| Title | Sepiolite Based Muds as an Alternate Drilling Fluid for Hot Environments |
|---|---|
| Authors | Gursat ALTUN, Ali Ettehadi OSGOUEI, M. Hakan OZYURTKAN, Umran SERPEN |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | Sepiolite muds, Hot wells, High temperature, High pressure differential, HTHP rheometer, Barite-weighted mud |
| Abstract | Drilling operations usually experience difficulties in hostile drilling conditions such as high temperature, high pressure, and extreme salinities. Such environments are encountered as drilling deep oil and gas wells, geothermal wells, and unconventional wells. Drilling hot wells experiences extreme difficulties in controlling drilling fluid properties. This fact comes into prominence particularly in geothermal fields. Safe and cost effective drilling in hot environments dictates the customization of a high performance drilling fluid. This study is an experimentally attempt to design the properties of a new high performance water based drilling mud in order to function adequately in the aforementioned conditions. For this purpose, sepiolite clay obtained from Eskisehir district of Turkey has been used to formulate this new mud system. The properties of mud samples were evaluated with temperatures up to 400oF, pressure differentials up to 500 psi, salt content from fresh to 260,000 ppm using commercial additives. Rheological properties of samples were determined using both conventional viscometer by 16 hours of aging at elevated temperatures and high temperature and high pressure (HTHP) rheometer. Fluid loss properties of samples were measured with standard API filter press and HTHP filter press. In addition, the filtration properties were also investigated with a dynamic filtration apparatus. Both rheometer and dynamic filtration apparatus were used to customize the properties of sepiolite mud system to mimic real borehole conditions. Properties of barite-weighted sepiolite mud samples were also examined. Results of the study reveal that sepiolite based muds provide good rheological properties up to 400oF. In addition, these muds are not sensitive to salt intrusion and yield better rheology with increasing salt content. Although sepiolite muds are known to have unacceptable high filtration rates, customized sepiolite muds in this study exhibit excellent filtration characteristics under both high temperature and pressure differential. Dynamic filtration rates less than 0.35 ml/min even for barite-weighted mud samples are obtained at 400oF of temperature and 500 psi of pressure differential. Rheological and filtration effectiveness of sepiolite muds in harsh conditions are experimentally demonstrated. In short, sepiolite muds might be a good alternative drilling fluid particularly in geothermal wells. |