Examination Research On The Hole-stability Property Of Silicate Drilling Fluids

Silicate drilling fluid is a sort of drilling fluid in which silicate kalium or silicate natrium is most disposal. Silicate natrium possess very strong restration stability of shale hydrate and avoiding well collapse. In 1930s, itwas used in more than 100 wellbores in gulf region by high thickness(20-50%) with problems of difficulty to control viscidity and maintenance disposal. By 1960s, Darley discovered that silicate drilling(<20%) have fine stability of wall of well and maked three hols with it. But silicate drilling fluid was few studied owing to polymer mud after 1960s.Due to environment problem of oil and compound mud, foreigns are broadly studying silicate drilling fluid again. After introducing the system, the borehole stability mechanism this paper is particularly analyzed. There are four aspects contributing the mechanism: (1) quickly plug pores and fractures near-wellbore, stop filtrate from entering formation and reduce pore pressure penetration; (2) constrain hydration of clay minerals in shale; (3) coordinate stability of other inorganic salts.After compound and prescription of silicate drilling fluid research, it was discovered:(1)for maintenance drilling fluid, silicate is selected by modulus(2.8-3.2) and adding quantity(2%-5%);(2) for KCl mud, Na/K of silicate is subordination; (3)organic disposal and clay mainly effect rheology and filter of silicate drilling fluid, and do not directly effect maintenance.On the base of above all, it is bringed forward: 3%～5%clay+1%～1.3%compoud alkali+4%～6%KCl+3%～5%compound silicate+0.8%～1.2%PTV+2%～3%SPNH+1%～2%aggregation mellow main +0.2%ABS+1%～2%SMT+0.2%antioxidant。...