Influence of Weighting Materials on the Properties of Oil-Well Cement

Abstract

The integrity of oil and gas wells is largely dependent on the cement job. Maintaining the properties of the cement layer throughout the life of a well is a difficult task, particularly in high-temperature and -pressure conditions such as those in deep wells. Cementing deep wells require slurries with high densities. Heavyweight cement systems are those designed with weighting materials. These materials have a higher specific gravity in comparison to cement. The purpose of this work is to investigate the influence of weighting materials on the properties of Class G oil-well cement and to make necessary recommendations for their use. The rheology, fluid loss, gas migration, and dynamic elastic properties of three cement slurries containing different weighting materials, namely, hematite, barite, and ilmenite, were studied. The results indicate that cement slurry designed with barite exhibits the best rheological behavior that would provide a perfect solution for deep wells where cement placement is a concern. The barite slurry had the lowest plastic viscosity. The plastic viscosity of the hematite and ilmenite-weighted systems was higher by 11.5 and 12.4%, respectively. The barite-based slurry also had the highest yield point of 84.3 lb f /100 ft 2 , whereas the yield points of hematite and barite cement were 37.9 and 29.5 lb f /100 ft 2 , respectively. Furthermore, the gel strengths of barite cement were the highest, with 10 s and 10 min gel strengths of 11.5 and 39.5 lb f /100 ft 2 , respectively. Ilmenite had the most positive impact on fluid loss control, which would be appropriate in high permeable formations. It had a fluid loss of 66 mL/30 min, lower than those of the hematite (80 mL/30 min) and barite (82 mL/30 min) systems. Furthermore, the best dynamic elastic properties were exhibited by the ilmenite system, with the smallest Young’s modulus (27.3 GPa) and the highest Poisson ratio (0.252). This would make the ilmenite to be very useful in developing heavyweight cement composites that could withstand severe external loads imposed on the casing and cement. The hematite cement was the most impermeable to gas migration, with a gas volume of 127.8 cm 3 , whereas the volume measured in the barite and ilmenite systems were 20.9 and 78% higher, respectively. This makes the hematite to be very useful in deep gas wells where gas migration control is important.

Effect of micro-magnesium oxide admixture on rheological and compressive strength properties of class G well cement

“…Figure 4D), the slurry mixed with type II microsized magnesium oxide is prone to higher thixotropy than the rivals from type I micro-sized magnesium oxide blended slurry. When cement slurry has different particle size and density constituents (e.g., the density of Portland cement is 3.15 g/cm 3 , the density of magnesium oxide is 3.58 g/cm 3 ), settling and packing will probably occur (Ahmed et al, 2020;Ahmed et al, 2019). These mechanisms may also cause this to occur.…”

Analysis of the Impact of Vermiculite on Hematite-Based Cement Systems

“…One of the major challenges in formulating heavyweight systems is the segregation of heavyweight particles under dynamic and static wellbore conditions . This issue results in a heterogeneous cement column that adversely affects the integrity of the cement sheath. , Several studies have investigated and proposed several suggestions to reduce cement segregation and enhance the cement sheath performance. Some authors proposed some anti-settling materials like perlite and laponite, while other studies modified the weighting materials either by decreasing their particles size or mixing different weighting materials …”

Effect of SiO2@PEGMA Composites on Mechanical Properties of Oil Well Cement

“…After the cementing operation, hardened cement pastes are required to effectively isolate the pay zone and provide protection and support for the casing, which is very important for oilfield development. − The safety and quality of cementing construction mainly depend on the performance of oil well cement. , Because cement is a brittle material, it is easy to produce micro-cracks and micro-annuli due to the subsequent operations such as perforation, fracturing, and the complex forces of underground rock formations, resulting in the failure of interlayer isolation between oil wells, which is not conducive to oilfield development. − Cementing is complex and challenging due to the intricacy of the geological conditions of the target layer.…”