Mechanical Properties Analysis And Material Modification Of Low-density Cement Stone With Floating Beads

Microsphere low density cement slurry system in low pressure and leakage formation security cementing plays a important role, is widely used in our country western deep wells with high temperature and gas storage well cementing. The sealing ability of low density cement slurry solidified into cement sheath in the well is directly related to the safety and production life of oil and gas wells. At home for study of microsphere low density cement slurry system to meet engineering application, research on the long-term mechanical properties of cement stone. Therefore, this paper by simulating actual working condition mechanical properties of microsphere low density cement slurry system were thorough testing and analysis, aiming at the shortage of mechanical properties of cement stone, preferably a fiber material mechanical modification, security in underground long-term sealing solid ability of low density cement ring.This paper on the research status at home and abroad were on the basis of sufficient investigation and research, and simulated field conditions of microsphere low density cement slurry system for the evaluation of mechanical experiment of comprehensive, detailed and in-depth. Tested at different ages, different temperature environment of cement stone compressive strength, tensile strength, uniaxial and triaxial cement mechanical properties, under cyclic loading cement mechanical properties; of cement stone pore size distribution, morphology, the value of porosity and permeability test analysis, from the point of view of microstructure analysis the macro mechanical phenomenon of cement, the cement ring mechanical model, integrity testing and damage theory method analysis of cement sheath failure mechanism; through the optimization of fiber materials to improve the mechanical properties of microsphere low density cement stones. On the basis of experimental research and theoretical study, the following conclusions are formed:(1) Microsphere low density cement has better compressive strength, and reduce the tensile strength, tensile and compressive strength is relatively small;(2) By cyclic loading experiments found that cement stone in the first week of cyclic loading in the larger compaction deformation, in the second to the fifth week loaded cement has good elastic deformation ability. In the sixth and seventh weeks of loading of cement stone plastic deformation increased significantly and that cement stone in the weeks after loading internal structure produce damage, loss of ability of elastic deformation;(3) The cement ring mechanical model were calculated, in high pressure water mud ring mainly for tensile failure, cement sheath the upper and middle sealing solid section sealing solid ability is good, section of the lower part of the sealing of the sealing ability is insufficient, to be to improve;(4) Through the complete experimental device of experiment, it is found that, the microsphere low density cement ring under high temperature curing environment prone to cracking phenomena of ontology, and cement slurry system in the water produced in the process of alkali aggregate reaction is lead to cement ring cracking of the important reasons.(5) Optimized FK fiber can effectively improve the tensile strength and deformation of low density cement recovery capability, effectively improve the microsphere low density cement ring under high temperature curing cracking phenomenon;(6) The incorporation of FK fiber after microsphere low density cement slurry liquidity, API fluid loss, thickening time, sedimentation stability to meet the requirements of the construction site.