The magnetic field dependent displacement effect and its correction in reference and relative dosimetry

Objective This study investigates the perturbation correction factors of air-filled ionization chambers regarding their depth and magnetic field dependence. Focus has been placed on the displacement or gradient correction factor Pgr. Besides, the shift of the effective point of measurement Peff that can be applied to account for the gradient effect has been compared between the cases with and without magnetic field. Approach The perturbation correction factors have been simulated by stepwise modifications of the models of three ionization chambers (Farmer 30013, Semiflex 3D 31021 and PinPoint 3D 31022, all from PTW Freiburg). A 10 cm x 10 cm 6 MV photon beam perpendicular to the chamber’s axis was used. A 1.5 T magnetic field was aligned parallel to the chamber’s axis. The correction factors were determined between 0.4 and 20 cm depth. The shift of Peff from the chamber's reference point Pref, ∆z, was determined by minimizing the variation of the ratio between dose-to-water Dw(zref+∆z) and the dose-to-air Dair(zref) along the depth. Main Results The perturbation correction factors with and without magnetic field are depth dependent in the build-up region but can be considered as constant beyond the depth of dose maximum. Additionally, the correction factors are modified by the magnetic field. Pgr at the reference depth is found to be larger in 1.5 T magnetic field than in the magnetic field free case, where an increase of up to 1% is obserbed for the largest chamber (Farmer 30013). The magnitude of ∆z for all chambers decreases by 40% in a 1.5 T magnetic field with the sign of ∆z remains negative. Significance In reference dosimetry, the change of Pgr in a magnetic field can be corrected by applying the magnetic field correction factor kB Qmsr when the chamber is positioned with its Pref at the depth of measurement. However, due to the depth dependence of the perturbation factors, it is more convenient to apply the ∆z-shift during chamber positioning in relative dosimetry.

Study on the Oil Displacement Effect and Application of Soft Microgel Flooding Technology

Due to the reservoir heterogeneity, there is still a lot of remaining oil that cannot be displaced by water flooding. Therefore, taking the whole injection-production flow field as the research object, the dominant channel is divided into macro and micro channel. Then the corresponding oil displacement system is adopted to realize the continuous flow diversion and effective expansion of swept volume. For micro channels, the soft microgel particle dispersion can be used. It is a novel flooding system developed in recent years. Due to its excellent performance and advanced mechanism, the oil recovery rate can be greatly improved. Soft microgel particle dispersion consists of microgel particles and its carrier fluid. After coming into porous media, its unique phenomenon of particle phase separation appears, which leads to the properties of "plugging large pore and leave the small one open", and the deformation and migration characteristic in the poros media. Therefore, particle phase separation of soft microgel particle dispersion is studied by using the microfluidic technology and numerical simulation. On this basis, by adopting the NMR and 3D Printing technology, the research on its oil displacement mechanism is further carried out. Furthermore, the typical field application cases are analyzed. Results show that, soft microgel particles have good performance and transport ability in porous media. According to the core displacement experiment, this paper presents the matching coefficient between microgels and pore throat under effective plugging modes. Also, the particle phase separation happens when injecting microgels into the core, which makes the particles enter the large pore in the high permeability layer and fluid enters into small pore. Therefore, working in cooperation, this causes no damage to the low permeability layer. On this basis, theoretically guided by biofluid mechanics, the mathematical model of soft microgel particle is established to simulate its concentration distribution, which obtained the quantitative research results. Furthermore, the micro displacement experiment shows that, microgels has unique deformation and migration characteristic in the poros media, which can greatly expand swept volume. The macro displacement experiment shows that, microgels have good oil displacement performance. Finally, the soft microgel particle dispersion flooding technology has been applied in different oilfields since 2007. Results show that these field trials all obtain great oil increasing effect, with the input-output ratio range of 2.33-14.37. And two field application examples are further introduced. Through interdisciplinary innovative research methods, the oil displacement effect and field application of soft microgel particle dispersion is researched, which proves its progressiveness and superiority. The research results play an important role in promoting the application of this technology.

Research on the Relationship Between Crude Oil Composition and Asp Flooding Effect

In recent years, ASP flooding has been widely applied and obtained the remarkable effect. During the ASP flooding process, the oil composition has a great effect on the interfacial tension, which plays a vital role in the oil displacement effect. However, through literature research, few have made a profound study on the effect of oil composition on the recover rate. As a result, it is very important to carry out relevant research. For the oil sample (I) and sample (II) from two different regions in DQ, the crude oil composition analysis is first carried out. After the mixing of oil system and ASP system, the distribution ratio of agent is obtained. Furthermore, the oil composition does have an impact on the interfacial tension and recovery rate, and its influence law is explored. Finally, its application is introduced and analyzed. Research results show that, compare with sample (II), the sample (I) has more heavy components. After the mixing of oil samples and ASP, more surfactant and alkali enters into the oil phase of sample (I). Therefore, based on the similar miscibility principle, the surfactant is more likely to leave the oil water interface and enter into the oil phase of sample (I), which has a negative effect on reducing the interfacial tension. Furthermore, the phenomenon of chromatographic separation aggravates the adsorption of surfactant on rock surface. Therefore, combining the above factors, the oil increment effect of sample (I) becomes worse. In additional, the results of field test verify the laboratory experiments. From the above research, we canconclude that the relationship between crude oil composition and ASP flooding is of great significance. As a result, this paper has carried out a lot of related research work and revealed the internal relationship between the two, which has important practical significance to improve the effect of increasing oil and reducing water in ASP flooding technology.

Comparison of Nanomaterials for Enhanced Oil Recovery in Tight Sandstone Reservoir

With dwindling conventional oil resources, the development of high-performance oil-displacing agents to exploit unconventional oil and gas resources has become a research focus, and new technical ideas have been proposed for petroleum engineering with the advancement of nanomaterials and technology. This study characterized the microscopic pore throat structure of the unconventional tight sandstone reservoir of Ordos Basin in China comprehensively by using high-resolution scanning electron microscopy, image panoramic mosaic technology, mineral quantitative scanning system, and 3D image of pore. A new nanofluid with diphenyl ether surfactants as shell and C10–C14 straight-chain hydrocarbon compounds as kernel was prepared according to the features of tight sandstone reservoirs. The basic physical properties of the nanofluid were evaluated and compared with those of three other generic oil-displacing agents to understand the oil-displacement effect and mechanism. Results show that this nanofluid remains relatively stable and dispersible with aging and its average particle size matches well with the pore throat size of the target reservoir, which increases the sweep volume effectively. Additionally, the change from oil-wet to water-wet can exert capillary imbibition. And the oil-water interfacial tension can be greatly reduced to the level of 10–2 mN/m because of nanofluid’s excellent interfacial activity, which improves the efficiency of oil washing in nano-scale pore throats. Finally, the core imbibition experiment further demonstrated the superiority of the nanofluid. Using the nanofluid in optimal concentration with cores of approximately 0.1 mD can achieve a recovery rate of 37.5%, which is higher than generic oil-displacing agents by up to 9%. This study demonstrates that the excellent performance of nanofluid in enhancing oil recovery and provides a reference for the development of unconventional reservoirs, which are difficult to function with generic agents.

Fabrication and Characterization of Clay-Polyethylene Composite Opted for Shielding of Ionizing Radiation

This study fabricated and characterized a self-sustaining hydrogenous content clay-polyethylene composite opted for ionizing radiation shielding. Composites designated A–G were fabricated each containing 0–30 wt% of recycled low density polyethylene (LDPE), respectively. To know the effects of the incorporated LDPE on the morphology, microstructural, compressive strength, thermal property and displacement effect on the vital elements were studied using scanning electron microscopy (SEM), X-ray diffractometry (XRD), universal mechanical testing machine, differential thermal analysis (DTA), Rutherford backscattering (RBS) technique and particle induced X-ray emission (PIXE), respectively. The bulk densities of the clay composites ranged between 1.341 and 2.030 g/cm3. The samples’ XRD analysis revealed similar patterns, with a sharp and prominent peak at angle 2θ equals ~26.11°, which matched with card number 16-0606 of the Joint Committee on Powder Diffraction Standards (JCPDS) that represents Aluminum Silicate Hydroxide (Al2Si2O5(OH)4), a basic formula for Kaolin clay. The compressive strength ranged between 2.52 and 5.53 MPa. The ratio of Si to Al in each composite is about 1:1. The dehydroxylation temperature for samples ranged between 443.23 °C and 555.23 °C.

Effects of Innovation on Employment: An Analysis at the Firm Level in Bolivia

This study quantifies the impact of process and product innovation on employment growth in Bolivia by using microdata from a survey on innovation conducted in Bolivia in 2016. Following the model of Harrison, Jaumandreu, Mairesse, and Peters (2008) and the adaptations for Latin America of Crespi and Tacsir (2013) and Elejalde, Giuliodori, and Stucchi (2015), we demonstrate that employment growth is explained by product innovation. On the other hand, we find no evidence of a displacement effect due to process innovation. With respect to innovation and work composition, we observe that the reation of qualified employment is slightly favored over that of unqualified employment.

Implications of trade network structure and population dynamics for food security and equality

Given trade's importance to maintaining food security, it is crucial to understand the relationship between human population growth, land use, food supply, and trade. We develop a metapopulation model coupling human population dynamics to agricultural land use and food production in "patches" (regions and countries) connected via trade networks. Patches that import sparingly or fail to adjust their demand sharply in response to changes in food per capita experience food insecurity. They fall into a feedback loop between increasing population growth and decreasing food per capita, particularly if they are peripheral to the network. A displacement effect is also evident; patches that are more central and/or import more heavily preserve their natural land states. Their reliance on imports means other patches must expand their agricultural land. These results emphasize that strategies for improving food security and equality must account for the combined effects of network topology and patch-level characteristics.

Next to Nothing: The Impact of the Norwegian Introduction Programme on Female Immigrants’ Labour Market Inclusion

In 2003, Norway implemented an ‘Introduction Programme’ that aimed to increase labour market inclusion among newly arrived immigrants. Its main objectives were to facilitate free courses in Norwegian language training and social studies, and education or on-the-job training. The participants were given an allowance to attend the programme. This paper uses administrative register data to evaluate the effect of the Norwegian introduction programme on female immigrants’ employment and earnings prospects. The sample consists of female immigrants from Asia or Africa who immigrated to Norway 18 months before or after the implementation of the introduction programme. The study measures their probability of being employed and their mean earnings 4–6 and 7–9 years after immigration. The results show that the Norwegian introduction programme had a small but significant effect on women’s employment, but not on their earnings. This article suggests that the small effect of the programme on employment and non-effect on earnings may imply a displacement effect rather than an improvement in language skills and labour market skills.