A Study On The Properties Of Oil Cement Stone In Ultra-deep Well

As the development of Daqing Oilfield in deep exploration, exploration wells have been more than 5000 meters deeper in the Xujiaweizi area. Because of the high level of average temperature gradient , more than 4℃/100 m), the temperature in the down hole will be more than 200℃. It is not only a big problem with cementing in high-temperature wells, but laso the severe challenges for oil well cement. Based on the HT condition of Xujiaweizi area, it is studied on the application of conventional oil well cement over 200℃. With x-ray deffractometer, scanning electron microscopy and triaxial stress testing machine, the characteristics of the composition of hydrates, microstructure, compressive strength, permeability and stress-strain of Class G oil well cement are tested and anlazyed from 200℃~240℃. In this paper, the effect of the temperature on the composition of hydrates, microstructure is proposed. Then the hydrating and hardening mechanisms of oil well cement is revealed under high temperature condition; and the laws of the strength and permeability both affacted by curing temperature studied, it is defined that reasonable range of the amount and the fineness of silica sand, the strength stabilizer. It is provided that the measure to inhibit strength retrogression and the optimized design scheme of HT cementing slurry system under 200℃~240℃; by analyzing the laws of the effect of the temperature and the confining pressure on the mechanical behavior of cement stones, it is aslo evaluated on mechanical characteristics of HT cementing slurry system under condition of triaxial stress. All above these provides the basis for the reasonable design of cementing slurry system for HT deep well.