No abstract

Adsorption is a rock surface phenomenon and has increasingly become popular, especially in particle-transport applications across many fields. This has drawn a remarkable number of publications from the industry and academia in the last decade, with many review articles focused on adsorption of polymers, surfactants, gas, and nanoparticles in porous media with main applications in Enhanced Oil Recovery (EOR). The discussions involved both experimental and modeling approaches to understanding and efficiently mimicking the particle transport in a bid to solve pertinent problems associated with particle retention on surfaces. The governing mechanisms of adsorption and desorption constitute an area under active research as many models have been proposed but the physics has not been fully honored. Thus, there is a need for continuous research effort in this field. Although adsorption/desorption process is a physical phenomenon and a reversible process resulting from inter-molecular and the intramolecular association between molecules and surfaces, modeling these phenomena requires molecular level understanding. For this reason, there is a wide acceptance of molecular simulation as a viable modeling tool among scientists in this area. This review focuses on existing knowledge of adsorption modeling as it relates to the petroleum industry cutting across flow through porous media and EOR mostly involving polymer and surfactant retention on reservoir rocks with the associated problems. The review also analyzes existing models to identify gaps in research and suggest some research directions to readers.

No abstract

No abstract

No 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.

Summary Fly ash, which is a pozzolan generated as a byproduct from coal-powered plants, is the most used extender in the design of lightweight cement. However, the coal-powered plants are phasing out due to global-warming concerns. There is the need to investigate other materials as substitutes to fly ash. Bentonite is a natural pozzolanic material that is abundant in nature. This pozzolanic property is enhanced upon heat treatment; however, this material has never been explored in oil-well cementing in such form. This study compares the performance of 13-ppg heated (dehydroxylated) sodium bentonite and fly-ash cement systems. The raw (commercial) sodium bentonite was dehydroxylated at 1,526°F for 3 hours. Cement slurries were prepared at 13 ppg using the heated sodium bentonite as partial replacements of cement in concentrations of 10 to 50% by weight of blend. Various tests were done at a bottomhole static temperature of 120°F, bottomhole circulating temperature of 110°F, and pressure of 1,000 psi or atmospheric pressure. All the dehydroxylated sodium bentonite systems exhibited high stability, thickening times in the range of 3 to 5 hours, and a minimum 24-hour compressive strength of 600 psi. At a concentration of 40 and 50%, the 24-hour compressive strength was approximately 800 and 787 psi, respectively. This was higher than a 13-ppg fly-ash-based cement designed at 40% cement replacement (580 psi).

No abstract