Study and Application of Scale Inhibition and Oil Displacement Integrated Fracturing Fluid

Abstract

Fracturing has become an effective method for enhancing reserves and production in the Ordos Basin. However, with the exploration of unconventional reservoirs such as the Chang 7 Group shale oil in Zhengning Oilfield, challenges like shallow burial depth, insufficient formation energy, high formation water salinity, and easy scaling have emerged as major obstacles to shale oil development. Fracturing operations face issues including poor fracturing fluid adaptability, poor treatment effects, and rapid production decline. This paper synthesizes a new type of block polyether structure imbibition oil displacement agent, with an oil sand washing rate of 74.9% for crude oil. A corrosion and scale inhibition system was developed to effectively chelate calcium scale, preventing the formation of calcium carbonate and inorganic deposits, with a scale inhibition rate of 92.5% for CaCO3. Additionally, a low-temperature gel breaker activator is evaluated, resulting in a broken gel viscosity of 1.78 mPa·s at 50°C. An integrated oil displacement and scale removal fracturing fluid is formed, exhibiting a core matrix damage rate of 14.7%. Field application of this integrated fluid system in three horizontal wells fractured in the Yanchang Formation shale oil reservoir of the Zhengning Oilfield demonstrated enhanced oil displacement and flowback performance, along with improved stimulated reservoir volume. The operational success rate reached 100%, with an post-fracturing oil meeting flowback rate of 7.8%.