FILTRATION REDUCTION MECHANISM OF ENVIRONMENTAL-FRIENDLY COMPOUND MODIFIED STARCH IN WATER-BASED DRILLING FLUIDS

In this paper, the environmental-friendly compound modified starch was introduced as the filtrate reducer in water-based drilling fluids. Firstly, a kind of compound modified starch (GCMS) was synthesized through both etherification modification and crosslinking modification. Then from the aspect of improve colloidal stability and filter cake quality of water-based drilling fluids, the filtration reduction mechanism of compound modified starch (GCMS) in water-based drilling fluids was detailedly investigated using infrared scanning dynamic stability analysis, CT scan characterization, particle size distribution analysis and permeability and compression coefficient measurement of filter cakes. It was concluded that complex network structure of GCMS formed by moderate cross-linking could significantly improve its high temperature stability, and enhancing the colloidal stability to improve particle size gradation of clay particles and the compressibility of filtrate cake is one of the filtrate reduction mechanisms of GCMS. This research demonstrates its feasibility or compatibility of compound modified starch (GCMS) as a filtrate reducer in water-based drilling fluids.