Shale formation

Burgess Shale, fossil formation containing remarkably detailed traces of soft-bodied biota of the Middle Cambrian Epoch (520 to 512 million years ago). Collected from a fossil bed in the Burgess Pass of the Canadian Rockies, the Burgess Shale is one of the best preserved and most important fossil formations in the world. Since it was discovered ...

Commercial grades of oil shale, as determined by their yield of shale oil, ranges from about 100 to 200 liters per metric ton (l/t) of rock. The U.S. Geological Survey has used a lower limit of about 40 l/t for classification of Federal oil-shale lands. Others have suggested a limit as low as 25 l/t. Shale, any of a group of fine-grained, laminated sedimentary rocks consisting of silt- and clay-sized particles. Shale is the most abundant of the sedimentary rocks, accounting for roughly 70 percent of this rock type in the crust of the Earth. Shales are often found with layers of sandstone or.The Bowland Shale Formation is anomalously rich in selenium (Se) at levels an order of magnitude greater than other black shales. The Mam Tor landslide, ...Oct 31, 2013 · The formation’s thickness ranges from about 500 ft on the eastern side and narrows to 200 ft on the western side. The percentage of total organic carbon, an important measure of a shale play’s productive potential (Table 3), in the Cline is relatively high compared with other formations and ranges anywhere from 2% to 7.5%. The shale’s ... The shale formation rock used in this study is from shale oil fields of the Songliao Basin (Northeast China), which is characterized by high organic matter content and rich minerals [34]. Considering that the large modulus of shale and the small diameter (∼10 mm) of the sample tube of the physical adsorption apparatus (standard instrument ...The Basics: Glass Formation - Glass formation is a simple process using silica, soda, lime and heat. Learn about glass formation and why you can only see through some objects. Advertisement Before we learn about the transparent armor of tom...The undivided sandstone body is called Pictured Cliffs because 1) of the long history of usage of that name, 2) it represents closing stages of marine deposition in the basin, 3) it is separated from Mesaverde group of the subsurface, and 4) it intertongues with Lewis shale and with Fruitland formation. Is of Late Cretaceous age.

The formation of schist is often associated with regional metamorphism, ... The original parent rock (or protolith) of mica schist is shale. Phyllite could also be considered the parent rock as mica schist is a more highly metamorphosed phyllite. References. Bonewitz, R. (2012).shale gas, natural gas obtained from sheetlike formations of shale, frequently at depths exceeding 1,500 metres (5,000 feet). Shales are fine-grained …The Spence Shale Member of the Langston Formation is a Cambrian (Miaolingian: Wuliuan) Lagerstätte in northeastern Utah and southeastern Idaho. It is older than the more well-known Wheeler and Marjum Lagerstätten from western Utah, and the Burgess Shale from Canada.Shale gas is a key source of onshore domestic energy for the United States and production of this resource is increasing rapidly. Development and extraction of shale gas requires hydraulic fracturing, which entails horizontal drilling, perforation of steel casing and cement grout using explosive charges, and expansion of fractures using fluids under high pressure.Tight gas is natural gas trapped within a rock with extremely low permeability —typically limestone or sandstone. This is not to be confused with shale gas, which is natural gas trapped within shale formations. [1] Tight gas is considered to be an unconventional source of natural gas because it requires significant hydraulic fracturing —a ...

Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al 2 Si 2 O 5 ( OH) 4) and tiny fragments ( silt -sized particles) of other minerals, especially quartz and calcite. [1]Shale is the dominant rock in the sedimentary record. It is also the subject of increased interest because of the growing contribution of shale oil and gas to energy supplies, as well as the potential use of shale formations for carbon dioxide sequestration and nuclear waste storage.The Green River formation, an oil-shale formation in Colorado, Utah, and Wyoming, is a potentially valuable source of synthetic crude oil. In eastern Germany and Poland the Kupferschiefer, a bituminous shale, is mined for copper, lead, and zinc. …addition, the large and rich Green River Formation (GRF) in the western United States has ...Heliobatis radians (stingray), Green River Formation, Fossil Butte National Monument.. The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah.The sediments are deposited in very fine layers, a …Commercial grades of oil shale, as determined by their yield of shale oil, ranges from about 100 to 200 liters per metric ton (l/t) of rock. The U.S. Geological Survey has used a lower limit of about 40 l/t for classification of Federal oil-shale lands. Others have suggested a limit as low as 25 l/t. 5 Feb 2013 ... It was formed from mud silt, clay, and organic matter. Shale gas is natural gas trapped within tiny pore spaces in shale formations. It is a ...

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The Marcellus Shale is a thick “blanket” formation that covers 95,000 square miles (61 million acres) across the Appalachian Basin.The case study is the shale formation in the Dingshan area, located in the Qijiang District of Chongqing, Southwest China, about 150 km away from Jiaoshiba Block of Fuling shale gas field. Figure 1 shows the location of the Dingshan area and the cross-section through Dingshan wells (Liu et al., 2017a; Hu et al., 2019). The NE-trending ...While the development of unconventional formations started in the Barnett Shale in the early 2000s with vertical wells, the application of horizontal drilling and hydraulic fracturing technologies began in 2003 [].These technologies unlocked the potential of shale formations, enabling operators to extend knowledge gathered from Barnett’s …Operators of wells permitted to produce from the Marcellus Shale formation are required to submit a production, waste and well status report to DEP semi-annually on or before Feb. 15 and Aug. 15 of each year. The report due on Feb. 15 shall include all information for the first time period from July 1 through Dec. 31 of the preceding year.

The presence of weak anisotropic shales within the sedimentary sequence can be shown to be an important control on toppling instability. The location of the shale formations whether at the toe, mid slope or near the slope crest will influence the failure mechanism and is the subject of ongoing research.1 Formation. 1.1 Formation. Shale forms when very fine-grained clay particles are deposited in water which settle at the bottom of water bodies. They are later compacted hence forming shale. 1.2 Composition. 1.2.1 Mineral Content. Albite, Biotite, Calcite, Chert, Chlorite, Dolomite, Hematite, Micas, Muscovite or Illite, Pyrite, Quartz, Silica ...According to the US Energy Information Administration (EIA) in 2011, the 1,750-square-mile (4,500 km 2) Monterey Shale Formation contained more than half of the United States's total estimated technically recoverable shale oil (tight oil contained in shale, as distinct from oil shale) resource, about 15.4 billion barrels (2.45 × 10 ^ 9 m 3). Nov 28, 2022 · Shale Formation. Shales are usually deposited in slow-moving water, and their reserves are often found in lakes, lagoonal deposits, river deltas, floodplains, and offshore water resources below the wave base. The fine and small particles that compose shale remain suspended in the water body for a long, and the larger particles settle at the bottom. Shale forms via compaction from particles in slow or quiet water, such as river deltas, lakes, swamps, or the ocean floor. Heavier particles sink and form sandstone and limestone, while clay and fine silt remain suspended in water. Over time, compressed sandstone and limestone become shale.Differential sticking occurs in an open hole when any part of the pipe becomes embedded in the mud cake. When this happens, sticking can result because the pressure exerted by the mud column is greater than the pressure of the formation fluids on the embedded section (Figure 5-7).In permeable formations, mud filtrate will flow from the well into the …From Higley, 2014 [3] The STACK (Sooner Trend, Anadarko Basin, Canadian and Kingfisher Counties) play of northern Oklahoma has generated an amount of interest in the past few years due to its large amount of potential oil and gas reserves. The STACK was first drilled by Newfield exploration in 2011 with its first wildcat well and announced ...Lacustrine Roseneath and Murteree shale formations showed good to excellent Kerogen quality of Type III and therefore imply late oil – dry gas generation potential. The TOC varied significantly, ranging from 0.81% to 5.36% in Roseneath shale (0.9–1.74 R o %) and from 0.5% to 6.69% in Murteree shale (1–2.7 R o %).2 Agu 2020 ... Shale consists of at least 30 percent clay, with varying amounts of quartz, feldspar, carbonates, iron oxides, and organic matter. Oil shale or ...Thus shales are considered as source rock as well as reservoir rock and seal too in terms of unconventional shale gas reservoirs. These shales have variability ...ADVERTISEMENT What is Shale? Shale is a fine-grained sedimentary rock that forms from the compaction of silt and clay-size mineral particles that we commonly call "mud." This composition places shale in a category of sedimentary rocks known as " mudstones ." Shale is distinguished from other mudstones because it is fissile and laminated.Dec 1, 2022 · For example, Eze-Aku Shale is similar to Barnett Shale, Horn River Shale, Niobrara Shale Formation, and Chattanooga/Woodford in silica-richness, whilst showing a similar volume of calcite and relatively lesser amounts of clay minerals than the Eagle Ford Shale (Green River) and Haynesville (Fig. 7 and Table 6). Correlation parameters vary ...

According to the US Energy Information Administration (EIA) in 2011, the 1,750-square-mile (4,500 km 2) Monterey Shale Formation contained more than half of the United States's total estimated technically recoverable shale oil (tight oil contained in shale, as distinct from oil shale) resource, about 15.4 billion barrels (2.45 × 10 ^ 9 m 3).

Materials. Shale blocks were obtained from an outcrop of Longmaxi Formation in Yanzi Village, Changning County, Yibin City, Sichuan province. The area is located in the west of Hubei and Chongqing ...The formation’s thickness ranges from about 500 ft on the eastern side and narrows to 200 ft on the western side. The percentage of total organic carbon, an important measure of a shale play’s productive potential (Table 3), in the Cline is relatively high compared with other formations and ranges anywhere from 2% to 7.5%. The shale’s ...According to the US Energy Information Administration (EIA) in 2011, the 1,750-square-mile (4,500 km 2) Monterey Shale Formation contained more than half of the United States's total estimated technically recoverable shale oil (tight oil contained in shale, as distinct from oil shale) resource, about 15.4 billion barrels (2.45 × 10 ^ 9 m 3).The hard and brittle shale formation is prone to collapse and instability, and the penetration of drilling fluid along the bedding reduces the mechanical properties of rock near the borehole wall, resulting in serious downhole accidents. Therefore, in this paper, the geomechanical parameters of the reservoir in the Longmaxi formation of Jiaoshiba were determined by field hydraulic fracturing ...This study aims to investigate mineralogy, depositional environment and rock mechanical properties of Cambay Shale Formation in Jambusar-Broach block of South Cambay Basin, India, by an integrated approach of combining wireline logs and laboratory studies. The study involves the analysis of spectral gamma ray (SGR) logs and laboratory studies of core samples using X-ray diffraction (XRD), thin ...Formation of Shale Shale, like all sedimentary rocks, forms as a result of the compaction and cementation of materials that have weathered and eroded off of other, pre-existing rocks. These...Oct 19, 2023 · Oil shale is a sedimentary rock. As it reaches its oil window, oil shale releases a liquid known as shale oil. Oil shale is the rock from which shale oil is extracted. Shale oil is similar to petroleum, and can be refined into many different substances, including diesel fuel, gasoline, and liquid petroleum gas ( LPG ). Siltstone. Siltstone is a clastic sedimentary rock that formed from grains whose sized between that of sandstone and mudstone. It can found different environmental conditions different color and textures. Siltstone generally are red and gray color with flat bedding planes. Darker colored siltstone have plant fossils and other carbon-rich matter.

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This video explains the technology of fracking using the example of the Iverson oil well, which drills into the Bakken shale formation near the U.S. city of Williston, North Dakota. Fast Fact. One of the first places hydraulic fracturing technology was used was the Barnett shale formation in northern Texas.The shale rock meets the two requirements. Therefore, osmosis diffusion cannot be ignored for the imbibition in the shale gas formation. Osmotic effect in the shale rock causes a non-linear relationship between imbibition mass and square root of time. This indicates that the traditional method, based on linear relationship, is not appropriate ...This vertical variability is associated with the diversity of the processes and conditions that are involved in shale rock formation. At the rock formation stage, organic matter content is controled on three processes: production, destruction and dispersion. The intensity of particular processes vary depending on the place of deposition. This group of fossils takes its name from the Burgess Shale rock formation, named by Walcott after nearby Mount Burgess in the Canadian Rockies. The ...Deposition began about 75 million years ago with the formation of the Pierre Shale, the base of the geologic formations in the park. Deposition ended about 28 million years ago with the Sharps Formation, the uppermost unit of Badlands stratigraphy. Erosion is the process of rocks gradually wearing away. The Badlands began eroding about …Oct 1, 2020 · Section snippets Field observations. Field production history of a horizontal well in the Marcellus shale area is shown in Fig. 1. Clearly, the gas production was significantly increased, and the water production rate was reduced after shut-in for six months (Cheng, 2012). As recently as 2002, the United States Geological Survey in its Assessment of Undiscovered Oil and Gas Resources of the Appalachian Basin Province, calculated that the Marcellus Shale contained an estimated undiscovered resource of about 1.9 trillion cubic feet of gas. [1]Formation of Shale Shale, like all sedimentary rocks, forms as a result of the compaction and cementation of materials that have weathered and eroded off of other, pre-existing rocks. These...Shale is the dominant rock in the sedimentary record. It is also the subject of increased interest because of the growing contribution of shale oil and gas to energy supplies, as well as the potential use of shale formations for carbon dioxide sequestration and nuclear waste storage.Gamma ray (GR) logs measure the natural radioactivity in formations and can be used for identifying lithologies and for correlating zones. Shale-free sandstones and carbonates have low concentrations of radioactive material and give low gamma ray readings. As shale content increases, the gamma ray log response increases because …From Higley, 2014 [3] The STACK (Sooner Trend, Anadarko Basin, Canadian and Kingfisher Counties) play of northern Oklahoma has generated an amount of interest in the past few years due to its large amount of potential oil and gas reserves. The STACK was first drilled by Newfield exploration in 2011 with its first wildcat well and announced ...The way shaliness affects a log reading depends on the amount of shale and its physical properties. It may also depend on the way the shale is distributed in the formation. Shaly material can be distributed in the formation in three ways: Shale can exist in the form of laminae between which are layers of sand. ….

The adsorption isotherm and flow mechanisms in shale matrix are assumed to be pressure-dependent for a certain shale sample, so the model for gas flow in shale formation is nonlinear. The diffusivity equation is widely used to describe single-phase flow in porous media under isothermal condition (Dake, 1978) (1) ∇ ⋅ (ρ k μ ∇ p) − ∂ ...ADVERTISEMENT What is Shale? Shale is a fine-grained sedimentary rock that forms from the compaction of silt and clay-size mineral particles that we commonly call "mud." This composition places shale in a category of sedimentary rocks known as " mudstones ." Shale is distinguished from other mudstones because it is fissile and laminated.Summary: Lewis shale. A series of more or less sandy shales and clays, of gray or drab color, very similar in character to Mancos shale. Includes, in varying abundance, thin calcareous lenses or concretions of impure limestone.The oil recovery in shale oil reservoirs is less than 10% ( Sheng, 2015a ), or 3-6%, according to the EIA 2013 report ( US DOE, 2013 ). The oil recovery in tight formations is also low. The gas recovery is 15-25% (Kuuskraa, 2013). A large percentage of the oil remains unrecovered without enhanced oil recovery (EOR) methods.Jan 3, 2023 · Current research on the variation in shale gas adsorption with formation depth primarily focuses on modeling using a combination of experimental data and the corresponding adsorption theory, such as the Langmuir equation, 3,5–7 supercritical Dubinin–Radushkevich (SDR) equation, 8 and Polanyi adsorption potential, 9 to develop a model for ... Oil shale is a type of sedimentary rock that is rich in kerogen. Kerogen is a part of rock that breaks down and releases hydrocarbons when heated. Hydrocarbons are substances made entirely of hydrogen and carbon. Petroleum and natural gas are probably the most familiar . hydrocarbons.The hydrocarbons in oil shale can be used as an …Oct 31, 2013 · The formation’s thickness ranges from about 500 ft on the eastern side and narrows to 200 ft on the western side. The percentage of total organic carbon, an important measure of a shale play’s productive potential (Table 3), in the Cline is relatively high compared with other formations and ranges anywhere from 2% to 7.5%. The shale’s ... Akata Formation. The Akata Formation is Paleocene in age. It is composed of thick shales, turbidite sands, and small amounts of silt and clay. The clay content resulted in it being a ductile shale formation which was squeezed into shale diapirs in the basin. The Akata Formation formed during lowstands in relative sea level and anoxic conditions.The Niobrara Shale is a shale rock formation located in Northeast Colorado, Northwest Kansas, Southwest Nebraska, and Southeast Wyoming. Oil as well as natural gas can be found deep below the earth's surface at depths of 3,000 - 14,000 feet. Fracking is used to extract these natural resources. Shale formation, The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico.. The Pierre Shale was described by Meek and Hayden in 1862 in the Proceedings of the Academy of Sciences (Philadelphia). They described it as a dark-gray shale, …, The Eagle Ford Shale is a hydrocarbon-producing geological formation of significant importance due to its capability of producing both natural gas and also more oil than other traditional shale plays. The shale play trends across Texas from the Mexican border into East Texas, roughly 50 miles wide and 400 miles long with an average thickness of ... , The organic-rich, thermally mature black shale in the Whitehill Formation of the lower Ecca Group is persistent in composition and thickness throughout the western part of the Karoo basin and may be the best prospect for a South African gas shale (USEIA, 2013)., DFIT analysis is critical and subjected to the interpreter’s understanding of the process and the formation properties. Hence, the applications of machine learning in fracture diagnostics and DFIT analysis were discussed. ... and S. Kalra, “Estimation of hydraulic fracture volume utilizing partitioning chemical tracer in shale gas formation ..., The formation of schist is often associated with regional metamorphism, ... The original parent rock (or protolith) of mica schist is shale. Phyllite could also be considered the parent rock as mica schist is a more highly metamorphosed phyllite. References. Bonewitz, R. (2012)., In summary, the fluid flow in shale formation is controlled both by the pore size and by the properties of pore walls (surfaces). Due to the larger Vt, V2, V3, and smaller surface …, Shales are most often used in geologic storage as a confining zone or caprock though recent investigations have shown potential for select shale formations to be used for CO 2 storage. Atlas V presents a map of these potential future storage opportunities, but provides no CO 2 storage resource values for organic-rich shale basins., Between the shale deposit and the floor of an aquifer (which is normally found no more than a few hundred metres below the surface) are numerous layers of rock that would prevent the infiltration of gas and …, Current research on the variation in shale gas adsorption with formation depth primarily focuses on modeling using a combination of experimental data and the corresponding adsorption theory, such as the Langmuir equation, 3,5–7 supercritical Dubinin–Radushkevich (SDR) equation, 8 and Polanyi adsorption potential, 9 to develop a model for ..., Shale forms via compaction from particles in slow or quiet water, such as river deltas, lakes, swamps, or the ocean floor. Heavier particles sink and form sandstone and limestone, while clay and fine silt remain suspended in water. Over time, compressed sandstone and limestone become shale., Apr 1, 2021 · Moreover, increasing the pore pressure in the shale formation and decreasing effective stress cause the shale to swell, reducing wellbore wall stability (Zoback, 2010). Furthermore, using drilling fluid with high salinity may cause the pore fluid to flow out of the formation, causing decreased pore pressure and resulting in the rapid formation ... , The Basics: Glass Formation - Glass formation is a simple process using silica, soda, lime and heat. Learn about glass formation and why you can only see through some objects. Advertisement Before we learn about the transparent armor of tom..., Current research on the variation in shale gas adsorption with formation depth primarily focuses on modeling using a combination of experimental data and the corresponding adsorption theory, such as the Langmuir equation, 3,5–7 supercritical Dubinin–Radushkevich (SDR) equation, 8 and Polanyi adsorption potential, 9 to develop a model for ..., The input parameters for the model were Q, ROP, SPP and RS. The ANN model predicted the formation pressure gradient with high R of 0.981 and 0.973 for training and testing respectively. Moreover ..., Differential sticking occurs in an open hole when any part of the pipe becomes embedded in the mud cake. When this happens, sticking can result because the pressure exerted by the mud column is greater than the pressure of the formation fluids on the embedded section (Figure 5-7).In permeable formations, mud filtrate will flow from the well into the …, The hard and brittle shale formation is prone to collapse and instability, and the penetration of drilling fluid along the bedding reduces the mechanical properties of rock near the borehole wall, resulting in serious downhole accidents. Therefore, in this paper, the geomechanical parameters of the reservoir in the Longmaxi formation of Jiaoshiba were determined by field hydraulic fracturing ..., Burgess Shale, fossil formation containing remarkably detailed traces of soft-bodied biota of the Middle Cambrian Epoch (520 to 512 million years ago). Collected from a fossil bed in the Burgess Pass of the Canadian Rockies, the Burgess Shale is one of the best preserved and most important fossil formations in the world. Since it was discovered ..., Almost 3.351 billion barrels of oil and 20.81 trillion cubic feet of natural gas are reserved in Eagle-ford shale formation (Speight, 2019). The Wolf-camp shale is a Wolfcampian-age organic rich formation that stretched out in strata below the earth’s surface covering the 3 sub basins of Permian basin, ..., n Shale instability. In this example, Pierre shale has been exposed to a mud comprising fresh water and bentonite gel. Because this fluid contains no inhibitors, water has entered the shale causing it to swell and weakening the formation. Continuous flow of mud has eroded the borehole leaving an enlarged hole that would be hard to log and complete., The Burgess Shale formation, in British Columbia, is the world's most famous fossil deposit. Its fossils include numerous soft body part fossils, which are highly uncommon; usually the soft parts ..., The Niobrara Shale is a shale rock formation located in Northeast Colorado, Northwest Kansas, Southwest Nebraska, and Southeast Wyoming. Oil as well as natural gas can be found deep below the earth's surface at depths of 3,000 - 14,000 feet. Fracking is used to extract these natural resources. , Shale forms via compaction from particles in slow or quiet water, such as river deltas, lakes, swamps, or the ocean floor. Heavier particles sink and form sandstone and limestone, while clay and fine silt remain suspended in water. Over time, compressed sandstone and limestone become shale., Horizontal drilling is an effective way to increase the capacity of shale formations. However, in the horizontal shale drilling, the major difficulties are the problems of the wellbore stability and the well collapse prevention. In this paper, a jointed-material model is adopted to simulate the strength anisotropy and the permeability anisotropy of the bedding shale. The model is used to ..., Shale formation is fine partiles that can remain suspended in water long afrer the larger particles of sand have deposited. Shales are typically deposited in very slow moving water and are often found in lakes and lagoonal deposits, in river deltas, on floodplains and offshore from beach sands., The Basics: Glass Formation - Glass formation is a simple process using silica, soda, lime and heat. Learn about glass formation and why you can only see through some objects. Advertisement Before we learn about the transparent armor of tom..., Shale gas, natural gas obtained from sheetlike formations of shale, frequently at depths exceeding 1,500 metres (5,000 feet). Shales are fine-grained sedimentary rocks consisting of silt- and clay-sized particles that were laid down hundreds of millions of years ago as organic-rich mud at the, Viscoelastic creep of Eagle Ford shale: investigating fluid-shale interaction; B. Bennion et al. Remediation of water and hydrocarbon phase trapping problems in low permeability gas reservoirs; M. Blauch et al. Marcellus shale post-frac flowback waters-where is the salt coming from and what are the implications? E. Brownscombe et al., Shale is a tightly packed sedimentary rock. The shale is very porous, but it is not very permeable. This allows the shale to hold a lot of oil/natural gas but makes it difficult to remove those energy sources. Recent technologies have made it possible to extract the oil and natural gas trapped in deep shale formations., Understanding shale’s growth drivers. Shales are organic mudstones consisting of silt and clay that have a complex and heterogenous mineralogic accumulation/thickness (formation), require custom engineering designs and completion stimulations (E&C), and are strongly guided by many above-surface planning and efficiency measures (P&E)., A total of six different shale samples used in this study were collected from various shale wells within the Lower Silurian Longmaxi Formation in the Sichuan Basin, China, which ranges from 2,517. ..., This vertical variability is associated with the diversity of the processes and conditions that are involved in shale rock formation. At the rock formation stage, organic matter content is controled on three processes: production, destruction and dispersion. The intensity of particular processes vary depending on the place of deposition., Chevron said Monday that the acquisition of Hess adds a major oil field in Guyana as well as shale properties in the Bakken Formation in North Dakota. ... on …, The problem of wellbore stability in hard brittle shale formations is an important research topic in the exploration and development of shale gas. To solve this problem, the adaptability of the plugging drilling fluid to wellbore stability in the hard brittle shale of the tertiary Dongying formation in Bohai Bay Basin, China, was investigated. The results show that the clay content of the hard ...