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.