In order to protect the modern environment, it is necessary to prevent well collapse, well loss and protect the oil and gas reservoir. For the formation with developed bedding and fracture, in order to prevent well collapse and leakage and reduce the damage to oil and gas reservoir, the drilling fluid is required to have strong sealing property, effectively seal the bedding and fracture of the formation, prevent the drilling fluid and its filtrate from entering the formation, so as to improve the pressure bearing capacity of the formation, stabilize the well wall, prevent well leakage and protect the oil and gas reservoir. Chongqing Chuandong Chemical Group will talk about the detailed values of potassium formate and sodium formate in weighting agent of drilling and completion fluid.

Solubility

The solubility of formate in water is very large. The solubility increases with the increase of atomic weight of alkali metal. The saturation concentration of cesium formate can be as high as 83%, the saturation concentration of potassium formate can be as high as 76%, and the saturation concentration of sodium formate can also be as high as 45% (the above are all weight percentage), and the dissolution rate is fast.

Density

Formate solution can be used to prepare clean salt water of different densities according to the needs, among which the highest density of cesium formate preparation can be as high as 2.32g/cm³, the highest density of potassium formate preparation can be as high as 1.58g/cm³, and the highest density of sodium formate preparation can also be as high as 1.33g/cm³.

Viscosity of formate solution

The formate brine solution can keep low viscosity even at high density, which will not cause the increase of drilling fluid viscosity. The viscosity of cesium formate saturated solution is only 2.8cp, that of potassium formate saturated solution is 10.9cp, and that of sodium formate saturated solution is 7.1cp.

PH of formic acid salt solution

Formate belongs to strong alkali weak acid salt, and the aqueous solution is weak alkaline. With the increase of formate concentration, the alkalinity increases. The PH value of cesium formate saturated solution is 9.0, that of potassium formate saturated solution is 10.6, and that of sodium formate saturated solution is 9.4.

Activity of formate solution

Formate can achieve low activity of aqueous solution. In the presence of semi permeable membrane, the activity of drilling and completion fluid is an important factor to keep the formation stable. See Table 1 for the activity of brine solution with different concentrations. From table 1, it can be seen that NaCl and CaCl₂ basically reach saturation when the concentration reaches about 30-40%, while potassium formate has higher solubility, which can reach over 76%, which shows that lower solution activity can be achieved and better inhibition operation can be achieved, which is very important for well wall stability.

Drilling fluid is related to wellbore stability and reservoir protection. Formate weighting agent has the above characteristics, and formate compounds are non-toxic, easy to biodegradation, environmentally friendly, especially the use of potassium formate is recognized by the drilling industry.