Drilling of oil and gas wells in the fields of Eastern Siberia is carried out in complex mining and geological conditions, which are caused by the presence of significant intervals of carbonate-halogen deposits, low reservoir pressures, high salinity of the formation water and the presence of tectonic faults. As a result of the use of monosalt drilling fluids on water basis, there is an increased cavernousness of the wellbore, a decrease in permeability of the wellbore zone and a decrease in well productivity. The objective need to improve the quality and technical and economic parameters of well construction requires the improvement of technologies for drilling wells and opening productive layers.
The formulation of the improved drilling fluid, which meets a number of significant conditions associated with the features of the geological section, has been developed. The fulfillment of the above conditions is ensured by the selected component composition and specific properties of the drilling fluid components. The basis of the drilling fluid is represented by a solution of three salts, as a result the total salinity of the filtrate of the drilling fluid is similar to the salinity of the formation water, the problems of limiting the negative consequences of the physicochemical interaction in the drilling fluid filtrate system - rock formation - formation fluids are solved. A certain combination of polymers and the introduction of calcium carbonate-based colmatate into the drilling fluid allow to limit the depth of penetration of the filtrate into the reservoir and preserve the reservoir properties of the formation. The drilling fluid contains an effective lubricant additive with surfactant, which helps to reduce the surface tension, softens the film water structure on the surface of pore space, partially prevents salt solubility, improves structural, mechanical, filtration and lubrication properties.
Laboratory work was performed to prepare and optimize the properties of the model drilling fluid; experiments were conducted to determine the permeability recovery coefficient. Experimental and industrial works were performed to test the developed drilling fluid formulation at the exploratory and production wells of Eastern Siberia. As a result of the application of the polysalt biopolymer drilling fluid formulation, an increase well production rate through new wells was achieved, the formulation showed high technological efficiency.
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