sequence was chosen torepresent a cyclic steam process. The clean, dry sample was saturated with10,000 ppm NaCl after measurement of the PV, porosity, and gas permeability. The sample was then confined in a core holder at a 1,500-psi overburdenpressure. Swi was achieved by flooding with the live crude oil with pressure. Swi was achieved by flooding with the live crude oil with a 200-psidifferential pressure across the sample and a 750-psi back-pressure. The samplewas then aged for 24 hours to allow equilibration of the fluids. The systemtemperature then was raised to 302 degrees F and any production from oil orrock thermal expansion was identified by allowing a period of 4 hours to elapsebefore the imbibition phase began. Spontaneous imbibition counterflowproduction was monitored by flowing brine across the top face of the rocksample and collecting effluent in a separator (Fig. 1). Initial oil production(over the first 10 minutes of brine flow) was associated with thermalexpansion. The backpressure then was reduced to ambient pressure and thedepletion production caused by internal gasdrive and/or steam flashing wasmonitored. The blind end of the core holder then was opened and the sample wassubjected to consecutive hot-water flood and steamflood. This sequence then wasrepeated on a fresh sample at 482 degrees F . Table 4 presents results of thesetests. The tests at 302 degrees F indicate that thermal expansion results inminimal recovery, imbibition plays a major role in producing oil from thematrix into the fracture network, depletion results in further appreciableproduction, and forced displacement by hot water or steam appears notproduction, and forced displacement by hot water or steam appears not to resultin further recovery. The tests at 482 degrees F indicate that the initial highproduction occurs as a result of gas evolution as the bubblepoint is breachedat the high temperature, further production occurs because of imbibition, anddepletion does not result in high production because the gas-drive mechanismhas already been exploited at the higher temperature. (Note that higherproduction may have been masked by distillation losses from the separator.)Note that firm conclusions cannot be drawn from the results of only two tests. Several further data points are required.