Objectives/Scope: Effective development of tight oil and gas depends on the generation of artificial fractures, and continuous and efficient development of tight oil and gas requires the use of proppants to maintain the diversion effect of artificial fractures. At present, the microscopic mechanism of damage to fracture conductivity of sand conglomerate reservoir is not clear.
Methods, Procedures, Process: Taking the sandstone conglomerate in Mahu sag as the research object, the experimental study on the fracture conductivity of the sandstone conglomerate in Mahu sag is carried out. First, the stress sensitivity analysis of the sandstone conglomerate is performed on a pore scale using a self-made permeability measurement method, then, the fracture width, pressure and flow rate are measured under the condition of fracture scale to analyze the change law of conductivity during fracturing fluid injection.
Results, Observations, Conclusions: The results show that the permeability of gravel decreases with the increase of confining pressure, and the stress sensitive damage is strong. After a cyclic loading condition, permeability will not recover to the initial value, causing irreversible damage to the pore and roar. As the fracturing fluid continues to be injected, a large amount of proppant becomes embedded in the fracture and leads to a decrease in conductivity. The whole diversion curve can be divided into two stages. In the first stage, the diversion damage is great, and in the second stage, the diversion damage decreases somewhat. The damage of conductivity is closely related to the content of clay minerals.With the increase of clay mineral content, the conductivity damage rate increases rapidly, especially the existence of illite and Aimonite mixed beds can significantly improve the conductivity damage rate.
Novel/Additive Information:The results provide a solution for the optimization of proppant concentration, the improvement of tight oil production and the study of gravel diversion damage mechanism in the Mahu area.