145
fracturing process starts with the fractures moving into the rock at right angles to the
horizontal wellbore, but as stress fields change underground to accommodate the
new opening, the crack often turns and runs parallel to the wellbore. This is very
inefficient for recovering gas, and the frack operation is halted. After the stress field
adjusts and the rock has had time to accommodate the stresses, a second frack treatment is performed months to years later to extend the cracks farther into the reservoir at right angles to the borehole.
Re-fracking is expensive, mostly because of the mobilization costs incurred
when virtually everything in terms of equipment and supplies has to be brought
back out to the well pad for a second attempt. Many operators avoid it by performing a “zipper frack,” which uses two parallel boreholes. The fracks are alternated
between the two holes zone by zone, and the stress produced by one is accommodated by the other. With the advent of zipper fracking, re-fracking has become much
less common, and many water impoundments are now dismantled after the wells are
completed. Even when a re-frack is required, operators will typically breach the
impoundment so that it will not hold water during the period of stress re-adjustment.
This helps protect them from the legal liability of having an attractive nuisance on
their well pad. The breach is repaired when needed to accumulate a water supply for
re-fracking.
Chemical additives on drill pads during fracking operations can prove to be
harmful or fatal to both wildlife and domestic animals if there are leaks or spills and
the chemicals enter the environment. A photograph was circulated widely by fracking opponents a decade ago that showed a dead cow next to a fracking operation in
the Haynesville Shale where biocide had leaked from a tank on the pad and flowed
into the nearby pasture. The cow lapped it up and was soon deceased (Fig. 8.1).
These types of events are rare, but do happen. Other pictures of dead cattle near
fracking sites can be found by searching the Internet.
Some frack additives like ethylene glycol are sweet and attractive to animals. It
is important for operators to maintain control of their inventories of the chemical
additives, not bring more on-site than is actually needed, and monitor the activities
of wildlife, domestic animals, and people in the areas surrounding the well pad.
Given the 24-hour nature of fracking operations, activity on the pad is likely to be
continuous and wildlife normally stays away. However, many of these wells are in
very remote, rural locations. The woods and pastures surrounding the pads may
attract various animals, sometimes with tragic results.
A source of long-term degradation to an ecosystem may result from the fragmentation of habitat crisscrossed by roads and pipelines. Fragmentation is a process
where large expanses of habitat are transformed into multiple, smaller patches that
are isolated from each other by barriers composed of habitats much different than
the original (Hagen et al. 2012). For example, excavating a wide road through a forest will separate two previously joined expanses of forest habitat with a line of
packed dirt that is definitely not forest habitat. Some plants and animals in the ecosystem can cross this boundary easily, but it may present an insurmountable barrier
to others. Different species are affected in different ways, depending on factors like
body size, ability to disperse, and other spatial, temporal, or biotic drivers. Because
8.2 Terrestrial Ecosystems
fracturing process starts with the fractures moving into the rock at right angles to the
horizontal wellbore, but as stress fields change underground to accommodate the
new opening, the crack often turns and runs parallel to the wellbore. This is very
inefficient for recovering gas, and the frack operation is halted. After the stress field
adjusts and the rock has had time to accommodate the stresses, a second frack treatment is performed months to years later to extend the cracks farther into the reservoir at right angles to the borehole.
Re-fracking is expensive, mostly because of the mobilization costs incurred
when virtually everything in terms of equipment and supplies has to be brought
back out to the well pad for a second attempt. Many operators avoid it by performing a “zipper frack,” which uses two parallel boreholes. The fracks are alternated
between the two holes zone by zone, and the stress produced by one is accommodated by the other. With the advent of zipper fracking, re-fracking has become much
less common, and many water impoundments are now dismantled after the wells are
completed. Even when a re-frack is required, operators will typically breach the
impoundment so that it will not hold water during the period of stress re-adjustment.
This helps protect them from the legal liability of having an attractive nuisance on
their well pad. The breach is repaired when needed to accumulate a water supply for
re-fracking.
Chemical additives on drill pads during fracking operations can prove to be
harmful or fatal to both wildlife and domestic animals if there are leaks or spills and
the chemicals enter the environment. A photograph was circulated widely by fracking opponents a decade ago that showed a dead cow next to a fracking operation in
the Haynesville Shale where biocide had leaked from a tank on the pad and flowed
into the nearby pasture. The cow lapped it up and was soon deceased (Fig. 8.1).
These types of events are rare, but do happen. Other pictures of dead cattle near
fracking sites can be found by searching the Internet.
Some frack additives like ethylene glycol are sweet and attractive to animals. It
is important for operators to maintain control of their inventories of the chemical
additives, not bring more on-site than is actually needed, and monitor the activities
of wildlife, domestic animals, and people in the areas surrounding the well pad.
Given the 24-hour nature of fracking operations, activity on the pad is likely to be
continuous and wildlife normally stays away. However, many of these wells are in
very remote, rural locations. The woods and pastures surrounding the pads may
attract various animals, sometimes with tragic results.
A source of long-term degradation to an ecosystem may result from the fragmentation of habitat crisscrossed by roads and pipelines. Fragmentation is a process
where large expanses of habitat are transformed into multiple, smaller patches that
are isolated from each other by barriers composed of habitats much different than
the original (Hagen et al. 2012). For example, excavating a wide road through a forest will separate two previously joined expanses of forest habitat with a line of
packed dirt that is definitely not forest habitat. Some plants and animals in the ecosystem can cross this boundary easily, but it may present an insurmountable barrier
to others. Different species are affected in different ways, depending on factors like
body size, ability to disperse, and other spatial, temporal, or biotic drivers. Because
8.2 Terrestrial Ecosystems