A geomechanical analysis of the influence of orientation and placement of jet slots on terrigenous reservoir permeability

The paper presents the results of a geomechanical analysis of the effects of the placement and orientation of jet slot channels on the well-bore area permeability of terrigenous reservoir in producing oil wells in the Perm region. Various scenarios for the formation of jet slot channels in the reservoir were outlined and assessed; the stress-strain state of the rocks was determined; and the effect of "unloading" on the permeability of rocks and the stability of the slot channels was assessed. The unloading of the rock mass near the jet slots was estimated from changes of average effective pressure. It was established that the best placement scheme for jet slot channels is a system of four slot channels with a phasing of 90°. The height difference between jet slots channels does not appear to be significant, because the slot channels interact with each other very weakly in the vertical direction. The influence of unloading of the rocks on the permeability of the reservoir at a pressure drawdown of 5 MPa was calculated. Functional dependence of all-round effective pressure on the permeability was based on the results of rock tests of the terrigenous reservoirs of the Shershnevskoye oil field. It is demonstrated that without additional work, reservoir permeability is significantly reduced during well exploration under specified conditions; however, the abrasive jet perforation effectively contributes to preservation of the initial permeability. It was also found that jet slot channels in the productive layers with the correct physicomechanical properties and the depression of 5 MPa are stable, since zones of inelastic deformations are very rare. Thus, in addition to increasing the filtration area in the well-bore-reservoir system, the abrasive jet perforation ensures the preservation of the reservoir permeability due to unloading of rocks from the operating stresses. The additional positive effect of the proposed technology is the possibility of azimuth orientation of the jet slots channels for different stress scenarios.