Within the territory of Eastern Siberia, during the development of oil-gas-condensate fields of the Nepa-Botuoba anteclise with the localization of deposits in the subsalt structural level of the geological section of Vendian age, there is an urgent problem of secondary precipitation of a complex of inorganic salts in the pore space of reservoir rocks and in oilfield equipment. Calcium chloride-type formation water for these deposits can reach a mineralization of over 300 g/l with a density of more than 1260 kg/m3. When organizing a system for maintaining reservoir pressure using commercial or transit waters as injection agents, the introduction of excess ionic strength into reservoir brines is associated with complications in the form of precipitation of easily soluble (halite), sparingly soluble (gypsum, calcite), and often polymineral (gypsocalcite) sediments, leading to a forced decrease in the permeability of the bottomhole formation zone, up to complete attenuation of the inflow. To dissolve salt deposits, a complex 2-stage treatment of the bottomhole zone is used by alternately pumping a 20% aqueous solution of NaOH and 12% HCl.
A lot of scientific research has been devoted to the problem of salt precipitation during the development of oil and gas condensate fields, and in general the issue is considered to be sufficiently worked out from the point of view of understanding chemical processes. However, due to the many factors influencing the intensity and type of sedimentation, universal tools for analyzing and predicting complications have not yet been developed. In the article highlights the existing experience in analyzing the operation of those subject to precipitation of poorly soluble gypsocalcite formations in the bottomhole zone of the formation and along the trunk of oil producing wells of the Yaraktinskoye oil and gas condensate field. The authors proposed analytical tools for indicating complications, tested for specific geological conditions. The proposed approaches are verified by hydrodynamic studies and the results of downhole work during ongoing well workover.
References
1. Oddo J.E., Tomson M.B., Method predicts well bore scale, corrosion, Oil and Gas Journal, 1988, V. 96, pp. 107–114.
2. Zimin S.V., Sabanchin I.V., Krasnov I.A. et al., Inorganic salt deposition under in situ conditions in Eastern Siberian reservoirs (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2020, no. 9, pp. 44-49, DOI: https://doi.org/10.24887/0028-2448-2020-9-44-49
