These data further establish that rotamers of acyclic carbohydrate derivatives that involve an eclipsed 1,3 interaction between substituents are energetically disfavored, a situation that is generally alleviated by rotation about an internal carbon-carbon bond to a different, gauche rotamer (sickle form). The short (three carbon) chains are more prone to populate more than one conformational state to a substantial extent, whereas prolongation of the chain tends to cause the molecule to favor one conformation more exclusively, this being the most extended arrangement compatible with avoidance of 1,3 interactions.It is suggested that application of the Karplus equation, to quantitative determinations of dihedral angles on rotamer populations, from data obtainable by present methods, is less likely to advance the understanding of conformational behavior of polysubstituted, acyclic chains in solution than a conservative, qualitative treatment, at least until experimental methods of greater finesse are developed.
Acrylamide/acrylic acid copolymers are effective fluid loss control additives in a wide range of oil well cements. Unlike HEC based fluid loss additives, these copolymers can be used with calcium chloride accelerator without significantly influencing fluid loss control. Another advantage of the copolymers is that the amount of fluid loss for a given concentration of polymer remains relatively constant over a wide range of temperatures. The use of acrylamide/acrylic acid copolymers has generally been restricted to wells below 60°C BHCT. Above that temperature chemical changes in the copolymer often lead to retardation of the cement.
This paper presents data related to the use of acrylamide/acrylic acid copolymers as fluid loss control agents in oil well cementing. A comparison of these polymers with HEC based fluid loss control additives is made. In addition, data related to the cause of acrylamide/acrylic acid copolymer retarding effects is presented.
Partial aluminum salts of alkyl orthophosphates (AAAO) are effective gelling agents for hydrocarbons. The simplified chemical model of AAAO gel presented in this paper is used to describe mechanisms for breaking AAAO gels in oil field applications. The preferred method of breaking is with acid. By selecting an appropriate acid system, delayed action breaking with a predetermined amount of viscosity reduction can be obtained.
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