Abstract
Seal element is an important component of roller-cone bit. In order to improve the sealing performance and service life of roller-cone bit under high temperature, a new seal structure with multi-segment arcs is designed and the structural parameters of this sealing ring are optimized by response surface method and finite element method. Firstly, the hydrogenated nitrile-butadiene rubber is used to improve the seal performance under high temperature, and the uniaxial, planar, and biaxial tensile experiments are carried out to study the constitutive model of this rubber. Then, a three-dimension transient thermo-mechanical coupling model is established. The comparison of sealing performance between the new structural seal and the traditional O-ring seal is implemented under high temperature through the proposed FEM and laboratory experiments. The results show that the new structural seal has lower contact pressure and Mises stress than the standard O-ring seal, and the service life of the former is almost twice of the later one. Additionally, a composite drill bit using the new structural seal is applied to a deep drilling. After servicing a certain time, it shows that the wearing capacity is very small. The results show that the new structure seal ring can adapt to high temperature environment and the optimization method is feasible.
Highlights
Roller-cone bits are widely used in the oil and gas exploration and development, especially in the hard and abrasive formations
The main contributions of the current work are: (1) the hydrogenated nitrile-butadiene rubber (HNBR) constitutive model is studied at high temperature by laboratory tensile experiments; and (2) a new multi-segment arcs seal is designed for the roller-cone bit by response surface method (RSM), which is validated to have a good sealing performance in deep well drilling
The parameters of the HNBR material constitutive model are obtained based on the stress-strain data in the test results of unaxial tensile, planar tensile, and biaxial tensile
Summary
Roller-cone bits are widely used in the oil and gas exploration and development, especially in the hard and abrasive formations. The main contributions of the current work are: (1) the HNBR constitutive model is studied at high temperature by laboratory tensile experiments; and (2) a new multi-segment arcs seal is designed for the roller-cone bit by RSM, which is validated to have a good sealing performance in deep well drilling. The parameters of the HNBR material constitutive model are obtained based on the stress-strain data in the test results of unaxial tensile, planar tensile, and biaxial tensile. RSM is applied to improve the sealing performance and service life of the new rubber seal It aims to reduce the Mises stress, contact pressure, and contact length using multi-objective optimization. Min M(x)= f (x1 ,x2 ,x3 ), C(x)= g (x1 , x2 , x3 ), L(x)= q (x1 , x2 , x3 )
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