Well fluid

In the oil field industry fluids such as well fluids, completion fluids and stimulation fluids [1,2,3] are used. It would be meaningful to know about these fluids and their corrosive characteristics since they have an adverse effect on rubber components such as packings, gaskets and seals exposed to such environment. The details of these fluids are given below. 

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Gas is sometimes produced at very high pressures which have to be reduced for efficient processing and to reduce the weight and cost of the process facilities. The first pressure reduction is normally made across a choke before the well fluid enters the primary oil / gas separator. 

Orkoulas G and Panagiotopoulos A Z 1999 Phase behavior of the restricted primitive model and square-well fluids from Monte Carlo simulations in the grand canonical ensemble J. Chem. Phys. 110 1581... 

Condensable Hquids also are recovered from high pressure gas reservoirs by retrograde condensation. In this process, the high pressure fluid from the reservoir produces a Hquid phase on isothermal expansion. As the pressure decreases isotherm ally the quantity of the Hquid phase increases to a maximum and then decreases to disappearance. In the production of natural gas Hquids from these high pressure wells, the well fluids are expanded to produce the optimum amount of Hquid. The Hquid phase then is separated from the gas for further processing. The gas phase is used as a raw material for one of the other recovery processes, as fuel, or is recompressed and returned to the formation. 

Figure 6-5 shows a stabilizer with reflux. The well fluid is heated with the bottoms product and injected into the tower, below the top, where the temperature in the tower is equal to the temperature of the feed. This minimizes the amount of flashing. In the tower, the action is the same as in a cold-feed stabilizer or any other distillation tower. As the liquid falls... 

Since the results for thermodynamics from the Yukawa potential, with A = 1.8, are similar to the results of the LJ potential, it is quite possible that the DHH closure may be applicable to the Yukawa potential. With A = 1.5, the thermodynamics of the square well fluid are also similar. Here, too, the DHH closure may be useful. However, the DHH closure has not been applied to either of these potentials. 

It has been shown that sulfidogenic bacteria injected into a reservoir with floodwater may survive higher temperatures in the formation and can be recovered from producing well fluids [1546]. These organisms may colonize cooler zones and sustain growth by degrading fatty acids in formation waters. 

The common method of treating rod-pumped wells is to periodically batch inhibitor into them. The treatment period for a given well is selected using empirical rules based on well production volumes. A successful and economic corrosion inhibition program must carefully control the inhibitor concentration in the well fluids. Environmental aspects and efficacious inhibitor usage necessitate the measurement of very low corrosion inhibitor concentrations. Inhibitor concentrations as low as one part per million are significant, thus... 

Furthermore, an a,P-ethylenically unsaturated aldehyde together with organic amines will form intermediate products, which are further reacted with a carboxylic acid, an organic halide, or an epoxide-containing compound [ 1760]. The final products are suitable corrosion inhibitors for preventing corrosion of steel in contact with corrosive brine and oil and gas well fluids. 

Fatty Acid Esters. Defoamers that are more environmentally acceptable than convential products are based on fatty acid esters of hydroxy alcohols, such as sorbitan monooleate [1908] or sorbitan monolaurate in combination with diethylene glycol monobutyl ether as a cosolvent [451]. These defoamer compositions are as effective as conventional materials, for example, those based on acetylenic alcohols are less toxic, especially to marine organisms, and are readily biodegradable. The defoamer compositions are used in water-based hydrocarbon well fluids during oil/gas well drilling, completion, and workover, especially in marine conditions. 

J. F. Argillier, A. Audibert, P. Marchand, A. Demoulin, and M. Janssen. Lubricating composition including an ester-use of the composition and well fluid including the composition. Patent US 5618780,1997. 

A. Audibert-Hayet, J. F. Argillier, and L. Rousseau. Filtrate reducing additive and well fluid (additif reducteur de filtrat et fluide de puits). Patent WO 9859014,1998. 

B. D. Burts, Jr. Well fluid additive, well fluid made therefrom, method of treating a well fluid, method of circulating a well fluid. Patent US 6323158,2001. 

D. E. Clark and W. M. Dye. Environmentally safe lubricated well fluid method of making a well fluid and method of drilling. Patent US 5658860, 1997. 

M. Jarrett. Nonionic alkanolamides as shale stabilizing surfactants for aqueous well fluids. Patent WO 9632455, 1996. 

F. Montgomery, S. Montgomery, and P. Stephens. Method of controlling porosity of well fluid blocking layers and corresponding acid soluble mineral fiber well facing product. Patent US 5222558, 1993. 

D. S. Treybig and R. G. Martinez. Process for preventing corrosion of a metal in contact with a well fluid. Patent US 4740320, 1988. 

A Unique Source of Potassium for Drilling and Other Well Fluids... 

Since the invention of rotary rigs, used for drilling oil and gas wells, scientists have been searching for fluids that will both facilitate the drilling process and provide maximum productivity once the well is completed. There are two prime requisites for all well fluids. These are ... 

The most sensitive test for identifying damage characteristic of a well fluid involves flowing the well fluid through a reservoir core. For fluids containing particulates, it is necessary to test both the whole fluid and the filtrate... 

Clay minerals, inevitably present in a petroleum formation, are sensitive to the type and concentration of ions contained in the well fluid filtrate lost to the reservoir. This sensitivity is demonstrated by a reduction in the permeability caused by the well fluid filtrate flowing through the core under investigation. 

The results, shown in Table II, quantify the adverse effect of common well fluid ions on permeability. Especially relevant are the data indicating that even calcium chloride/calcium bromide fluids cause some permeability reduction, although the cause of the adverse interaction is obscure. 

Table II. Formation Damage Effected by Clear Well Fluids...

Figure 1. Composition and Concentration Effects of Potassium Based Clear Well Fluids on Core Permeabilities.

Time, Minutes Well Fluid Properties Disintegration State of Volclay Tablet Conventional Tetrapotassium Pyrophosphate ... 

Not only should well fluids be compatible with reservoir fluids and minerals, but they must also be stable at surface conditions. One disadvantage of conventional halide fluids is their tendency to crystallize at ambient temperatures. Solutions containing varing amounts of TKPP were exposed to constant temperatures as low as -76°F (-60°C) for a period of 30 hours. No crystallization was observed at any temperature above 36°F (2°C) even at concentrations as high as 60% by weight. At low fluid densities, less than 11.7 ppg, there is no evidence of TKPP crystallization even at temperatures as low as 30°F(-1°C), the freezing point of most fresh water drilling fluids. 

One property of drilling fluids that has received only minimal attention in the past is corrosiveness imparted by various additives. Additives improve the requisite properties of well fluid substantially and, hence, increase in corrosiveness is usually ignored. 

Paralleling the corrosion problem is one involving compatibility of any well fluid with nonmetallic materials used in well completion apparatus. All injection wells and many producing wells are equipped with packers to isolate the casing annulus from the high temperature, pressure, and salinity characteristic of the petroleum reservoir environment. Conventional packers, as well as other well tools, utilize elastomeric materials to mechanically seal appropriate locations. 

An example of some of the newer regulations is the restriction against the use of the popular mud dispersant, chrome lignosulfonate. It is expected that this regulation is merely the initial step toward ruling out the use of all heavy metal salts commonly employed in the formulation of well fluids because of their toxicity to aquatic life and humans. This means that the use of zinc and lead, in addition to chromium, may not be allowed in the future. At least one major oil company has already taken steps in this direction by ruling out the use of heavy metal salts in any well fluid in their worldwide operations. 

Solutions of TKPP have been shown to have unique and advantageous properties for use in formulating a wide variety of well fluids. Its reasonable cost, worldwide availability, and nontoxic properties make it a preferred additive for use in many petroleum applications. It has been shown to be a most effective salt with respect to inhibiting hydration and swelling of clay minerals commonly encountered in drilling operations and/or reservoirs. Avoiding clay problems is the major impetus for the incorporation of potassium ions in well fluids, and the use of TKPP provides advantages over and above those available from other potassium salts. 

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