Drilling in a natural gas hydrate formation is challenging due to the poor consolidation of the formation and the potential evaporation of the hydrate.The unreasonable down-hole pressure of the drilling fluid can not ...Drilling in a natural gas hydrate formation is challenging due to the poor consolidation of the formation and the potential evaporation of the hydrate.The unreasonable down-hole pressure of the drilling fluid can not only lead to the wellbore instability,but also change the predrilling condition of the natural gas hydrate formation,thus leading to an instable wellbore.In this paper,the integrated discrete element method(DEM)-computational fluid dynamics(CFD)work flow is developed to study the wellbore instability due to the penetration of the drilling fluid into the hydrate formation during crack propagations.The results show that the difference between in-situ stresses and overpressure directly affect the drilling fluid invasion behavior.The lower hydrate saturation leads to an easier generation of drilling fluid flow channels and the lower formation breakdown pressure.The breakdown pressure increases with the increase of hydrate saturation,this also indicates that hydrates can enhance the mechanical properties of the formation.The induced cracks are initially accompanied with higher pressure of the drilling fluid.According to the rose diagram of the fracture orientation,a wider orientation of the fracture distribution is observed at higher pressure of the invasion fluid.展开更多
Objective: To analyze the accuracy and specificity of recent studies to compare the ability of predicting fluid responsiveness with Passive Leg Raising (PLR) by using invasive or non-invasive techniques during passive...Objective: To analyze the accuracy and specificity of recent studies to compare the ability of predicting fluid responsiveness with Passive Leg Raising (PLR) by using invasive or non-invasive techniques during passive leg raising. Data Sources: MEDLINE, EMBASE and the Cochrane Database of Systematic Reviews were systematically searched. Study Selection: Clinical trials that reported the sensitivity, specificity and area under the receiver operating characteristic curve (AUC) between the responder and non-responder induced by passive leg raising and Volume Expansion (VE) in critical ill patients were selected. 246 studies were screened, 14 studies were included for data extraction, which met our inclusion criteria. Data Extraction: Data were abstracted on study characteristics, patient population, type and amount of VE, time of VE, definition of responders, position, techniques used for measuring hemodynamic change, number and percentage of responders, the correlation coefficient, sensitivity, specificity, best threshold and area under the ROC curve (AUC). Meta-analytic techniques were used to summarize the data. Data Synthesis: A total of 524 critical ill patients from 14 studies were analyzed. Data are reported as point estimate (95% confidence intervals). The pooled sensitivity and specificity of invasive techniques were 80% (73% - 85%) and 89% (84% - 93%) respectively with the area under the sROC of 0.94. While, the pooled sensitivity and specificity of non-invasive techniques were 88% (84% - 92%) and 91% (86% - 94%) respectively with the area under the sROC of 0.95. The pooled DOR of invasive techniques was 32.2 (13.6 - 76.8), which was much lower than that of non-invasive techniques with the value of 64.3 (33.9 - 121.7). Conclusions: The hemodynamic indexes changes induced by PLR could reliably predict fluid responsiveness. Non-invasive hemodynamic techniques with their accuracy and safety can benefit the daily work in ICUs. Because the number of patients included in the present trials was small, further studies should be undertaken to confirm these findings.展开更多
Background: Non-invasive goal directed fluid therapy during deceased donor renal transplant (CRT) may reduce the incidence of delayed graft function. Plethysmograph Variability Index (PVI) has been shown to predict fl...Background: Non-invasive goal directed fluid therapy during deceased donor renal transplant (CRT) may reduce the incidence of delayed graft function. Plethysmograph Variability Index (PVI) has been shown to predict fluid responsiveness during surgery. This pilot study evaluated the feasibility of goal directed fluid administration protocol based upon PVI studying the incidence of delayed graft function (DGF) in renal transplant recipients. Methods: Twenty patients underwent primary CRT. The Control group received intravenous fluid (IVF) at a calculated constant rate. The Treatment group received a baseline IVF infusion throughout the surgery. PVI values greater than 13% were treated with 250 ml boluses of IVF. Primary end point was DGF;total IVF administration and urinary biomarker NGAL levels were secondary endpoints. Results: Treatment group at every time point received significantly less IVF. There was no significant difference in incidence of DGF between the groups. 2 patients in the Control group and 6 in the Treatment group developed DGF. NGAL was not associated with the group assignment or total IVF given (p < 0.2). Conclusions: The effectiveness of goal directed fluid therapy with non-invasive dynamic parameters has not been validated in renal transplant surgery and larger prospective studies are needed to determine its utility in renal transplantation.展开更多
Breaker fluids are designed to dissolve filter cakes by breaking their long-chain molecules,thereby removing solid deposits on the wellbore wall.Although breaker fluids are not intended to infiltrate the hydrocarbon r...Breaker fluids are designed to dissolve filter cakes by breaking their long-chain molecules,thereby removing solid deposits on the wellbore wall.Although breaker fluids are not intended to infiltrate the hydrocarbon reservoir,they can invade and cause formation damage by altering sandstone reservoirs'wettability and relative permeability.This can lead to a reduction in the overall reservoir performance.This study coupled tripartite methods to investigate the potential impact of breaker invasion and transport in hydrocarbon reservoirs and its multiscale effect on the performances of sandstone reservoirs.We utilized experimental,analytical,and numerical methods to assess and predict the susceptibility of reservoirs to breaker fluid invasion and transportation.Our experimental and empirical investigations considered varying breaker fluid formulations to evaluate the effects of breaker fluid concentration,formation temperature,and solution gas-oil ratio(GOR)on residual-oil saturation(ROS)and oil-water relative permeability.By adopting the ROS and relative permeability associated with the 50%v/v breaker fluid mixture,the performance of the hydrocarbon reservoir was numerically simulated under the limiting scenarios of no-invasion,moderate-invasion,and deep-invasion of breaker fluid.The results indicate a positive correlation between breaker fluid concentration and ROS,highlighting the risks that breaker fluid invasion and deep infiltration pose to hydrocarbon recovery.Further,results show that both live-oil condition(LOC)and dead-oil condition(DOC)reservoirs are susceptible to the detrimental impacts of breaker fluid infiltration,while their invasion can reduce hydrocarbon recovery in both LOC(-6%)and DOC(-28%).The multi-scale effects on reservoir performance are more pronounced at near-wellbore and DOC than at far-field and LOC.Findings from this work provide valuable insights into the complexity of breaker-fluid invasion in sandstone reservoirs and the mitigation of associated risks to reservoir performance.展开更多
基金funded by National Natural Science Foundation of China(No.51874253,No.U19A2097,U20A20265)the National Key R&D Program of China(No.2018YFC0310200)。
文摘Drilling in a natural gas hydrate formation is challenging due to the poor consolidation of the formation and the potential evaporation of the hydrate.The unreasonable down-hole pressure of the drilling fluid can not only lead to the wellbore instability,but also change the predrilling condition of the natural gas hydrate formation,thus leading to an instable wellbore.In this paper,the integrated discrete element method(DEM)-computational fluid dynamics(CFD)work flow is developed to study the wellbore instability due to the penetration of the drilling fluid into the hydrate formation during crack propagations.The results show that the difference between in-situ stresses and overpressure directly affect the drilling fluid invasion behavior.The lower hydrate saturation leads to an easier generation of drilling fluid flow channels and the lower formation breakdown pressure.The breakdown pressure increases with the increase of hydrate saturation,this also indicates that hydrates can enhance the mechanical properties of the formation.The induced cracks are initially accompanied with higher pressure of the drilling fluid.According to the rose diagram of the fracture orientation,a wider orientation of the fracture distribution is observed at higher pressure of the invasion fluid.
文摘Objective: To analyze the accuracy and specificity of recent studies to compare the ability of predicting fluid responsiveness with Passive Leg Raising (PLR) by using invasive or non-invasive techniques during passive leg raising. Data Sources: MEDLINE, EMBASE and the Cochrane Database of Systematic Reviews were systematically searched. Study Selection: Clinical trials that reported the sensitivity, specificity and area under the receiver operating characteristic curve (AUC) between the responder and non-responder induced by passive leg raising and Volume Expansion (VE) in critical ill patients were selected. 246 studies were screened, 14 studies were included for data extraction, which met our inclusion criteria. Data Extraction: Data were abstracted on study characteristics, patient population, type and amount of VE, time of VE, definition of responders, position, techniques used for measuring hemodynamic change, number and percentage of responders, the correlation coefficient, sensitivity, specificity, best threshold and area under the ROC curve (AUC). Meta-analytic techniques were used to summarize the data. Data Synthesis: A total of 524 critical ill patients from 14 studies were analyzed. Data are reported as point estimate (95% confidence intervals). The pooled sensitivity and specificity of invasive techniques were 80% (73% - 85%) and 89% (84% - 93%) respectively with the area under the sROC of 0.94. While, the pooled sensitivity and specificity of non-invasive techniques were 88% (84% - 92%) and 91% (86% - 94%) respectively with the area under the sROC of 0.95. The pooled DOR of invasive techniques was 32.2 (13.6 - 76.8), which was much lower than that of non-invasive techniques with the value of 64.3 (33.9 - 121.7). Conclusions: The hemodynamic indexes changes induced by PLR could reliably predict fluid responsiveness. Non-invasive hemodynamic techniques with their accuracy and safety can benefit the daily work in ICUs. Because the number of patients included in the present trials was small, further studies should be undertaken to confirm these findings.
文摘Background: Non-invasive goal directed fluid therapy during deceased donor renal transplant (CRT) may reduce the incidence of delayed graft function. Plethysmograph Variability Index (PVI) has been shown to predict fluid responsiveness during surgery. This pilot study evaluated the feasibility of goal directed fluid administration protocol based upon PVI studying the incidence of delayed graft function (DGF) in renal transplant recipients. Methods: Twenty patients underwent primary CRT. The Control group received intravenous fluid (IVF) at a calculated constant rate. The Treatment group received a baseline IVF infusion throughout the surgery. PVI values greater than 13% were treated with 250 ml boluses of IVF. Primary end point was DGF;total IVF administration and urinary biomarker NGAL levels were secondary endpoints. Results: Treatment group at every time point received significantly less IVF. There was no significant difference in incidence of DGF between the groups. 2 patients in the Control group and 6 in the Treatment group developed DGF. NGAL was not associated with the group assignment or total IVF given (p < 0.2). Conclusions: The effectiveness of goal directed fluid therapy with non-invasive dynamic parameters has not been validated in renal transplant surgery and larger prospective studies are needed to determine its utility in renal transplantation.
文摘Breaker fluids are designed to dissolve filter cakes by breaking their long-chain molecules,thereby removing solid deposits on the wellbore wall.Although breaker fluids are not intended to infiltrate the hydrocarbon reservoir,they can invade and cause formation damage by altering sandstone reservoirs'wettability and relative permeability.This can lead to a reduction in the overall reservoir performance.This study coupled tripartite methods to investigate the potential impact of breaker invasion and transport in hydrocarbon reservoirs and its multiscale effect on the performances of sandstone reservoirs.We utilized experimental,analytical,and numerical methods to assess and predict the susceptibility of reservoirs to breaker fluid invasion and transportation.Our experimental and empirical investigations considered varying breaker fluid formulations to evaluate the effects of breaker fluid concentration,formation temperature,and solution gas-oil ratio(GOR)on residual-oil saturation(ROS)and oil-water relative permeability.By adopting the ROS and relative permeability associated with the 50%v/v breaker fluid mixture,the performance of the hydrocarbon reservoir was numerically simulated under the limiting scenarios of no-invasion,moderate-invasion,and deep-invasion of breaker fluid.The results indicate a positive correlation between breaker fluid concentration and ROS,highlighting the risks that breaker fluid invasion and deep infiltration pose to hydrocarbon recovery.Further,results show that both live-oil condition(LOC)and dead-oil condition(DOC)reservoirs are susceptible to the detrimental impacts of breaker fluid infiltration,while their invasion can reduce hydrocarbon recovery in both LOC(-6%)and DOC(-28%).The multi-scale effects on reservoir performance are more pronounced at near-wellbore and DOC than at far-field and LOC.Findings from this work provide valuable insights into the complexity of breaker-fluid invasion in sandstone reservoirs and the mitigation of associated risks to reservoir performance.
