Hydraulic fracturing has proven to be one of the most efficient and common completion methods to increase well productivity in mature oil fields with tight sandstone formations. However, the efficiency of the overall completion process is influenced not only by the applied fracturing technology but also by the well completion methods and production approach – especially in wells with long perforation intervals.

Nowadays, multistage fracturing systems have become widely used for more effective fracture placement and optimization of inflow profiles. This technology is mostly applied in an openhole section of horizontal wells where such completion requirements are most critical. However, the development of existing vertical wells can also benefit from the technology allowing selective stimulation of production zones, which could not be efficiently fractured otherwise. The approach described in the paper covers the candidate selection, recompletion technique, stimulation and production process applied for the oilfield in West Kazakhstan.

The sample well had been in production for several preceding years completed with perforations (up to 182 meters) at four main oil-bearing zones. Previously, there was done acidizing treatment which gave two-fold increase in production, but full potential of the well was not achieved. It was identified that the most of the inflow had been coming from only 43% of perforations while the rest intervals did not contribute to production. To achieve the coverage of all productive layers with fractures and involve all layers into production, it was decided to recomplete the well with four-stage completion system with ball activated multishiftable frac sleeves.

Four stage completion system was installed in the cased old well and multiple fracturing stimulation was performed successfully. The job is a subject for further testing process of each treated zone, but the effectiveness of applied technology had already been proved as the overall production surplus more than four times. The operator considers replication of similar approach to the other wells in the oilfield.

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