Hydraulic fracturing de-facto is the most common stimulation technique that is employed worldwide. Russia is following the same trend and most of the new and old wells are considered for hydraulic fracturing. However, eventually as more and more reservoirs become depleted operators are looking forward to formations with so called “hard-to-recover” deposits in order to sustain hydrocarbon production.

These “hard-to-recover” deposits include:

  • Unconventional shale pays similar to US – Bazhenov and Domanik formations.

  • Caspian, Arctic, and Sakhalin offshore

  • Eastern Siberia green fields

  • Mature fields and formations where conventional stimulation is not as effective as expected due to variety of reasons.

This paper is focused on fracturing experience of mature fields.

Our experience shows that post-fracturing well productivity for mature fields can be altered but not limited to several issues:

  • It can be severely reduced in case of multi-phase flow inside the fracture due to non-Darcy effects when bottomhole flowing pressure is significantly below bubble point pressure.

  • At the other extreme, heavy and viscous formation fluids lead to rapid fracture conductivity degradation due to proppant flowback. Excessive proppant flowback leads to the necessity of frequent wellbore clean-out operations, reduces lifetime of the artificial lift system and down-hole equipment. These conditions call for wider and more permeable fractures in order to obtain desired production rates and overcome negative geological features.

  • Fracture breakthrough into a water layer also leads to ineffective stimulation.

  • Well conditions such as cement bond and overall well aging.

There are several technologies and techniques that could possibly be used (and used nowadays) to overcome cited problems, but most of them have applicability limitations. The paper is focused on first two – conductivity increase and fracture deterioration. One of the solutions that is capable to cope with conductivity related problems and proppant flowback issue and doesn't have application limits was found to be unconventionally rod- shaped proppant. In comparison with conventional round proppant, it provides higher fracture conductivity with integrated flowback control due to random alignment of proppant rods. Conventional method of proppant flowback control widely used in industry is resin coated proppant (RCP). Significant benefit of rod-shaped proppant over conventional RCP is that it does not have any limitations on bottomhole temperature and pressure as flowback prevention happens due to physical interaction between rods and not chemical bonding due to resin, does not require any chemical activation, chemicaly inert and, does not have special flowback requirements.

Since the introduction of rod-shaped proppant in Russia in 2011, more than 90 fracturing treatments have been successfully carried out with this unconventional proppant inside the country. Well production analysis proved that rod-shaped proppant was more effective than conventional proppant. In most cases we observed productivity increase over conventional treatments. Further, no proppant flowback issues were detected on wells fractured with rod-shaped proppant. This paper is addressed to the experience of use of rod-shaped proppant in challenging mature low temperature reservoirs with high formation fluid viscosity.

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