Coiled tubing

However, coiled tubing drilling is limited to slim holes, and the reliability of some of the drill string components such as downhole motors needs further improvement. Presently, the cost of building a new customised CTD rig limits the wider application of this emerging technology. 

New technology is applied to existing fields to enhance production. For example, horizontal development wells have been drilled in many mature fields to recover remaining oil, especially where the remaining oil is present in thin oil columns after the gas cap and/or aquifer have swept most of the oil. Lately, the advent of multi-lateral wells drilled with coiled tubing have provided a low cost option to produce remaining oil as well as low productivity reservoirs. 

Keywords production decline, economic decline, infill drilling, bypassed oil, attic/cellar oil, production potential, coiled tubing, formation damage, cross-flow, side-track, enhanced oil recovery (EOR), steam injection, in-situ combustion, water alternating gas (WAG), debottlenecking, produced water treatment, well intervention, intermittent production, satellite development, host facility, extended reach development, extended reach drilling. 

Normally acid would be allowed to soak for some time and then back-produced if possible along with the impairing products. One of the advantages of using coiled tubing is that it can be inserted against well head pressure so the well does not have to be killed a potentially damaging activity. 

Other Cell Designs. Although not used in the United States, another important cell is based on designs developed by ICl (90). Cells of this type are used by British Nuclear Fuels pic and differ from the cells shown in Figures 2 and 3 in two ways (/) the anodes used are made of the same hard, nongraphitized carbon, but are more porous and 2) the cathodes are formed from coiled tubes and provide additional cooling (91). 

For non-Newtonian (power law) fluids in coiled tubes, Mashelkar and Devarajan Trans. Inst. Chem. Eng. (London), 54, 108-114 [1976]) propose the correlation... 

Rhodes, and Scott Can. j. Chem. Eng., 47,445 53 [1969]) and Aka-gawa, Sakaguchi, and Ueda Bull JSME, 14, 564-571 [1971]). Correlations for flow patterns in downflow in vertical pipe are given by Oshinowo and Charles Can. ]. Chem. Eng., 52, 25-35 [1974]) and Barnea, Shoham, and Taitel Chem. Eng. Sci, 37, 741-744 [1982]). Use of drift flux theoiy for void fraction modeling in downflow is presented by Clark anci Flemmer Chem. Eng. Set., 39, 170-173 [1984]). Downward inclined two-phase flow data and modeling are given by Barnea, Shoham, and Taitel Chem. Eng. Set., 37, 735-740 [1982]). Data for downflow in helically coiled tubes are presented by Casper Chem. Ins. Tech., 42, 349-354 [1970]). 

Heat-transfer coefficients in clean coiled-tube evaporators for seawater are shown in Fig. 11-24 [Hillier, Proc. Jn.st. Mech. Eng. (London ), 1B(7), 295 (1953)]. The tubes were of copper. 

Description These exchangers are typically a series of stacked helical-coiled tubes connected to manifolds, then inserted into a casing or shell. They have many advantages hke spiral-plate designs, such as avoiding differential expansion problems, acceleration effects of the helical flow increasing the heat transfer coefficient, and compactness of plot area. They are typically selected because of their economical design. 

Another growing field is that of nonmetallic heat exchanger designs which typically are of the shell and tube or coiled-tubing type. The graphite units were previously discussed but numerous other materi- s are available. The materials include Teflon, PVDF, glass, ceramic, and others as the need arises. 

The shape of the coohng and warming curves in coiled-tube heat exchangers is affected by the pressure drop in both the tube and shell-sides of the heat exchanger. This is particularly important for two-phase flows of multicomponent systems. For example, an increase in pressure drop on the shellside causes boiling to occur at a higher temperature, while an increase in pressure drop on the tubeside will cause condensation to occur at a lower temperature. The net result is both a decrease in the effective temperature difference between the two streams and a requirement for additional heat transfer area to compensate for these losses. 

The effect of tube radius and coil aspect ratio on the onset of radial mixing in coiled tubes was investigated using the above equations. In Table 5, the dimensions of the coiled tubes examined are given and the curves relating (H) and (u) in Figure 8. 

Figure 8. Graphs of (H) against (u) for Different Coiled Tubes...

Almost all designs of WT boilers have multiple banks of special-purpose tubes (water walls, boiler bank, tube bundles, etc.), although a particular type of WT boiler, the coil boiler, typically has only one coiled tube. 

Coil boilers are available as fully automatic package units, typically ranging in size from 15 to 300 boiler hp (500 lb/hr-10,000 lb/hr). Most designs employ forced circulation and a single, continuous spiral, helical-wound coiled tube that hangs inside the furnace. The coil is subjected to intense heat release from a gas or oil burner. 

With regard to operational considerations, the recirculation pump pressure gauges (which measure pressure differentials and consequently indicate possible blockage in the coiled tube) require frequent calibration. Regular cleaning and good housekeeping are also required, especially within the furnace area. 

When silica levels increase, hydroxide alkalinity measurements become increasingly important to ensure maximum silica solubilization and the reduction of risk of silica deposition. This is especially so for coil boilers because, more than any other boiler type, the use of hydroxide is critical in keeping the waterside surface of the coiled tube clean and deposit free. 

The coiled-tube component of a pressure gauge that coils or uncoils dependent upon pressure inside the tube. 

This technique bus been applied by Rhodes and Younger(107) to obtain the values of h0 for condensation of a number of organic vapours, by Pratt(92) to obtain the inside coefficient for coiled tubes, and by Coulson and Mehta(i08) to obtain the coefficient for... 

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