Application of FCM new environmentally friendly film-forming drilling fluid in highly dispersive and easily sloughing strata in the Yila Mountain area of Xizang

Abstract:

The Yila Mountain area in Xizang has complex geological conditions with extensive water-sensitive formations characterized by strong dispersion and sloughing. The strata primarily consist of altered ultramafic rocks with serpentinization， hydrotalcitization， and magnetitization， among which the serpentine content ranges from 63% to 84.4%， while the hydrotalcite content varies between 13.7% and 36.3%. The alteration zones occur repeatedly with thicknesses reaching hundreds of meters. During drilling operations， frequent issues happen such as borehole wall collapse， borehole shrinkage， sticking and burial of drilling strings， and low borehole completion rates， leading to frequent downhole accidents and severely affecting the drilling efficiency. Based on the analysis of rock and mineral composition， this paper examines and summarizes the impact of such highly dispersible and easily sloughing strata on drilling operations. Through comparative analysis of the performance and on-site application effects of traditional PHP drilling fluid， low-solid anti-collapse drilling fluid， and the FCM environmentally friendly film-forming drilling fluid， an optimal environmentally friendly film-forming drilling fluid system suitable for such strata was selected and successfully applied in four boreholes. This effectively improved drilling efficiency and yielded favorable application results. Additionally， combined with engineering practice， drilling techniques such as casing while drilling for reaming and drilling fluid solid-phase control tailored to such highly dispersible and easily sloughing strata were summarized， providing references for similar strata construction.