Evaluation and Optimization on Profile Control for a Fractured Reservoir

Profile control is the main measurement to solve water channeling in fractured reservoir development. Facing the difficulties in evaluating and optimizing of profile control in fractured reservoir and from the perspective of fine reservoir simulation and effectiveness evaluation, a series of research was carried out. The problems of the water channeling and profile controlling of an offshore fractured reservoir were figured out. Experimental research on gel sealing of fractures was conducted, and a dual medium reservoir dynamic model for profile control was established based on the lab results and the seepage mechanism of the gel sealing formation. The comprehensive reservoir model was used to simulate and evaluate the profile control effect of the plugging agent on both reservoir formation and production performance, as well as to optimize the profile control parameters. Then, the results indicate that the plugging agent mainly acts on the fractures, significantly increasing the residual resistance coefficient through adsorption and plugging. Also, the matrix has a viscous effect on the plugging agent. The water absorption profile and water drive path are improved via plugging agent effect on matrix and fractures, gradually from protruding along fractures to uniformly flooding along the matrix and fractures, ultimately increasing the water injection sweep efficiency. Meanwhile, the production improvement is reflected on the above reservoir change by plugging. During the validity period, the water breakthrough time delays, with the dropped water cut, increased oil production and matrix reserves output, and the weakened fracture characteristics. After the validity, the effect may deteriorate, which is a guidance for multiple rounds of profile control. Finally, three key parameters for profile control are optimized. It is recommended to place the slug within a distance of 0.3 times of the well spacing. The amount of plugging agent should be considered economically, taking into account of both cumulative oil increment and oil increment per unit plugging agent. The timing of profile control to seal high permeability fractures is recommended to be as early as possible. The study establishes the relationship of plugging agents with both fractured reservoir formation and production performance with a dual medium reservoir model based on experiments and theories of profile control, which is of certain significance for scientific and comprehensive evaluation of the profile control effect in a fractured reservoir, and also provides guidance for parameters optimization such as slug position, plugging agent dosage, and the timing.