A joint industry project was established to study barite sag mechanisms and to develop field guidelines to manage the consequences. A simple empirical model was developed to compare sag potential for a wide range of fluid types. In the study, physical properties of the mud, wellbore conditions, and characteristics of the weighting material were shown to have a large influence on sag behaviour. The study also included direct measurements of the properties of settled weight-material beds. These results provide new insight into the mechanisms of barite sag and how best to manage problems in the field. Data from the tests clearly demonstrate that the parameters affecting sag are interrelated and seldom act in isolation. For all muds tested, the highest sag occurred at low annular velocities over angles from 60-75. Drill-pipe rotation was particularly beneficial in minimising barite settlement. Rotation also assisted in re-distributing barite deposits formed on the low side of the hole. The improved understanding of the mechanisms of barite sag enabled development of practical field guidelines. Case history studies presented in the paper demonstrate how the results of the work together with better field monitoring have been successfully applied to manage the effects of barite sag in HP/HT and extended-reach drilling operations. P. 89

Copyrght 199S, IADCBPE Asia Pacific Drilling Technology 7his paper was pre~red for presentafron at the 198 lADC/SPE Asia Pacific Ddiling Conference hekf in Jakarta, Indonesia, 7-9 September 1998. W$ paper was selaoted for presentation by an lADC/SPE Program Committee following rewew of information wntained in an abatraof submitted by the author(s). Contents of the Wmr. as presented, haw not been retiewed by the Intemationat Asswiation of Drilfing Contraofors or the Society of Petroleum Engineers and are subject to correction by the author(s). The material, es presented, does not necessarily reflect any psltion of the IADC or SPE, their oficere, or memberx. Papers presented at the fAN/SPE meetings are subject to pub ficetion rhew by Editorial Committees of the IADC and SPE. Electronic reproduction, distribution, or storage of any part of this paper for commercial pupsee without the written consent of the Society of Pelroleum Engineers is prohibtad. Permission to reprcduce in prhrt is restricted to an abstract of not more than 3W words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presentad. Write Ubrarian, SPE, PO, Box WSES6, Richardson, TY. 7508S.W, U. S.A., fax 01-972-952-943s. AbstractA joint industry project was established to study barite sag mechanisms and to develop field guidelines to manage the consequences. A simple empirid model was developed to compare sag potential for a wide range of fluid types, In the study, physical properties of the mud, wellbore conditions, and characteristics of the weighting materiat were shown to have a large influence on sag behaviour. The study also included direct measurements of tie properties of settled weight-material beds. These results provide new insight into the mechanisms of barite sag and how best to manage problems in the field. Data from the tests clearly demonstrate that the parameters tiecting sag are interrelated and seldom act in isolation, For all muds tested, the highest sag occurred at low annular velocities over angles from 60-75°. Drill-pipe rotation was particularly beneficial in minimizing barite settlement. Rotation also assisted in re-distributing barite deposits formed on the low side of the hole.The improved understanding of tie mechanisms of barite sag enabled development of practicat field guidelines. Case history studies presented in the paper demonstrate how the results of the work together with ktter field monitoring have been successfully applied to manage the effects of barite sag in HP/HT and extended-reach drilling operations.