If the organic material is preserved and properly heated after burial, oil and natural gas might be produced. The presence of organic debris in black shales makes them the candidates for oil and gas generation. An oxygen-poor environment also provides the proper conditions for the formation of sulfide minerals such as pyrite, another important mineral found in most black shales. If a large amount of oxygen was present, the organic debris would all have decayed. Any oxygen that entered the environment quickly reacted with the decaying organic debris. In addition, this black color almost always implies that the shale formed from sediment deposited in an oxygen-deficient environment. Just one or two percent organic materials can impart a dark gray or black color to the rock. See the article: " What is Shale Gas?" Black and Gray ShaleĪ black color in sedimentary rocks almost always indicates the presence of organic materials. Shale gas plays: Since the late 1990s, dozens of previously unproductive black organic shales have been successfully developed into valuable gas fields. United States' needs for twenty years or more. These enormous shale reservoirs hold enough natural gas to serve all of the In Louisiana, and the Fayetteville Shale in Arkansas. The Marcellus Shale in the Appalachians, the Haynesville Shale Horizontal drilling and hydraulic fracturing revolutionized drilling technology and paved the way for developing several giant natural gas fields. This method is known as " horizontal drilling." Zone" through the reservoir rock (see illustration). This produced a well with a very long "pay To drill horizontally through the shale rock unit. This technique is knownĪs " hydraulic fracturing" or "hydrofracing."ĭrillers also learned how to drill down to the level of the shale and turn the well 90 degrees These fractures liberated some of the gasįrom the pore spaces and allowed that gas to flow to the well. Pressure that was high enough to fracture the shale. That they could increase the permeability of the shale by pumping water down the well under That the gas has difficulty moving through the shale and into the well. Producing gas from the Barnett Shale was a challenge. The Barnett Shale of Texas was the first major natural gas field developed in a shale reservoir rock. Some of the largest natural gas deposits in the world. This discovery was significant because it unlocked Oil and natural gas that is trapped within the tiny pore spaces of shale. In the late 1990s, natural gas drilling companies developed new methods for liberating
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