| With the decreasing of the conventional oil and gas resources,the tight sandstone reservoir is a new hotspot in oil and gas exploration and development.Compared with conventional reservoir horizontal wells,the horizontal wells of tight sandstone reservoirs have long horizontal displacement and large friction torque,which leads to complicated trajectory of wellbore.These factors determine that the horizontal wells in the tight sandstone reservoirs are more complicated during the drilling process,and often the drill strings are bending in the wellbore and even occurs self-locking.Therefore,it is very important to predict the friction torque of the drill string in the tight sandstone through the theoretical calculation model.In this paper,based on the study of the geological characteristics of the tight sandstone reservoirs,soft-string model and stiff-string model of the drill string friction torque are established considering the factors such as the trajectory parameters of the wellbore,the viscous resistance of the drilling fluid and the influence of the drill string buckling.Aiming at the phenomenon that the shape of the drill string and the shape of the wellbore are not consistent when drilling in the horizontal well of the tight sandstone reservoir,the method of discretization is used as the node to analyze the joint.The cubic trapezoidal interpolation method is used to fit the well trajectory,and building the friction torque calculation model of the horizontal well the tight sandstone reservoir.And the numerical calculation algorithm of the new friction torque model is compiled by MATLAB software,and the complexity and calculation time of numerical calculation are optimized.Finally,on the basis of field examples,LANDMARK software and discretization model are used to analyze and calculate a well in the research area respectively.By calculating the comparative analysis,it can be concluded that the new discretization model is more accurate.The reasonableness and accuracy of the friction coefficient prediction model of the horizontal well in the tight sandstone reservoir are verified,and the necessary technical support is provided for the field engineering practice. |
