BASE OF WEIGHTED PLUGGING MORTAR Russian patent published in 2002 - IPC

FIELD: plugging mortars used in cementing of casing strings of oil and gas wells in interval of abnormally high formation pressures and temperatures from 22 to 120 C. SUBSTANCE: base of weighted plugging mortar includes oil-well portland cement with regulator of processing properties and weighting additive in the form of Magbar weighting additive presenting homogeneous mixture of mas.pt. of magnetite and 1 mas.pt. of barite with the following ratio of ingredients, wt.%: portland cement, 25-40; Magbar, 60-75; regulator of processing properties, 0-4 of portland cement weight. Base of weighted plugging mortar may contain expanding additive of magnesium oxide MgO, calcium oxide CaO, gypsum in amount of 0-4% of portland cement weight. Regulator of processing properties may be used in the form of reducer of plugging mortar water loss - sulfocell, carboxymethyl cellulose in amount of 0-1.0% of portland cement weight, or reagents in the form of retarders-plasticizers nitrilotrimethylenephosphoric acid NTF, C-3 in amount of 0-0.5% of portland cement weight. Technical result of said invention consists in trouble-free cementing of casing strings in zone of abnormally high formation pressure, brine, mineralized water, fresh water due to higher sedimentation stability, earlier strength of plugging stone within wide temperature range from 35 to 120 C, high density up to 2.5 g/cu.cm with simultaneous provision of the remaining parameters of mortar and stone such as water loss, pumpability, resistance to corrosion. EFFECT: higher efficiency. 4 cl, 4 tbl, 1 ex