Research On Theory And Application Of Casing Friction Analysis In Complex Structure Wells

As drilling and completion technology in complex structure wells becomes increasingly mature, it has been a new trend that the complex structure wells are used for the oil and gas exploration.In contrast to routine wellbore, the complex structure wells are generally of outstanding characteristics, such as large horizontal displacement, long high-angle tangent section, big drag friction and torque, and etc. All these characteristics would bring difficulties to tripping the casing pipe in casing process and even results in that the casing pipe can’t be tripped safely in some wells. Therefore, it is of great importance to predict the casing friction in complex structure wells by theoretical model.First, this paper carries on the data fitting to the inclinometer data by the method of cubic spline interpolation. Then this paper establishes the soft rod model and the rigid rod model of the casing pipe respectively by the analysis of force exerted on casing string according to the fitted well trajectory. In addition, it puts forward a new segmented calculation model of casing pipe friction in complex structure wells. In this new model, the soft rod model is used for friction calculation of medium, long radius well section, while the rigid rod model is used for that of short radius well section. By doing so the model overcomes their respective limitations of both models to make the prediction more accurate. During the establishment of this model, this paper takes the effect of pipe buckling on friction calculation into consideration. Finally, a software system is developed with C#language based on the established theoretical model. And this system is used to analyze the casing friction in complex structure wells and provides necessary technical support for in-situ engineering practice.