Investigation on the effects of ultra-high pressure and temperature on the rheological properties of oil-based drilling fluids

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Title: Investigation on the effects of ultra-high pressure and temperature on the rheological properties of oil-based drilling fluids
Author: Ibeh, Chijioke Stanley
Abstract: Designing a fit -for -purpose drilling fluid for high -pressure , high -temperature (HP /HT ) operations is one of the greatest technological challenges facing the oil and gas industry today . Typically , a drilling fluid is subjected to increasing temperature and pressure with depth . While higher temperature decreases the drilling fluid ?s viscosity due to thermal expansion , increased pressure increases its viscosity by compression . Under these extreme conditions , well control issues become more complicated and can easily be masked by methane and hydrogen sulfide solubility in oil -base fluids frequently used in HP /HT operations . Also current logging tools are at best not reliable since the anticipated bottom -hole temperature is often well above their operating limit . The Literature shows limited experimental data on drilling fluid properties beyond 350 ?F and 20 ,000 psig . The practice of extrapolation of fluid properties at some moderate level to extreme -HP /HT (XHP /HT ) conditions is obsolete and could result in significant inaccuracies in hydraulics models . This research is focused on developing a methodology for testing drilling fluids at XHP /HT conditions using an automated viscometer . This state -of -the -art viscometer is capable of accurately measuring drilling fluids properties up to 600 ?F and 40 ,000 psig . A series of factorial experiments were performed on typical XHP /HT oil -based drilling fluids to investigate their change in rheology at these extreme conditions (200 to 600 ?F and 15 ,000 to 40 ,000 psig ) . Detailed statistical analyses involving : analysis of variance , hypothesis testing , evaluation of residuals and multiple linear regression are implemented using data from the laboratory experiments . I have developed the FluidStats program as an effective statistical tool for characterizing drilling fluids at XHP /HT conditions using factorial experiments . Results from the experiments show that different drilling fluids disintegrate at different temperatures depending on their composition (i .e . weighting agent , additives , oil /water ratio etc ) . The combined pressure -temperature effect on viscosity is complex . At high thresholds , the temperature effect is observed to be more dominant while the pressure effect is more pronounced at low temperatures . This research is vital because statistics show that well control incident rates for non - HP /HT wells range between 4 % to 5 % whereas for HP /HT wells , it is as high as 100 % to 200 % . It is pertinent to note that over 50 % of the world ?s proven oil and gas reserves lie below 14 ,000 ft subsea according to the Minerals Management Service (MMS ) . Thus drilling in HP /HT environment is fast becoming a common place especially in the Gulf of Mexico (GOM ) where HP /HT resistant drilling fluids are increasingly being used to ensure safe and successful operations .
URI: http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2569
Date: 2009-05-15

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Investigation on the effects of ultra-high pressure and temperature on the rheological properties of oil-based drilling fluids. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2569 .

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