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Spontaneous imbibition is auniversal phenomenon in nature, which plays asignificant role in the two-phase flow of gas reservoirs with water. To quantitatively evaluate the spontaneous imbibition be...

Formation damage caused by well drilling, completion, oil testing, oil recovery, and stimulation seriously affects oil and gas production, the evaluation of which plays an important role in the process of oilfield development. Thus, it is necessary to study formation damage mechanism from micro scale. In this study, two sets of displacement experiments were conducted using two sandstone samples and two chemical reagents. Each set was divided into three processes: first formation water injection, reverse chemical reagents injection and second formation water injection. According to the results of displacement experiments, the permeability changes of two sandstone samples were analyzed and the formation damage rates of different experimental processes were calculated respectively. In addition, we analyzed the formation damage of the two samples from the macroscopic aspect according to the changes of inlet pressure curves. We compared the pore structure changes of sandstone samples at different experiment processes by computed tomography (CT) images, and found the particle migration phenomenon. Based on the core sensitive regions observed by CT images, the pore network models of the sensitive regions were extracted to quantitatively characterize the change of pore structure parameters (pore radius, throat radius, coordination number and tortuosity). Finally, we designed a two-dimensional microscopic seepage channel model according to the real core structure. The flow rule of solid particles in fluid was simulated by finite element method, and the reason of reservoir clogging was analyzed. Through this study, we found that the injection of chemical reagents increased the inlet pressure and led to the decrease of core permeabilities. There was a negative correlation between the export rate of particle migration and matrix deformation degree. Cited as : Wang, Z., Li, H., Lan, X., Wang, K., Yang, Y., Lisitsa, V. Formation damage mechanism of a sandstone reservoir based on micro-computed tomography. Advances in Geo-Energy Research, 2021, 5(1): 25-38, doi: 10.46690/ager.2021.01.04

Background. Thoracic aortic aneurysm or dissection (TAAD) is a group of life-threatening diseases. Genetic etiology lead to some special characteristics on age of onset, clinical phenotype, and timing of intervention. Herein, we initiated a prospective trial to determine the prevalence of pathogenic variants in TAAD patients and to elucidate the traits related to harboring pathogenic variants. One hundred and one unrelated TAAD patients were sequenced and analyzed for 23 TAAD associated genes using a targeted PCR and next generation sequencing-based panel. Results. A total of 47 variants were identified in 52 TAAD patients (51.5%) including 6 pathogenic, 1 likely pathogenic and 40 variants of uncertain significance. The pathogenic or likely pathogenic (P/LP) variants in 4 disease-causing genes were carried by 1 familial and 6 sporadic cases (6.9%). Besides one familial TAAD, the FBN1 gene also harbored more than half of the P/LP variants in sporadic ones. The individuals with the age of onset less than 50 years and normotension massively increased the genetic risk. Conclusions. The TAAD cases with younger age at diagnosis and normotension were more likely to carry a P/LP variant, thus routine genetic testing will be beneficial to better prognosis through a genetically personalized care prior to acute rupture or dissection.

In this paper, discrete model of three-phase grid- connected inverter was introduced. In order to restrain the bifurcation and ensure the stable operation of the system, the controller parameter design method based on reduced order Jacobian matrix was proposed. The controller parameters were designed. To proof the proposed method, Jacobian matrix eigenvalue traces diagram and bifurcation diagram of the three-phase grid-connected current were drawn. The three phase grid-connected current simulation has been completed based on PSIM. The results show that the proposed scheme was correct and feasible, the design difficulty of controller parameter was reduced largely.

The ultra-deep dolomite reservoir of the Permian Qixia Formation in northwest Sichuan is important for hydrocarbon reservoirs, but the mechanism of dolomite genesis is complex and has long been controversial, thus requiring further elucidation. By studying the dolomite with different types in the Permian Qixia Formation, northwest Sichuan Basin, this paper, based on outcrop sections observation and core description, seeks to find out the dolomitizing fluids' source and the dolomite's genetic mechanism by analyzing the dolomite's rock-mineral and geochemical characteristics. Various technologies are applied, including rock thin section observation, cathode luminescence, carbon and oxygen isotope analyses, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), and inclusion homogenization temperature and salinity. Results show that the dolomite is mainly classified into silty-fine dolomite (Md1), fine-medium dolomite (Md2), medium-coarse dolomite (Md3), and saddle dolomite (SD) filled in the pores. Md1 is formed in the early shallow-burial stage; the dolomitizing fluids are mainly derived from the early seawater sealed in carbonate sediments; and the penesaline seawater is formed by the seepage reflux under a moderate evaporitic environment. Md2 and Md3 are formed in the middle and late shallow-burial stages. Of these two types, Md2 is formed earlier, and the dolomitizing fluids are primarily derived from the seawater sealed in the early stage and partially derived from the residual evaporated seawater and hydrothermal fluids. In contrast, Md3 is formed later, and the dolomitizing fluids are the mixture of the seawater sealed in the early stage and the hydrothermal fluids formed in the late stage. In addition, Md3 was affected by the hydrothermal process more significantly during the formation. SD is deposited and formed when the saturated hydrotherm upwells along with the fracture system in the late stage. This study provides a significant reference for understanding the source and action mechanism of multi-stage dolomitizing fluids and expands the exploration field of the deep dolomite reservoir.

Mulching is a major production mode with highly effective use of water in the hydrothermal deficient area of northwest China. However, given the differences in environments and crop species among regions, it is important to further understand whether the mulching-induced changes in soil temperature are beneficial to crop production. Here, we used winter wheat to study the effect of mulching on soil temperature, soil water content, dry matter and yield. Two 3-year field experiments were conducted at two sites over 6 consecutive years (2012–2015 at site 1, and 2015–2018 at site 2) in the semiarid rainfed thermal deficient areas of northwest China. In each experiment, three mulching treatments, including straw strip mulching (SSM), plastic film mulching (PFM) and non-mulching (CK), were tested in a replicated randomized block design. Compared with CK, SSM and PFM significantly increased grain yield by 18.6–69.1 % and 35.5–61.3 % in 2012–2017 growing seasons, except that there was no significant difference in the wet year (2017–2018). In the SSM treatment, soil temperature generally decreased at different growth stages, resulting in a slight decline of 0.9–1.9 ℃ in the 0–25 cm soil layer, whereas in the PFM treatment, soil temperature increased before the jointing stage and decreased subsequently. SSM reduced the daily variable amplitude of soil temperature by decreasing the maximum soil temperature, whereas PFM produced the same effect by decreasing the maximum soil temperature and increasing the minimum soil temperature, which could promote the winter wheat vegetative growth and yield formation in the six experimental years. SSM and PFM decreased accumulated soil temperature from the overwintering stage to maturity stage by 60.1–234.6 ℃ and 30.5–148.5 ℃, respectively. The beneficial effect of the change in soil temperature in SSM and PFM plots expanded the storage capacity of winter wheat. Overall, the moderately cooling effect of mulching was conductive to promoting vegetative growth and expanding storage capacity, ultimately improving crop yield. Our results suggest that SSM can be adopted for sustainable winter wheat production in semiarid rainfed areas under thermal deficient conditions.

Water consumption is closely related to crop growth and development, and optimizing its characteristics will be beneficial to water saving and high yield of crops. To find out the more promising cultivation technology to optimize water consumption characteristics and improve crop water productivity for winter wheat, a four-year field experiment in 2015–2019 was conducted in a randomized and complete block design in the Loess Plateau of northwest China. The experimental treatments: (i) whole plastic-film mulching (PFM), coverage rate was approximately 100%, (ii) straw strips mulching (SSM), including the alternating straw strip (0.5 m) and plant strip (0.35 m), and the coverage rate was 59%, (iii) conventional flat planting without mulching (CK). The obtained results showed that PFM and SSM increased the contribution rate of precipitation to evapotranspiration; inhibited evaporation but promoted transpiration to a great extent; reduced soil water storage consumption in the 0–60 cm but promoted it in the 150–200 cm soil layer; reduced soil water storage consumption at the early growth stage but promoted it at the middle growth stage compared with CK. In 2015–2019, compared with CK, PFM and SSM respectively decreased soil water consumption by 12.4% and 10.6% in the 0–60 cm soil layer, but increased it by 46.6% and 27.7% in the 150–200 cm soil layer. PFM and SSM reduced evapotranspiration by 20.1% and 14.4% before the jointing stage due to the low water consumption intensity, but increased it by 26.8% and 11.1% from jointing to blooming stage due to the high water consumption intensity. Besides, PFM and SSM respectively improved crop water productivity by 20.1% and 19.1%, improved precipitation use efficiency by 20.0% and 18.6%, and eventually increased grain yield by 18.1% and 16.5%. SSM was less effective than PFM, but taking the friendly sustainability into consideration, SSM would probably be a potential practice to develop the rainfed agriculture.

Qixia Formation in northwest Sichuan has a complex structure, ultra-deep burial, high temperature and high pressure, thin reservoir and fractures development, and it is difficult to simulate the gas reservoir numerically. Based on existing geological understanding, in this paper, the tracking attribute parameters of three-dimensional seismic data bodies are optimized by ant tracking technology. Through the automatic extraction crack system of differential bodies, a three-dimensional geological model considering natural fractures is established. Using embedded discrete cracks and MRST numerical simulation open-source program, a numerical simulator of deep carbonate gas reservoirs in northwest Sichuan has been formed, and the development mechanism of Qixia Formation in northwest Sichuan is demonstrated. The research work in this paper has a certain theoretical guiding significance for the efficient development of deep carbonate gas reservoirs in northwest Sichuan.

A 59-year-old Chinese woman was referred to our department in November 2005 for erythematous lesions of the chest, the back, and the limbs that had appeared six months before, with no obvious cause. The rash faded upon diascopy. The affected area had gradually extended, merged into a large patch, and spread to both arms. Three months earlier, rice-grain or broad bean-sized erythema had appeared on both thighs, and the affected area had gradually increased and partly merged. The patient did not report [...]