Distribution of annular fluid temperature due to fluid displacement between wellbore and formation during shale oil drilling
The temperature distribution of annular fluid during shale oil drilling with oil-based drilling fluid can be affected by the fluid displacement condition between wellbore and near-wellbore rock formation.In this study,a prediction model of the annular fluid temperature distribution in shale oil wells was established based on fluid flow and heat transfer theory.The influence of the fluid displacement on the flow mode of the annular mixed fluid and the thermal physical parameters of the flu-id were considered in the model.Based on the model,the annular fluid temperature distribution under different displacement conditions was investigated.In addition,the influence of the displacement location,fluid type,displacement flow rate on the annular fluid temperature were analyzed.The results show that,when fluid displacement occurs,the fluid temperature in the annulus is higher than that under the normal drilling fluid circulation condition.If the fluid displacement occurs at the bottom of the well,there will be no obvious inflection point on the annular fluid temperature distribution curve.While the displace-ment occurs at other locations,there will be an obvious inflection point on the curve,and the location of the inflection point on the temperature disdribution curve is well corresponded to the displacement occurrence location.Furthermore,compared with shale oil with low specific heat,the annular fluid temperature will be higher when drilling fluid is displaced by formation water with high specific heat.In addition,when the intrusion rate of the formation fluids is greater than the leakage rate of the drilling fluid in wellbore,the higher the displacement rate,the higher the annulus fluid temperature.
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