查看更多>>摘要：The recent developments in low-permeability oil and gas reservoir mining technology have led to the application of various forms of well fracturing models to determine the physical formation parameters and flow laws in porous media.However,most related studies have been aimed at conducting a pressure transient analysis after the formation of fractures,ignoring the pressure change characteristics during fracture formation.In this study,a fracture growth model based on vertical fractured wells was established and solved using the source function theory and boundary element method.The rationality of the model calculation method was verified by the superposition principle.The pressure change laws before and after fracture growth were analyzed,and the model was subjected to hydraulic fracturing experiments.The results showed that with the increase in the local pressure at the bottom of the well,main fractures,branch fractures,and microfractures were generated in three stages.When the fracture was formed,the pressure and pressure derivative curves fluctuated but gradually returned to a stable state under the fracture shape with the extension of the flow time.Moreover,from the main fracture to the microfracture stage,the pressure recovery time period was gradually shortened.The fitting results of the analysis model and fracturing experiment were found to be accurate,providing a theoretical support for analyzing the transient pressure changes during the formation of complex fractures.The different curve characteristics also provide a new reference basis for evaluating the fracture propagation behavior and predicting the fracture conductivity.
查看更多>>摘要：The aim of this work is to examine and estimate the ultimate recovery from Turkey's largest oil reserve(1.85 billion barrels)utilizing a new approach called mining-assisted heavy oil production(MAHOP)and conventional steam injection horizontal production(CSHP)method.In MAHOP,declines(tunnels)are excavated from the surface to the reservoir and proceed along the reservoir's bottom.Fan-shaped steam injection holes are drilled from the upper and lower sides of the reservoir with conventional steam-assisted gravity drainage(SAGD).The suggested CSHP method uses conventional vertical wells as steam injectors and produces heated oil from newly drilled horizontal well pairs.To reach this goal,an experimental scaled model and a numerical model have been designed and developed.Laboratory studies have been carried on three different wettability environments to observe the effect of wettability on the ultimate recovery.The oil recovery obtained from MAHOP at different wettability environments varied with higher steam injection temperatures.The highest recovery(71.73%)was realized in water-wet rock.However,in the CSHP method,the maximum recovery was lower(48.11%).It was believed that the temperature altered the wettability of oil-wet rock to more water-wet,which contributed to incremental oil recovery.However,higher steam injection temperatures greater than 140 ℃ had no significant effect on incremental oil recovery.Furdiermore,asphaltene precipitation,especially in the oil-wet system and alteration of wettability to more water-wet increased oil production.
查看更多>>摘要：Surfactant flooding is a proven method employed to improve the recovery of crude oil from subsurface reservoirs but the knowledge about microemulsion formation,factors related to their stability,and the trapping mechanism of crude oil components in a microemulsion is still not clear for designing of injection fluid for specific crude type.The interaction mechanisms of four crude oils with surfactant-brine solutions were studied in this work for better insight into the molecular level mechanisms during surfactant flooding.UV-visible absorption and fluorescence spectra of the separated maltene and asphaltene fractions indicate the structural difference of the components in the molecular level,particularly,the size of the fused aromatic rings(FAR)present within individual bulk crude sample.Moreover,the FTIR spectra of the separated asphaltenes from the crude samples clearly showed the subtle difference in the functional groups present in respective FAR structures.Well-characterized compositionally different crude oils were mixed with four different surfactant-brine solutions(anionic-SDS,AOS,cationic-CTAB,and neutral-TX-100)and examined using UV-visible absorption and fluorescence spectroscopic approach.Detailed analysis of the acquired absorption and fluorescence spectra of the crude oil-surfactant-brine solutions distinctly demonstrate the entrapment of different crude oil components within the micelles formed by surfactants of different charges while the synchronous fluorescence spectra show the entrapment of specific size FARs within the specific micellar microenvironment.The results exhibit that the anionic surfactant entraps the smaller size(2-4)FARs whereas cationic and neutral surfactants entrap small as well as medium size(2-6)FARs within the formed micelles in the microemulsions.The present spectroscopic study signifies the importance of molecular-level interaction mechanisms for customized designing of surfactant solutions for maximizing crude oil recovery from petroleum reservoirs.
查看更多>>摘要：Dissolution of liquefied carbon dioxide in a turbulent tubing flow for geologic sequestration in aquifers is simulated.The problem is solved by a two-fluid approach in a three dimensional formulation.For accurate calculation of the droplet dissolution rate,an evolution of droplet size distribution along a tubing is modelled by the population balance equation accounting for droplet breakup,coalescence and interphase mass transfer.The dissolution rate in a horizontal tubing is rather slow due to gravity-induced droplet stratification.The dissolution process in a horizontal tubing is compared with that in a coiled tubing wound on a horizontal reel.In a coiled tubing flow,droplet stratification significantly decreases due to the gravity force causing periodical motion of droplets across the tubing.At relatively high flow velocities,CO2 droplets are well-dispersed even across a horizontal tubing.Droplet dissolution is rather fast in this case,and a notable difference in the dissolution rates in straight and coiled tubing is not observed.An effect of the flow rate on the dissolution process at different tubing diameters is illustrated.Thus,numerical studies show that a coiled tubing can be efficiently used for intensification of liquefied carbon dioxide dissolution for relatively low and moderate flow rates.
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