Working performance of a nylon-cord packer rubber cylinder and its influencing factors

Although a nylon-cord packer rubber cylinder is suitable for open-hole well conditions with small wellbore, irregular wall and high formation pressure, it is disadvantageous with low pressure bearing capacity and poor sealing performance. In order to improve the working performance of a nylon-cord rubber cylinder, it is necessary to clarify the material parameters of the rubber cylinder and cord on the basis of tensile test and Gough-Tangorra theory. A three-dimensional numerical simulation model for a nylon-cord rubber cylinder was established, and its accuracy was verified based on laboratory tests. Besides, the change laws of the stress and contact stress of nylon-cord rubber cylinder under different setting pressures were studied, and the effects of cord angle, cord layer amount and cord spacing on the pressure bearing capacity and sealing performance of the packer rubber cylinder were analyzed systematically. And the following research results were obtained. First, the maximum setting pressure, maximum working pressure and residual deformation of nylon-cord rubber cylinder measured in the tests are 70 MPa, 50 MPa and 3.2%, respectively. Second, the three-dimensional numerical simulation model for nylon-cord rubber cylinder is established based on REFINE 265 unit, and the error between the simulation result and the test result is about 15%, which can satisfy the needs of engineering analysis. Third, with the increase of the cord angle from 14° to 20°, the cord stress increases linearly and the rubber stress and contact stress decrease slightly. Fourth, as the number of cord layers increases from 2 to 8, the rubber stress and contact stress decrease significantly, and the decrease rate of the cord stress increases with the highest decrease amplitude up to 64%. Fifth, with the increase of cord spacing from 1.4 mm to 2 mm, the rubber stress and cord stress increase synchronously and the contact stress decreases. In conclusion, the research results provide a theoretical basis for improving the working performance of nylon-cord rubber cylinder. © 2020, Natural Gas Industry Journal Agency. All right reserved.