Capillary imbibition of the mud filtrate into the reservoir during drilling is involved, together with filtration flow, in increasing the water saturation of the bottomhole zone. At the same time, the ratio of capillary imbibition and filtration flow depends on a large number of factors, some of which cannot be directly measured, or this measurement is quite laborious, such as the contact angle of wetting phase, the radius of the pore channels, the initial saturation of the reservoir with gas, water and oil, relative phase permeability. Also, in addition to capillary absorption, other physico-chemical processes occur, the separate influence of each of which is quite difficult to identify. Moreover, the most important thing is to characterize the reservoir as a whole, and not to separate individual factors, the combination of which can reduce the accuracy of the forecast in other situations. To determine the nature of the interaction of the reservoir with the drilling fluid filtrate, it is proposed to use a complex parameter, which combines the above properties of the reservoir rock, namely, capillary pressure and relative permeability of the aqueous phase. Capillary pressure contains data about the radius of the pore channels and the contact angle. This article presents the results of studies by the gravimetric method of the kinetics of capillary imbibition of sandstone rock samples with the aqueous phase of the drilling fluid, determined during the experiment. As a result, the sensitivity of a gas-saturated reservoir to capillary imbibition of the aqueous phase is determined taking into account its initial water saturation without the need for instrumental measurements of porosity, permeability and capillary pressure. Options of capillary absorption at initial water saturation of 0, 10, 20 and 50% were considered. The classification of reservoir rocks based on the complex parameter can simplify the task of selecting the optimal drilling fluid to solve the problem of reducing the formation damage during the initial drilling into the formation.
References
1. Zonn M.S., Dzyublo A.D., Kollektory yurskogo neftegazonosnogo kompleksa severa Zapadnoy Sibiri (Collectors of the Jurassic oil and gas complex in the north of Western Siberia), Moscow: Nauka Publ., 1990, 88 p.
2. Tiab D., Donaldson E C., Petrophysics: theory and practice of measuring reservoir rock and fluid transport, Elsevier Inc., 2004, 926 p.
3. Borozdin S.O., Podgornov V.M., Reservoir sensitivity to physical and chemical process under invasion zone building (In Russ.), Gazovaya promyshlennost’, 2016, no. 4 (736), pp. 21–25.
4. Mikhaylov N.N., Motorova K.A., Sechina L.S., Geological wettability factors of oil and gas reservoir rocks (In Russ.), Neftegaz.ru, 2016, no. – № 3. – S. 80–90.
5. Mezentsev D.N., Tupitsyn E.V., Ledovskaya T.I. et al., Recovery of wettability of core samples in preparation to filtration research (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2012, no. 11, pp. 60–61.
6. Li K., Chow K., Horne R.N., Effect of initial water saturation on spontaneous water imbibition, SPE-76727-MS, 2002, DOI: https://doi.org/10.2118/76727-MS
