Page 498 - Enhanced Oil Recovery in Shale and Tight Reservoirs

462 Enhanced Oil Recovery in Shale and Tight Reservoirs

14.6 Zipper fracture
Instead of drilling and hydraulically fracturing one well at a time, mul-
tiple wells are drilled from a pad site; after one stage in one well is fractured,
during the time to prepare for fracture the next stage at this well, wireline
and perforation operations take place and a stage is fractured in another
well. The fractures have a zipperlike configuration, as shown in Fig. 14.2
in which other configurations are presented. This figure shows two well
fracture patterns. A similar pattern can be practiced in four wells and multi-
ple wells. For the conventional fracturing configuration, well 1 and well 2
are independently fractured with each stage fractured sequentially from
the toe to the heel. For the zipper fracturing configuration, after one stage
from well 1 is fractured, another stage from well 2 is fractured to the early
stage, and the sequence is repeated. The objective is to generate the fracture
complexity near the tips of fractures. For the Texas two-step configuration,
the sequence of fracturing stages for a single well is altered. After the first
stage near the toe is fractured, the second stage toward the heel is fractured;
next the third fracture is initiated between the two previously fractured. The
middle fracture has a reduced half-length because it is generated in the stress
alteration region by the previous fractures. In the modified zipper fracturing
configuration, the staggered fracture pattern allows the individual stimulated
reservoir volume (SRV) extents for each lateral overlap, generating both

Figure 14.2 Various fracturing figurations (numbers indicate sequence).