Abstract

Due to the depletion of developed fields with conventional hydrocarbon (HC) reserves, it is currently important to study the impact of chemical reagents being part of acidic compositions for bottomhole zone treatment in tight Domanic rock wells. In the Bavlinskoye field, productive reservoirs of low permeability Domanic sediments are represented by carbonaceous differences of rocks, with interlayers of low permeability and rich in organic matter lime-siliceous or siliceous-calcareous rocks, as well as minor fractured rock interlayers in the cross-section. The basic method of enhanced oil recovery from carbonate reservoirs is compositions based on hydrochloric acid (HCl), the application of which allows to restore reservoir permeability due to the formation of new highly conductive pore channels ("wormholes"). The effectiveness of this method depends primarily on the depth of penetration of the active acid into the reservoir and on the completeness of reservoir rock dissolution in the acid solution. Experimental studies have shown that the structure of these channels is determined by the operating conditions of the formation, including temperature, the rate of injection of the acid solution, the filtration properties of the formation, and the properties of the reagents. In the process of treating the bottom-hole formation zone (BHZ) with industrial hydrochloric acid HCl, its maximum impact on the rock occurs in the near-wellbore zone (NWZ). In the remote zone of the reservoir, the reaction of acid with the rock is less intense due to the partial loss of its activity. As the result, this wellbore zone is treated more intensively to form the maximum number of dissolution channels at the expense of the depth of channels penetration into the remote reservoir zone. Often, the low efficiency of acid treatments on low-permeability reservoirs of Domanic deposits necessitates their repeated implementation. Therefore, physicochemical improvements of the composition formula and designing acid treatment with due consideration for the whole variety of factors affecting the efficiency are of topical importance. To increase success of carbonate matrix acid treatment, it is necessary for wormholes to penetrate deeply into the reservoir with the minimum volume of acid. It is the optimal injection rate of a certain acid composition that creates the conditions under which a minimum volume of acid solution is required to form the most effective wormhole channel. The full consideration of factors that significantly affect the efficiency of the impact (geological and physical parameters of productive strata and technological parameters related to the characteristics of reservoir development) would very likely help to choose the optimal structure and design of acid exposure. The main function of acids during the reservoir bottomhole treatment is relatively fast and complete dissolution of the rock matrix and the components in contact with reservoirs that clog the void space. The mechanism of this interaction is determined by their mineralogical composition and surface condition, as well as, to a large extent, by the nature, concentration of acids, and physical conditions of the dissolution process. Due to this, the rate and completeness of dissolution of solids can vary within wide limits depending on the specific downhole conditions. Under Agreement 14.607.21.0195 and as part of the Federal Target Program “Research and Development in Priority Directions for the Development of the Russian Science and Technology Complex in 2014–2020”, Almetyevsk State Oil Institute carries out work on the theme “Development of Scientific and Technological Solutions for the Development of Unconventional Reservoirs (Domanic Deposits) and Hard-to-Recover Oil 144 __________________________________________________________________________________ Сетевое научное издание «Нефтяная провинция». № 3(19) 2019 http://www.vkro-raen.com (Bituminous Oil) Based on Experimental Studies”, which is focused on improving the process of production intensification with application of acid compositions in wells drilled in Domanic deposits. Emerging new conditions of development of non-conventional oilfields provide for application of enhanced approaches in studying the features of acid treatments on Domanic sediments. Based on the assessment of existing standards governing the conduct of flooding research, the authors propose a methodology for conducting filtration experiments with acidic compositions for wells bottomhole treatment. In this work we show the results of studies evaluating the efficacy of compositions used for BHT with intensifying fluid influx into wells drilled in Domanic sediments.

Key words:

domanic sediments, flooding research, core material, permeability, acid composition, low permeability reservoir.

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