New additives for minimizing cement body permeability

An experimental investigation was carried out with a new away of cement add itives replacing some of the currently used ones. In this study, the cement slurry pressure was monitored during the setting of the cement. Two time-c ycles of cement expansion and contraction were observed This is due to the individual contribution of each component in the cement mixture. To obtain the optimum tightness of the cement, final contraction in the cycle is cruc ial for blockage of gas migration. Concentrations of the additives were obt ained experimentally in this study for which the cyclic pressure behavior o f the cement was optimized and the permeability reduced for the best final cement results. The parameters investigated in this study were as follows: pressure applied on the slurry with time compressive strength and permeabil ity of the set cement. The major causes of the early microfractures are the incomplete cement-water reaction, low compressive strength of the set ceme nt, and the sudden change in the hydrostatic pressure as the cement changes its phase from a liquid to a solid state. The fluid loss and free wafer co ntent were measured and controlled for each sample. Three new cement additives were investigated one was used to eliminate the microannulus with the pipe while the other two were used to eliminate the m icrofractures within the cement body. An appropriate amount of Ironite Spon ge concentration eliminated the microannulus with the pipe. The optimum amo unt of synthetic rubber powder needed during the optimum two-cycle expansio n-contraction process was also obtained under reservoir conditions. The Anc horage clay concentration in the mixture that migrates for a limited time m inimizes the cement body pores. This concentration can also be optimized Th is paper reports the appropriate amounts of X-C polymer, Anchorage clay, Ir onite Sponge, and synthetic rubber needed to optimize the compressive stren gth and eliminate both microfracture and microannulus. There are certain li mits to the amount and type of synthetic rubber powder for which microfract ures are eliminated The article reports an experimental approach that can b e used to eliminate gas migration through a cement design that is environme ntally safe and inexpensive, using recyclable materials.