Experimental research on the sealing ability of borehole packers

Maksym Dorokhov,Volodymyr Biletskyi,Ivan Kostriba

doi:10.15587/1729-4061.2016.74831

Abstract

With the use of a full factorial experimental design based on a BoxHunter rotatable central composite plan for second order response surfaces, it was possible to obtain a statistical mathematical model of the impact of the diametrical tension, the test pressure, and the radial clearance between the thrust bush and the casing as well as the shear modulus of the material on the amount of contact pressure, which is represented by a polynomial of the second order. The research was carried out on the laboratory model of the PJSC “Ukrnafta” (Poltava, Ukraine). The analysis of this model shows that an essential impact on the sealing ability of the selfsealing ring (the value of contact pressure) is made by the following series of factors: the test pressure, the diametrical tension, the radial clearance, and the shear modulus of the compaction material. Moreover, the test pressure factor is characterised by nonlinearity, which manifests itself in intersections of the hypersurface response. The study has experimentally determined the patterns of distributing contact pressure along the length of the conjugate surface between the ring and the casing, characterized by a decreasing contact pressure from the edge of the working bite to the supporting section of the ring. The research has demonstrated that it is possible to manage directly the sealing ability of borehole packers, particularly by changing the geometric parameters of the packer compaction.

Highlights

Special devices known as packers are used to detach individual sections of oil and gas wellbores for their repairing or operation or for checking the impermeability of blowout preventers and wellhead equipment
The packer, which is based on a rubber self-sealing ring, is designed to test blowout preventers and wellhead equipment during underground repair work of wells
The full factorial experimental design was based on a Box-Hunter central composite rotatable plan of the second order and was used to develop a statistical mathematical model of the impact of the diametrical tension Δ, mm, the test pressure P, MPa, the radial clearance δ between the thrust bush and the casing pipe, mm, and the shear modulus of the material σsm, MPa, on the amount of contact pressure, MPa, which is represented by a second order polynomi

Summary

Introduction

Special devices known as packers are used to detach individual sections of oil and gas wellbores for their repairing or operation or for checking the impermeability of blowout preventers and wellhead equipment. Their main sealing element is rubber [1]. The current world market of equipment for the construction or operation of oil and gas wells is characterized by a variety of packers on the basis of self-sealing rings. The packer, which is based on a rubber self-sealing ring, is designed to test blowout preventers and wellhead equipment during underground repair work of wells. Given that impermeability of borehole packers is a comprehensive measure of their technical characteristics, its research is in a particular focus of scientists

Analysis of previously published data and a statement of the problem

The purpose and tasks of the study

The research results on contact pressure

Discussion of the results of studying contact pressure

Conclusions