Abstract
The rubber packing element is one of the most important parts of deep-well test packers, but the existing rubber packing elements are insufficient to meet the requirements of field use as the stratum temperature and pressure rise as drilling becomes deeper. In this study, a rubber material formulation that meets the actual needs of the field (can withstand a high temperature and high pressure of 215 °C/105 MPa) was designed. Based on this, a mathematical model of the packer’s rubber packing elements was established, and its structure was analyzed using finite element software. Furthermore, the rubber packing elements produced according to this design were verified in an indoor simulation experiment. The results of structural analysis show that the best sealing was achieved when the end-face inclusion angle of the rubber packing element was set at around 40°, the length of the rubber packing element was between 60 and 80 mm, and the hardness was greater than or equal to 90 HA. Under the experimental conditions of 105 MPa and 215 °C, the experimental device stabilized at a pressure for 62 h and the pressure drop was 0.3 MPa, meaning that the elements passed the experiment and, thus, they can go through the setting-down process and function well in normal works. For the rubber packing elements with a sealing capacity and temperature resistance of 105 MPa and 215 °C, respectively, developed in this paper, their sealing reliability was verified through indoor simulation experiments, providing an important guarantee in terms of the smooth implementation of deep-well testing and the completion of operations at high temperature and high pressure.
Highlights
The key for packers in terms of providing setting-down sealing lies in their rubber packing elements, and the mechanical properties of rubber packing elements at high temperature are the main factors affecting their sealing ability [1,2]
The rubber material of rubber products used in oil fields is often strongly eroded under different working conditions, resulting in failure of rubber products and leakage [5]
Structure and Physical Parameters of Packer Rubber Packing Elements The rubber packing elements used in the experiment were structured with three rubber packing elements combined together to provide sealing; the inclusion angle of the end rubber packing elements was processed to 40◦ chamfer and its material was the rubber corresponding to the associated formula, with fluororubber as the main component
Summary
The key for packers in terms of providing setting-down sealing lies in their rubber packing elements, and the mechanical properties of rubber packing elements at high temperature are the main factors affecting their sealing ability [1,2]. Xu [13] fitted the constitutive model of hydrogenated nitrile rubber (HNBR) according to the experimental data, and studied the influence of temperature (120 ◦C) and stress relaxation on the rubber sealing system of the packer using finite element analysis software. Gong [20] observed the corrosion behavior of AFLAS, FKM and HNBR rubber in a CO2-H2S coexistence environment with a high-temperature and high-pressure autoclave, The FKM rubber had the best corrosion resistance and aging resistance These studies and analyses mainly focus on the rubber packing element made of nitrile rubber, and the temperature and pressure involved in the research are all below 100 MPa and 200 ◦C, which cannot meet the further demand of oil drilling. A set of rubber packing elements of a deep-well test packer at 105 MPa and 215 ◦C was developed, which provides an important guarantee for the smooth implementation of deep-well test completion operations at high temperature and high pressure. The greater the gap between the sealing element surface and the casing wall, the greater the minimum required setting-down force
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