STUDYING UNSTEADY-STATE FLOW IN HORIZONTAL WELLS
Gilfanov E.F.
DOI https://doi.org/10.25689/NP.2019.1.71-89
Abstract
The paper presents analysis of pressure transient tests in a horizontal well over a long development period, effect of injection on a horizontal well production rate, and pressure transient test interpretation problems. Geological environment is a combination of interbedded layers with different physical and chemical properties. Each geological block is characterized by inherent dynamic stress system. In case of rapid-rate reservoir development, pressure events result in difference between rock stresses in the adjacent zones. Pressure decline tests in producing wells give higher net-pay thickness values than pressure buildup tests. Yusupov and Medvedsky’s studies show that long-term production can be accompanied by fracturing. Pressure transient test curve for a horizontal producing well demonstrates continuous linear flow, which can probably be due to a fracture presence. The injection well testing curve reveals parameters typical of fractures, though hydrofrac jobs were not performed in that well. Reservoir cooling due to injection of cold water with temperature significantly lower than reservoir temperature results in elastic stress decrease and reservoir fracturing in injection wells under pressures applied during water-flooding. By now, we know that significant difference between reservoir temperature and the injected water temperature results in reservoir fracturing, which is proved by pressure decline curve for the injection well, where long-term injection entailed self-induced hydraulic fracturing. Fracture closure stress increases with reservoir pressure depletion, resulting in lower fracture conductivity. Long-term observations revealed fracture dimensions variability
References
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Authors
Gilfanov E.F., Head Specialist, LUKOIL-Engineering Limited KogalymNIPIneft Branch Office in Tyumen, Tyumen, Russian Federation E-mail: geogil60@mail.ru
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