Modeling Studies of Cold Water Injection Into Fluid-depleted, Vapor-dominated Geothermal Reservoirs PDF Download
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Author: C. Calore
Publisher:
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Category : Geothermal reservoirs
Languages : en
Pages :
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Author: C. Calore
Publisher:
ISBN:
Category : Geothermal reservoirs
Languages : en
Pages :
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Book Description
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Category :
Languages : en
Pages :
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Reinjection experiments in the strongly fluid-depleted reservoir of Larderello have revealed the possibility of increasing production rates and overall heat extraction by injection into high permeability, low pressure zones of the reservoir (Giovannoni et al., 1981; Cappetti et al., 1983; Bertrami et al., 1985). A large fraction (over 80%) of the injected water was recovered as steam in the most favorable area and, despite the short distance between injection and producing wells (the minimum distance being about 150 m), no significant temperature change has been observed in the latter, after 3 years of injection at a rate ranging from 10 to 50 kg/s (Bertrami et al., 1985). The physical processes involved in cold water injection into a ''superheated'' fractured reservoir are not yet fully understood, and this insufficient knowledge of the fundamental mechanisms limits the possibility of forecasting future reservoir behavior and optimizing the heat extraction process. Numerical simulation can be a very effective tool in the study of the complex phenomena involved, allowing a rapid examination of different situations and conditions, a systematic investigation of the effects of various parameters on reservoir performance, and some insight into long term behavior. We have performed simulation experiments on simple one-dimensional, porous and fractured reservoir models in order to study the migration of injected water, thermodynamic conditions in the boiling zone, heat extraction, and vapor generation. A two-dimensional radial porous medium model, with some characteristics typical of the high productivity zones of Larderello, has, also been applied for studying the- evolution. of the shape and the thermodynamic conditions of the injection plume in the presence of gravity, reservoir heterogeneities and anisotropy.
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Languages : en
Pages : 27
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Recent reservoir pressure and steam flow rate declines at The Geysers geothermal field in California have attracted interest in studies of increased cold water injection into this system. In this paper, numerical studies of such injection into a fractured vapor-dominated reservoir are conducted using a two-dimensional radial, double-porosity model. The results obtained indicate that cold water injection into superheated (low-pressure) zones will greatly enhance the productivities of steam wells. Injection into two-phase zones with significant liquid reserves in the matrix blocks does not appear to aid in steam recovery until most of the original liquid reserves are depleted. Sensitivity studies are conducted over the range of fracture and matrix permeabilities applicable to the Geysers. The sensitivity of the grid size is also conducted, and shows very large grid effects. A fine vertical space discretization near the bottom of the reservoir is necessary to accurately predict the boiling of the injected water. 28 refs., 15 figs., 3 tabs.
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Languages : en
Pages : 10
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Vapor-dominated geothermal reservoirs such as Larderello, Italy, and The Geysers, California, are fundamentally water-short systems. This is apparent from the relatively low pressures in the natural state, typically about 35 bars at 1000 m depth, which is much below hydrostatic pressures. It is also apparent from the high heat content of the produced fluids, typically superheated steam. Large-scale production from these systems has caused reservoir pressures and well flow rates to decline, leading to an underutilization of installed electrical generating capacity. Clearly, these reservoirs are beginning to run out of fluid, while heat reserves in place are still enormous. (At Larderello, there is a long-term trend of increasing formation temperatures in the upper productive zones of the reservoir; Sestini, 1970). Reinjection of colder waste waters, or injection of waters from a source other than the geothermal reservoir, is the primary means by which dwindling fluid reserves can be replenished. A considerable body of field experience with injection has been accumulated at Larderello and The Geysers; the results have been mixed. There are well documented cases where injection has increased flow rates of nearby wells. Return of injected fluid as steam from production wells has been observed directly through chemical and isotopic changes of produced fluids (Giovannoni et al., 1981; Nuti et al., 1981). In other cases injection has caused thermal interference and has degraded the temperature and pressure of production wells. Water injection into depleted vapor zones gives rise to complex two-phase fluid flow and heat transfer processes with phase change. These are further complicated by the fractured-porous nature of the reservoir rocks. An optimization of injection design and operating practice is desirable; this requires realistic and robust mathematical modeling capabilities.
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Category : Geothermal engineering
Languages : en
Pages : 356
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Author:
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Category : Geothermal engineering
Languages : en
Pages : 362
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Category : Power resources
Languages : en
Pages : 922
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Author: E. Okandan
Publisher: Springer Science & Business Media
ISBN: 9400936915
Category : Technology & Engineering
Languages : en
Pages : 327
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During the oil crisis of 1973, we suddenly became aware that fossil fuel resources are limited and will be exhausted soon if new alternatives are not put into use immediately. Conservation measures and extensive research on new sources of energy has eased the demand on fossil fuels, especially crude oil. Geothermal energy as an alternative; source had its share in this devel opment and electricity producing capacity increased from 700 to 4700 MWe during 1970 to 1985. Geothermal reservoir engineering emerged as an impor tant field in the assessment of geothermal sources. During the 25 years of its development, several areas were identified that needed further at tention for the correct description and interpretation of reservoir be havior. This fact as accepted by all operators is vital for the steady and continuous operation of power plants. During this NATO ASI, a detailed review of theory and field case his tories on geothermal reservoir engineering was presented. In understanding .the reservoir, conceptual models, natural state models, well bore measure ments, transient and tracer testing provide data which are indispensable. They are powerful tools in understanding reservoir behavior provided we know how to interpret them. During lectures the theory and practical applications of these interpretive methods were discussed.
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Languages : en
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The basic physical phenomena associated with geothermal injection are reviewed; problems associated with its numerical simulation are discussed; and the results of some numerical studies are presented. The particular problems chosen for study are: injection of cold water into a thin (single layer) reservoir; a five-spot production/injection configuration in a thin (single layer) reservoir; injection of cold water into a thick (multi-layer) reservoir; and injection of cold water into a one-dimensonal vertical column, representing a cross section of Larderello geothermal reservoir. (MHR).
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Languages : en
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