Study on Wellbore Stability of Multilateral Wells under Seepage-Stress Coupling Condition Based on Finite Element Simulation

The use of multilateral wells is an important method to effectively develop complex oil reservoirs, and wellbore stability research of multilateral wells is of great importance. In the present study, the effects of formation fluids and rock damage were not taken into account by the wellbore stability model. Therefore, finite element analysis (FEA) software was used to establish a three-dimensional (3D) seepage-stress FEA model for the multilateral junctions. The model was used to analyze the wellbore stability of multilateral wells and study influences of wellbore parameters and drilling fluid density on wellbore stability at multilateral junctions. Simulation results show that the wellbore diameter insignificantly affects wellbore stability. When the angle between the main wellbore and branches enlarges to 45°, the equivalent plastic strain decreases by 0.0726, and the wellbores become more stable; when the angle is larger than or equal to 45°, the region prone to wellbore instability transfers from the multilateral junctions to the inner of multilateral wellbores. When the azimuth of wellbores is along the direction of the minimum horizontal principal stress, the equivalent plastic strain decreases by 78.2% and the wellbores are most stable. Moreover, appropriately increasing the drilling fluid density can effectively reduce the risk of wellbore instability at the multilateral junctions. A model has been developed that allows analysis of multilateral wellbore stability under seepage-stress coupling condition

High In Situ Stress Anisotropy Lead to Formation of Complex Fracture Patterns

During the process of water injection, due to solid particle deposition and foreign liquid intrusion, the formation near the wellbore was contaminated and blocked. As a result, water injection rate reduced and failed to meet the injection requirements. In order to improve water injection rate and improve oil recovery of offshore oilfields, hydraulic injection tests were carried out in controlled laboratory conditions. In general, the formation of complex fracture patterns is an ideal outcome of the hydraulic fracturing stimulation seeks to achieve. In situ stress condition is an inherited geological condition one can only adopt to. By comparing test results of different experiments that had varied stress and hydraulic injection conditions imposed, we can investigate their impact on the fracture patterns created. This paper presents laboratory evidences to support that if the hydraulic injection condition is managed properly, a complex fracture pattern is possible even under a high in situ stress anisotropy. Even if the in situ stress condition has a large anisotropy, proper hydraulic stimulation operations can still cause complex fracture patterns and thus provide good stimulation efficiency

Household Livelihood Strategies and Dependence on Agriculture in the Mountainous Settlements in the Three Gorges Reservoir Area, China

This study explores the extent to which farmers in the Three Gorges Reservoir area remain highly dependent on agriculture despite rapid urbanization and industrialization. The study focuses on the factors that determine a household’s choice of livelihood strategy, with a particular focus on the production of and dependence on agricultural products. Using a sustainable livelihoods approach and survey data from farmers in the Three Gorges Reservoir area in China, the study provides a descriptive statistical analysis and ordinal logistic regression model that shows that close to 56% of households exhibit a low dependence on agriculture. The following variables had a significant influence on livelihood strategy: the maximum years of education of any household member; the age of the household head; the number of laborers in a household; household location; and formal and informal social networks. Regardless of whether the household had children, house value and fixed assets had no significant influence on livelihood strategy. According to the analysis results, we put forward the suggestions that government departments increase investment in infrastructure and make loan policies more favorable for farmers so as to encourage rural able-person to use their social networks to actively establish businesses at migrant destinations

Platinum Nanoparticles Loaded on Metal–Organic Complexes as New and Recyclable Catalysts for the Hydrogenation of Nitroarenes

A very simple and facile method of synthesizing Pt nanoparticles (NPs) deposited on Pt–bpy metal–organic complexes (bpy = 4,4′-bipyridyl) has been developed. No additional capping agents or solid supports are required. The formation of Pt NPs–bpy composites was largely dependent on the molar ratio of metal to bpy. When the molar ratio of Pt to bpy is more than 1:2, Pt NPs were deposited onto the surface of the formed Pt–bpy complexes. This was demonstrated by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. When the molar ratio of Pt to bpy is less than or equal to 1:2, Pt NPs are difficult to form. Moreover, the Pt NPs–bpy composites were used as a heterogeneous catalyst toward the hydrogenation reaction of the nitroarenes bearing different steric and electronic groups. The catalyst could be recycled for at least six cycles without catalytic activity loss

Does intensified chemotherapy increase survival outcomes of osteosarcoma patients? A meta-analysis

Study Design: Meta-analysis. Background: Although some new insights have been offered for clinical and scientific relevance, minor progress has been made in osteosarcoma treatment after a dramatic survival improvement in the late 1980s with the addition of chemotherapy to surgery. Intensified chemotherapy strategies have been suggested to increase the survival rate of patients with osteosarcoma. We performed this study to access whether intensified chemotherapy strategiesincreased survival outcomes of osteosarcoma patients compared with conventional chemotherapy strategies. Methods: MEDLINE/PubMed, EMBASE, BIOSIS Previews, and Cochrane Library were searched from database set up to October2016. Randomized controlled trials (RCTs) and comparative clinical trials (CCTs) on intensified versus conventional chemotherapy strategies for osteosarcoma patients met the inclusion criteria, and the methodological quality standard were retrieved and reviewed. Data on participant characteristics, interventions, follow-up period, and outcomes were extracted from the included studies and analyzed by Review Manager 5.3. Results: 12 studies (8 RCTs and 4CCT) involving 4112 patients were selected. There were no significant differences between intensified and conventional chemotherapy strategies group in 3-year event-free survival (OR, 1.01; 95% CI, [0.74–1.37]; P = 0.97), 5-year event-free survival (OR, 1.00; 95% CI, [0.86–1.17]; P = 0.97), and 5-year overall survival (OR, 1.04; 95% CI, [0.87–1.26]; P = 0.64), and good histologic response to preoperative chemotherapy (OR, 1.12; 95% CI, [0.78–1.60]; P = 0.55). Pooled analysis of local recurrence rate showed that local recurrence rate was significantly decreased in the intensified group compared with that in the conventional group (OR, 0.60; 95% CI, [0.42–0.85]; P = 0.004). Conclusions: Intensified chemotherapy might not be a preferred treatment for all of the osteosarcoma patients. Keywords: Meta-analysis, High dosage, Chemotherapy, Osteosarcom

Isolation and Characterization of Shigella flexneri G3, Capable of Effective Cellulosic Saccharification under Mesophilic Conditions ▿ †

A novel Shigella strain (Shigella flexneri G3) showing high cellulolytic activity under mesophilic, anaerobic conditions was isolated and characterized. The bacterium is Gram negative, short rod shaped, and nonmotile and displays effective production of glucose, cellobiose, and other oligosaccharides from cellulose (Avicel PH-101) under optimal conditions (40°C and pH 6.5). Approximately 75% of the cellulose was hydrolyzed in modified ATCC 1191 medium containing 0.3% cellulose, and the oligosaccharide production yield and specific production rate reached 375 mg g Avicel−1 and 6.25 mg g Avicel−1 h−1, respectively, after a 60-hour incubation. To our knowledge, this represents the highest oligosaccharide yield and specific rate from cellulose for mesophilic bacterial monocultures reported so far. The results demonstrate that S. flexneri G3 is capable of rapid conversion of cellulose to oligosaccharides, with potential biofuel applications under mesophilic conditions