Analysis And Application Of Casing String By Nonlinear Finite Element Method

This paper is on the research of whole casing string, and has built the entire casing string nonlinear mechanics model. It has synthetically thought over the influence of factors such as the interval and contact state between casing pipe and hole wall, hole curvature, startup force of stabilizer, resilience etc, and has also thought over the deformation harmony of casing pipe and neighboring set upright device at the same time, and can comparatively accurately describe the force and deformation state of casing string. Meanwhile, aiming at this nonlinearity mechanics problem that the contacting between casing string and borehole wall occurring randomly, have made up "multi direction gap element" and built up casing string nonlinear finite element unit theory, according to the basic theory of "gap element". This theory not only makes the random contact friction casing string and borehole wall at different depth of well and different circumference directions, renitent rigidity of stabilizer, especially the rub state of elastic stabilizer and borehole wall be reasonably described, but also is a kind of effective calculation method.Both Delphi' casing string stress analysis software, and the calculation analysis of Daqing oil field directional well casing string show that calculation of casing string's centering degree is in accord with the internal peg-top testing data of casing string, and also validate the correctness and reliability of based mechanics model and theory method. According to the datum of 141 cemented well, establishing connection between centering degree and cementation index of casing string, thus the relation of well cementation quality and centering degree can be described quantificationally, and educe that 82% casing string centering degree is the premise to pledge high quality well. Also provide the technology parameter for casing string centering degree analysis and casing string design. At the same time use established relation between centering degree and cementation index of casing string to simulate and forecast the cementation index of uncemented well, so that the quality of well cementing can be checked. The casing string stress analysis software provides a kind of practical technology method for reasonable casing string design, calculating installation seat of stabilizer and ensuring well cementation quality.