High Strength Granular Sealing Material Increases Efficiency of Primary Cementing and Squeeze Cementing

Abstract

Abstract The use of high strength granular materials in cement slurries has proved beneficial for cementing casing and squeeze cementing operations in Permian in Basin oil and gas wells. The addition of 1 to 4 lb of ground walnut shells to each sack of cement made possible successful high column cementing jobs in fields where high fill-ups normally cannot be obtained because of lost circulation. In squeeze cementing operations the number of cementing stages required for shutting off water was reduced by the addition of walnut shells to the last 50 per cent of the volume of cement slurry. Introduction The high hydrostatic head, created in the annulus when cementing casing, frequently is the cause of loss of slurry into weak formations or formations containing fractures or vugs. Common precautions taken to reduce this loss are reducing the density of the slurry adding effective sealing agents to the slurry, or both. One phase of this paper concerns the use of high strength granular sealing materials in cement slurry to seal openings into formations so that the slurry may be pumped to the desired level behind the casing. In squeeze cementing operations neat cement often fails to effect a complete seal because of the tendency of the slurry to enter only the weakest zones. This is indicated by the number of stages frequently required to stop the flow of water or gas. The intrusion of cement slurry into each perforation in a water or gas producing zone is probably necessary to eliminate flow completely, and a high final squeeze pressure may be a means of assuring entry of cement into each perforation or zone of weakness. The second phase of this paper concerns the use of high strength granular materials in cement slurries to obtain a high final squeeze pressure.