اثر مقاومت ژله اي دوغاب سيمان در جلوگيري از نفوذ گاز

The Effect of Gel Strength of Cement Slurry in Preventing Gas Migration

Previous research on annular gas flow has shown that the behavior of cement between its fluid and set states is the controlling factor that may allow gas entry. This transition phase of cement previously has not been recognized in slurry design since its importance was not fully understood and since test procedures for its definition has not been presented or established. To predict the occurrence of annular gas flow and to design cement slurries capable of helping to prevent annular gas flow, it is necessary to define the slurry characteristics at the beginning and the end of this transition period as well as the period of time of the transition state. Test techniques have been developed to study the start of this transition period. Additional tests have been conducted to define the condition of cement required to prevent gas entry. The test techniques developed to define this transition period of cement slurry are described. Numerous job variables such as pumping time, placement time, slurry composition, and circulating temperature and pressure were investigated to evaluate their influence on transition time. A method for using transition time and static gel strength (SGS) development data to help predicting annular gas flow and to evaluate annular gas flow control materials, is discussed.