Abstract:

In the fracturing process of shale oil in Subei Basin, there has been a notable incompatibility between the oil displacement agent and the fracturing fluid. This issue leads to a reduction in the viscosity of the fracturing fluid and can even trigger chemical reactions that result in precipitation, adversely affecting both fracturing efficiency and productivity. To address this, a new fracturing-displacement agent（HDFD） has been developed specifically for shale oil. This agent is composed of maleic anhydride（C₄H₂O₃）, polyoxyethylene aliphatic alcohol ether（HO（CH₂CH₂O）_m（CH₂）_nCH₃）, anionic polyacrylamide（（C₃H₅ON）_n）, and white oil, produced through chemical synthesis and physical blending methods. In laboratory evaluations, the HDFD displayed an apparent viscosity of 9~12 mPa·s, a drag reduction rate of over 70%, an oil-water interfacial tension of 5×10^-3 mN/m, and a 40% increase in oil displacement efficiency at a 2×10^-3 kg/L concentration. Compared with the“drag reduction emulsion + high temperature oil displacement agent” system used in the field, these results suggest that HDFD performs exceptionally well in reducing drag in fracturing fluids and enhancing oil displacement. Field tests conducted on two wells using this agent showed a daily oil production increase of 40.6% and 84.6%, respectively. These outcomes confirm that HDFD is effective for use in the shale oil reservoir of the second member in Subei Basin and holds significant promise for future applications in integrated shale oil fracturing and displacement technologies.

Key words: Subei Basin, shale oil, fracturing-displacement, imbibition replacement, performance evaluation