Cover Those Elbows Isotopes Go Underground

active isotopes: underground ... Low-level radioactivity counter at National Science and Engineering Corp. labo- ratory ... Carr of Isotopes, Inc., a ...
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Cover Those Elbows Just as sweaters and coats wear out first at the elbows, so does insulation on pipe elbows —i.e., until the advent of jackets for ells ^ A L M O S T since the first use of insulated lines, maintenance engineers have faced the problem of abuse a n d d a m a g e to insulation. Some years ago, a l u m i n u m jackets to cover insulated .lines got a n enthusiastic reception, b u t ells were n o t included because of fabrication difficulties. If an ell was jacketed, it was a sitefabricated j o b — i n most cases, an expensive process. Because of attachment needs, jackets for ells m a d e u p of m a n y sections proved difficult, if not impractical, to remove and reinstall. T o cover ells, insulation material, plastic enough to apply over chicken wire a n d which hardened with time, came into wide use. This nonmetal jacketed elbow insulation invited abuse from passers-by. Often elbows project into areas which raise chances for t h e m t o b e accidentally b u m p e d with resultant damaged insulation. I n addition, vibration a n d shrinkage help make insulation on ells short-lived without protection. T w o southwestern fabricators of a l u m i n u m have come u p with economical a n d easy-to-install jackets to cover insulated ells. Both companies—Childers Manufacturing Co., Houston, Tex., a n d Preformed Metal Products Co. (Premetco), Shreveport, La.—developed twopiece a l u m i n u m jackets for ells. Precision m a d e , t h e jackets are available in sizes to fit several diameters of pipe, each of which m a y be covered with several different thicknesses of insulation. T h u s , for example, a l u m i n u m jackets to fit an 8-inch nominal size ell covered with insulation from 1 to 3 inches in 0.5-inch increments a r e n o w stock items. T h e jackets (see figure) a r e d e signed to fit snugly over a n insulated elbow and join smoothly with jackets

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covering straight lines. These companies say the jackets have a n internal moisture barrier applied a t the factory. According to Childers, their jackets can be installed with a l u m i n u m sheet metal screws. O n the other hand, Premetco recommends a special adhesive it m a n u factures, although they also say straps or screws can be used. First announced last year, alumin u m jackets for ells have received an even more enthusiastic welcome than straight aluminum jacketing did. " W h y m o t h e r necessity d i d n ' t bring us simple jackets for ells sooner," quips a n engineer, "could go down as one of t h e deeper mysteries of plant m a i n t e n a n c e . " B.F.G.

Isotopes Go Underground A d d another role for radioactive isotopes: underground petroleum tagging IVADIOISOTOPES

are

going

under-

ground—to boost oil production. Used as tracers, they help m a p t h e underground flow of fluids. T h e result: better knowledge of rock formations in oil a n d gas fields. W h e n a n oil field starts to peter out, engineers often inject gas or water u n d e r pressure into the pool to squeeze more oil to the surface.

Two-piece aluminum jackets to cover insulated pipe elbows fit snugly to the insulation and join smoothly with jackets covering straight p i p e

Otherwise more than half the oil might remain locked in the earth. But injection is not enough. T o determine how efficient the secondary recovery process is, it is necessary to know what happens to the injected gas or water—how much is doing the j o b a n d h o w m u c h is being wasted or lost. M a n y types of tracers—fluorescent dyes, boron compounds, ammonia, helium, carbon monoxide among them—have

Injecting radioactive krypton gas into pressurizing well a t oil field. Krypton-85 was pressurized t o almost 1 0 0 times atmospheric pressure so that it would flow into the well VOL. 50, NO. 5

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MAY 1958

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REPORTS a b a n d o n e d mines, quarries, or other reservoirs. T h e stored material can then be identified, should it seep out of the reservoir into adjacent mines or wells or into water supplies a n d homes. Esso S t a n d a r d Oil Co., for instance, tagged 200,000 barrels of oil stored in a n a b a n d o n e d slate q u a r r y with tritiated octadecene. A subsurface leak in the pipeline carrying the oil to storage was revealed when oil with a small a m o u n t of radioactivity showed u p in a water well along its route.

Low-level radioactivity counter at National Science and Engineering Corp. laboratory, c a p a b l e of detecting 2 disintegrations per minute in a standard liter of gas

been used to check underground flow. Most such materials have drawbacks. T h e ideal tracer, for instance, should behave as closely as possible to the material being traced ; it should mix readily with it and flow in a similar m a n n e r through the rock. Moreover, the tracer must be detectable in very dilute concentrations. And it should be both safe to handle and inexpensive. I n m a n y ways, radioactive isotopes fit these requirements. Compounds useful as underground tracers include: krypton-85, tritium gas, tritiated water, and tritiated or carbon-14-labelcd methane. None of these is found in appreciable q u a n tities in natural gas or ground water. And each can be detected in such dilute quantities (one p a r t per trillion or less) that it need add little to the natural radioactivity already present in gas at the output well. I n tagging something as large as an oil pool, it is desirable to use an isotope that is relatively safe, is low in cost (tritium costs about $2.00 per curie), a n d has a long half life (tritium has a half life of about 12.5 years and krypton-85 about 9.5 years), points out Seym o u r Rothchild of New England Nuclear Corp., a leading producer of radioactive chemicals. Some commonly used compounds containing tritium, such as water, methane, and long-chain hydrocarbons, he adds, are now available from stock. 26 A

Often all t h a t is needed in a repressurizing study is a measurement of the time for gas to flow from the injection well ' to the producing well. A single isotope, added as a short pulse, indicates how permeable the underground formation is. Structural barriers show u p , even with relatively crude measurements. W i t h more precise work, the flow of fluid can be m a p p e d in all directions a n d channeling or t u r b u lent flow is detected. T w o or more isotopes provide still more information. I n one comm o n situation, the producing well is surrounded by four outside wells (one at each corner of a square), into which gas or water is p u m p e d . Tagging each injection well with a different tracer shows how m u c h each contributes to oil output. Nuclear Science a n d Engineering Corp. has worked with Carter Oil Co. since late 1956 on such experiments in the Southwest. It injected m e t h a n e into one well, krypton into another, and took samples at seven producing wells in w h a t Nuclear Science claims was the first such project using more t h a n one tracer. Samples are analyzed in a low-level laboratory counter to measure concentration a n d the time needed for a given a m o u n t of pressurizing gas to escape through the producing well. Isotopes can also be used to tag gas or oil stored underground in

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Isotopes have other uses, too, as underground tracers. T h e y can be added to drilling mud to supply a n idea of underground formations and conditions, for instance. And they can b e used to locate gas leaks behind well casings. Use of radioisotopes to answer problems in secondary recovery is still experimental, cautions D . R . Carr of Isotopes, Inc., a company which has been active in the field. Problems of tracer selection and injection a n d sampling patterns must be worked out for each application. T h e isotopes must b e analyzed accurately, too, especially if the sample contains more than one tagged material. O n the other h a n d , Carr claims, the cost of underground labeling is not high. If tritium or krypton is used, only a few h u n d r e d dollars worth of isotopes is needed. Calibration costs run to about the same figure. Carr estimates the total cost for injection may reach a few thousand dollars. Homogeneous labeling of storage reservoirs may run to about $2.00 to $3.00 per million cubic feet of stored gas. Carbon-14 is more expensive (for the same a m o u n t of radioactivity), but even so the cost of the isotope is only a minor p a r t of total injection cost. Because measurement of the tracer normally requires special laboratory equipment, however, it cannot be d o n e a t the wellhead. T h e inconvenience of shipping samples to the laboratory is small, nevertheless. Carr predicts routine use of isotopes for petroleum recovery and storage engineering in the near future. T h e cost a n d trouble involved are slight, he points out, in comparison with the potential savings. {Continued on page 30 A)