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Scale formation and accumulation is a major concern for Russian production companies. In Western Siberia, most wells produce fluids via Electric Submersible Pumps (ESP), and it is believed that up to 30% of the ESP failures result from scale damage. Despite that scaling is commonly first recognized at the ESPs, it can ultimately affect the whole production system. The most efficient treatment strategy to prevent scale induced damage in the tubular, including ESP, is scale inhibition. Traditionally, this involves an inhibitor squeeze treatment which is a localized inhibitor placement covering the near-wellbore area or the continuous injection of the inhibitor via a capillary tube. However, these techniques are designed to protect the production system. Squeeze treatments in hydraulically fractured formations are not always effective. Scale inhibitors together with compatible borate fracturing fluids can be used for a more effective scale inhibitor placement throughout the created hydraulic fracture to prevent scale formation from the reservoir level to the production system. This technique combines hydraulic fracturing and scale inhibition into one treatment resulting in operational simplicity. Since 2008, the combined fracturing/scale treatments have been successfully applied in the Krasnoleninskoe oil field in Western Siberia. This paper outlines the learning procedure and presents designs, testing and monitoring results from the campaign conducted at Krasnoleninskoe oil field (including Talinskaya and Em-Egovskaya sections).

Since 2015, the technology of multistage fracturing (hereinafter MSHF) in horizontal wells has become widespread in Bashneft-Dobycha's fields. MSHF applies to newly-drilled and side-tracked wells (hereinafter ST wells). To date, more than 100 multifracked wells have been put on stream. The post-MSHF well productivity decreases over time because of the degrading fracture conductivity and depletion of the reserves in the earlier stimulated zones. The most effective method to restore well productivity is refracturing, which was proven in directional wells. For refracturing, the assemblies that contain frac sleeves activated by dropping the balls of various diameters are mostly used. For openhole isolation of intervals, annular hydraulic-set packers are normally used, without cementing a horizontal borehole section. The application of these MSHF assemblies makes it difficult to further perform interval-wise refracturing. The challenging factors include multiple open intervals after performing all the frac stages and the tight hole in the sleeve intervals, even if milled. One of the refracturing methods tested in Bashneft-Dobycha's horizontal wells was ‘blind’ fracturing. This is the most easy-to-use method, which is not time-consuming either. The effect of these jobs was low, as the most depleted intervals were refractured. In 2019, a combined technology of abrasive jet perforation and subsequent refracturing through an abrasive jet perforating tool (abrasive jet perforation + fracturing) was proposed for multifractured horizontal wells. The application of the abrasive jet perforation + frac technology allowed for successful selective re-injection of acid and proppant into the selected intervals of the horizontal borehole. By now, Bashneft-Dobycha has refractured 10 multistage horizontal wells by means of the abrasive jet perforation + frac technology. One trip included three refrac stages maximum. All the treatment were successful, substantially increasing well productivity indices.