最近，当在西北中国在盆学习一些煤气的领域时，我们发现小浪的方面脑叶在薄沙水库的鉴定上有大影响。从 H 形成，在有煤气忍受的薄沙身体的顶的思考，有在二片弱山峰方面脑叶之间的主要小浪脑叶。总是，有另一座山峰的混合从一座薄沙...最近，当在西北中国在盆学习一些煤气的领域时，我们发现小浪的方面脑叶在薄沙水库的鉴定上有大影响。从 H 形成，在有煤气忍受的薄沙身体的顶的思考，有在二片弱山峰方面脑叶之间的主要小浪脑叶。总是，有另一座山峰的混合从一座薄沙水库的顶反映了的更低的。那使识别沙水库困难。以便解决这，许多前面的模型用典型的井木头被建立。2D 合成侧面用 Ricker 小浪被生产学习在小浪方面脑叶和薄沙位置和频率的效果之间并且在振幅和薄沙身体之间的关系。我们开发了下列结论：首先，在一个更浅的位置识别薄沙更容易。第二，把沙身体思考与方面脑叶区别开来的一个好方法由把侧面与不同频率窗口作比较。第三，用振幅属性描述沙程度有用、有效。展开更多
Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and ...Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and sometimes random microcracking near coalesced fracture formation alters the mechanical properties of the nearby virgin material. Individual microcrack characterization is also significant in quantifying the material changes near the fracture faces （i.e. damage）. Acoustic emission （AE） monitoring and analysis provide unique information regarding the microcracking process temporally, and infor- mation concerning the source characterization of individual microcracks can be extracted. In this context, laboratory hydraulic fracture tests were carried out while monitoring the AEs from several piezoelectric transducers. In-depth post-processing of the AE event data was performed for the purpose of under- standing the individual source mechanisms. Several source characterization techniques including moment tensor inversion, event parametric analysis, and volumetric deformation analysis were adopted. Post-test fracture characterization through coring, slicing and micro-computed tomographic imaging was performed to determine the coalesced fracture location and structure. Distinct differences in fracture characteristics were found spatially in relation to the openhole injection interval. Individual microcrack AE analysis showed substantial energy reduction emanating spatially from the injection interval. It was quantitatively observed that the recorded AE signals provided sufficient information to generalize the damage radiating spatially away from the injection wellbore.展开更多
The use of hydrodynamic pressure wave generated from the action of a fast acting valve as well as acoustic reflectometry in the detection of anomalies like leaks, deposits and blockages in a pipe or fluid flow system ...The use of hydrodynamic pressure wave generated from the action of a fast acting valve as well as acoustic reflectometry in the detection of anomalies like leaks, deposits and blockages in a pipe or fluid flow system in the context of the prevailing scientific theories in fluid flow is discussed. The focus of this paper is the application of the theories to more complex scenarios involving multi-phase fluid flow, specifically, two-phase and two-component fluid flow. The principal concern is the determination of acoustic velocity in a two-phase flow regime;which is problematic because it varies with mixture composition along multiphase flowlines. A technique for simulating flow regimes in the laboratory using stacked S-shaped pipes is presented as well as a discussion of the results from a computational fluid dynamics model.展开更多
Moran considered a dam whose inflow in a given interval of time is a continuous random variable. He then developed integral equations for the probabilities of emptiness and overflow. These equations are difficult to s...Moran considered a dam whose inflow in a given interval of time is a continuous random variable. He then developed integral equations for the probabilities of emptiness and overflow. These equations are difficult to solve numerically;thus, approximations have been proposed that discretize the input. In this paper, extensions are considered for storage systems with different assumptions for storage losses. We also develop discrete approximations for the probabilities of emptiness and overflow.展开更多
This work studies the influence of a commercial dispersion of multi wall carbon nanotubes （MWCNT） on the hydration of a class G cement paste, at room and elevated down-hole temperatures. The MWCNT dispersion was pro...This work studies the influence of a commercial dispersion of multi wall carbon nanotubes （MWCNT） on the hydration of a class G cement paste, at room and elevated down-hole temperatures. The MWCNT dispersion was produced with a solids concentration of 3.0 % by mass and an anionic surfactant as dispersing agent. Cement pastes with water-to-cement ratio of 0.45 and additions of solid MWCNT by mass of cement up to 0.50 % were studied. Isothermal calorimetry results showed a clear retardation of the hydration of cement caused by the surfactant contained in the MWCNT dispersion. Nevertheless, thermogravimetric evaluations showed that once the hydration reaction resumed, the retardation effect of the surfactant did not have a negative impact on the amount of hydration products precipitated. It was concluded that the commercial MWCNT dispersion presents a good potential to be applied in oil well cement pastes.展开更多
Our database tracking of USA water usage per well indicates that traditionally shale operators have been using, on average 3 to 6 million gallons of water; even up to 8 million for the en- tire life cycle of the well ...Our database tracking of USA water usage per well indicates that traditionally shale operators have been using, on average 3 to 6 million gallons of water; even up to 8 million for the en- tire life cycle of the well based on its suitability for re-fracturing to stimulate their long and lateral ho- rizontal welis. According to our data, sourcing, storage, transportation, treatment, and disposal of this large volume of water could account for up to 10% of overall drilling and completion costs. With in- creasingly stringent regulations governing the use of fresh water and growing challenges associated with storage and use of produced and flowback water in hydraulic fracturing, finding alternative sources of fracturing fluid is already a hot debate among both the scientific community and industry experts. On the other hand, waterless fracturing technology providers claim their technology can solve the concerns of water availability for shale development. This study reviews high-level technical issues and opportunities in this challenging and growing market and evaluates key economic drivers behind water management practices such as waterless fracturing technologies, based on a given shale gas play in the United States and experience gained in Canada. Water costs are analyzed under a variety of scenarios with and without the use of （fresh） water. The results are complemented by surveys from several oil and gas operators. Our economic analysis shows that fresh water usage offers the greatest economic return. In regions where water sourcing is a challenge, however, the short-term economic advantage of using non-fresh water-based fracturing outweighs the capital costs required by waterless fracturing methods. Until waterless methods are cost competitive, recycled water usage with low treatment offers a similar net present value （NPV） to that of sourcing freshwater via truck, for in- stance.展开更多
Robust guidance algorithm using only line-of-sight rate measurement is proposed for the interceptor with passive seeker.The initial relative distance,initial closing velocity and their error boundaries are employed to...Robust guidance algorithm using only line-of-sight rate measurement is proposed for the interceptor with passive seeker.The initial relative distance,initial closing velocity and their error boundaries are employed to obtain their estimations according to the interceptor-target relative kinematics.A robust guidance law based on sliding mode control is formulated,in which the boundary of target maneuver is needed and the chattering phenomenon inevitably exists.In order to address the defects above,an estimation to the boundary of the target acceleration is proposed to improve the robust guidance law and the Lyapunov stability analysis is included.The main feature of the robust guidance algorithm is that it reduces the influence of the relative distance,the closing velocity and the target maneuver on the interception and enhances the effect of line-of-sight rate.With two worst conditions of initial measured distance and initial measured closing velocity,performances of the proposed guidance laws are verified via numerical simulations against different target maneuvers.展开更多
基金financial support for much of the early development of the AE analysis methods was provided by the U.S. Department of Energy (DOE) (Grant No. DE-FE0002760)
文摘Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and sometimes random microcracking near coalesced fracture formation alters the mechanical properties of the nearby virgin material. Individual microcrack characterization is also significant in quantifying the material changes near the fracture faces （i.e. damage）. Acoustic emission （AE） monitoring and analysis provide unique information regarding the microcracking process temporally, and infor- mation concerning the source characterization of individual microcracks can be extracted. In this context, laboratory hydraulic fracture tests were carried out while monitoring the AEs from several piezoelectric transducers. In-depth post-processing of the AE event data was performed for the purpose of under- standing the individual source mechanisms. Several source characterization techniques including moment tensor inversion, event parametric analysis, and volumetric deformation analysis were adopted. Post-test fracture characterization through coring, slicing and micro-computed tomographic imaging was performed to determine the coalesced fracture location and structure. Distinct differences in fracture characteristics were found spatially in relation to the openhole injection interval. Individual microcrack AE analysis showed substantial energy reduction emanating spatially from the injection interval. It was quantitatively observed that the recorded AE signals provided sufficient information to generalize the damage radiating spatially away from the injection wellbore.
文摘The use of hydrodynamic pressure wave generated from the action of a fast acting valve as well as acoustic reflectometry in the detection of anomalies like leaks, deposits and blockages in a pipe or fluid flow system in the context of the prevailing scientific theories in fluid flow is discussed. The focus of this paper is the application of the theories to more complex scenarios involving multi-phase fluid flow, specifically, two-phase and two-component fluid flow. The principal concern is the determination of acoustic velocity in a two-phase flow regime;which is problematic because it varies with mixture composition along multiphase flowlines. A technique for simulating flow regimes in the laboratory using stacked S-shaped pipes is presented as well as a discussion of the results from a computational fluid dynamics model.
文摘Moran considered a dam whose inflow in a given interval of time is a continuous random variable. He then developed integral equations for the probabilities of emptiness and overflow. These equations are difficult to solve numerically;thus, approximations have been proposed that discretize the input. In this paper, extensions are considered for storage systems with different assumptions for storage losses. We also develop discrete approximations for the probabilities of emptiness and overflow.
文摘This work studies the influence of a commercial dispersion of multi wall carbon nanotubes （MWCNT） on the hydration of a class G cement paste, at room and elevated down-hole temperatures. The MWCNT dispersion was produced with a solids concentration of 3.0 % by mass and an anionic surfactant as dispersing agent. Cement pastes with water-to-cement ratio of 0.45 and additions of solid MWCNT by mass of cement up to 0.50 % were studied. Isothermal calorimetry results showed a clear retardation of the hydration of cement caused by the surfactant contained in the MWCNT dispersion. Nevertheless, thermogravimetric evaluations showed that once the hydration reaction resumed, the retardation effect of the surfactant did not have a negative impact on the amount of hydration products precipitated. It was concluded that the commercial MWCNT dispersion presents a good potential to be applied in oil well cement pastes.
文摘Our database tracking of USA water usage per well indicates that traditionally shale operators have been using, on average 3 to 6 million gallons of water; even up to 8 million for the en- tire life cycle of the well based on its suitability for re-fracturing to stimulate their long and lateral ho- rizontal welis. According to our data, sourcing, storage, transportation, treatment, and disposal of this large volume of water could account for up to 10% of overall drilling and completion costs. With in- creasingly stringent regulations governing the use of fresh water and growing challenges associated with storage and use of produced and flowback water in hydraulic fracturing, finding alternative sources of fracturing fluid is already a hot debate among both the scientific community and industry experts. On the other hand, waterless fracturing technology providers claim their technology can solve the concerns of water availability for shale development. This study reviews high-level technical issues and opportunities in this challenging and growing market and evaluates key economic drivers behind water management practices such as waterless fracturing technologies, based on a given shale gas play in the United States and experience gained in Canada. Water costs are analyzed under a variety of scenarios with and without the use of （fresh） water. The results are complemented by surveys from several oil and gas operators. Our economic analysis shows that fresh water usage offers the greatest economic return. In regions where water sourcing is a challenge, however, the short-term economic advantage of using non-fresh water-based fracturing outweighs the capital costs required by waterless fracturing methods. Until waterless methods are cost competitive, recycled water usage with low treatment offers a similar net present value （NPV） to that of sourcing freshwater via truck, for in- stance.
基金supported by the National Natural Science Foundation of China under Grant Nos.61333011,61421063,and 61433011
文摘Robust guidance algorithm using only line-of-sight rate measurement is proposed for the interceptor with passive seeker.The initial relative distance,initial closing velocity and their error boundaries are employed to obtain their estimations according to the interceptor-target relative kinematics.A robust guidance law based on sliding mode control is formulated,in which the boundary of target maneuver is needed and the chattering phenomenon inevitably exists.In order to address the defects above,an estimation to the boundary of the target acceleration is proposed to improve the robust guidance law and the Lyapunov stability analysis is included.The main feature of the robust guidance algorithm is that it reduces the influence of the relative distance,the closing velocity and the target maneuver on the interception and enhances the effect of line-of-sight rate.With two worst conditions of initial measured distance and initial measured closing velocity,performances of the proposed guidance laws are verified via numerical simulations against different target maneuvers.
