Wetting crude oil

Far from a wellbore, the velocity of reservoir fluids is about one linear foot per day. Near a wellbore, the velocity can increase one-hundred fold. A static or quasi-static test such as the sessile drop (contact angle) test may not represent the dynamic behavior of the fluids in the field. The dynamic Wilhelmy device gives results which are comparable in interface velocity to the field displacement rate. The interface in the Wilhelmy test described here moved at a steady rate of 0.127 mm/sec or 36 ft/day. The wetting cycle for a hybrid-wetting crude oil system was not affected by moving at a rate less than 1 ft/day. 

Annex A8—Test Method for Dehydration of a Sample of Wet Crude Oil,... 

A8.1.1 This test method is for dehydrating a sample of wet crude oil (>0.1 % water) prior to fractional distillation. 

A8.4.1 The dehydration of a sample of wet crude oil requires apparatus such as that shown in Fig. 1 composed of A8.4.1.1 Distillation flask, with two side arms. In place of the differential pressure manometer in the second sidearm, a capillary is fitted for the passage of nitrogen into the liquid. When a sample is suspected of containing emulsified water or significant amounts of clay or sediment, or both, additional risk to glass apparatus is involved. In this case remove gross water and sediment and use a metal flask for dewatering. 

A8.6.1 Cool the charge to a temperature not lower than 0°C. Decant any bulk water which may be present. Weigh by difference to the nearest g, into a chilled distillation flask containing some pieces of glass or porcelain, a given volume of wet crude oil. 

Natural Gas Natural gas is a combustible gas that occurs in porous rock of the earth s crust and is found with or near accumulations of crude oil. It may occur alone in separate reservoirs, but more commonly it forms a gas cap entrapped between petroleum and an impervious, capping rock layer in a petroleum reservoir. Under high-pressure conditions, it is mixed with or dissolved in crude oil. Natural gas termed dry has less than 0.013 dmVm (0.1 gaLlOOO fF) of gasoline. Above this amount, it is termed wet. 

The output from oil fields, after secondary and tertiary processing [7], is considered wet oil. It consists of oil field brine, crude oil and natural gases containing a high COj content and in certain circumstances it may also contain small amounts of H2S. Wet oil can also contain solid particles from the bedrock. 

Pipelines Pipelines carrying wet gas and crude oil present a corrosion hazard and are protected accordingly by coatings and/or inhibitors. Limitations of corrosion monitoring arise from sampling, in relation to the sampling and interval, and access problems for subsea pipelines (major trunk lines). 

Most of the liquid fuels in use today are obtained from crude oil, also called petroleum, a brownish-green to black colored viscous oil found under the crust of the Earth either on shore or off shore. This oil either flows out by itself due to underground gas or hydrostatic pressure, or it is mechanically pumped out. Petroleum almost always occurs along with gas called natural gas. When the oil well contains both oil and gas it is called a wet well, and when it contains only gas it is called a dry well. 

Interpretation of NMR well logs is usually made with the assumption that the formation is water-wet such that water occupies the smaller pores and oil relaxes as the bulk fluid. Examination of crude oil, brine, rock systems show that a mixed-wet condition is more common than a water-wet condition, but the NMR interpretation may not be adversely affected [47]. Surfactants used in oil-based drilling fluids have a significant effect on wettability and the NMR response can be correlated with the Amott-Harvey wettability index [46]. These surfactants can have an effect on the estimation of the irreducible water saturation unless compensated by adjusting the T2 cut-off [48]. 

The computer interface system lends itself well to the determination of interfacial tension and contact angles using Equation 3 and the technique described by Pike and Thakkar for Wilhelmy plate type experiments (20). Contact angles for crude oil/brine systems using the dynamic Wilhelmy plate technique have been determined by this technique and all three of the wetting cycles described above have been observed in various crude oil/brine systems (21) (Teeters, D. Wilson, J. F. Andersen, M. A. Thomas, D. C. J. Colloid Interface Sci., 1988, 126, in press). The dynamic Wilhelmy plate device also addresses other aspects of wetting behavior pertinent to petroleum reservoirs. 

Some crude oils contain components which can oxidize and change wettability (12, 25) so tests on reservoir oil samples must be performed in an oxygen-free environment. Exposure to air had a marked effect on the wetting cycle of one crude oil discussed below. 

Figure 7. Wetting cycles of crude oil SS1473 tested in an open beaker. (Reproduced with permission from ref. 21. Copyright 1988 Society of Petroleum Engineers.)...

This study demonstrated two aspects of measurement of wettability of crude oils. Exposure to air can cause changes in the wetting cycle. This was not true of normal paraffins such as hexadecane, which yielded stable wetting cycles for days and weeks when exposed to air. Equilibration of the crude oil/brine/solid system also caused changes in the wetting behavior. From this study it is not clear whether the changes were due to equilibration of the oil and brine phases or the aging of the solid in the oil phase. It is likely that both affect the measurement. 

Field Desalting of Wet Crude in Kuwait by Chawla expands upon the principles describing electrostatic treating that are discussed in other papers in this section A specific oil-treating/desalting system is described. 

Production of wet crude had been a growing fiald problem ir. Kuwait. Trie need to treat wet crude was felt for quite some time. Application of right technology and installation of proper desalting facilities were needed to solve this problem. Thus It was decided to Install electrostatic desalting plants progressively in Kuwait s oil fields. By the end of 1986, Ita plants, (6 conventional (AC] and 8 dual polarity (AC/DC)2 with a total capacity of over 790,000 STB/D of treated crude have been Installed. 

All the plants have been installed in the existing gathering centres and these Installations had to conform to existing facilities and available plant area. Certain relocations and modifications of the existing facilities were done to accommodate the new plant. For gas separation from wet crude, one bank or existing two-phase gas-oil separatory has been segregated ar.d tied into the wet system. 

The skimmed oil Is collected and transferred to wet crude tank. Water from the SPI separator is discharged to induced air floatator. This unit is composed of four floatation cells. Each cell is equipped with a motor driven self-aerating rotor meonanistn. As the rotor spins, minute bubbles are generated ar.d oil and suspended solid particles attach to the gas bubbles as tney rise to the surface. Tne oil and suspended solids gather in a dense froth on the surface and are removed from the cell by skimmer paddles and collected in a scum tank. Then skum is pumped out of scum tank to the inlet of SPI separator by skum return pump. 

Wet foams in which the liquid lamellae have thicknesses on the same scale or larger than the bubble sizes. Typically in these cases the gas bubbles have spherical rather than polyhedral shape. Other synonyms include gas dispersion and kugelschaum . If the bubbles are very small and have a significant lifetime, the term microfoam is sometimes used. In petroleum production the term is used to specify crude oil that contains a small volume fraction of dispersed gas. See also Foam. 

A solution of 4-[2-(5-ethyl-2-pyridyl)ethoxy]nitrobenzene (60.0 g) in methanol (500 ml) was hydrogenated at room temperature under one atmospheric pressure in the presence of 10% Pd-C (50% wet, 6.0 g). The catalyst was removed by filtration and the filtrate was concentrated under reduced pressure. The residual oil was dissolved in acetone (500 ml)-methanol (200 ml). To the solution was added a 47% HBr aqueous solution (152 g). The mixture was cooled, to which was added dropwise a solution of NaN02 (17.3 g) in water (30 ml) at a temperature not higher than 5°C. The whole mixture was stirred at 5°C for 20 min, then methyl acrylate (112 g) was added thereto and the temperature was raised to 38°C. Cuprous oxide (2.0 g) was added to the mixture in small portions with vigorous stirring. The reaction mixture was stirred until nitrogen gas evolution ceased, and was concentrated under reduced pressure. The concentrate was made alkaline with concentrated aqueous ammonia, and extracted with ethyl acetate. The ethyl acetate layer was washed with water and dried (MgS04) The solvent was evaporated off to leave methyl 2-bromo-3- 4-[2-(5-ethyl-2-pyridyl)ethoxy]phenyl propionate as a crude oil (74.09 g, 85.7%). 

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