The shale revolution that started in the U.S. is starting to spread around the world. American technology has unlocked production in tight gas and oil and gas shale plays in Canada and the U.S. by using horizontal drilling and multistage hydraulic fracturing. Shale rock is formed by sedimentation of clay particles in deep waters. When the sedimentation has occurred in waters with limited circulation and lack of oxygen, the shale turns rich in organic content. Deep rifts in the seabed or locked-in seas are favorable for creating organic black shale. If the black shale has consecutively been buried by kilometers of eroded material, and thus been exposed to high temperatures and pressure for a long geologic time, the shale rocks may constitute the source in petroleum systems.
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