This paper describes CIU triaxial tests to determine the mechanical properties of shale cores from deep boreholes in the North Sea. The tests carried out at CENPES´s Rock Mechanics Laboratory employ a geotextile side drain to accelerate the phases of saturation, consolidation and equilibrium of pore pressure during undrained axial loading. The saturation and consolidation phases are carried out under elevated backpressure. A simulated pore fluid is used in the pore pressure line. In order to avoid damage to the equipment caused by corrosion, a new top cap adapted with a small pressure transducer was developed. The undrained shear phase is conducted at slow axial strain rate that is selected to allow adequate redistribution of pore pressure throughout the samples. Five consolidated undrained triaxial tests were conducted under a range of confining pressure from 9 to 20 MPa with 5 MPa of backpressure. The strength behavior for this shale can be described using a linear Mohr-Coulomb strength criterion with effective cohesion of 7,2 MPa and an effective angle of internal friction of 10,6°. The mainly contribution of the used methodology is the reduction of the total testing time, optimizing the usage of the triaxial equipment.