ABSTRACT:

Various additives had been used to improve the properties of oil well cement. Perlite is a material that occurs naturally and abundantly as a result of cooling the volcanic lava. The aim of this study is to examine the prospect of applying perlite particles (PP) for oil well cement. Two cement formulations (with and without perlite particles) were prepared under high temperature and high pressure. The impacts of PP on the properties of well cement such as density variation, viscosity, gel strength, compressive strength, Young's modulus and permeability were examined. The results showed an enhancement in the rheological properties when PP was added. For instance, viscosity was reduced by 29.7% and gel strength was enhanced by 41.1% compared to the base cement. PP was able to reduce the variation of cement density to very low percentage of 0.9%. Addition of Perlite particles reduced the Young's modulus of the cement by 40% in comparison with the 0% PP. Incorporating 3% PP improved the compressive strength of cement by 15.8% in comparison with the base cement. However, there is a slight increase in the permeability because of using PP, but it is still in the recommended value.

1. Introduction

In Petroleum industry, while drilling the development or exploration wells, a drilling fluid is used to prevent the entering of formation fluids into the wellbore by providing hydrostatic pressure. Then, the casing is run into the well to endure the forces of collapse and burst. After that, a slurry of cement is pumped to fill the annulus between the steel casing and rock formation (Nelson and Guillot, 2006). The slurry starts to harden gradually, and the cement sheath is formed. The cement sheath plays a vital role in the well integrity by providing zonal isolation of a variety of fluids (such as gas, oil, and water), protecting the casing string against corrosion and providing mechanical support. The failure of cement sheath can lead to annulus pressurization, migration of formations fluid to the surface and blowout in disastrous cases. The hazard of cement failure can be diminished by designing a high-performance cement sheath that warrants the essential integrity of the well, reduces the risk of damage coming from the accumulated material produced by the process of physicochemical and stops the formation's fissures at the interface between cement and casing and between cement and rock (Krakowiak et al., 2015).

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