Perforating and Hydraulic Proppant Fracturing in Western Siberia, Russia

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractHydraulic proppant fracturing is developing rapidly in the oil fields in western Siberia and is seen as the most important means to improve oil production from both existing and newly drilled wells. The oil fields vary in size and reservoir quality, with a majority of the developed fields showing permeabilities of 1 to 30 mD. Reservoirs are layered, and fracturing vertical wells in general seems to give higher productivity compared to horizontal wells that are not being hydraulically fractured. This result is most likely because the vertical permeability is much lower than the horizontal permeability.To maximize production from these wells, coarse-sized proppant must be placed using the least-damaging and lowestviscosity fluid systems. For production optimization, the trend is currently "larger (proppant sizes) and bigger (jobs)," using the lowest acceptable polymer loading in the frac fluids, which minimizes gel damage.This paper describes the conflicts that can arise between the requirement to place large amounts of coarse propping material using low viscosity fluids and the perforation size and condition that is needed to do so. These conflicts can lead to job scenarios in which screenouts take place.During fracturing operations in wells in west Siberia, some screenouts did take place. An investigation of the screenouts revealed that the major cause of the screenouts is reduced width development at the perforations associated with the "stress cage." Guidelines were developed to reduce the influence of the near-wellbore stress cage and prevent screenouts. In addition to these guidelines, future solutions are proposed that may avoid the stress cage and place coarse proppant more efficiently.

Drilling and Completion Challenges for Deep, Tight Gas Exploration Wells Onshore Northern Oman

“…Our preferred way of perforating tight gas exploration wells is by hydraulic jetting on CT. Usually four slots of 1 0 m length (33 ft, 90 o phasing) are created for e ach fracturing stage. Since this p erforation method is used, all formations could be broken-down (successful fracture initiation), while this was often not possible when perforating with explosives ("stress caging", Warpinski 1983;Surjaatmadja et al 1994;van Gijtenbeek and Pongratz 2004). Less difficult formations are perforated with 2 7/8 in.…”

Successful Hydraulic Fracturing Techniques in Horizontal Wells for Sandstone Formations in the Permian Basin

“…When perforating for hydraulic fracturing, deep penetration into the formation is not required; it has been observed in studies that the fracture initiation point is at the cement/formation interface and not along the perforation tunnel. 4 The hole size or EHD that is chosen for limited-entry fracturing will affect the total number of holes in the wellbore and the number of holes that can be placed at each perforation cluster. With smaller hole sizes, more perforations can be used, and the designed fluid distribution can be matched closely to the desired fluid distribution.…”