Page 499 - Enhanced Oil Recovery in Shale and Tight Reservoirs

Other enhanced oil recovery methods 463

near- and far-field complexity with the reservoir. Each fracture stage for the
second well propagates into the stress alteration region by the two previously
propagated fractures from the first well, combining concepts of the zipper and
Texas two-step patterns (Soliman et al., 2010; Curnow and Tutuncu, 2016).
When completing horizontal wells one at a time, after a single stage is
fractured, it takes 2e3 h for the wireline operation to set plugs and perforate
the next stage. By completing multiple wells, this waiting time can be used.
In addition to cut operation time off, zipper and modified zipper fracturing
patterns can increase fracture complexity, and therefore, improve oil
recovery.
For the multiwell frac patterns to work there are three primary factors
(Jacobs, 2014):
(1) Existence of conductive natural fractures,
(2) Impact the stress shadow may have on hydraulic fracturing between two
wells,
(3) Ability to change the pressure within the natural fractures between two
wells.

14.7 Refracturing

Statistically, refracturing jobs show more field success than field
failures. Vincent (2010, 2011) used specific field cases to illustrate refractur-
ing mechanisms. These mechanisms include enlarged fracture geometry,
increased fracture height in vertical wells, greater lateral coverage in hori-
zontal wells or initiation of more transverse fractures, restored or increased
fracture conductivity, reorientation of existing fractures, etc.

14.8 Diversion technology in fracturing

In displacement processes in conventional reservoirs, diversion tech-
nology is used to improve the sweep efficiency of displacing fluids. Similarly,
diversion technology in fracturing is to increase the fracturing fluid to enter
more or all zones so that more fractures are generated, or sometimes more
fracture complexity is obtained. This can be achieved mechanically or
chemically. Mechanical diversion uses mechanical parts like different
packers, retrievable bridge plugs, sliding sleeves and ball sealers. Chemical
diversion uses viscous fluids or soluble particulate diverters. The main
purpose of these diversion methods is to divert the fluid from high-
permeability zones to lower-permeability zones or temporarily block the