Deviation from Planned Well Path through Accumulated Cutting Bed in High-Angle and Horizontal Wells – a Case Study in one Western-Siberian Oilfield

Abstract

In recent years, thanks to telemetry systems, measurement while drilling and geo-steering technologies, drilling directional and horizontal wells has been improved significantly. But still there are a lot of complications in directional drilling operations. Cutting transportation is a serious challenge in high angle and horizontal wells. High mud flow rate is required to clean cuttings from the wellbore which is not always practically possible. High flow rates can lead to formation fracturing and result in mud loss. In addition, downhole motor's optimal fluid rate range may limit the value of fluid rate. In high-angle and horizontal wells, it is necessary to take into account presence of cutting bed as an inevitable fact and try to conduct all of the operation based on this fact. For example, while drilling horizontal or extended reach wells, it is not recommended to pull the drilling string out before cleaning the wellbore with high mud flow rate. Also, build rate must be calibrated based on cutting bed effect on bending moment and accordingly build rate. In this work, the effect of cutting bed on build rate and deviation from the planned path for horizontal and highly deviated wells has been investigated. In "Rhinoceros" and "ANSYS", downhole elements shape, their characteristics and their interactions with each other have been simulated and analyzed. The simulation is done based on data from a real case in West-Siberian oil-field. Using Finite Element Method jammed cutting around the stabilizer have been modeled and its effect on wellbore deviation from planned path has been investigated. Jammed cutting has been simulated like a gravelly sand soil that increases the accuracy of the simulation. In the previous works, jammed cutting around stabilizer has been modelled as an increase in diameter that in this work, this assumption has been corrected.