Water shale

Total Salinity. The salinity control of oil-base mud is very important for stabilizing water-sensitive shales and clays. Depending upon the ionic concentration of the shale waters and of the mud water phase, an osmotic flow of pure water from the weaker salt concentration (in shale) to the stronger salt concentration (in mud) will occur. This may cause a dehydration of the shale and, consequently, affect its stabilization. 

Final composition of the aqueous phase. The final compositions of the waters resulting from the three dissolution experiments have been summarized and listed together with compositions of waters from natural systems (Table VI). The experimental and natural basalt waters have very similar compositions. However, the experimental quartz monzonite water has a higher than natural K content while the shale water has higher than natural K and Na contents. The HCO3 content of each of the experimental waters is higher than the content of its natural counterpart while the oposite is true for 04. 

Estimation of Iodine when unconibined and in combination.—The minute proportion of this element, which has often to be sought in plants, bituminous and othor shales, waters, and even in the air, has taxed the inventive powers and researches of chemists for methods, of which the accuracy might he commensurate with the evident difficulty of the task undertaken. Fortunately, iodine oomports itself with a few bodies in such a characteristic way, offering indications so marked as not to be surpassed in this respoct by any other substance known. These are starch, silver, and palladium and by proper modifications in the applications of only these three bodies, the methods for the flstimation of iodine, as well when free as when combined, are not exceeded by any other class, either in their accuracy or extent. 

Problems in Analyzing Samples. The samples encountered in this study fall into three general categories geological (oil shale and spent shale), waters (process waters), and petroleum (shale oil). The chemical treatments required for these materials have been adapted from conventional methods commonly used for the analysis of similar materials. However, analysis of the oil shales has presented several problems not common to other geological materials. 

The flow of water through a semi-permeable membrane (clay, shale) from water with a small concentration of dissolved solids to water with a greater concentration is called osmosis (e.g. Bredehoeft et al., 1982 Neuzil, 1986). The osmotically-induced flow of water occurs because of a difference in vapour pressure across the membrane (Hinch, 1980). The aqueous activity will be relatively small in water with a relatively large concentration of dissolved solids, because more water molecules are bonded on the dissolved ions (Hinch, 1980). In a sandstone-shale sequence with water of equal chemical concentration, the aqueous activity of the shale water will be less than that of the sandstone-water, because water molecules are adsorped on the large mineral surfaces of the shale (Hinch, 1980). As a consequence, the water salinity differences that may exist in sandstone-shale sequences in the intermediate and deep subsystems of burial-induced groundwater flow may actually be in osmotic equilibrium. 

The basic problem of the interaction of drilling fluids with shale formations is an imbalance in the chemical potential of the water in the drilling fluid and in the shale. During the compaction of the shale, water is expelled and the clay-water ratio increases (see eq 96, for example). The presence of the exchange cations associated with the surface of the clay causes the water activity in the shale awsh to decrease as the water content decreases. The chemical potential / wsh of the water in the shale is given by... 

Gaudlip, A.W., Paugh, L.O., and Hayes, T.D. (2008). MarceUus Shale water management challenges in Pennsylvania, in Proceedings of SPE Shale Gas Production Conference, Fort Worth, TX, November 16-18, 2008. Society of Petroleum Engineers, Allen, TX. 

Marcellus Shale) water contamination from a spill of fracturing fluids Methane contamination of multiple drinking water wells methane in private wells Transferable results due to common types of impacts ... 

Water Quality. AH commercial oil shale operations require substantial quantities of water. AH product water is treated for use and operations are permitted as zero-discharge facHities. In the Unocal operation, no accidental releases of surface water have occurred during the last four years of sustained operations from 1986 to 1990. The Unocal Parachute Creek Project compliance monitoring program of ground water, surface water, and process water streams have indicated no adverse water quaHty impacts and no violations of the Colorado Department of Health standards (62). 

Solids. Proper handling and disposal techniques can obviate potential problems associated with the soHd waste-retorted shale. Retorted shale disposal and revegetation have posed no adverse environmental impacts at the Unocal Parachute Project (62). EarHer studies carried out using Paraho and Lurgi retorted shales indicated that these materials behave as low grade cements (63,64) and can be engineered and compacted into high density materials (Pig. 11) and water impervious stmctures (Table 15). 

Although numerous mud additives aid in obtaining the desired drilling fluid properties, water-based muds have three basic components water, reactive soHds, and inert soHds. The water forming the continuous phase may be fresh water, seawater, or salt water. The reactive soHds are composed of commercial clays, incorporated hydratable clays and shales from drilled formations, and polymeric materials, which may be suspended or dissolved in the water phase. SoHds, such as barite and hematite, are chemically inactive in most mud systems. Oil and synthetic muds contain, in addition, an organic Hquid as the continuous phase plus water as the discontinuous phase. 

Potassium hydroxide [1310-58-3] is occasionaHy used for alkalinity control. This is particularly tme for some polymer and lime muds where a low sodium level is desired. The potassium level of such muds is quite low but has been attributed by some to provide stabHity to water-sensitive shale formations (68,93). 

A variety of methods have been devised to stabilize shales. The most successful method uses an oil or synthetic mud that avoids direct contact between the shale and the emulsified water. However, preventing direct contact does not prevent water uptake by the shale, because the organic phase forms a semipermeable membrane on the surface of the wellbore between the emulsified water in the mud and the water in the shale. Depending on the activity of the water, it can be drawn into the shale (activity lower in the shale) or into the mud (activity higher in the shale) (95—97). This osmotic effect is favorable when water is drawn out of the shale thus the aqueous phase of the oil or synthetic mud is maintained at a low water activity by a dding a salt, either sodium chloride or more commonly, calcium chloride. The salt concentration is carried somewhat above the concentration required to balance the water activity in the shale to ensure water movement into the mud. 

High initial cost and environmental restrictions prevent use of oil and synthetic muds in many cases where shale problems are expected. It is necessary then to treat a water-base mud to minimize the destabilizing effect of the drilling fluid. Salts, polymers, and other organic materials are added to the mud to reduce the water sensitivity of the shale, shale sweUing, and weakening arising from mud contact, or the rate of water uptake by the shale. 

Addition of a salt can transform the shale by cation exchange to a less sensitive form of clay, or reduce the osmotic swelling effect by reducing the water activity in the mud below that which occurs in the shale. These effects depend on the salt concentration and the nature of the cation. Salts containing sodium, potassium, calcium, magnesium, and ammonium ions ate used to varying degrees. 

Sodium chloride has long been used as a shale stabilizer because of low cost, wide availabiUty, and its presence in many subsurface formations. The inhibitive nature of salt muds increases as the salt content increases from seawater to saturated sodium chloride. In addition to the sodium chloride consumed aimuaHy for drilling fluid, considerable quantities are incorporated while drilling salt zones. This material has been used more for minimizing washouts in salt zones than for stabilizing shales. High salt levels have found appHcation in deep water drilling (7). 

A variety of shale-protective muds are available which contain high levels of potassium ions (10). The reaction of potassium ions with clay, well known to soil scientists, results in potassium fixation and formation of a less water-sensitive clay. Potassium chloride, potassium hydroxide, potassium carbonate [584-08-7] (99), tetrapotassium pyrophosphate [7320-34-5] (100), and possibly the potassium salts of organic acids, such as potassium acetate [127-08-2] (101) and formate, have all been used as the potassium source. Potassium chloride is generally preferred because of its low cost and availabihty. 

A more recent addition to the Hst of shale protective water-base muds is a system developed around concentrated solutions of methyl glucoside [3149-68-6]. At concentration of 25% by weight and above, methyl glucoside appears to stabilize water-sensitive shales on pat with a typical oil- or synthetic-base mud (122). Eady field trials have been encouraging but much remains to be done before this material is considered a success (123). 

Sohd materials, such as gilsonite and asphalt, and partially soluble sulfonated asphalt may also be added to plug small fractures in exposed shale surfaces and thereby limit water entry into the formation (105,124). The asphalts are oxidized or treated to impart partial solubiUty. These materials may be softened by the downhole temperature, causing them to deform and squeeze into small openings exposed to the borehole. Laboratory tests designed to evaluate shale-stabilizing muds have confirmed the beneficial action of these materials (125) (see also Soil STABILIZATION). 

Oil reservoirs are layers of porous sandstone or carbonate rock, usually sedimentary. Impermeable rock layers, usually shales, and faults trap the oil in the reservoir. The oil exists in microscopic pores in rock. Various gases and water also occupy rock pores and are often in contact with the oil. These pores are intercoimected with a compHcated network of microscopic flow channels. The weight of ovedaying rock layers places these duids under pressure. When a well penetrates the rock formation, this pressure drives the duids into the wellbore. The dow channel size, wettabiUty of dow channel rock surfaces, oil viscosity, and other properties of the cmde oil determine the rate of this primary oil production. 

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