shale gas production process
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Shale gas production process
How it works Wells are drilled vertically to intersect the shale formations at depths that typically range
from 6,000 to more than 14,000 feet. Above the target depth the well is deviated to achieve a horizontal
wellbore within the shale formation, which can be hundreds of feet thick. Wells may be oriented in a direction
that is designed to maximize the number of natural fractures present in the shale intersected. These natural
fractures can provide pathways for the gas that is present in the rock matrix to flow into the wellbore.
Horizontal wellbore sections of 5,000 feet or more may be drilled and lined with metal casing before the well is
ready to be hydraulically fractured.
Hydraulic fracturing Beginning at the toe of the long horizontal section of the well, segments of the
wellbore are isolated, the casing is perforated, and water is pumped under high pressure (thousands of pounds
per square inch) through the perforations, cracking the shale and creating one or more fractures that extend
out into the surrounding rock. These fractures continue to propagate, for hundreds of feet or more, until the
pumping ceases. Sand carried along in the water props open the fracture after pumping stops and the pressure
is relieved. The propped fracture is only a fraction of an inch wide, held open by these sand grains. Each of
these fracturing stages can involve as much as 10,000 barrels (420,000 gallons) of water with a pound per
gallon of sand. Shale wells have as many as 25 fracture stages, meaning that more than 10 million gallons of
water may be pumped into a single well during the completion process. A portion of this water is flowed back
immediately when the fracturing process is completed, and is reused. Additional volumes return over time as
the well is produced.
New Exploration Techniques:
Direct Hydrocarbon or Mineral Indicators
A combination of non-invasive techniques (seismic, magnetic resonance, etc.) in Direct Hydrocarbon and
Mineral Indicators, in order to detect the presence of hydrocarbons and minerals, to determine where to drill
exploratory wells, and step-outs. (see below for more information)
3D Mathematical Modeling / GAMLS / Neural Networks
In addition, new methods of processing well-log data from a field can reveal overlooked reserves, or possible
extensions to existing fields. GAMLS is one such software program, which allows geologists, geophysicists,
engineers, and petro-physicists to evaluate old fields, look for step-outs, and to analyze the potential of new
producing zones. (see below for more information)
New Drilling / Production Techniques:
Take horizontal drilling in the shale to new levels. In addition to drilling the shale zone and perforating the
shale, we will now perforate the boundary regions above and below the shale. This may seem not only counter-
intuitive: won't it result in formation damage? Won't it release all the unwanted formation fluids and gases
(salt water, nitrogen, etc.)?
Benefits of perforating the shale and the perfing into the boundary regions:
Getting the oil from thin zones: Where shale has served as a seal for a small gas cap in a thin zone, it gives one
the ability to effectively exploit the reservoir and extract the hydrocarbons effectively, without the water, etc.
(example: Red Fork / Pennsylvanian sands in the MidContinent region).
Recovering hydrocarbons from depleted zones where there is nothing left but very thin zone of gas, with
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massive water behind it.
Perf the boundary region: Using the shale as both seal and controlled fracture / conduits where there is a
massive water sand or massive carbonate reservoir with gas cap, (example: Mississippian in northern
Oklahoma).
Perf the salt: Shale gas on the edge of anhydrites or salt seals: perf into the anhydrite.Why? If you treat the anhydrite, it will change volume (swell) and will add pressure to the shale gas & will
stimulate production.