A factory fracturing model of multi-well cluster in Sulige gas field, NW China

Sulige gas field is a typical low-permeability reservoir in China. According to desert landform features along with the regional hydrologic feature and the existing fracturing technology and operational conditions, a factory-like fracturing method suitable for Sulige gas field is established to improve techniques and production organization. This method includes five key parts: (1) centralized water supply mode (water source well supply+artificial lake storage); (2) highly efficient fracturing process (two mature multi-stage fracturing technologies, sliding sleeve fracturing for vertical wells and open-hole packer fracturing for horizontal wells); (3) pipeline operation mode with seven procedures, including well drift and flushing perforation etc; (4) high efficiency operation equipment; (5) recovery of fracturing flow-back fluid. This method shortens the preparation and operation period of fracturing treatment and also relieves the pressure on environment. Pilot tests were carried out in 11 well groups in total. Sixty-seven stages of fracturing in 14 wells were successfully completed within 42 days, representing a reduction of fracturing operation cycle of more than 50%, and an encouraging improvement in efficiency. Key words: Sulige gas field, factory fracturing, big well group, water supply, fracturing process, pipeline operation, fluid recovery, high efficiency, environment friendl

Effect of Formic Acid and Inoculants on Microbial Community and Fermentation Profile of Wilted or Un-Wilted Italian Ryegrass Silages during Ensiling and Aerobic Exposure

Wilted (around 35% DM) or un-wilted (around 35% DM) Italian ryegrass treated with three additives (formic acid, FA; Lactobacillus plantarum, LP; Lactobacillus buchneri, LB) was utilized to evaluate the effects of the dry matter (DM) contents on the microbial community and fermentation characteristics, which was ensiled for 60 days in a laboratory-scale silo, followed by 3 days of aerobic exposure. Significantly lower pH and higher lactic acid (LA) contents were observed in the LP-treated group ensiled at both DM contents (differences were significant when p < 0.05). The contents of LA, acetic acid (AA), numbers of lactic acid bacteria (LAB) and ammonia nitrogen (NH3-N) in the FA-treated group were significantly lower than those in other treatments (p < 0.05). L. buchneri was the dominant bacteria after 60 days fermentation, while Enterobacteria became prevalent after 3 days of aerobic exposure. L. buchneri was found in the LB-treated group with higher acetic acid. Although the best fermentation quality was observed in the LP-treated silages, the aerobic stability was lowest compared to other groups (p < 0.05). In conclusion, our findings suggest that the DM content of Italian ryegrass affected its epiphytic microbial community and the effectiveness of the different type of additives. Formic acid was more suitable for un-wilted Italian ryegrass silage, L. plantarum had a better effect in wilted Italian ryegrass silage, and L. buchneri prolonged the aerobic stability of Italian ryegrass. DM content and purpose of ensiling should be the key factors for choosing different types of additives for Italian ryegrass silage

Field test of volume fracturing for horizontal wells in Sulige tight sandstone gas reservoirs, NW China

Based on the development degree of natural micro-fractures, rock brittleness and two-direction stress and other geological conditions of the Sulige gas field, the feasibility of using volume fracturing to increase production was analyzed and verified by field test. The Sulige gas field, a typical tight sandstone gas reservoir, has developed natural micro-fractures, with fracture complex index of 0.3−0.5, rock brittleness index distribution in the 36−52 and two-direction stress heterogeneity factor of 0.17. From the development experiences of unconventional gas reservoirs abroad, the geological conditions in the Sulige gas field is suitable for volume fracturing. Through lab experiments and pilot field tests, a volume fracturing technology for horizontal wells has been developed, which features “fracturing with low-viscosity liquid, carrying proppant with high-viscosity liquid, combination of multi-scale proppants, and massive fracturing at a high injection rate”. The technique had been applied in 42 wells of the Sulige tight gas field by the end of 2013. The initial production of wells treated by this approach is 1.2 times that of the adjacent wells treated by conventional fracturing, indicating that the technique can enhance the production of the horizontal wells in the Sulige gas field substantially. Key words: Sulige gas field, tight sandstone, volume fracturing, natural fracture, brittleness, horizontal well, microseismic monitorin

Developing and validating clinical models to identify candidates for allergic rhinitis pre-exposure prophylaxis

AbstractPurpose Few risk-forecasting models of allergic rhinitis (AR) exist that may aid AR pre-exposure prophylaxis (PrEP) in clinical practice. Therefore, this study aimed to develop and validate an effective clinical model for identifying candidates for AR PrEP using a routine medical questionnaire.Methods This study was conducted in 10 Chinese provinces with 13 medical centers (n = 877) between 2019 and 2021. Clinical characteristics and exposure history were collected via face-to-face interviews. Well-trained physicians diagnosed patients with AR based on skin prick test results and clinical performance. The least absolute shrinkage and selection operator model was used to identify potential risk factors for AR, and the logistic regression model was used to construct the risk-forecasting model. Predictive power and model reliability were assessed using area under the receiver operating characteristic curve and calibration curves, respectively.Results This study diagnosed 625 patients with AR who had positive responses to at least one indoor or outdoor allergen and 460 to at least one outdoor pollen allergen. Two nomograms were established to identify two types of AR with various sensitization patterns. Both models had an area under curve of approximately 0.7 in the development and internal validation datasets. Additionally, our findings found good agreement for the calibration curves of both models.Conclusion Early identification of candidates for AR PrEP using routine medical information may improve the deployment of limited resources and effective health management. Our models showed good performance in predicting AR; therefore, they can serve as potential automatic screening tools to identify AR PrEP candidates