An experimental study to evaluate the efficiency of silicate drilling fluids on the stabilization of shale layers

Regarding the increasing production from unconventional reservoirs, especially shale reservoirs, it is essential to determine appropriate drilling fluid in drilling operations to have maximum efficiency. Selective performance of drilling fluids may increase the formation penetration rate and increase the drilling efficiency. This paper compares the three types of drilling fluids to compare their rheological properties and provide the best drilling fluid composition for shale stabilization. This paper can bring reliable experimental results for petroleum industries, especially drilling operations, to reduce the formation damage and shale instabilities in subsurface formations. To perform the tests under the same conditions, the formulation of all samples is the same in terms of both utilized polymers to determine the effect of other compositions in selected drilling fluids. For the silicate drilling fluid, since silicates perform well at higher pH (potential of hydrogen), the pH of the silicate drilling fluid is increased to 11 by the addition of sodium hydroxide (NaOH). The lowest decrease in fluid viscosity is related to silicate fluids, indicating the more excellent thermal stability of these types of drilling fluid than glycol and potassium chloride (KCl). Plastic viscosity (PV) is about 20 cP for silicate drilling fluids, while it has the minimum value for glycol drilling fluids after heating. It is about 7.5 cP. Apparent viscosity (AV) is about 23 cP for silicate drilling fluids, while it has the minimum value for glycol drilling fluids after heating. It is about 11 cP. The yield point (YP) before heating is almost the same for different fluids, but after heating the drilling fluids, the reflux point for silicate and glycol drilling fluids is significantly reduced. The yield point is about 6.5 Ib/100ft(2) for silicate drilling fluids, while it has the maximum value for glycol drilling fluids after heating. It is about 8 Ib/100ft(2).