METHOD OF CREATING SCREENING CURTAIN WHEN DRILLING HIGH-PRESSURE STRATA SATURATED WITH STRONG CHLORIDE-CALCIUM BRINES Russian patent published in 2020 - IPC E21B21/08 

FIELD: oil, gas and coke-chemical industries.

SUBSTANCE: invention relates to construction of oil and gas wells and, in particular, to a method for isolation of high-pressure strata saturated with strong chloride-calcium brines, for continuation of accident-free drilling on underlying oil and gas collector. When implementing the method, injection capacity of the high-pressure formation is determined and the buffer pack is pumped using potassium carbonate before the magnesian-phosphate plugging solution. After contact of potassium carbonate with formation waters saturated with salts of calcium chloride, chemical precipitation of potassium carbonate in form of calcium carbonate (insoluble chalk) takes place. Coefficient of solubility K₂CO³ (in g per 100 g of water) is 111.0 at 20 °C and 139.2 at 80 °C, density is 2.428 g/cm³, which considerably increases efficiency of the screening curtain (due to formation of a larger volume of insoluble residue). Then, cement is pumped to developing zone for absorption. After a certain period of time, chemical precipitation of calcium carbonate takes place. After that, cement plug is crimped, crushed and further drilled. Isolation of high-pressure strata saturated with strong chloride-calcium brines is carried out by creating a complex chemical and physical barrier in the bottomhole formation zone.

EFFECT: higher efficiency of wells fixation, possibility of drilling continuation to underlying oil and gas reservoirs.

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