Oilfields with carbonate reservoir usually are highly anisotropic. Often, a well can penetrate intervals that differ in permeability by orders of magnitude, which is especially aggravated in the case of horizontal wells. Such a difference in permeability leads to uneven recovery of reserves, early water cut growth and so on. In case of fractured reservoirs during well acidizing the injection agent goes through fractures almost. It leads to increasing size of fractures. In case of cavernous reservoirs, injecting acid connects highly permeable channels over time and subsequently fluids mainly go through these channels. Selective well acidizing allows to block highly permeable channels temporary and let the acid go to rock matrix directly. Applying of selective allows to join low permeable rock matrix, increase wells productivity and effective wellbore length. Accordingly, applying selective well acidizing is effective way of production maintenance.
In this paper, we are considering effectiveness analysis of using gel-acid systems for production stimulation. The material is based on experience of using gel-acid systems during selective acidizing wells of Yurubcheno-Tokhomskoye field with fractured carbonate reservoir. The analysis was carried out according to the time of contact between gel-acid system and rock, the dynamics of wells productivity, growth such parameters as water cut and gas-oil ratio (GOR). As a result, we’ve made some guidances for the technology optimization according to experimental data of Yurubcheno-Tokhomskoye field. Summing up, we could say that applying of selective well acidizing shows better results than usual well acidizing. Selective well acidizing allows to minimize risks of early water cut and GOR growth through high permeable zones and to improve productivity index of wells significantly. The technology could be replicated to similar oilfield, consisting of carbonate reservoirs with dual porosity and fluidal contacts.
References
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