MODEL OF ANNULAR PRESSURE LOSS FOR SLIMHOLE AND ITS APPLICA TION IN JILIN OILFIELD

The calculation of annular pressure loss for slimhole is different from that of conventional well. Based on sufficient test data analysis and by regression, this paper establishes the empirical model of slimhole annular pressure loss affected by rotary drill string and eccentric buckling. The model of annular pressure loss for slimhole is established on the basis of the model for conventional well. The empirical equation of distinguishing drilling fluid state by Reynolds number in axial flow and Tyler number of rotation is also presented. Hydraulics optimization and drilling rheological parameter optimization are programmed. Calculations indicate that the ratio of the annular pressure loss and drilling string internal pressure loss is upto 25%~30%. Based on the data from the well Miao 1-40 in Jinn Oilfield, the theoretical model and lab test data are field verified. Field verification indicates that the relative error of pressure loss in the slim hole is less than 6%, when the pressure loss is predicted by the model established. Thus, the model is proven to meet fully the needs of engineering operation. The hydraulics of well Miao 5-40 in the oilfield is predicted. The accuracy of the model is also indicated by the prediction.