Exploration Engineering in petroleum industry is a high-tech and high-level industry. The most important thing for such a high-tech and high-level project is to ensure construction safety and improve drilling efficiency. The thick mud skin formed on the hole wall during drilling causes the problems of longer operation time, more sedimentation at the bottom of the hole and insufficient exposure of the aquifer before the pumping test. Therefore, Sodium Hexametaphosphate will be purchased and used to soak the aquifer before the mechanical well flushing to achieve good results in the pumping test
The main components of chemical mud used in drilling are clay powder, soda ash, polyacrylonitrile amine salt, potassium humate, potassium Polyacrylamide, etc. Clay powder and soda ash are indispensable. The mud skin is mainly composed of clay powder, and soda ash determines the pH value of the mud to be 8-9, which is weakly alkaline, and the mixing of clay powder and soda ash has a stabilizing effect.
The principle, dosage calculation, soaking time and operation steps of well flushing by soaking aquifer with sodium hexametaphosphate are as follows
(1) A certain proportion of sodium hexametaphosphate is added into the water to prepare the well flushing fluid, which is weakly acidic and neutralized by ACID and alkali, reducing the pH value of the mud and weakening the stability.
(2) The liquid tension is reduced, which can ensure that the water solution can well penetrate into the rock fracture, effectively contact with the mud skin and the filling clay in the fracture, and has weak corrosion to the drilling tool.
(3) Because the clay surface of dispersed mud is negative, when the phosphate radical of sodium hexametaphosphate is adsorbed on the clay surface, the negative charge of the clay surface is enhanced, so that the repulsive force between clay particles is significantly increased. At the same time, the polymer macromolecule has a large water film, which effectively enhances the hydration of clay particles. With the thickening of the hydration film of clay particles, the clay particles are dispersed and the wellbore mud is destroyed effectively.
(4) It has complexation effect on clay. Sodium hexametaphosphate complexes with calcium and magnesium ions in clay to form water-soluble complex. Therefore, complexation reduces the concentration of calcium and magnesium ions. The water-soluble complex is not easy to coalesce and precipitate, and is easy to be discharged out of the hole during well flushing.
To ensure the preparation of a certain concentration of sodium hexametaphosphate well flushing fluid to soak the aquifer section and make the pumping test achieve good results, the quality of sodium hexametaphosphate can not be ignored. The reason why sodium hexametaphosphate is widely used in the industry is the production of hot phosphoric acid, with clear aqueous solution, less impurities and less consumption.
