Synergistic Effect of Oxidation Dissolution and Acid Fracturing in Improving Shale Gas Production Capacity

Abstract

Shale gas is an extremely important unconventional oil and gas resource, and its efficient development can effectively alleviate the current tense energy situation. However, shale gas reservoirs often have extremely poor permeability, and reservoir transformation has become a key technology for achieving their efficient development. However, the commonly used hydraulic fracturing technology is difficult to achieve its target production capacity, and other engineering technologies related to reservoir transformation urgently need to be proposed and attempted. The synergistic operation of oxidation dissolution and acid fracturing may provide new ideas for the effective transformation of shale reservoirs. To this end, a comparative analysis was conducted on the synergistic effects of oxidation dissolution and acid fracturing operations in improving shale gas production capacity. The research results indicate that the dissolution effect of oxidants is more effective than acid solution in the transformation process of shale reservoirs. The use of acid only widens the crack width from the initial 4.4 mm to the final 5.1 mm. However, the use of oxidants will result in the final width of hydraulic fractures reaching 8.3 mm. Meanwhile, the effects of acid concentration and oxidant concentration on hydraulic fracture conductivity and shale gas production capacity were investigated. The results indicate that increasing the acid concentration below the low concentration range can significantly enhance the fracture conductivity, thereby promoting the production capacity of shale gas. However, within a higher concentration range, its effect on shale gas production is significantly limited. It is recommended to set the acid concentration design value at 0.5 wt% during the acidizing and fracturing reservoir transformation process of the shale gas reservoir in Changning block. In addition, an increase in the concentration of oxidants can widen the width of fractures and increase permeability, thereby promoting the migration and extraction of shale gas. To avoid the increase in development costs caused by high oxidant concentration in the working fluid, it is recommended to design the oxidant concentration at 3 wt%.