Using an Elastic, Expandable Sealant System for Zonal Isolation of Maroon Wells: a Laboratory Study

Abstract

An oil and gas well cementing in Gachsaran formation, where sustained annular pressure has been reported in many wells, presents a big challenge in Maroon field. The main challenges are preventing gas migration and achieving zonal isolation using a competent cement sealant system which is able to withstand downhole stresses and high temperatures during production cycles. Unlike conventional cement systems, properties, such as, high Poisson's ratio and low Young's modulus compared to that of the rock were optimized in the new system to achieve mechanical resistance and durability. The use of elastic-expandable additives to solve problems in oil well cementing has been investigated in recent years by several research groups in the petroleum industry. This study includes the laboratory examination of the effect of an elastic-expandable additive on the physical properties of a new cement sealant system. In the research process, a candidate well was selected and the properties of the used cement slurry in a problematic section of the well were evaluated in the laboratory. Then, the elastic-expandable additive was added as an elastic agent and the improvements in the cement slurry and stone properties were studied. This article discusses the problems associated with the conventional cement used in the candidate well and gives the detail of the improvements in cement properties obtained by adding the elastic-expandable additive to the cement slurry formulation as an elastic agent. The elastic-expandable additive increases the Poisson's ratio and expansion set cement, but it decreases the Young's modulus and fluid loss of the cement slurry. In addition, to prevent gas migration and achieve zonal isolation, there is an optimum concentration of the elastic-expandable additive at which the maximum compressive strength is reached. The results of this study can be used to optimize the cement slurry design in any given set of conditions.