Differences between axial and shearing mechanical characteristics of gelled crude oil under different shear conditions

In the rheological testing system, gelled crude oil is obviously anisotropic after shearing treatment. Due to the anisotropy of gelled crude oil, the existing pipeline unsteady flow numerical model is not suitable any more. In this paper, Shengli crude oil and Nanyang crude oil were as examples to compare the differences between shearing mechanical characteristics and axial mechanical characteristics under different shearing conditions and analyze their anisotropy. Preshear treatment was conducted on crude oil under different shear rates and shear time, and shear stress relaxation tests and axial compression relaxation tests were carried out respectively. Then, the test data were fitted, and shear relaxation modulus and axial compression relaxation modulus of gelled crude oil under the same condition were compared. It is shown that axial compression relaxation modulus is much higher than shear relaxation modulus of gelled crude oil under the same condition, and the difference between shear relaxation modulus and axial compression relaxation modulus will become larger with the increasing of shear rate and shear time. In other words, anisotropy is more significant. The research results provide the theoretical and technical support for the shutdown basis and restart of gelled crude oil pipelines.