The chemical industry magazine, Chemical Engineering Progress, August 2012 issue featuring Shale Gas, is eye-opening as to the source of the 60 year thing and many other things. In this issue on page 41, the article Getting Gas Out of the Ground the following quotes provide the full information on the 60 year thing. I have added some capitalization. 1) TECHNOLOGIES DEVELOPED in the oil and gas industry over the past 60+ years ARE NOW BEING USED to produce shale gas. 2) UNTIL RECENTLY, most natural gas came from what are known as conventional reservoirs. This conventional gas is typically trapped in relatively small, porous zones in rock formations such as sandstones, siltstones, and carbonates. Such gas is relatively easy to recover.” 3) “Unconventional gas, on the other hand, is obtained from low-permeability reservoirs in coals, tight sand formations, and shales. These accumulations of gas tend to be diffuse and spread over large geographic areas. As a result, unconventional gas is much more difficult to extract”. 4) “An individual well in an unconventional gas reservoir produces less gas over a longer period of time than a well in a conventional reservoir, which has a higher permeability. Thus many more wells must be drilled in unconventional gas reservoirs to recover a large percentage of the original gas in place (the amount of gas in the formation before any wells have been drilled and produced, OGIP), than are needed for a conventional reservoir.” 5) “Usually vertical wells with an unconventional gas reservoir must be stimulated to produce commercial-scale volumes at commercial-scale flowrates. This normally involves a large hydraulic fracture treatment (discussed later).” This verifies the recent practice of unconventional gas extraction through horizontal hydraulic fracturing. A few other tidbits from this article: On page 42, details are provided on horizontal drilling. 6)“It is common to drill horizontally to a distance of 3,000 – 10,000 feet in length and perform 10-30 fracture stages down the length. In many reservoirs, THE HORIZONTAL WELLBORE IS ABOUT 5,000 FEET.” On page 55 AND 56, in the article, Environmental Considerations of Shale Gas Development, the section on “Water Footprint”. 7) “Water footprint is perhaps the most contentious environmental issue associated with unconventional gas development.” 8)”Current practice invovles drilling multiple wells FROM ONE OR TWO PADS ON A WELL FIELD, and constructing hundreds of well fields within each development area.” 9) “During the construction of well fields, water must be found (sourced), HUNDREDS OF THOUSANDS OF TRUCKLOADS MUST TRANSPORT WATER TO WELL HEADS for hydraulic fracturing of the shale gas to initiate gas production, TENS OF MILLINOS OF BARRELS OF BRINE (collected as flowback water and produced water) must be reused or disposed of in an environmentally acceptable manner.” 10) Since water and waste management account for a large portion of the annual operating costs of shale gas development, the economical and environmentally acceptable management of these streams is critical to the sustainable development of shale gas plays.” 11) LOCAL WATER QUALITY MAY BE COMPROMISED AT SEVERAL STATGES OF SHALE GAS EXTRACTION. Gaining access to the well site involves building access forads for heavy equipment to transport drilling rigs, pioe, and water. Transporting material to the site and site perpartion can cause erosion. DRILLING THROUGH AQUIFERS CAN CONTAMINATE WATER SUPPLIES IF PROPER PRECAUTIONS ARE NOT TAKEN TO ISOLATE THE AQUIFER FROM THE WELLBORE.” 6) “One of the most important developments in recent years to reduce the water footprint is the practice of reusing the flowback water (the fracture fluids that return to the surface after completion of a well) from one well to supplement a portion of the water volume required for the nexst well’s hydraulic fracture treatment.” 12) Reusing this water reduces the potential for environmental impact by reducing air emissions and carbon footprint, water transportation requirements, truck traffic densities, and road wear, and generally results in greater STAKEHOLDER ACCEPTANCE. Even this reuse, however, is transportation intensive – moving 1 million gallons of flow back water from one well to the next requires more than 200 truck loads. Furthermore, the reused water is only about 20-25% of the total 4-5 million gal of water tyupically needed to fracture the next well.” There is considerably more information in this magazine I could quote, but this one from page 36 nails the real issue 13) “It certainly appears to be a golden age for natural gas in the US, but a vital question remains, For Whom?” The answer is given, 14) “New US natural gas supplies are playing a key role in this anticipated industrial renaissance, particularly for the chemical and petrochemical segments.”
Posted on: Thu, 11 Sep 2014 12:09:15 +0000