Helge Hodne

Effects of time and shear energy on the rheological behaviour of oilwell cement slurries

In the present study, it has been evaluated if the configuration of the high-speed mixer propeller blades used in cement slurry preparation done in accordance with API specifications [Specification for Materials and Testing for Well Cements, API Spec. 10, 5th edn., 1990.] does influence the input of mixing energy applied to the cement slurry. It has been shown that the term specific mixing energy (SME) is not valid for all types of slurries. It has also been shown through a comparison between a Vicat apparatus series of experiments and a consistometer study that there is no direct link between the consistometer data and the initial set of a cement slurry. Furthermore, the Vicat test was found not to give the initial set either. Finally, the study investigated the effect of mixing energy input on viscous properties and gel formation properties of the slurries. A drop in viscosity as a function of mixing energy has previously been considered to be a result of a structural breakdown. In the present study, it is suggested that this drop is a result of change in cement morphology.

Experimental study on the synthesis and characterization of aplite rock-based geopolymers

This paper presents a new method for geopolymer synthesis of ground aplite rock. The resulting geopolymers were easy to manufacture and exhibited promising mechanical properties. Compressive strength testing, X-ray diffraction, and scanning electron microscope analyzes were performed. The results indicated that in manufacturing, the aplite-based geopolymers, potassium-containing systems gave noticeable improvements in comparison with sodium-containing systems. Rheological behavior of the geopolymeric slurry showed non-Newtonian behavior. The Bingham and Herschel–Bulkley models were selected to simulate the viscosities of the slurries. The Bingham model fitted to the measured data with an average deviation of 1.65 (lbf/100 ft2) while the Herschel–Bulkley model showed large deviations from the experimental data.

Long-term durability of rock-based geopolymers aged at downhole conditions for oil well cementing operations

The long-term integrity of rock-based geopolymers was studied in corrosive environments. The geopolymers were cured for 7 days at ambient conditions. Afterwards, the geopolymers were exposed to crude oil, brine and H2S in brine at 100 °C and elevated pressures. The compressive strength, tensile strength, weight and volume changes were measured prior and after 3, 6 and 12 months of exposure. The measurements showed a turning point after 6 months of ageing. Whereas the compressive strength and tensile strength started to increase when the specimens were exposed to crude oil and brine, the specimens that were exposed to H2S experienced some degradation. Permeability of geopolymers before exposure and after 12 months of exposure to the crude oil and brine was very low. The permeability of the specimens which were exposed to H2S was not measureable. Substantial volume changes were observed for the geopolymers which were exposed to H2S and brine.

Development and Characterization of Norite-Based Cementitious Binder from an Ilmenite Mine Waste Stream

This is an open access article distributed under the Creative Commons Attribution License, originally published in Advances in Materials Science and Engineering.

The Influence of Drilling Fluid Rheological Properties on Primary Solids Control

Throughout the last decades, the design and performance of the primary solid control devices have changed significantly. Some five decades ago, the circular motion shakers dominated the marked. These shakers operated by sending the drilling fluid downhill a vibrating screen. Thereafter appeared the elliptical motion or linear motion shakers where the cuttings particles were vibrated upwards a tilted screen. Onto these shakers, the use of double screen decks and finally triple screen decks became common. Within the last years also the vacuum devices appeared.Throughout the last two decades, there has been an effort to increase the g-forces on these shakers and the industry seems to have preferred the high g-force devices recently. Laboratory studies, however, has indicated that the very high g-forces are not necessary to perform proper solids control. Instead, different vibration modes interacts with the gel structure of the drilling fluid and remove yield stresses. Hence, the fluid becomes mobile for flow through the screen.Flow through screens is strongly dependent on the extensional properties within the drilling fluid rheology. Drilling fluids with high extensional viscosity seldom has a very strong gel structure, and are generally not affected equally much by vibrations. This explains why solids control is more difficult using a KCl/polymer water based drilling fluid than if using an oil based drilling fluid.This article focuses on describing how the drilling fluid rheological properties alter during primary solids control. It is based on theoretical analysis, rheological studies in the laboratory and finally on practical applications in two recent exploration drilling operations. The solids control efficiency resulting from using different screen configurations is outside the scope of this article, as this topic requires a higher focus on separation technology.Copyright

Drilling Fluid Weight Material Sedimentation—Sedimentation of Suspensions

The authors describe tests studying sedimentation kinetics for various suspensions used in the oil well drilling industry. The tests are run using equipment that allows study of the sedimentation process as a function of temperature, drill string rotation, and fluid composition. The equipment used, described in detail by T. Omland et al. (2009) of this series of two papers, allows comparison studies to detect the effects from these operational elements. The study involves use of fluids commonly used in the oil field to link these laboratory experiments to real applications.