NMR serves as an important technique for probing rock pore space,such as pore structure characterization,fluid identification,and petrophysical property testing,due to the reusability of cores,convenience in sample pr...NMR serves as an important technique for probing rock pore space,such as pore structure characterization,fluid identification,and petrophysical property testing,due to the reusability of cores,convenience in sample processing,and time efficiency in laboratory tests.In practice,NMR signal collection is normally achieved through polarized nuclei relaxation which releases crucial relaxation messages for result interpretation.The impetus of this work is to help engineers and researchers with petroleum background obtain new insights into NMR principals and extend existing methodologies for characterization of unconventional formations.This article first gives a brief description of the development history of relaxation theories and models for porous media.Then,the widely used NMR techniques for characterizing petrophysical properties and pore structures are presented.Meanwhile,limitations and deficiencies of them are summarized.Finally,future work on improving these insufficiencies and approaches of enhancement applicability for NMR technologies are discussed.展开更多
Unconventional hydrocarbon reservoirs in layered formations,such as tight sandstones and shales,are continually being developed.Hydraulic fracturing is a critical technology for the high-efficiency development of hydr...Unconventional hydrocarbon reservoirs in layered formations,such as tight sandstones and shales,are continually being developed.Hydraulic fracturing is a critical technology for the high-efficiency development of hydrocarbon reservoirs.Understanding the stress field and stability of the formation interface is vital to understanding stress propagation,preferably before the growing hydraulic fracture contacts the formation interface.In this study,models are developed for computing the stress field of hydraulic fracture propagation near the formation interface,and the stress fields within and at the two sides of the formation interface are analyzed.Four failure modes of the interface under the impact of hydraulic fracture propagation in its vicinity are identified,and the corresponding failure criteria are proposed.By simulating the magnitude and direction of peak stress at different parameters,the failure mode and stability of the formation interface are analyzed.Results reveal that when the interface strength is weak,the formation interface fails before the growing hydraulic fracture contacts it,and its stability is significantly related to a variety of factors,including the type of formation interface,rock mechanical properties,far-field stress,structural parameters,distance between the hydraulic fracture and formation interface,and fracturing execution parameters.展开更多
Dear Editor, Triacylglycerols （triglycerides） （TAGs）, as the major storage forms of energy, mainly are stored in adipocytes, myocytes, enterocytes, hepatocytes, and mammary epithelial cells in mammals, oilseeds i...Dear Editor, Triacylglycerols （triglycerides） （TAGs）, as the major storage forms of energy, mainly are stored in adipocytes, myocytes, enterocytes, hepatocytes, and mammary epithelial cells in mammals, oilseeds in plants, and lipid droplets in microorgan- isms （Yen et al., 2008）. Aside from energy storage, TAGs have essential functions in multiple physiological processes. In plants, TAGs are crucial for seed oil accumulation, germina- tion, and seedling development （Zhang et al., 2005, 2009）. Notably, TAGs derived from plants and microorganisms could serve as the feedstock for biofuels production （Deng et al., 2009）. Therefore, understanding of the molecular basis of TAGs bio- synthesis and storage is of considerable economic importance.展开更多
基金financially supported by the National Science Foundation for Distinguished Young Scholars(51525404)the National Science and Technology Major Project(No.2016ZX05002002)the National Science and Technology Major Project(2016ZX05048-004-006)。
文摘NMR serves as an important technique for probing rock pore space,such as pore structure characterization,fluid identification,and petrophysical property testing,due to the reusability of cores,convenience in sample processing,and time efficiency in laboratory tests.In practice,NMR signal collection is normally achieved through polarized nuclei relaxation which releases crucial relaxation messages for result interpretation.The impetus of this work is to help engineers and researchers with petroleum background obtain new insights into NMR principals and extend existing methodologies for characterization of unconventional formations.This article first gives a brief description of the development history of relaxation theories and models for porous media.Then,the widely used NMR techniques for characterizing petrophysical properties and pore structures are presented.Meanwhile,limitations and deficiencies of them are summarized.Finally,future work on improving these insufficiencies and approaches of enhancement applicability for NMR technologies are discussed.
基金supported by National Natural Science Foundation of China (51704251)National Science and Technology Major Project of the Ministry of Science and Technology of China (2016ZX05006-002)。
文摘Unconventional hydrocarbon reservoirs in layered formations,such as tight sandstones and shales,are continually being developed.Hydraulic fracturing is a critical technology for the high-efficiency development of hydrocarbon reservoirs.Understanding the stress field and stability of the formation interface is vital to understanding stress propagation,preferably before the growing hydraulic fracture contacts the formation interface.In this study,models are developed for computing the stress field of hydraulic fracture propagation near the formation interface,and the stress fields within and at the two sides of the formation interface are analyzed.Four failure modes of the interface under the impact of hydraulic fracture propagation in its vicinity are identified,and the corresponding failure criteria are proposed.By simulating the magnitude and direction of peak stress at different parameters,the failure mode and stability of the formation interface are analyzed.Results reveal that when the interface strength is weak,the formation interface fails before the growing hydraulic fracture contacts it,and its stability is significantly related to a variety of factors,including the type of formation interface,rock mechanical properties,far-field stress,structural parameters,distance between the hydraulic fracture and formation interface,and fracturing execution parameters.
基金This work was supported by grants from the National Natural Science Foundation of China，from National Nonprofit Institute Research Grants
文摘Dear Editor, Triacylglycerols （triglycerides） （TAGs）, as the major storage forms of energy, mainly are stored in adipocytes, myocytes, enterocytes, hepatocytes, and mammary epithelial cells in mammals, oilseeds in plants, and lipid droplets in microorgan- isms （Yen et al., 2008）. Aside from energy storage, TAGs have essential functions in multiple physiological processes. In plants, TAGs are crucial for seed oil accumulation, germina- tion, and seedling development （Zhang et al., 2005, 2009）. Notably, TAGs derived from plants and microorganisms could serve as the feedstock for biofuels production （Deng et al., 2009）. Therefore, understanding of the molecular basis of TAGs bio- synthesis and storage is of considerable economic importance.
