A review of the various treatments of oil-based drilling fluids filter cakes

Treatment of the filter cake layer after drilling is essential for better cement integrity and to retain the original reservoir permeability. Compared to water-based filter cake, oil-based mud filter cake removal is more sophisticated as oil encloses the filter cake’s particles. Therefore, oil-based mud clean-up requires wettability alteration additives (mutual solvents and/or surfactants) for permitting acid/filter cake reaction. With an appropriate acid, microemulsions were reported to be very efficient in cleaning oil-based filter cakes, due to their low interfacial tension and high acid solubility. The objective of this paper is to provide an overview of the different techniques and treatment solutions utilized in oil-based filter cake clean-up. Furthermore, a synopsis of the various treatments for drilling fluids densified with different weighting materials is presented. Subsequently, the research limitations and opportunities have been highlighted for future work. In the light of the review that has been presented in this paper, it's recommended to conduct further investigation on some areas related to filter cake removal. The removal of filter cake formed from weighting materials other than barite, calcium carbonate, ilmenite, and manganese tetroxide needs to be investigated thoroughly. Additionally, the overall efficiency of oil-based mud removal needs to be studied under wide ranges of temperature, salinity, and pH. The utilization of surfactant-free microemulsions in filter cake treatment could also be investigated.

Enzymatic and Oxidizing Agents for the Decomposition of Polymers Used in the Composition of Drilling Muds

The article presents the results of research on the influence of enzymatic and oxidizing agents on polymers used in drilling mud technology. The research used calcium hypochlorite, urea peroxide, sodium persulfate, amylase and cellulase. This allowed us to determine the optimal concentrations of these agents in order to reduce the rheological parameters of drilling muds. The ability of enzymes and oxidants to decompose colloids used in the composition of drilling muds was determined on the basis of measurements of their rheological parameters and the influence of oxidants and enzymes on the properties of filter cakes. The final effect of the presented research was the development of a drilling mud treatment method before the cementing procedure and the development of washer fluids containing enzymatic or oxidizing agents to be used to prepare the borehole for the cementing procedure. The drilling muds selected for the research contained starch and cellulose polymer colloids, which allowed for the selection of appropriate agents depending on the type of polymer set used in the drilling mud. Positive results were obtained regarding the possibility of thinning the drilling mud immediately before cementing, as well as the possibility of using oxidants and enzymes in the composition of washer fluids.

Dewatering fine solid suspension by using steam pressure filtration

Steam pressure filtration is the combination of mechanical and thermal in one equipment. This process shows the advantages in comparison to conventional pressure filtration by the characteristic of its distinction mechanism. Application of steam pressure filtration can be listed: dewatering the suspension of fine solid, remove the contaminant, dangerous chemical, dissolved ions, protecting the human health as well as the environment. This paper shows the mechanism of steam pressure filtration as well as the result of tests, the comparison related to the efficiency between steam pressure filtration and conventional pressure filtration. The steam pressure filtration shows the high efficiency in mechanical displacement phase in both input parameters: solid volume fraction of suspension and the height of filter cake. The residual moisture content and saturation of filter cake using steam pressure filtration are lower 10÷20% than those values of filter cake using conventional pressure filtration. Moreover, some preliminary tests taking account to the drying phase of steam pressure filtration are also showed. The moisture of fine material filter cakes is around 6÷13%. Through the result of tests, interpretation and discussion, the application of steam pressure filtration is possible in the field of mineral processing and metallurgy.

Particle movements provoke avalanche-like compaction in soft colloid filter cakes

During soft matter filtration, colloids accumulate in a compressible porous cake layer on top of the membrane surface. The void size between the colloids predominantly defines the cake-specific permeation resistance and the corresponding filtration efficiency. While higher fluxes are beneficial for the process efficiency, they compress the cake and increase permeation resistance. However, it is not fully understood how soft particles behave during cake formation and how their compression influences the overall cake properties. This study visualizes the formation and compression process of soft filter cakes in microfluidic model systems. During cake formation, we analyze single-particle movements inside the filter cake voids and how they interact with the whole filter cake morphology. During cake compression, we visualize reversible and irreversible compression and distinguish the two phenomena. Finally, we confirm the compression phenomena by modeling the soft particle filter cake using a CFD-DEM approach. The results underline the importance of considering the compression history when describing the filter cake morphology and its related properties. Thus, this study links single colloid movements and filter cake compression to the overall cake behavior and narrows the gap between single colloid events and the filtration process.

HAZARDOUS WASTE CLASSIFICATION: REVIEW OF WORST CASE TO LESS WORST CASE METAL SPECIES WITH A WORKED EXAMPLE FOR A CONTAMINATED SOIL

The classification of waste as either hazardous or non-hazardous, especially for mixtures such as contaminated soils, ashes, filter cakes and sludges, is not straight forward. In particular, as the laboratories can only measure total metal concentrations, both the European and the UK technical guidance state that if the classifier doesn’t know exactly which metal species is in their waste, then they should start from a worst case species and use lines of evidence to work towards a more reasonable (less hazardous) species. However, the guidance doesn’t define or list worst case nor less worst case species. While some authors have documented worst case species, this is only in relation to documenting the concentrations at which each hazard property is triggered for a given worst case species. This paper addresses this gap. It documents how to define both the worst case species and more importantly, lists less worst case species for 32 elements and 204 metal species; species based on those listed in the European legislation but also supplemented by species that haven’t (yet) been included in this legislation but are significant nevertheless. For each species, the paper tabulates the hazard property that triggers first, metal concentrations, conversion factors and other metadata, species by species, in descending order of hazard. Finally, to demonstrate how to use the data, either manually or by utilizing commercial software, the paper will give a worked example for a contaminated soil, showing how classifiers can use the list to help move from a worst case to a less worst case species.

Sugarcane filter cake application to coffee crop and soil physical attributes

Filter cakes are solid organic byproducts of the sugarcane industry that are generally used as fertilizers for crops such as coffee. Filter cake application has improved soil chemical, physical and microbiological attributes, especially for weathered soils. This study aimed to evaluate the influence of filter cake applications on the soil attributes cultivated with coffee in a Cerrado region. The study was conducted in a commercial coffee crop area (coffee cultivar Topázio MG 1190) in a Dystrophic Oxisol. The experimental design used was randomized blocks, in a factorial scheme of 4 x 4, with four doses of filter cake applied in the planting furrow (0, 4, 8, 12 L m-1) and four soil depths (0-0.1, 0.1-0.2, 0.2-0.3, 0.3-0.4 m). Soil density, soil mechanical resistance to root penetration, moisture, porosity (micro, macro, and total) and aggregate stability were evaluated. In general, the application of sugarcane filter cake over a long period has little effect on the soil's physical attributes, regardless of the filter cake rate used in the coffee crop. Only the soil porosity is affected by 12 L m-1 of filter cake, increasing the micro and macroporosity of the soil and promoting adequate conditions for the growth of coffee root, which can generate large soil water retention, benefiting coffee crops in the long-term.