Problems of the use of lightweight cement in oil and gas well fixing and possible solutions

The article presents the results of the selection of the grouting mortar made out of the cement that does not comply with the state standard (GOST) for cementing the upper part of the column during the construction of an oil well. The object of study was the cement grade PСT III-ob 5-50 GOST 1581-96. The study used the additives that, according to the literary sources, are able to enhance the cement technological parameters. The additives were calcium chloride (CaСl2), sodium chloride, magnesium chloride (MgCl2), gypsum (CaSO4·2H2O), marble chips (MK-100), silica fume (МК-65, МК-85), caustic soda (NaOH) and calcined soda (Na2CO3), as well as high and low viscosity polyanionic cellulose. The following technological parameters were determined: the mortar density, the mortar paste spreadability, water separation, the thickening of the mortar, the ultimate bending and ultimate compression strength of the cement stone. The study was conducted taking into account the domestic and international standards. The test results show that the use of the agents such as NaCl, MgCl2, CaСl2, Easy SET, МК-100, and CaSO4·2H2O enhances the water separation of the mortar and the strength properties of the cement stone. However, the agents used to improve water separation (low viscosity polyanionic cellulose, high viscosity polyanionic cellulose, Na2CO3, МК-65, and МК-85) significantly reduce the strength properties of the cement stone. The columns can be fixed with the above mentioned cement using agents such as CaCl2 (2 % of the cement mass), NaCl (1.2 %), MgCl2 (1 %), and the hardening agent Easy SET (1 % of the cement mass).

grouting mortar, lightweight cement, cementing, density, water separation, strength, bending, compression, spreadability