Research and Development of the Lightweight Corrosion-Resistant Cement Blend for Well Cementing in Complex Geological Conditions

Is a fact that well cementing in highly permeable rocks is complicated by a high content of hydrogen sulfide, overoming a large number of difficulties. There is an accelerated destruction of cement stone, the absorption of the cement and the impossibility to reach its level of design in the annular space, which leads to a significant problems and failures at the cement performance and as a result to the casing leak and remedial cementing techniques. We are going to present the results of the analysis and laboratory testing, evaluation and analysis of cement slurries for fixing high-permeability rocks containing hydrogen sulfide. In the conclusion was revealed that there is no effective cement slurry wich will be solution with hydrogen sulfide resistance and qualitatively colmation ability of absorbing horizons. Evaluating the effectiveness of cement slurries and the cement sheaths was carried out through laboratory studies performed at the Drilling Department of the Ukhta State Technical University Laboratory testing to determine chemical characterization and performance evaluation of cement slurries and cement sheaths were carried out using both standard Russian and foreign testing procedures and equipment for cement testing according to GOST and API standarts. In addition, the cement sheath integrity for corrosion was testing according to the procedure proposed by Doctor of Science Victor Solomonovich Danyushevsky using the corrosion resistance coefficient. Based on the laboratory testing, evaluation and analysis, it was designed a new composition of lightweight corrosion resistant cement slurry (application for invention № 2016117871 of 05.05.2016) on the basis of Portland cement IG HSR-1, treated with the sulfated synthetic polymer (Gas block), expanding additive (EA) and granulated foam glass (GFG). The addition of granular foam glass makes possible to reduce the density of the cement, in order to improve the efficiency of pore and cracks colmatation upon high permeability rocks acting as a necessary expanding additive. The treatment of cement slurry by gas acting blocking additive decreasing permeability of the cement sheath, as a result, the quality of the wells barriers increases under the conditions of hydrogen sulfide attack. In general, the lightweight corrosion-resistant blend allows to reduce the permeability of cement sheath and to use it for improve the quality of cements contaning hydrogen sulfide coming from highly permeable rock layers. Established and defined physic-mechanical properties and parameters of the blend and cement stone, their changes with variation of the concentration and dispersion of the granulated foamed glass. With the corrosion resistance factor was found that designed cement slurry and sheath have a corrosion resistance to hydrogen sulfide attack. In conclusion the operations manual for the second intermediate and production casing string for exploratory wells at the Alabushin field was compiled. In this operations manual was implemented the laboratory testing of cements and cementing materials as an essential part of the cementing process, taking into account the complexity of the geological conditions.