Unatego Landowners Association

Otego - Unadilla - Butternuts Area Residents

                                Evolution of a Shale Play

Typically, development of a shale play has three distinct phases, from the discovery stage, through drilling and reservoir evaluation, to production.  The timeframe for this process can take several years.

 

STAGE 1: Discovery & Planning - the stage during which all of the initial reservoir knowledge is gathered. Extensive analysis, including coring and seismic analysis, establishes the economic viability of the play during this phase and helps determine the techniques to be used to optimize the development. The effectiveness of planning accomplished in the discovery stage depends largely upon knowledge of the reservoir.

 

STAGE 2: Drilling & Reservoir Evaluation - the operational phase with the focus on applying the planned techniques most efficiently to maximize reservoir contact and lower cost per unit. It is in this stage of development that the issues concerning infrastructure and practical efficiencies are addressed. And this is the present state of several currently hot shale plays.

 

STAGE 3: Production Phase - focuses on optimizing reservoir drainage, which in U.S. shale gas plays typically requires stimulation, usually by hydraulic fracturing. The efficiency of these completion operations can have significant impact during the production phase; with proper fracturing and placement of proppants, some shale wells have been producing for decades.

 

SHALE "ISSUES"

Along with its geographic abundance and enormous production potential, gas shale presents a number of challenges – starting with the lack of an agreed-upon industry standard for what exactly comprises shale.

Shale makes up more than half the earth’s sedimentary rock but includes a wide variety of vastly differing formations. Within the industry, the generally homogenous, fine-grained rock can be defined in terms of its geology, geochemistry, geo-mechanics and production mechanism – all of which differ from a conventional reservoir, and can differ from shale to shale, and even within the same shale.

Nevertheless, all shale is characterized by low permeability, and in all gas-producing shales, organic carbon in the shale is the source. Many have substantial gas stored in the free state, with additional gas storage capacity in intergranular porosity and/or fractures. Other gas shales grade into tight sands, and many tight sands have gas stored in the adsorbed state.

Since these various conditions determine the production mechanism of the various shales, knowledge of local reservoir characteristics is of vital importance in keeping development costs under control and optimizing production over the life of the reservoir.

Also, since every shale play is different (due to the unique nature of shale), every basin, play, well and pay zone may require a unique treatment.

Currently the newest play is in the 54,000-square mile Appalachian Basin, but the Marcellus formation is not a new discovery. Prior to 2000, this low-density, vertically fractured shale formation was explored with a number of successful vertical gas wells, many of which have produced – slowly but surely – for decades. However, not until 2000 with the introduction of techniques pioneered in the Barnett shale, did Marcellus wells begin to yield significantly improved production rates.

The Marcellus shale ranges in depth from 4,000 to 8,500 feet, with gas currently produced from hydraulically fractured horizontal wellbores. Horizontal lateral lengths exceed 2,000 feet, and, typically, completions involve multistage fracturing with more than three stages per well.

 

For an in-depth look at the technical side of gas drilling, please go to: http://www.halliburton.com/public/shale/pubsdata/H06377.pdf

 

 

          Drilling Non-Permeable Shales (Barnett, Marcellus)

 When a well is drilled, steel casing and surrounding layers of concrete are installed to isolate the well from drinking water aquifers through which the well penetrates. The depths at which this “surface casing” must extend are regulated.  In Barnett Shale operations in Texas, the surface casings are typically set to a depth of 1,200 – 1,300 feet, more than 400 feet below the Trinity Aquifer. After it is determined that the well can produce natural gas, additional strings of casing and tubing are set through the aquifers to provide even greater separation between the gas stream and the fresh water tables. States also require documentation of drinking water aquifer intervals, the design and installation of surface casing relative to those intervals, and the reporting of characteristics of the wellbore along with completion and production data to protect water resources.

To review the 2000 EPA Report on the chemical make-up of "produced water" (water recovered from the drilling process), click here: EPA Gas Drilling Chemicals.pdf

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In order to release natural gas from low permeability shale, such as the Barnett in Texas or Marcellus in NY & PA, small cracks or fractures must be created in the rock — much like a windshield might be spidered or fractured if struck by a stone — to allow the gas to flow. “Fracing” is the process in which a mixture of sand, water and lubricants is pumped into the underground formation under high pressure to break open tiny fractures. These fractures are designed to release natural gas trapped inside the shale.

During fracing, water and sand are pumped under high pressure into the rock formation, creating tiny cracks in the shale and allowing gas to escape.

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Pipelines are necessary to get the natural gas from the wellhead to market. While the diameter of the pipeline may vary depending on its function, they are all similar to normal utility pipelines that currently deliver gas to your home or office, and thus pose no elevated safety issues. New pipelines may be installed through traditional open trenching, boring underneath the ground, or a combination of the two.


For information on the NY State Department of Agriculture and Markets' guidelines for pipeline construction across farming land, please click here: http://www.agmkt.state.ny.us/AP/agservices/WEBAPConstrGuides.pdf 

For a more complete overview of pipeline technology & proceedures, please click here: http://www.ipd.anl.gov/anlpubs/2008/02/61034.pdf

For information for landowners with forest lands, please click here: http://rnrext.cas.psu.edu/PDFs/FL%20Winter08.pdf 

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