Saltwater

Health nd Safety Factors. Isophorone is considered moderately toxic by ingestion and skin contact. Some rat tumor formation evidence has been found (264), but no demonstration as a human carcinogen has been proven. Isophorone is considered an Environmental Protection Agency (EPA) priority pollutant, and has a permissible acute toxicity concentration of 117, 000 ///L to protect freshwater aquatic life, 12, 900 ///L to protect saltwater aquatic life, and 5, 200 ///L to protect human life (265). Isophorone is mildly toxic by inhalation, but because of its low volatiUty it is not a serious vapor hazard. 

Fig. 14. Effects of iron (—), nickel (-), and copper (...) contaminant levels on the saltwater corrosion performance of magnesium AZ91 alloy containing...

Under mechanical and environmental stresses, composites are dimensionally stable. They maintain their shape and functionaHty, a critical requirement in such appHcations as dish antennas, constmction girders, and in appHance and business machines. Color and surface texture can often be molded into an FRP product for long lasting, low maintenance permanent surface appearance. Boats are a good example. The surface color is molded in and requires minimum maintenance, an advantage in saltwater environments. 

Pipes, valves, fittings, and almost all other components of small equipment are now available in plastic or ceramics, which do not corrode in salt water and are less expensive than the metals now used. Synthetic detergents are now available for use with seawater, although a final rinse with freshwater may be desired. Saltwater sewage can be treated successfully. Dual water systems using freshwater and seawater are already in use on ships and in many island resort hotels. Many of these also have seawater systems for fire fighting. This trend will grow. 

A notable example of controlled water reuse was utilization of secondary sewage effluent from the Back River Wastewater Treatment Plant in Baltimore by the Sparrows Point Works of Bethlehem Steel (6). The Sparrows Point plant was suppHed primarily by weUs located near the brackish waters of Baltimore harbor. Increased draft on the weUs had led to saltwater intmsion. Water with chloride concentration as high as 10 mg/L is unsuitable for many steelmaking operations. Rollers, for example, are pitted by such waters. However, treated effluent from the Back River Plant can be used for some operations, such as coke quenching, and >4 x 10 m /d (10 gal/d) are piped 13 km to Sparrows Point. This arrangement has proved economical to both parties for >40 yr. 

Calcium chloride is found in the marine environment. The elemental composition of seawater is 400 ppm calcium, 18,900 ppm chlorine, and many organisms and aquatic species are tolerant of these concentrations. Toxicity arises either from the invasion of freshwater in otherwise saltwater environments or possible toxic doses of calcium chloride from spills, surface mnoff, or underground percolation into typically freshwater streams or aquifers. Various agencies have guidelines for calcium and chloride in potable water (41). The European Economic Community (EEC) is the only agency to have a minimum specification for calcium in softened water. 

Excellent resistance to saltwater corrosion and biofouling are notable attributes of copper and its dilute alloys. High resistance to atmospheric corrosion and stress corrosion cracking, combined with high conductivity, favor use in electrical/electronic appHcations. 

A relatively small number of studies have reported on the effects of cumene on plants, fish, and other organisms. Studies of the effects of cumene on fresh and saltwater fish indicate the lowest reported toxic concentration (LC q) for fishes was 20 to 30 mg/L (18). The solubiUty of cumene is about 50 mg/L (19). Among invertebrates, the lowest reported concentration that was toxic to test organisms was 0.012 mg/L after 18 hours (20). The only available data on the effect of cumene on aquatic plants indicate that the photosynthesis of several species was inhibited at concentrations from 9 to 21 mg/L (19). 

Owing to the stability of the uranyl carbonate complex, uranium is universally present in seawater at an average concentration of ca. 3.2/rgL with a daughter/parent activity ratio U) of 1.14. " In particulate matter and bottom sediments that are roughly 1 x 10 " years old, the ratio should approach unity (secular equilibrium). The principal source of dissolved uranium to the ocean is from physicochemical weathering on the continents and subsequent transport by rivers. Potentially significant oceanic U sinks include anoxic basins, organic rich sediments, phosphorites and oceanic basalts, metalliferous sediments, carbonate sediments, and saltwater marshes. " ... 

Other natural sources, such as alkaline and saltwater lakes, are usually quite local in their effect on the environment. Sulfurous gases from hot springs also fall into this category in that the odor is extremely strong when close to the source but disappears a few kilometers away. 

If the air inlet is subjeeted to saltwater eontamination, the rotor and stator blades should be eheeked for pitting. Severe pitting near the blade roots may lead to struetural failures. The manufaeturer should be informed of severe pitting. 

The average specific gravity of minerals in the earth s crust is taken to be 2.7. The average specific gravity of saltwater is taken to be 1.07. If the average sedimentary rock porosity is assumed to be 10%, then the total theoretical maximum overburden pressure gradient (lb/fp)/ft becomes... 

Inhibited Muds—Dispersed Systems. These are water-base drilling muds that repress the hydration and dispersion of clays. There are essentially four types of inhibited muds lime muds (high pH), gypsum muds (low pH), seawater muds (unsaturated saltwater muds, low pH), and saturated saltwater muds (low pH). 

Low Solids Muds—Nondispersed Systems. These muds contain less than 3-6% solids by volume, weigh less than 9.5 Ib/gal, and may be fresh or saltwater ba se. The typical low solids systems are flocculent, minimum solids muds, beneficiated clay muds, and low solids polymer muds. Most low solids drilling fluids are composed of water with varying quantities of bentonite and a polymer. The difference among low solids systems lies in the varying actions of different polymers. 

Seawater muds or brackish water muds are saltwater muds. Saltwater muds are defined as those muds having salt (NaCl) concentrations above 10,000 ppm, or over 1%, salt the salt concentration can vary from 10,000 to 315,000 ppm (saturation). 

Seawater muds are composed of bentonite, thinner (lignosulfonate or lignosulfonate and lignite), and an organic filtration control agent. The typical formulation of a seawater mud is 3.5 Ib/bbl of alkali (2 Ib/bbl caustic soda and 1.5 Ib/bbl lime), 8 to 12 Ib/bbl of lignosulfonate, and 2 to 4 Ib/bbl of bentonite to maintain viscosity and filtration. Another approach is to use bentonite/thinner (ligno-sulfonate)/freshwater premix, and mix it with seawater that has been treated for hardness. This technique will be discussed in the saturated saltwater muds section. 

The liquid phase of saturated saltwater muds is saturated with sodium chloride. Saturated saltwater muds are most frequently used as workover fluids or for drilling salt formations. These muds prevent solution cavities in the salt formations, making it unnecessary to set casing above the salt beds. If the salt formation is too close to the surface, a saturated saltwater mud may be mixed in the surface system as the spud mud. If the salt bed is deep, freshwater mud is converted to a saturated salt water mud. 

Saturated saltwater muds can be weighted to more than 19 Ib/gal. Saturated saltwater muds conditioned with organic colloids to control filtration can be... 

A modified saturated saltwater mud is prepared with bentonite clay by a special technique. First, bentonite is hydrated in freshwater, then treated with lignosulfonate and caustic soda. This premix is then mixed with saltwater (one-part premix to three-part saltwater). The mixture builds up a satisfactory viscosity and develops filtration control. Thinning of the mud is accomplished by saltwater dilutions additional premix is required for viscosity and water loss control. 

Figure 4-120. Practical limits on solids content in saltwater mud (75,000 ppm chlorides) [26], (Courtesy Baroid Drilling Fluids, Inc.)...

Clear Brines. Brine solutions are made from formation saltwater, seawater, or bay water, as well as from prepared saltwater. They do not contain viscosifers or weighting materials. Formation water-base fluids should be treated for emulsion formation and for wettability problems. They should be checked on location to ensure that they do not form a stable emulsion with the reservoir... 

Prepared saltwater completion fluids are made of fresh surface water, with sufficient salts added to produce the proper salt concentration. Usually, the addition of 5 to 10% NaCl, 2% CaClj, or 2% KCl is considered satisfactory for clay inhibition in most formations. Sodium chloride solutions have been extensively used for many years as completion fluids these brines have densities up to 10 Ib/gal. Calcium chloride solutions may have densities up to 11.7 lb/ gal. The limitations of CaClj solutions are (1) flocculation of certain clays, causing permeability reduction, and (2) high pH (10 to 10.5) that may accelerate formation clays dispersion. In such cases, CaC12-based completion fluids should be replaced with potassium chloride solutions. Other clear brines can be formulated using various salts over wide range of densities, as shown in Figure 4-123 [28]. 

The variation is independent of the mud weight, pressure, or temperature, but is sensitive to fluids other than gas, such as oil or saltwater. Figure 4-266 shows the resistivity variations for a Til m mud. If we assume that a change of 10% can be detected, then the alarm could be given again for a free gas or oil volumetric concentration of 2 to 5%. 

The normal formation pressure gradient is the density of a column of saltwater of length Zy is expressed in psi-ft in customary units. Table 4-134 gives normal gradient values for areas around the world. Note that for freshwater or quasi-freshwater Gj = 0.433 psi/ft = 8.345 Ib/gal. 

Upon shutting in the well, the pressure builds up both on the drillpipe and casing sides. The rate of pressure buildup and time required for stabilization depend upon formation fluid type, formation properties, initial differential pressure and drilling fluid properties. In Ref. [143] technique is provided for determining the shut-in pressures if the drillpipe pressure is recorded as a function of time. Here we assume that after a relatively short time the conditions are stabilized. At this time we record the shut-in drillpipe pressure (SIDPP) and the shut-in casing pressure (SICP). A small difference between their pressures indicates liquid kick (oil, saltwater) while a large difference is evidence of gas influx. This is true for the same kick size (pit gain). 

Burst Assumed external pressure gradient of saltwater = 0.465 psi/ft and formation pore (gas) pressure gradient = 0.65 psi/ft. Gas weight is neglected. Safety factor = 1.1. 

Figure 4-452. Effect of pH on corrosion fatigue in aerated saltwater. (From Ref. [197].)...

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