|
|
|
题名
|
作者
|
年代
|
出处
|
被引量
|
| 1 | Simulating the Effect of Hydrate Dissociation on Wellhead Stability During Oil and Gas Development in Deepwater显示文摘It is well known that methane hydrate has been identified as an alternative resource due to its massive reserves and clean property. However, hydrate dissociation during oil and gas development(OGD) process in deep water can affect the stability of subsea equipment and formation. Currently, there is a serious lack of studies over quantitative assessment on the effects of hydrate dissociation on wellhead stability. In order to solve this problem, ABAQUS finite element software was used to develop a model and to evaluate the behavior of wellhead caused by hydrate dissociation. The factors that affect the wellhead stability include dissociation range, depth of hydrate formation and mechanical properties of dissociated hydrate region. Based on these, series of simulations were carried out to determine the wellhead displacement. The results revealed that, continuous dissociation of hydrate in homogeneous and isotropic formations can causes the non-linear increment in vertical displacement of wellhead. The displacement of wellhead showed good agreement with the settlement of overlying formations under the same conditions. In addition, the shallower and thicker hydrate formation can aggravate the influence of hydrate dissociation on the wellhead stability. Further, it was observed that with the declining elastic modulus and Poisson's ratio, the wellhead displacement increases. Hence, these findings not only confirm the effect of hydrate dissociation on the wellhead stability, but also lend support to the actions, such as cooling the drilling fluid, which can reduce the hydrate dissociation range and further make deepwater operations safer and more efficient. | LI Qingchao CHENG Yuanfang ZHANG Huaiwen YAN Chuanliang LIU Yuwen | 2018 | Journal of Ocean University of China2018，17，1： | 11 |
| 2 | Numerical Analysis of Wellbore Instability in Gas Hydrate Formation During Deep-Water Drilling显示文摘Gas hydrate formation may be encountered during deep-water drilling because of the large amount and wide distribution of gas hydrates under the shallow seabed of the South China Sea. Hydrates are extremely sensitive to temperature and pressure changes, and drilling through gas hydrate formation may cause dissociation of hydrates, accompanied by changes in wellbore temperatures, pore pressures, and stress states, thereby leading to wellbore plastic yield and wellbore instability. Considering the coupling effect of seepage of drilling fluid into gas hydrate formation, heat conduction between drilling fluid and formation, hydrate dissociation, and transformation of the formation framework, this study established a multi-field coupling mathematical model of the wellbore in the hydrate formation. Furthermore, the influences of drilling fluid temperatures, densities, and soaking time on the instability of hydrate formation were calculated and analyzed. Results show that the greater the temperature difference between the drilling fluid and hydrate formation is, the faster the hydrate dissociates, the wider the plastic dissociation range is, and the greater the failure width becomes. When the temperature difference is greater than 7℃, the maximum rate of plastic deformation around the wellbore is more than 10%, which is along the direction of the minimum horizontal in-situ stress and associated with instability and damage on the surrounding rock. The hydrate dissociation is insensitive to the variation of drilling fluid density, thereby implying that the change of the density of drilling fluids has a minimal effect on the hydrate dissociation. Drilling fluids that are absorbed into the hydrate formation result in fast dissociation at the initial stage. As time elapses, the hydrate dissociation slows down, but the risk of wellbore instability is aggravated due to the prolonged submersion in drilling fluids. For the sake of the stability of the wellbore in deep-water drilling through hydrate formation, the drilling fluid with low temperatures should be given priority. The drilling process should be kept under balanced pressures, and the drilling time should be shortened. | ZHANG Huaiwen CHENG Yuanfang LI Qingchao YAN Chuanliang HAN Xiuting | 2018 | Journal of Ocean University of China2018，17，1： | 8 |
| 3 | Fabrication and characterization of Ba Ce_(0.8)Y_(0.2)O_(2.9)-Ce_(0.85)Sm_(0.15)O_(1.925) composite electrolytes for IT-SOFCs显示文摘The Ba Ce0.8Y0.2O2.9-Ce0.85Sm0.15O1.925 composite electrolytes were prepared with Ba Ce0.8Y0.2O2.9(BCY) and Ce0.85Sm0.15O1.925(SDC). The SDC and BCY powders were mixed in the weight ratio of 95:5, 85:15, and 75:25, respectively(named as BS95, BS85, and BS75). Because of the composite effect between the SDC and BCY phases, the BS95 and BS85 exhibit improved conductivity compared with the pure SDC and BCY. The conductivity of BS95 is higher than that of BS85, indicating that the composite effect of BS95 is greater than that of BS85. Nevertheless, the composite effect in BS75 does not exist. Hence, we conclude that the composite effect in the BCY-SDC composites will decrease with the increase of the amount of BCY and even disappear when the amount of BCY exceeds a certain value. In our case, the optimum composition of the composite electrolyte is 95 wt% SDC and 5 wt% BCY. The BS95 has the highest conductivity(σ1t=0.07808 S cm-1, at 800 °C) and the fuel cell based on the BS95 shows the best performance(the maximum power density reaches as high as 526 mw cm-2 at 750 °C). The encouraging results suggest that the BCY-SDC composites are the very promising electrolyte materials for IT-SOFCs. | Ji Yu Ning Tian Yufu Deng Guannan Li Ling Liu Liying Cheng Peng Gao Qingchao Pan Yuancheng Wang Xiuyan Chen Kezhen Qi | 2015 | Science China Chemistry2015，58，3： | 1 |
| 4 | Microparticle Effect of Carbon Dioxide Hydrate Crystal Nucleus in Reaction Kettle显示文摘This study analyzed the partial effect of carbon dioxide hydrate in reaction kettle experiments.The particle and bubble characteristics of the crystal nucleus during carbon dioxide hydrate decomposition were observed under the microscope.The results showed that in the temperature range of 0.5℃–3.5℃,the pressure range of 3 MPa–5.5 MPa,phase characteristics in the reaction kettle changed in a complex fashion during carbon dioxide hydrate formation.During hydrate decomposition,numerous carbon dioxide bubbles were produced,mainly by precipitation at high temperatures or in the hydrate cage structure.The hydrate crystal nucleus initially exhibited fluidity in the reaction.However,as the reaction progressed,the hydrate crystal nucleus migrated upward under the influence of gravity and carbon dioxide diffused into the aqueous phase.Next,the hydrate was formed and accumulated,finally forming a solid carbon dioxide hydrate layer. | Yujie Bai Youquan Huang Guangsheng Cao Xiaohan Nan Qingchao Cheng Lei Wang Tong Du | 2021 | Journal of Renewable Materials2021，9，4： | 0 |
您所在的机构暂未开通此部分的功能，请联系管理员