Exploration and development practices have proved that staged volumetric fracturing stimulation in horizontal wells is a key technology for tight sandstone gas development,and reservoir sweet spot is an important basi...Exploration and development practices have proved that staged volumetric fracturing stimulation in horizontal wells is a key technology for tight sandstone gas development,and reservoir sweet spot is an important basis for the perforation position selection and staged fracturing in the process of well location deployment and reservoir stimulation.Tight sandstone reservoirs are usually characterized by sandstone and mudstone interlayers with different thicknesses,and complex natural fracture distribution and geostress state.It is hard to predict“geological-engineering”dual sweet spots,and these two kinds of sweet spots are usually in different zones.As a result,there lacks a basis for the optimization of fracturing parameters to stimulate tight sandstone reservoirs.This paper establishes a geological sweet spot prediction model which takes into account total hydrocarbon content,reservoir porosity and other factors,then puts forward a 3D multi-scale engineering sweet spot evaluation method which takes into account lithology,fracture morphology,fracture mechanical behavior,and dilatation and shear dilation effect,andfinally a“geological-engineering”dual sweet spot evaluation model for tight sandstone reservoirs.Two wells in the tight sandstone gasfield in the Linxing Block of the Ordos Basin were selected as a case,and the dual sweet spot profiles,fracturing pressure and SRV were compared and analyzed.The results show that:1)shear dilation angle influences the distribution of engineering sweet spots at the most in the study area,followed by dissipated energy,elastic modulus and fracture energy;2)the geological sweet spot zone with a high coefficient is not necessarily the pay zone with high shale gas production;3)the engineering sweet spot zone with a high coefficient needs lower fracture pressure and can be stimulated relatively sufficiently;4)high-quality geological sweet spots and high-quality engineering sweet spots are poorly consistent in spatial location.In conclusion,the stimulation of tight sandstone gas reservoirs shall take geological sweet spot as the basis and engineering sweet spot as the guarantee,and the distribution of dual sweep spots should be considered comprehensively.The multi-scale“geological-engineering”dual sweet spot evaluation method proposed in this paper provides important technical support for the prediction of sweet spots of the tight sandstone gas and the optimization of development schemes in the study area.展开更多
AIM:To investigate the role of 18 F-fluorodeoxyglucose positron emission tomography(FDG-PET) in the diagnosis of small pancreatic cancer. METHODS:This study involved 31 patients with proven invasive ductal cancer of t...AIM:To investigate the role of 18 F-fluorodeoxyglucose positron emission tomography(FDG-PET) in the diagnosis of small pancreatic cancer. METHODS:This study involved 31 patients with proven invasive ductal cancer of the pancreas.The patients were divided into 3 groups according to the maximum diameter of the tumor:TS1(maximum tumor size≤2.0 cm) ,TS2(>2.0 cm and≤4.0 cm) or TS3-4(>4.0 cm) .The relationships between the TS and various diagnostic tools,including FDG-PET with dual time point evaluation,were analyzed. RESULTS:The tumors ranged from 1.3 to 11.0 cm in diameter.Thirty of the 31 patients(97%) had a positive FDG-PET study.There were 5 patients classified as TS1,15 as TS2 and 11 as TS3-4.The sensitivity of FDG-PET,computed tomography(CT) and magnetic resonanceimaging(MRI) were 100%,40%,0%in TS1,93%,93%,89%in TS2 and 100%,100%,100%in TS3-4. The sensitivity of FDG-PET was significantly higher in comparison to CT and MRI in patients with TS1(P< 0.032) .The mean standardized uptake values(SUVs) did not show a significant difference in relation to the TS(TS1:5.8±4.5,TS2:5.7±2.2,TS3-4:8.2±3.9) ,respectively.All the TS1 tumors(from 13 to 20 mm) showed higher SUVs in FDG-PET with dual time point evaluation in the delayed phase compared with the early phase,which suggested the lesions were malignant. CONCLUSION:These results indicate that FDG-PET with dual time point evaluation is a useful modality for the detection of small pancreatic cancers with a diameter of less than 20 mm.展开更多
Western Guizhou is a favorable region for coalbed methane(CBM)exploration and development in Guizhou Province.Affected by complex geological conditions,the heterogeneity of middle-high rank coal reservoirs is strong,a...Western Guizhou is a favorable region for coalbed methane(CBM)exploration and development in Guizhou Province.Affected by complex geological conditions,the heterogeneity of middle-high rank coal reservoirs is strong,and the geological and engineering control effects on enrichment and high productivity of CBM are significantly different.This paper comparatively analyzes the characteristics of middle-and high-rank coal reservoirs in the western Guizhou region,revealing the productivity characteristics and gas/water production rules of typical middle-high rank CBM high-yield wells.Moreover,it establishes a geological-engineering control model for the enrichment and high productivity of CBM in middle-high-rank coal seams in the western Guizhou region and analyzes the exploration and development potential and direction of middle-high-rank CBM in the region.The results are as follows.First,the middle-rank coal in the western Guizhou region is represented by the Liupanshui coalfield,where cleats and fractures are well developed,the content of macropores and mesopores is relatively high,the permeability is good,and the adsorption capacity is relatively weak.The high-rank coal is represented by the Zhina coalfield,where micropores are well developed,the permeability is greatly affected by burial depth,and the adsorption capacity is strong.Second,the difference in the characteristics of middle-rank and high-rank coal reservoirs in the western Guizhou region is mainly reflected in the pore-permeability conditions and adsorption capacity.The porosity and permeability of middle-rank coal samples are both greater than those of high-rank coal samples,and the development of secondary microfractures is the main reason for the relatively high permeability of middle-rank coal,while the well-developed micropores in high-rank coal provide more space for CBM preservation.Third,the CBM highyield wells in middle-rank coal seams in the western Guizhou region have the characteristics of“relatively high water production and high gas production,”while those of high-rank coal seams have the characteristics of“low water production and high gas production”or“high water production and low gas production.”The gas content and permeability of the coal reservoirs are the common constraints on whether CBM in middle-high rank coal seams can be highly productive under complex geological conditions.Fourth,the enrichment and high productivity of CBM in middle-high rank coal seams under complex geological conditions is the result of the synergistic matching of depth structure hydrology and adaptive fracturing production techniques.The CBM enrichment model,reservoir reformability,and gas/water production characteristics under geological and engineering synergistic control are unique and complex.Fifth,the middle-high rank coal seams in the western Guizhou region exhibit the basic resource characteristics of high gas content and high CBM resource abundance.Carrying out a precise evaluation of the CBM dual sweet spot system and reservoir volume stimulation are important guarantees for the efficient exploration and development of CBM in the western Guizhou region.展开更多
文摘Exploration and development practices have proved that staged volumetric fracturing stimulation in horizontal wells is a key technology for tight sandstone gas development,and reservoir sweet spot is an important basis for the perforation position selection and staged fracturing in the process of well location deployment and reservoir stimulation.Tight sandstone reservoirs are usually characterized by sandstone and mudstone interlayers with different thicknesses,and complex natural fracture distribution and geostress state.It is hard to predict“geological-engineering”dual sweet spots,and these two kinds of sweet spots are usually in different zones.As a result,there lacks a basis for the optimization of fracturing parameters to stimulate tight sandstone reservoirs.This paper establishes a geological sweet spot prediction model which takes into account total hydrocarbon content,reservoir porosity and other factors,then puts forward a 3D multi-scale engineering sweet spot evaluation method which takes into account lithology,fracture morphology,fracture mechanical behavior,and dilatation and shear dilation effect,andfinally a“geological-engineering”dual sweet spot evaluation model for tight sandstone reservoirs.Two wells in the tight sandstone gasfield in the Linxing Block of the Ordos Basin were selected as a case,and the dual sweet spot profiles,fracturing pressure and SRV were compared and analyzed.The results show that:1)shear dilation angle influences the distribution of engineering sweet spots at the most in the study area,followed by dissipated energy,elastic modulus and fracture energy;2)the geological sweet spot zone with a high coefficient is not necessarily the pay zone with high shale gas production;3)the engineering sweet spot zone with a high coefficient needs lower fracture pressure and can be stimulated relatively sufficiently;4)high-quality geological sweet spots and high-quality engineering sweet spots are poorly consistent in spatial location.In conclusion,the stimulation of tight sandstone gas reservoirs shall take geological sweet spot as the basis and engineering sweet spot as the guarantee,and the distribution of dual sweep spots should be considered comprehensively.The multi-scale“geological-engineering”dual sweet spot evaluation method proposed in this paper provides important technical support for the prediction of sweet spots of the tight sandstone gas and the optimization of development schemes in the study area.
文摘AIM:To investigate the role of 18 F-fluorodeoxyglucose positron emission tomography(FDG-PET) in the diagnosis of small pancreatic cancer. METHODS:This study involved 31 patients with proven invasive ductal cancer of the pancreas.The patients were divided into 3 groups according to the maximum diameter of the tumor:TS1(maximum tumor size≤2.0 cm) ,TS2(>2.0 cm and≤4.0 cm) or TS3-4(>4.0 cm) .The relationships between the TS and various diagnostic tools,including FDG-PET with dual time point evaluation,were analyzed. RESULTS:The tumors ranged from 1.3 to 11.0 cm in diameter.Thirty of the 31 patients(97%) had a positive FDG-PET study.There were 5 patients classified as TS1,15 as TS2 and 11 as TS3-4.The sensitivity of FDG-PET,computed tomography(CT) and magnetic resonanceimaging(MRI) were 100%,40%,0%in TS1,93%,93%,89%in TS2 and 100%,100%,100%in TS3-4. The sensitivity of FDG-PET was significantly higher in comparison to CT and MRI in patients with TS1(P< 0.032) .The mean standardized uptake values(SUVs) did not show a significant difference in relation to the TS(TS1:5.8±4.5,TS2:5.7±2.2,TS3-4:8.2±3.9) ,respectively.All the TS1 tumors(from 13 to 20 mm) showed higher SUVs in FDG-PET with dual time point evaluation in the delayed phase compared with the early phase,which suggested the lesions were malignant. CONCLUSION:These results indicate that FDG-PET with dual time point evaluation is a useful modality for the detection of small pancreatic cancers with a diameter of less than 20 mm.
基金supported by the“Belt and Road”Innovation Cooperation Project of Jiangsu Province(Grant No.BZ2022015)the National Natural Science Foundation of China(No.42030810 and 42102207)Geological Exploration Foundation of Guizhou Province(No.52000021MGQSE7S7K6PRP).
文摘Western Guizhou is a favorable region for coalbed methane(CBM)exploration and development in Guizhou Province.Affected by complex geological conditions,the heterogeneity of middle-high rank coal reservoirs is strong,and the geological and engineering control effects on enrichment and high productivity of CBM are significantly different.This paper comparatively analyzes the characteristics of middle-and high-rank coal reservoirs in the western Guizhou region,revealing the productivity characteristics and gas/water production rules of typical middle-high rank CBM high-yield wells.Moreover,it establishes a geological-engineering control model for the enrichment and high productivity of CBM in middle-high-rank coal seams in the western Guizhou region and analyzes the exploration and development potential and direction of middle-high-rank CBM in the region.The results are as follows.First,the middle-rank coal in the western Guizhou region is represented by the Liupanshui coalfield,where cleats and fractures are well developed,the content of macropores and mesopores is relatively high,the permeability is good,and the adsorption capacity is relatively weak.The high-rank coal is represented by the Zhina coalfield,where micropores are well developed,the permeability is greatly affected by burial depth,and the adsorption capacity is strong.Second,the difference in the characteristics of middle-rank and high-rank coal reservoirs in the western Guizhou region is mainly reflected in the pore-permeability conditions and adsorption capacity.The porosity and permeability of middle-rank coal samples are both greater than those of high-rank coal samples,and the development of secondary microfractures is the main reason for the relatively high permeability of middle-rank coal,while the well-developed micropores in high-rank coal provide more space for CBM preservation.Third,the CBM highyield wells in middle-rank coal seams in the western Guizhou region have the characteristics of“relatively high water production and high gas production,”while those of high-rank coal seams have the characteristics of“low water production and high gas production”or“high water production and low gas production.”The gas content and permeability of the coal reservoirs are the common constraints on whether CBM in middle-high rank coal seams can be highly productive under complex geological conditions.Fourth,the enrichment and high productivity of CBM in middle-high rank coal seams under complex geological conditions is the result of the synergistic matching of depth structure hydrology and adaptive fracturing production techniques.The CBM enrichment model,reservoir reformability,and gas/water production characteristics under geological and engineering synergistic control are unique and complex.Fifth,the middle-high rank coal seams in the western Guizhou region exhibit the basic resource characteristics of high gas content and high CBM resource abundance.Carrying out a precise evaluation of the CBM dual sweet spot system and reservoir volume stimulation are important guarantees for the efficient exploration and development of CBM in the western Guizhou region.
