Effective completion design in hydraulic fracturing(HF)is crucial for optimizing production in unconventional reservoirs.Traditional geometric designs often fail to account for geological and engineering heterogeneity...Effective completion design in hydraulic fracturing(HF)is crucial for optimizing production in unconventional reservoirs.Traditional geometric designs often fail to account for geological and engineering heterogeneity,leading to suboptimal stimulation.This study introduces a mechanism-guided data-driven model for optimized completion design that covers the entire process from sweet spot evaluation to stage and cluster optimization.For geological sweet spot evaluation,a mechanism-guided weighted K-medoids clustering model was developed by assigning weights to petrophysical parameters based on their correlation with production profiles.Engineering sweet spots were characterized using bottomhole mechanical specific energy(MSEb)and minimum horizontal in-situ stress(Shmin).The completion design optimization employed dynamic programming and a hybrid multi-objective optimization approach(NSGA-II),integrating geological and engineering sweet spots with operational constraints.The study showed a positive correlation between high-quality geological sweet spots and production(average correlation coefficient of 0.34),and a negative correlation between fluid allocation and engineering sweet spots(correlation coefficient of−0.46).Field application in the Jimsar Sag,Xinjiang,demonstrated that the proposed model significantly outperforms traditional geometric designs.Test wells showed an average 186%increase in cumulative production per 100 m over three months compared to conventional wells.The key findings of this work provide a novel technical pathway for optimized completion design of unconventional reservoirs with significant engineering applicability.展开更多
Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used la...Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.展开更多
SAUMZ 1 and SAUMZ 2 are two forage maize varieties reproduced by distant hybridization.In a randomized block experiment,their fresh forage yield and dry matter yield were investigated on the basis of growth period,lea...SAUMZ 1 and SAUMZ 2 are two forage maize varieties reproduced by distant hybridization.In a randomized block experiment,their fresh forage yield and dry matter yield were investigated on the basis of growth period,leaf stage,and effective accumulated temperature.The nutritional components were measured in a near infrared diffuse reflectance spectroscopy.Referring to the concept of forage grading index,a formula was constructed to calculate the total digestible energy.The investigated characters and indexes were adapted to suitable models of growth dynamics.The results showed that these two varieties have strong heterosis in fresh forage yield,dry matter yield,and total digestible energy.Their growth dynamics were adapted to Logistic models described by general equation y=k/（1＋ae-bx）.The forage grading indexes of these two varieties were decreased linearly along with the increasing of their leaf stage.The stopping point of fast growing period of total digestible energy estimated on the basis of leaf stage was suggested to be used as optimal harvesting stage of forage maize.The optimal harvesting stage was estimated to be tasseling stage for SAUMZ 1 and 19.50-leaf stage for SAUMZ 2.展开更多
The Mahu oilfield in the Junggar Basin of Xinjiang has the characteristics of poor reservoir quality,large horizontal stress difference,and strong heterogeneity,which poses challenges in oil production due to the uncl...The Mahu oilfield in the Junggar Basin of Xinjiang has the characteristics of poor reservoir quality,large horizontal stress difference,and strong heterogeneity,which poses challenges in oil production due to the unclear hydraulic fracture geometry,large fracturing effectiveness difference among wells/stages,and the lack of automation in stage and cluster designs.To address the above issues,this study proposes systematically intelligent designs for stage and cluster parameters in the tight conglomerate oil reservoir in the Ma131 well area.First,through sensitivity analysis,the key parameters for stage division(storage coefficient,brittleness index,and minimum horizontal principal stress)are identified,and a stage di vision algorithm is developed based on the similarity of these key parameters.In order to quickly calculate the productivity of different cluster designs,a single cluster production prediction dataset was established by using the fracturing-production integrated numerical simulation method.Based on the results of fracturing stage division,cluster spacing and injection volume are quickly optimized using the above dataset,and the cluster locations are optimized with the objective of balanced fracture initiation and propagation.Finally,the automatic designs of fracturing stage and cluster starting from the well logging data is realized.Then,the proposed optimization method is applied to a practical well and both the production and profit are increased with the optimized designs.The proposed method can efficiently and intelligently optimize the stage and cluster designs for horizontal wells with the consideration of fracture propagation,productivity,and economic benefits,which helps provide theoretical and meth odological support for fracturing designs in unconventional reservoirs such as the tight conglomerate oil reservoirs in this work.展开更多
Abstract. In this paper, we consider a stage structure population model with two lifestages, immature and mature, with harvesting mature population and stocking immaturepopulation. It is shown that under suitable hypo...Abstract. In this paper, we consider a stage structure population model with two lifestages, immature and mature, with harvesting mature population and stocking immaturepopulation. It is shown that under suitable hypotheses there exists a globally asymptoti-cally stable positive equilibrium. The effect of the delay on the populations at equilibriumand the optimal harvesting policy for mature population are also considered.展开更多
基金supported by the National Natural Science Foundation of China(Grant/Award Nos.:52310001009 and 52122401).
文摘Effective completion design in hydraulic fracturing(HF)is crucial for optimizing production in unconventional reservoirs.Traditional geometric designs often fail to account for geological and engineering heterogeneity,leading to suboptimal stimulation.This study introduces a mechanism-guided data-driven model for optimized completion design that covers the entire process from sweet spot evaluation to stage and cluster optimization.For geological sweet spot evaluation,a mechanism-guided weighted K-medoids clustering model was developed by assigning weights to petrophysical parameters based on their correlation with production profiles.Engineering sweet spots were characterized using bottomhole mechanical specific energy(MSEb)and minimum horizontal in-situ stress(Shmin).The completion design optimization employed dynamic programming and a hybrid multi-objective optimization approach(NSGA-II),integrating geological and engineering sweet spots with operational constraints.The study showed a positive correlation between high-quality geological sweet spots and production(average correlation coefficient of 0.34),and a negative correlation between fluid allocation and engineering sweet spots(correlation coefficient of−0.46).Field application in the Jimsar Sag,Xinjiang,demonstrated that the proposed model significantly outperforms traditional geometric designs.Test wells showed an average 186%increase in cumulative production per 100 m over three months compared to conventional wells.The key findings of this work provide a novel technical pathway for optimized completion design of unconventional reservoirs with significant engineering applicability.
基金Projects(51409154,41372289)supported by the National Natural Science Foundation of ChinaProjects(2015JQJH106,2014TDJH103)supported by Research Fund of Shandong University of Science and Technology,China
文摘Second lining stability, which is the last protection in tunnel engineering, is critically important. The theological properties of the surrounding rock heavily affect second lining stability. In this work, we used laboratory triaxial compressive rheological limestone tests to study nonlinear creep damage characteristics of surrounding rock mass in construction projects. We established a nonlinear creep damage constitutive model for the rock mass, as well as a constitutive model numerical implementation made by programming. Second, we introduced a new foam concrete with higher compression performance and good ductility and studied its mechanical properties through uniaxial and triaxial tests. This concrete was used as the filling material for the reserved deformation layer between the primary support and second lining. Finally, we proposed a high efficiency and accuracy staged optimization method. The minimum reserved deformation layer thickness was established as the optimization goal, and the presence of plastic strain in the second lining after 100 years of surrounding rock creep was used as an evaluation index. Reserved deformation layer thickness optimization analysis reveals no plastic strain in the second lining when the reserved deformation minimum thickness layer is 28.50 cm. The results show that the new foam concrete used as a reserved deformation layer filling material can absorb creep deformation of surrounding rock mass, reduce second lining deformation that leads to plastic strain, and ensure long-term second lining stability.
基金the National Projects of Development Plan of the State Key Fundamental Research of China (973 Program,2009CB118400)
文摘SAUMZ 1 and SAUMZ 2 are two forage maize varieties reproduced by distant hybridization.In a randomized block experiment,their fresh forage yield and dry matter yield were investigated on the basis of growth period,leaf stage,and effective accumulated temperature.The nutritional components were measured in a near infrared diffuse reflectance spectroscopy.Referring to the concept of forage grading index,a formula was constructed to calculate the total digestible energy.The investigated characters and indexes were adapted to suitable models of growth dynamics.The results showed that these two varieties have strong heterosis in fresh forage yield,dry matter yield,and total digestible energy.Their growth dynamics were adapted to Logistic models described by general equation y=k/（1＋ae-bx）.The forage grading indexes of these two varieties were decreased linearly along with the increasing of their leaf stage.The stopping point of fast growing period of total digestible energy estimated on the basis of leaf stage was suggested to be used as optimal harvesting stage of forage maize.The optimal harvesting stage was estimated to be tasseling stage for SAUMZ 1 and 19.50-leaf stage for SAUMZ 2.
基金the National Natural Science Foun dation of China(Grant No.52374043)the Key Program of Na tional Natural Science Foundation of China(Grant No.52234003).
文摘The Mahu oilfield in the Junggar Basin of Xinjiang has the characteristics of poor reservoir quality,large horizontal stress difference,and strong heterogeneity,which poses challenges in oil production due to the unclear hydraulic fracture geometry,large fracturing effectiveness difference among wells/stages,and the lack of automation in stage and cluster designs.To address the above issues,this study proposes systematically intelligent designs for stage and cluster parameters in the tight conglomerate oil reservoir in the Ma131 well area.First,through sensitivity analysis,the key parameters for stage division(storage coefficient,brittleness index,and minimum horizontal principal stress)are identified,and a stage di vision algorithm is developed based on the similarity of these key parameters.In order to quickly calculate the productivity of different cluster designs,a single cluster production prediction dataset was established by using the fracturing-production integrated numerical simulation method.Based on the results of fracturing stage division,cluster spacing and injection volume are quickly optimized using the above dataset,and the cluster locations are optimized with the objective of balanced fracture initiation and propagation.Finally,the automatic designs of fracturing stage and cluster starting from the well logging data is realized.Then,the proposed optimization method is applied to a practical well and both the production and profit are increased with the optimized designs.The proposed method can efficiently and intelligently optimize the stage and cluster designs for horizontal wells with the consideration of fracture propagation,productivity,and economic benefits,which helps provide theoretical and meth odological support for fracturing designs in unconventional reservoirs such as the tight conglomerate oil reservoirs in this work.
基金the National Natural Science Foundation of China and Natural Science Foundation of Henan Province.
文摘Abstract. In this paper, we consider a stage structure population model with two lifestages, immature and mature, with harvesting mature population and stocking immaturepopulation. It is shown that under suitable hypotheses there exists a globally asymptoti-cally stable positive equilibrium. The effect of the delay on the populations at equilibriumand the optimal harvesting policy for mature population are also considered.
