An Improved Foam Modeling Technique and Its Application to Petroleum Drilling and Production Practice

Foam is one of the most common used multiphase fluid in Underbalanced Drilling (UBD) and Managed Pressure Drilling (MPD). Because of its low density, high capacity of lifting and carrying cuttings, low cost and compatibility with formations, foam has become more superior than the conventional drilling mud when depleted reservoir pressure, severe lost circulation, or unstable borehole are encountered. In general, the success of foam applications rely on the understanding of the fundamentals of foam rheology in downhole conditions. Foam rheology has been studied for decades. Conventional foam rheological models such as Power Law, Bingham Plastic, Herschel-Bulkley to explain foam behavior usually fail to interpret the monitored circulating pressure changes in operation, not to mention foam behaviors in downhole. Understanding bubble size and foam texture impacts at different foam quality ranges in the foam model development become very significant. A new foam rheological model based on Low-Quality Regime (LQR) and High-Quality Regime (HQR) behaviors is developed. This new model, which originally came from comprehensive foam flow experiments, together with the visualization of foam texture and bubble distribution, is proved to be easily and conveniently implemented for industry use in this study. The model requires nine model parameters – three (uwRef, ugRef,DPRef) to define the transition region, four to capture Power-Law rheology in both HQR and LQR (KH, nH, KL, nL), and two to describe the sensitivity of steady-state pressure drops as a function of gas and liquid velocities in both regimes (mH, mL). With the newly developed foam model, we apply it in the following two foam applications in petroleum industry, in which the foam rheology and foam handling are the main concerns for successes. First of all, a foam drilling and wellbore clean-up application with foam is investigated. These scenarios consider foam circulation into 10000 ft long wells at different inclination angles with a long vertical, inclined, or horizontal trajectory. The results are compared with two existing foam modeling techniques, so-called Chen et al.’s model (based on the correlations for wet foams only) and Edrisi and Kam’s model (based on wet- and dry-foam rheological properties with five model parameters). The conclusions show that, with or without formation fluid influx, the new foam model demonstrates the robustness of the new modeling technique in all scenarios capturing foam flow characteristics better, whenever the situation forms stable fine-textured foams or unstable coarse-textured foams. Second, foam-assisted mud cap drilling for gas migration situation, which simulatesthe process with accurate foam characteristics when foams are used to suppress gas kicks under certain well and fluid conditions, is presented. The new foam model with Two Flow Regimes is used throughout the simulation process. The results show how mud-cap drilling parameters (such as pressure, foam density (or equivalent mud weight), foam velocity, and foam quality) change at different operating conditions and scenarios. Moreover, a set of field data from a wellbore clean-up with foam operation is demonstrated and the circulating pressure changes provide the evidence of Two Flow Regimes

Functioning of a synthetic lignocellulolytic microbial consortium:The effect of conditions on dynamics of interactions and functioning

The rich polysaccharide sugar content (75%) of lignocellulosic biomass (LCB) makes it a perfect resource for production of liquid fuels and industrial building blocks. Various LCB-degrading microbial consortia from different sources, with a set of “core” strains, have drawn attention. In particular, a bacterial-fungal consortium denoted SWT, consisting of two bacteria (Citrobacter freundii so4 and Sphingobacterium sp. w15) and one fungus (Coniochaeta sp. 2T2.1) has shown superior LCB degradation performance when growing on wheat straw (WS). This thesis starts with an overview (Chapter 1) of microbial LCB degradation processes and a summary of previous studies, with a focus on LCB-degrading microbial consortia and relevant enzyme families. To disentangle the mechanisms of bacterial-fungal synergisms in the SWT consortium, we set out to use genome and metabolic potential analyses (Chapter 2); compare the transcriptomes of strain 2T2.1 growing alone or in the SWT consortium on wheat straw (WS) (Chapter 3); examine the effect of abiotic conditions on bacterial-fungal synergisms and degradation performance (Chapter 4); examine the transcriptome profiles of both bacteria and fungal strain 2T2.1 at different conditions over time (Chapter 5); and analyze the identity of bacterial strain w15 (Chapter 6). The here-studied bacterial-fungal consortium showed great potential to serve as a model for the functioning of LCB-degrading consortia, with diverse functions assigned to each member strain: the main degrader Coniochaeta sp. 2T2.1, hemicellulose degradation assistant S. paramultivorum w15, and the system helper C. freundii so4. The excellent enzymatic potential of this consortium can be further explored for microbial biotechnology developments

A Study on Nonthermal Irreversible Electroporation of the Thyroid.

BackgroundNonthermal irreversible electroporation is a minimally invasive surgery technology that employs high and brief electric fields to ablate undesirable tissues. Nonthermal irreversible electroporation can ablate only cells while preserving intact functional properties of the extracellular structures. Therefore, nonthermal irreversible electroporation can be used to ablate tissues safely near large blood vessels, the esophagus, or nerves. This suggests that it could be used for thyroid ablation abutting the esophagus. This study examines the feasibility of using nonthermal irreversible electroporation for thyroid ablation.MethodsRats were used to evaluate the effects of nonthermal irreversible electroporation on the thyroid. The procedure entails the delivery of high electric field pulses (1-3 kV/cm, 100 microseconds) between 2 surface electrodes bracing the thyroid. The right lobe was treated with various nonthermal irreversible electroporation pulse sequences, and the left was the control. After 24 hours of the nonthermal irreversible electroporation treatment, the thyroid was examined with hemotoxylin and eosin histological analysis. Mathematical models of electric fields and the Joule heating-induced temperature raise in the thyroid were developed to examine the experimental results.ResultsTreatment with nonthermal irreversible electroporation leads to follicular cells damage, associated with cell swelling, inflammatory cell infiltration, and cell ablation. Nonthermal irreversible electroporation spares the trachea structure. Unusually high electric fields, for these types of tissue, 3000 V/cm, are needed for thyroid ablation. The mathematical model suggests that this may be related to the heterogeneous structure of the thyroid-induced distortion of local electric fields. Moreover, most of the tissue does not experience thermal damage inducing temperature elevation. However, the heterogeneous structure of the thyroid may cause local hot spots with the potential for local thermal damage.ConclusionNonthermal irreversible electroporation with 3000 V/cm can be used for thyroid ablation. Possible applications are treatment of hyperthyroidism and thyroid cancer. The highly heterogeneous structure of the thyroid distorts the electric fields and temperature distribution in the thyroid must be considered when designing treatment protocols for this tissue type

Design and Implementation of connected antenna array for ultra-wide applications.

An integrated eight-element antenna array has been proposed for ultra-wideband (UWB) applications. It consists of eight UWB antenna elements and an eight-way binary-tree modified Wilkinson power divider. Any two adjacent elements in the array are connected to each other and share a common side, thus leading to a connected antenna array. Moreover, this arrangement can be utilized to avoid grating lobe level at higher frequencies. Each antenna element comprises a square ring patch and is excited by a tapered balun to achieve low cross-polarization levels. In order to validate the design, a prototype has been fabricated and measured. Both simulated and measured results confirm that the proposed integrated antenna array achieves a good performance of a reflection coefficient below -10 dB from 2.9 GHz to 10.8 GHz, including stable radiation patterns with low side lobe and cross-polarization levels, thus the antenna is promising for applications in UWB imaging systems

Design and Investigation of Differential-Fed Ultra-Wideband Patch Antenna with Polarization Diversity

A novel single- or dual-polarized ultra-wideband (UWB) patch antenna fed by coupled feeding mechanism is proposed. The single-polarized antenna consists of a square ring patch and two ?-shaped patches which are coupled to the radiating patch. The vertical portions of the ?-shaped patches are connected to the microstrip lines which are printed on the bottom layer of the grounded FR4 substrate. To realize the differential feeding mechanism for enhancing the polarization purity, a tapered balun is employed to excite the antenna. Further to provide dual linear orthogonal polarizations, another pair of ?-shaped patches is added in the single-polarized UWB antenna. The dual-polarized UWB antenna prototype can achieve two orthogonal polarizations with an impedance bandwidth (?dB) of 113% and isolation of over 25?dB across the entire frequency band

Design of a low-profile wideband patch antenna with L-shaped feeding mechanism

This paper has presented the design of a novel low-profile wideband patch antenna. The antenna structure is formed of three layers of substrates with the radiating patches on the top, the grounded patches in the middle and the feeding portion at the bottom. The large operating frequency bandwidth has been obtained due to the L-shaped feeding technique. Moreover, the low cross-polarization level can also be achieved as the feeding structure can be regarded as the preferred differential feeding. The obtained results can confirm that the proposed antenna has achieved a wide impedance bandwidth (VSWR ≤ 2) of about 60% (3-5.5 GHz) and the whole height of the antenna is 6 mm (around 0.06λ l at the lowest operating frequency). The obtained cross-polarization level is less than-30dB compared with co-polarization

An Empirical Study of Evaluation Index System and Measure Method on City’s Soft Power: 17 Cities in Shandong Province

Based on the research of city’s soft power at home and abroad, the current study was intended to build an evaluation index system and analyzed the city’s soft power of 17cities in Shandong Province in 2010. Both the qualitative and quantitative methods were adopted. Frequency statistical method was used to build the evaluation index system of city’s soft power, and AHP and CRITIC methods were used to determine index weight. By using the evaluation system, data from Shandong 2010 statistic yearbook and SPSS18.0, the researchers analyzed the soft power of 17 cities in Shandong province, and finally constructed a measure model for city’s soft power. Results indicated that this model is practically viable and consistent with the real situation of the soft power of 17cities in Shandong Province. It is the researchers hope that this measure model would provide reference for government’s decision-making in the development of promoting urbanization

24-GHz Circularly Polarized Substrate Integrated Waveguide-Fed Patch Antenna

This paper has presented the design of a 24-GHz patch antenna with characteristics of good circular polarization, simple structure and easy fabrication. The printed antenna consists of two layers of substrates with the lower one for achieving a short-ended substrate integrated waveguide (SIW) and the upper one for supporting the rectangular radiating patch. The left-handed circularly polarized wave has been obtained by etching a 450 rotated cross-shaped slot on the broad wall of the SIW. The obtained results can confirm that the proposed antenna has achieved an impedance bandwidth (|S 11 | ≤-10 dB) of 23.1-25.3GHz and the 3-dB axial ratio bandwidth of 23.2-24.7GHz