Geology, geography and global energy

Scientific and Technical Journal

Investigation of the formation process for oil wells in the bottom-hole zone of the Unvinskoye field

2013. №1, pp. 72-77

Dordzhiev Anatoliy A. - Assistant, Kalmyk State University, 4 Suseev st., Elista, Republic of Kalmykia, Russian Federation, 358000, pgs-kgu@yandex.ru

Yerofeev Artem A. - Post-graduate student, National Research Perm Polytechnical University, 29 Komsomolskiy Ave, Perm, Russian Federation, 614000, erofeev.a@bk.ru

The article describes the creation of bottom-hole formation zone (BhFZ) oil wells in the Unvinskoye field (Perm Region). It adds that these zones are often located near the bottom of impaired permeability-face zones (PFZs), which complicate the extraction of their oil reserves. Subsequently, the critique mulls several reasons for the decrease in PFZs’ permeability, with these likely to include colmatation voids. The latter, the paper relates, process fluids during construction and maintenance of wells, reservoir deformation, oil degassing, and organic and inorganic deposit placement. Ongoing qualitative and quantitative assessments of reservoir-found BhFZs have revealed a pressure build-up curve during unsteady well-trial conditions. However, as the review notes, the causes of permeability reduction in specific cases have yet to be determined. At this stage, the commentary shifts its focus to summarizing the results of a PFZ-based BhFZ study, citing the example of two producing wells in the Unvinskoye field (in Bobrikovsky terrigenous sediment deposit). Unvinskoye’s average depth is 2194 m, while the saturation pressure of the initial hydrocarbon (oil and gas) reserves are respectively placed at 14.22 MPa and 22.9 MPa. When operating the wells, the research paper says, down-hole pressure sometimes appears during the oil-gas saturation stage. This may be one cause of PFZs’ degraded reservoir quality; another may be deformations in the pore space leading to slight changes in the zones’ structural formation. In conclusion, the blueprint states that diagnosis of the face-zone condition could be implemented via a hydrodynamic method based on pressure recovery. The long-term objective should be, it indicates, to determine the causes behind permeability changes in the PFZ and to mitigate or prevent them through reliance on hydrodynamic analyses and geological field data.

Key words: bottom-hole zone,producing wells,effective permeability

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