With the deepening of understanding of the protection of oil and gas layers, reducing the content of solid particles, especially clay particles in drilling fluids, plays an important role in preventing the clogging of the solid particles in the pores of the oil and gas layers and improving the recovery factor. The potassium formate drilling fluid can avoid plugging to the greatest extent and improve the productivity of the reservoir. It is also one of the tools to liberate the reservoir.

The commonly used drilling fluid for drilling production wells is water-based mud, because the drilling fluid column pressure during drilling is generally greater than the formation pressure. Under the effect of pressure difference, water and clay in the drilling fluid will invade the oil and gas layer, causing various damages to the oil and gas layer.

(1) Expand the clay in the production layer

(2) Destroy the continuity of oil flow

(3) Produce water lock effect and increase oil and gas flow resistance

(4) Precipitate is formed in the bottom gap

(5) Mud invasion of solid particles of drilling fluid

Therefore, in order to better adapt to the characteristics of the Carboniferous formation in this well, the formulation of solid-free drilling fluid system was optimized. During construction, on-site construction personnel achieved near-balanced drilling by reasonably controlling the pressure difference, while increasing the mechanical drilling speed and reducing the damage of drilling fluid to the oil and gas layer.

The potassium formate drilling fluid system has no solid phase, and has little wear on machinery and drilling tools. It is not easy to form mud in the drill pipe, which is conducive to the requirements of diamond small-diameter drilling and rope core technology; there is a better prime flow Drag reduction and lubricating properties can reduce the delivery pressure; it contains a large number of organic polymers, combined with different inorganic salts, can effectively inhibit the expansion and dispersion of formations and cuttings.

The water activity of the aqueous solution of potassium formate decreases rapidly with the increase of the concentration of potassium formate, the solubility is as high as 76%, which can greatly reduce the activity of the drilling fluid and effectively prevent the collapse of the well wall.

Due to the reasonable use of the drilling fluid system, the formation damage is minimized. The use of potassium formate drilling fluid has played a decisive role in the discovery and protection of oil and gas layers, which has been highly recognized by the drilling industry.