Evaluation of laboratory techniques for assessing scale inhibition efficiency

Injecting chemical inhibitors is the most common method to mitigate mineral scaling in the oil industry. As such, the effectiveness of the techniques employed to evaluate performance of chemical scale inhibitors and apply the appropriate dosage is a very important aspect to be considered during the design of a scale prevention treatment. In this paper, the kinetics of scale formation and its inhibition are studied using a conventional bottle test, a dynamic tube blocking rig and a recently developed in-situ flow visualization rig. Calcium carbonate scaling brine was prepared at two saturation indices (SI) of 2.1 and 2.8 at 50 °C and run through the rigs at flow rate of 20 ml/min. The conventional polphosphinocarboxylic acid (PPCA) inhibitor was used for the inhibition study at concentration ranging between 0.5 and 10 ppm. The MICbulk determined from bottle test and supported with the in-situ turbidity MICbulk for SI of 2.1 and 2.8 are 1 ppm and 8 ppm respectively. For the same SI values, a considerably lower concentration of PPCA, 0.5 ppm and 4 ppm for the surface inhibition test using the capillary rig were obtained compared to MICsurface of 4 ppm and 8 ppm from the in-situ visualization technique. The surface visualization technique enables the range of concentration of inhibitors at which both bulk and surface scaling are completely controlled to be determined. The different techniques are shown to give complementary information for different stages of crystallization process and inhibition

Development of a novel once-through flow visualization technique for kinetic study of bulk and surface scaling

There is a considerable interest to investigate surface crystallization in order to have a full mechanistic understanding of how layers of sparingly soluble salts (scale) build on component surfaces. Despite much recent attention, a suitable methodology to improve on the understanding of the precipitation/deposition systems to enable the construction of an accurate surface deposition kinetic model is still needed. In this work, an experimental flow rig and associated methodology to study mineral scale deposition is developed. The once-through flow rig allows us to follow mineral scale precipitation and surface deposition in situ and in real time. The rig enables us to assess the effects of various parameters such as brine chemistry and scaling indices, temperature, flow rates, and scale inhibitor concentrations on scaling kinetics. Calcium carbonate (CaCO3) scaling at different values of the saturation ratio (SR) is evaluated using image analysis procedures that enable the assessment of surface coverage, nucleation, and growth of the particles with time. The result for turbidity values measured in the flow cell is zero for all the SR considered. The residence time from the mixing point to the sample is shorter than the induction time for bulk precipitation; therefore, there are no crystals in the bulk solution as the flow passes through the sample. The study shows that surface scaling is not always a result of pre-precipitated crystals in the bulk solution. The technique enables both precipitation and surface deposition of scale to be decoupled and for the surface deposition process to be studied in real time and assessed under constant condition

A kinetic study of barium sulphate formation in presence of scale inhibitor in a flowing system

The formation of barium sulphate is a persistent problem affecting the oil and gas industry. Due to its high insolubility and resistance to chemical/mechanical treatment, it is difficult to remove when formed. Barium sulphate formation can be predicted using thermodynamic models; nevertheless it is imperative to understand the kinetics of barium sulphate in order to predict more accurately the rate at which these scales are being formed and to identify the correct remediation technique. Several research works have been conducted on the kinetics of barium sulphate both in bulk precipitation and on surface deposition; however these studies were often conducted in a closed system (e.g. bulk jar test) and measurements were taken off-line. In a closed system normally the saturation ratio decreases as function of the time as scaling occurs. In the current study an experimental set-up has been designed to study the kinetics of bulk and surface scaling processes in-situ, in an open system and measurements were taken in real-Time. This work presents a kinetic study of barium sulphate with the absence and presence of scale inhibitors (diethylene triamine penta methylene phosphonic Acid (DETMP) and poly-phosphino carboxylic acid (PPCA)) on bulk precipitation and surface deposition. In the study, a turbidity probe was used to follow the bulk precipitation, whereas surface deposition was assessed by analysing image taken of the stainless steel surface at different time intervals

La question de la différenciation dans le lien gémellaire : quand les différences ne suffisent pas à se différencier

L’analyse d’une situation clinique, concernant la prise en charge psychothérapeutique de frères jumeaux homozygotes âgés de 11 ans, conduit à s’interroger sur leur différenciation. Cette question, centrale dans la dynamique gémellaire, nous a semblé importante à préciser au vu de sa complexité et des multiples facettes qui la composent (conscientes et inconscientes). L’idée d’une différenciation pouvant se révéler quelque peu forcée et apparente, tel un processus inachevé, a émergé de cette analyse. Les mécanismes psychiques en jeu chez les jeunes sujets et leur entourage dans ce processus de différenciation, sont ainsi abordés. Ces réflexions ont permis parallèlement de soutenir les interrogations portant sur le cadre des entretiens ou setting thérapeutique. En effet, la question de la mise en place de lieux distincts et/ou d’un espace commun se pose régulièrement dans des prises en charge psychothérapeutiques d’enfants jumeaux. Il nous apparaît nécessaire en outre, de penser et repenser ces différentes modalités de cadre, en résonance avec l’état de différenciation des deux frères.Background. – The differentiation process is both a crucial and central issue in gemellar psychodynamics. It is a complex, multifaceted process (conscious and unconscious) and therefore important to specify. This approach in parallel prompted important questions concerning what would be the best therapeutic setting in the perspective of a psychotherapeutic treatment, particularly concerning the need for a separate setting or not for each child. Method. – This study is based on the analysis of a clinical case concerning 11 years old twin boys under psychotherapeutic treatment. Findings. – Different stages and their dynamics in the psyche that underlie the differentiation process are analysed, both in the twins and in those close to them. A hypothesis emerged which suggested that differentiation can be forced on and be more seemingly established than truly accomplished. As for the modalities of a therapeutic setting, they need to be thought over again and again in close echo to the twins state of differentiation. Conclusion. – In twins, differentiation can be more apparent than achieved. Therefore, the state of the differentiation process needs to be determined because it closely interacts with the choice of the therapeutic setting

Surface engineering of wrought and additive layer manufactured Ti-6Al-4V alloy for enhanced load bearing and bio-tribocorrosion applications

The beneficial effect of surface engineering on the wear and corrosion performance of Ti-6Al-4V alloy for biomedical purposes has recently gained a lot of interest. To date, researchers have shown TiN ceramic coatings to be an effective strategy to improve the poor tribocorrosion properties of Ti-based alloys. However, coating degradation and adhesions remains a major hurdle to overcome for successful clinical translation. Recently, a duplex TPON + TiN treatment process on Ti-alloy has been suggested for applications involving with high contact loads. For the first time, this technique was extended to the Additive Layer Manufactured (ALM) Ti-6Al-4V alloys in an attempt to enable load bearing patient personalised implants. The bio-tribology and corrosion resistance of the coated ALM materials were compared with that of the coatings on conventional wrought manufactured alloy for orthopaedic applications. XRD analysis showed that the coatings on both substrates are primarily composed of TiN. The Knoop microhardness technique proved a tribologically effective diffusion layer with a case depth of 35–45 μm. The LC2 and LC3 values were measured above 40 N and 60 N which is an excellent cohesive and adhesive strength for these types of the coatings. Electrochemical measurements in both static and sliding conditions showed a quick recovery capability of the protective layer in 25% Foetal Bovine Serum (FBS) diluted in Phosphate Buffered Saline (PBS) electrolyte. The static electrochemical measurements also showed reduced corrosion current densities when compared to that of the bulk Ti-alloy. Coating on both substrates showed an excellent wear resistance which is correlated to the enhanced load bearing capacity of the coated surfaces. While the coating thickness was 3–6 μm, the wear depth was only 0.3 μm after 2 h of reciprocating sliding wear test