Calculation Model of Annular Pressure Loss in Slim Hole Considering Drill String Rotation, Eccentricity and Joint

Abstract

Slim-hole drilling technology has the advantages of high yield, low environmental protection and low cost, and it has been gradually paid attention to by various oil fields in recent years. However, in hydraulics calculation, especially the calculation of annular pressure loss, the established models by different researchers through laboratory experiments are often not universal and practical. The key point of this problem is that there is a big difference between laboratory experiment parameters and genuine parameters in the field. Therefore, in this study, an annular drilling fluid flow model is established by using numerical simulation technology. Then, a mixed level orthogonal experiment is carried out with four annulus sizes, four groups of drilling fluid rheological parameters, four common annulus flow velocity, four eccentricities and 16 drill pipe rotation speeds, and the experimental results is fitted into an influencing factor of drill string rotation suitable for slim holes. Finally, considering the influence of drill string eccentricity and drill string joint on the annulus pressure loss of slim hole, a model of annulus pressure loss is suitable for slim hole. It can be seen that the calculation results of the model are consistent with the data of laboratory experiments. In addition, to verify the accuracy of the model, the model established in this study was applied to Mahu oilfield, and the average error rate is only 4.6%, which indicates the applicability of this model in the field. Therefore, this model can be applied to design and calculate hydraulic parameters of slim hole and guide engineering practice.