Study On Wear Prediction And Anti - Wear And Anti - Friction Measures Of Deep Shaft Casing

Casing wear often occurs in the drilling process of deep well and ultra deep well, resulting in serious drilling accident and economic loss; hence, it is quite necessary to study casing wear deeply. The reason, influence factor and wear mechanism and main failure modes of casing wear were analyzed on the basis of data research.Based on sufficient research and analysis of casing wear, according to simulation principle, the contact stress between model casing and drill pipe is equal to that of the practical casing and drill pipe. Self-made wear tester was made to study the casing behavior, the research contents and results were summarized as follows:(1)The relationship of contact stress and casing wear were studied under different contact forces respectively with10kN/m、12kN/m、15kN/m for140-hour wear test;(2) Wear test with different rotation speed (70r/min、120r/min、215r/min) for140hours were used to analyze the effect of rotation speed of drill pipe on casing wear.(3) Two types of drilling fluid for140-hour wear test were selected to study the influence of drilling fluid on casing wear.(4)Three types of casing materials of J55> N80、P110were used to research effect of steel grade on casing wear.(5) In order to explore the effect of continuous loads and discontinuous loads on casing wear, wear test were performed in two different drilling fluids for40h.(6) Three A wear-resisting materials and four B wear-resisting materials were selected in wear test for40hours, to evaluate wear resistance of different wear resistant belts.On the basic of a large number of wear experiments of casing and drill pipe,wear loss and wear coefficient were calculated under various experimental conditions according to the derivation of "wear efficiency model",provide basic parameters for casing wear prediction;The residual strength of casing is calculated under the different degree of wear and tear through the model; Combined with a deep well, this paper discussed the coefficient of borehole curvature, wear on the casing wear, and calculate the residual wall thickness, the internal pressure and collapse resistance.Finally, on the basis of comprehensive research on casing wear in this paper, some measures of reducing casing friction and wear were proposed in terms of monitoring of casing wear, drilling process, selection of drilling fluid, wear resistant belts and drilling pipe protector.