The Pressure Relief and Permeability Increase Mechanism of Crossing-Layers Directional Hydraulic Fracturing and Its Application

AbstractIn order to reduce roof-floor blind area of hydrofracture in underground mines, expand influenced range of fracturing, improve the effect of hydrofracture, a pressure relief and permeability increase model of hydraulic fracturing was built on the basis of analysing the mechanism of crack initiation and the characteristics of fracture development. After discussing the mechanism of directional hydraulic fracturing and carrying out related numerical simulation, a directional hydraulic fracturing technique was proposed. The coal fracture development distribution rule in the process of directional hydraulic fracturing was analysed, and the directional hydraulic fracturing technique was applied in the F15-31010 mining workface of The Twelfth Coal of Pingdingshan Coal Mining Group. The results show that single-drill hole fracturing effective radius rise to 6m under the pressure of 27Mpa, which is 3-5 times more than before, and the average concentration of single-drill hole gas drainage promote to 87.5%, average flow up 55.6% than no-directional hydraulic fracturing. All these suggest that the technology obtains remarkable effect, and has a high application value

Case Report: Extragonadal Yolk Sac Tumors Originating From the Endometrium and the Broad Ligament: A Case Series and Literature Review

Yolk sac tumors (YSTs) of the endometrium and the broad ligament are very rare, with only 29 cases and one case of each other reported before in the English literature. Due to lack of standard guidelines, the treatment strategies of these diseases are controversial. Here, we share two cases of YSTs originating from the endometrium and the broad ligament respectively and review related literature. A 35-year-old woman was diagnosed with endometrial YST in our center and underwent surgery followed by chemotherapy with BEP (bleomycin, cisplatin and etoposide) regimen for six courses. After follow-up for 21 months, there is still no evidence of relapse. Another 36-year-old woman was admitted to our department with YST of the broad ligament. She was treated with surgery followed by chemotherapy with BEP regimen and was lost to follow-up after completing therapy. The case of endometrial YST we shared was similar to cases reported before, while the case with YST of the broad ligament we shared was the second case reported worldwide. Both of these two cases were treated with surgery combined with chemotherapy with BEP regimen

Fabrication of Nickel Nanostructure Arrays Via a Modified Nanosphere Lithography

In this paper, we present a modified nanosphere lithographic scheme that is based on the self-assembly and electroforming techniques. The scheme was demonstrated to fabricate a nickel template of ordered nanobowl arrays together with a nickel nanostructure array-patterned glass substrate. The hemispherical nanobowls exhibit uniform sizes and smooth interior surfaces, and the shallow nanobowls with a flat bottom on the glass substrate are interconnected as a net structure with uniform thickness. A multiphysics model based on the level set method (LSM) was built up to understand this fabricating process by tracking the interface between the growing nickel and the electrolyte. The fabricated nickel nanobowl template can be used as a mold of long lifetime in soft lithography due to the high strength of nickel. The nanostructure–patterned glass substrate can be used in optical and magnetic devices due to their shape effects. This fabrication scheme can also be extended to a wide range of metals and alloys

Finite element analysis of pipeline underpassing high fill based on in-situ monitoring

The safety of oil and gas pipelines has become an important factor influencing the national economy. With the vigorous development of pipeline engineering, oil and gas pipelines often inevitably intersect with various traffic routes. In the western mountainous area of China, it is very common for the oil and gas pipelines undercrossing the high fill embankment, where the oil and gas pipelines generally have a buried depth of 1 m to 3 m, and they are prone to be affected by the uneven settlement of the overlying soil of the upper embankment, resulting in the risk of extrusion shear fracture. Therefore, studying the interaction between the pipelines and the high fill embankment and accurately evaluating their safety have become the essential consideration for oil and gas pipelines crossing the high fill embankment in complex mountainous area. Herein, the stress, strain and deflection response of the pipeline under the high fill embankment of the logistics outer ring road in Guiyang Shuanglong Airport Economic Zone was analyzed with the in-situ monitoring and finite element method, and the threshold of monitoring and early warning was inversely calculated based on the critical instability state of the pipeline. According to the results, the maximum cumulative settlement of pipeline in the study area is 17.3 mm, the maximum difference of uneven settlement is 4 mm, and the maximum internal offset is 16.1 mm, which indicate that the stress, strain and deflection of the pipeline is much smaller than the allowable value, so the pipeline is safe. In general, the research results could provide guidance for the monitoring, early warning and safety assessment of oil and gas pipelines

Kinetic characteristics of coal gas desorption based on the pulsating injection

In order to understand the kinetic characteristics of coal gas desorption based on the pulsating injection (PI), the research experimentally studied the kinetic process of methane desorption in terms of the PI and hydrostatic injection (HI). The results show that the kinetic curves of methane desorption based on PI and HI are consistent with each other, and the diffusion model can best describe the characteristics of methane desorption. Initial velocity, diffusion capacity and ultimate desorption amount of methane desorption after PI are greater than those after HI, and the ultimate desorption amount increases by 16.7–39.7%. Methane decay rate over the time is less than that of the HI. The PI influences the diffusion model parameters, and it makes the mass transfer Biot number Bi′ decrease and the mass transfer Fourier series F0′ increase. As a result, PI makes the methane diffusion resistance in the coal smaller, methane diffusion rate greater, mass transfer velocity faster and the disturbance range of methane concentration wider than HI. Therefore, the effect of methane desorption based on PI is better than that of HI. Keywords: Pulsating injection, Hydrostatic injection, Methane desorption, Kinetic characteristic