Abstract: A method of treating a hydrocarbon producing formation located downhole in a borehole, where the borehole has been cased and subsequently perforated, and the formation produces excessive water and an inadequate quantity of hydrocarbons through the perforations. Salt water is forced to flow down a tubing string, through the perforations, and out into the payzone. Thereafter, a spacer of fresh water follows the salt water, and thereafter a soluble alkali silicate solution flows behind the fresh water. Another spacer fluid of fresh water is forced to flow behind the silicate, followed by dilute acid. Next, the acid is displaced from the borehole and is forced out into the formation with flushing fluid, and the wellbore is then produced. The flow of the recited material through the perforations follows along the path of least resistance, which also is the flow path of the water intrusion. The salt water and silicate react with one another to form a barrier which prevents the water from invading the formation.