Research and performance evaluation of high-temperature resistant advanced borehole wall protection bentonite gel liquid

Abstract:

To address the issues of low core recovery in fractured formations during core drilling and the limited effectiveness of conventional borehole wall protection technologies， this paper proposes a technical approach of "advanced borehole wall protection" and develops a high-temperature resistant advanced borehole wall protection bentonite gel liquid. Through material screening and orthogonal experiment optimization， the optimal formula was determined as 2% Hebei drilling-grade bentonite， 8% sepiolite， and 20% Portland cement. Laboratory performance tests indicate that the gel liquid has an apparent viscosity of 87.5 mPa·s at room temperature and its apparent viscosity exceeds 150 mPa·s after aging at 150 ℃ for 16 h. The total filtration time is only 68 s. The compressive strength of the formed filter cake reaches 2.4 MPa after drying at 150 ℃ for 48 h. Furthermore， the gel liquid exhibits good permeability and cementation capabilities in high-temperature and high-pressure sand bed simulation experiments. This gel liquid can be injected in advance without completely consolidating the formation， thereby enhancing the formation''s overall integrity. It provides a new solution for improving core recovery and drilling efficiency in fractured formations and holds promising engineering application prospects.