The Effect Of Low-Water-Loss Additives, Squeeze Pressure, And Formation Permeability On The Dehydration Rate Of A Squeeze Cementing Slurry

Abstract

The Effect of Low-Water-Loss Additives, Squeeze Pressure, and Formation Permeability on the Dehydration Pressure, and Formation Permeability on the Dehydration Rate of a Squeeze Cementing Slurry Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract In an effort to improve the success ratios of squeeze cement jobs, recent studies were made of the effects of fluid-loss control additives, differential pressures, formation permeability, and placement techniques on the performance of squeeze cement slurries. The studies showed that the rate of filter cake build-up is the most important factor to be considered in squeeze cementing. They further showed that this rate is a function of the variables listed and can be calculated by Darcy's equation for flow of liquids through a permeable media. Use of Darcy's equation showed that fluid-loss additives currently in use function by reducing the permeability of the filter cake. This slows down the rate at which filtrate can be forced through the filter cake and controls the dehydration rate of the slurry. This paper presents data relating the effects of the various factors on the dehydration rate of the slurry, and shows how a knowledge of well conditions and mechanisms of filter cake build up, along with good control over slurry properties can provide an appreciable improvement in the success ratios of squeeze cementing operations. GENERAL DISCUSSION Squeeze cementing is a remedial cementing technique which has always been difficult. Since the introduction of low-water-loss additives for cement; however, the success ratio has consistently increased. These additives have made possible many placement techniques which previously would have been impossible. An understanding of the factors which influence water loss and filter cake formation is a great aid in the selection of the optimum slurry properties and placement techniques. In order to attain a successful squeeze job, it is necessary to properly place the cement slurry. The slurry consists of finely divided particles mixed with enough water to contact all of the particles. As the slurry is forced against a permeable formation, particles will be filtered out on the face of the formation to form a filter cake. In most squeeze jobs, it is desirable to form this filter cake—but it is necessary to control its growth rate.