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In deeper wells, high pressure and temperature post cementing operations put extreme stresses on the cement sheath and dramatically affect the cement integrity. So, the design of the cement slurry is very important to ensure the durability and long-term integrity of the cement sheath. The design should lead to a better zonal isolation and strengthen the bonding with the casing. Furthermore, it should help to shield the casing from corroding and unpredictable shock loads in deeper zones and sustain plugs to control the lost circulation in fractured and high permeability zones. Different additives were used to provide these functions such as; polymers, fibers, and bio-medicine in concrete history. Because of their large surface areas and small size, those particles are highly being used in the petroleum industry in the latest decades. In this study, the usage of polypropylene fibers (PPF) is evaluated for oil well cement at high pressure and high temperature (HPHT) condition. The polypropylene fibers were added to the base cement in a different amount to evaluate its influence on enhancing the performance of cement. The results obtained showed that adding polypropylene fiber to the base cement has a negligible effect on cement density, rheological properties, and free water. Using polypropylene fiber (0.75% base weight of cement (BWOC)) with the base cement reduced the thickening time by 75%; from 317 minutes to 78 minutes. The addition of Polypropylene fiber (0.5% BWOC) increased the compressive strength of class G cement by 17.8%. Polypropylene fiber can be used as an alternative material for silica floor in shallow wells. Polypropylene fiber has a significant effect on reducing the porosity and the permeability of the base cement.

Nanotechnology provides a wide variety of methods to resolve industrial issues, which could not be addressed previously using customary methods. It helps enable researchers to alter properties of bulk materials at the nanometer scale. Various nanomaterials have been successfully applied in many areas of petroleum engineering, particularly in drilling fluids, lost circulation, enhanced oil recovery (EOR), and cementing. This study examines the mechanical and microstructural properties of oil well cement with nanozeolite. During this research, API Class G cement was used with various concentrations of nanozeolite. Compressive strength development of Class G cement, with and without nanozeolite, was studied using an ultrasonic cement analyzer (UCA) for 24 hours under high-pressure and high-temperature (HP/HT) conditions. The porosity and permeability of set Class G cement admixed with nanozeolite was also analyzed in an automated permeameter/porosimeter after 24 hours of curing. Microstructural examination of cement samples was performed using scanning electron microscopy (SEM). Three important parameters during well cementing operations included time to achieve 50- and 500-psi compressive strength and time to achieve 2,000-psi compressive strength. These parameters were significantly altered by adding a small percentage of nanozeolite to the neat Class G cement. The addition of nanozeolite resulted in a decrease in transition time and accelerated achievement of 2,000-psi strength. Furthermore, the porosity and permeability of the set Class G cement specimens with nanozeolite decreased substantially, thus indicating a dense microstructure of the matrix. This was confirmed by microstructural investigations using SEM. Nanozeolite is nonhazardous, nontoxic and is compatible with API Class G cement. Nanozeolite can be an effective oil well cement additive because it enhances early strength, and the final compressive strength helps improve cement durability. The accelerated compressive strength development can help decrease wait-on-cement (WOC) time, thus lowering operation costs. Additionally, denser microstructure can help restrain the invasion of corrosive formation fluids.

Growing demand to drill High Pressure High Temperature (HPHT) wells requires improved technology to overcome the HPHT challenges. Oil well cementing has a greater impact on the production potential of a well as compared to other operational actions. A successful cementing job is dependent on how quickly and efficiently cement achieves strength. Achieving desired mechanical properties of cement becomes harder and complex at HPHT conditions. A wide variety of admixtures are commonly mixed with the oil well cement slurries to deal with the extensive range of pressure and temperature to acquire enhanced mechanical properties depending on the combination of admixture used. Carbon Nanotubes (CNT), declared as "Miracle Material", have been one of the most recent admixtures being used to achieve the desired mechanical properties of cement slurries. This paper highlights the study carried out to examine the mechanical properties comprising compressive strength of oil well cement slurries integrating chemical additives and CNT under high pressure high temperature (HPHT) conditions. Three different percentages of functionalized multi-walled CNT's (MWCNT), at 0.1%, 0.25% and 0.5% bwoc, were mixed with Type-G oil well cement together with other additives used in HPHT applications. Compressive strength investigations (Destructive and UCA) were carried out on those slurries. SEM investigations were also conducted on selected MWCNT mixes. The study indicated that incorporation of MWCNT, at a very small percentage, in cement slurries resulted in a significant increase in the compressive strength values.