Microbially induced carbonate precipitation(MICP)catalyzed by S.pasteurii has attracted considerable attention as a bio-cement that can both strengthen and seal geomaterials.We investigate the stress sensitivity of pe...Microbially induced carbonate precipitation(MICP)catalyzed by S.pasteurii has attracted considerable attention as a bio-cement that can both strengthen and seal geomaterials.We investigate the stress sensitivity of permeability reduction for the initially high-permeability Berea sandstone(initial permeability∼110 mD)under various durations of MICP-grouting treatment.The results indicate that after 2,4,6,8 and 10 cycles of MICP-grouting,the permeabilities decrease incrementally by 87.9%,60.9%,38.8%,17.3%,and then 5.4%compared to the pre-grouting condition.With increasing the duration of MICP-grouting,the sensitivity of permeability to changes in stress gradually decreases and becomes less hysteretic.This stress sensitivity of permeability is well represented by a power-law relationship with the coefficients representing three contrasting phases:an initial slow reduction,followed by a rapid drop,culminating in an asymptotic response.This variation behavior is closely related to the movement and dislocation of the quartz framework,which is controlled by the intergranular bio-cementation strength.Imaging by scanning electron microscopy(SEM)reveals the evolution of the stress sensitivity to permeability associated with the evolving microstructures after MICP-grouting.The initial precipitates of CaCO3 are dispersed on the surfaces of the quartz framework and occupy the pore space,which is initially limited in controlling and reducing the displacement between particles.As the precipitates continuously accumulate,the intergranular slot-shaped pore spaces are initially bonded by bio-CaCO3,with the bonding strength progressively enhanced with the expanding volume of bio-cementation.At this stage,the intergranular movement and dislocation caused by compaction are reduced,and the stress sensitivity of the permeability is significantly reduced.As these slot-shaped pore spaces are progressively filled by the bio-cement,the movement and dislocation caused by compaction become negligible and thus the stress sensitivity of permeability is minimized.展开更多
The effective stress of marine sediments frequently shifts owing to natural or anthropogenic factors,and a broad spectrum of processes fundamentally require accounting for sediment responses to such changes.Marine sed...The effective stress of marine sediments frequently shifts owing to natural or anthropogenic factors,and a broad spectrum of processes fundamentally require accounting for sediment responses to such changes.Marine sediments hosting natural gas hydrates have been regarded as a prospective energy reservoir,and depressurization-driven production efficiency hinges largely on the effective absolute permeability of hydrate-bearing strata.Yet,how this permeability evolves during depressurization remains unresolved,and whether pore-hosted hydrates impede or enhance it remains ambiguous.This study probes the permeability response of hydrate-bearing sands to cyclic loading through isotropic compression/swelling and water flow tests.Results reveal that methane hydrate presence curbs the void-ratio decline yet amplifies the effective-void-ratio reduction during isotropic loading.The effective absolute permeability of hydrate-bearing sands declines with rising hydrate saturation and increasing mean effective stress,and permeability stress sensitivity intensifies at higher hydrate saturations and lower mean effective stresses.The introduced model accurately predicts void-ratio changes during isotropic loading and unloading.Coefficients for strengthening,normal filling,and enhanced filling effects are introduced and quantified to disentangle the positive and negative influences of methane hydrate,with the negative filling effect exceeding the positive strengthening effect by one order of magnitude for quartz sands.展开更多
In recent years,a series of major natural gas exploration discoveries and breakthroughs have been achieved in deep and ultra-deep carbonate gas reservoirs in the Sichuan Basin,and all discovered gas reservoirs are cha...In recent years,a series of major natural gas exploration discoveries and breakthroughs have been achieved in deep and ultra-deep carbonate gas reservoirs in the Sichuan Basin,and all discovered gas reservoirs are characterized by great burial depth,complex pore structures and high formation temperature and pore pressure.In order to accurately predict the gas flow rate of single well in high temperature and high pressure(HTHP)gas reservoirs and clarify the gas flow characteristics under formation conditions,this paper establishes a productivity simulation experimental device and method based on the formation temperature and pore pressure of carbonate gas reservoirs in the Middle Permian Qixia Formation of northwestern Sichuan Basin and the Upper Sinian Dengying Formation of central Sichuan Basin.Then,the cores of above mentioned gas reservoirs are selected to carry out the productivity simulation experiment under HTHP.Finally,the gas flow characteristics are studied.And the following research results are obtained.First,the newly established productivity simulation experimental device and method suitable for the conditions of 160℃ formation temperature and 100 MPa pore pressure is used to predict the natural gas AOF(absolute open flow)of Well S-1 in the Qixia Formation gas reservoir of northwestern Sichuan Basin.And the prediction result is better accordant with the calculation result of theoretical model,with a relative error of only 2.12%.Second,based on the Klinkenberg permeability under surface conditions,the single-well gas flow rate calculated from the productivity simulation experiment is better accordant with the gas flow rate from field completion testing;while based on the Klinkenberg permeability under formation conditions,the single-well gas flow rate calculated from the productivity simulation experiment is better accordant with the AOF.Third,the change of formation temperature and pore pressure has a significant influence on rock permeability,and the permeability is more sensitive to stress than to temperature.Fourth,to carry out the reservoir stress sensitivity experiment and the productivity simulation experiment,it is required that core samples be recovered to the formation conditions for aging,or the experimental results may have characteristics of strong stress sensitivity and cannot be used for reservoir engineering evaluation directly.In conclusion,the production rate and AOF of HTHP gas wells can be predicted accurately by means of productivity simulation experiment,based on drilling core samples.In addition,the Klinkenberg permeability under formation conditions can be evaluated by using the relational expression between surface or Klinkenberg permeability under formation conditions and single-well gas flow rate,combined with gas well testing data.展开更多
基金funded by the National Natural Science Foundation of China(Grant No.51604051)the Natural Science Foundation of Chongqing(Grant No.CSTB2022NSCQ-MSX0372).
文摘Microbially induced carbonate precipitation(MICP)catalyzed by S.pasteurii has attracted considerable attention as a bio-cement that can both strengthen and seal geomaterials.We investigate the stress sensitivity of permeability reduction for the initially high-permeability Berea sandstone(initial permeability∼110 mD)under various durations of MICP-grouting treatment.The results indicate that after 2,4,6,8 and 10 cycles of MICP-grouting,the permeabilities decrease incrementally by 87.9%,60.9%,38.8%,17.3%,and then 5.4%compared to the pre-grouting condition.With increasing the duration of MICP-grouting,the sensitivity of permeability to changes in stress gradually decreases and becomes less hysteretic.This stress sensitivity of permeability is well represented by a power-law relationship with the coefficients representing three contrasting phases:an initial slow reduction,followed by a rapid drop,culminating in an asymptotic response.This variation behavior is closely related to the movement and dislocation of the quartz framework,which is controlled by the intergranular bio-cementation strength.Imaging by scanning electron microscopy(SEM)reveals the evolution of the stress sensitivity to permeability associated with the evolving microstructures after MICP-grouting.The initial precipitates of CaCO3 are dispersed on the surfaces of the quartz framework and occupy the pore space,which is initially limited in controlling and reducing the displacement between particles.As the precipitates continuously accumulate,the intergranular slot-shaped pore spaces are initially bonded by bio-CaCO3,with the bonding strength progressively enhanced with the expanding volume of bio-cementation.At this stage,the intergranular movement and dislocation caused by compaction are reduced,and the stress sensitivity of the permeability is significantly reduced.As these slot-shaped pore spaces are progressively filled by the bio-cement,the movement and dislocation caused by compaction become negligible and thus the stress sensitivity of permeability is minimized.
基金jointly supported by the National Natural Science Foundation of China(Grant 42025702)the Natural Science Foundation of Shandong Province(Grant ZR2022YQ54)the Taishan Scholars Program(No.tsqn202306297)。
文摘The effective stress of marine sediments frequently shifts owing to natural or anthropogenic factors,and a broad spectrum of processes fundamentally require accounting for sediment responses to such changes.Marine sediments hosting natural gas hydrates have been regarded as a prospective energy reservoir,and depressurization-driven production efficiency hinges largely on the effective absolute permeability of hydrate-bearing strata.Yet,how this permeability evolves during depressurization remains unresolved,and whether pore-hosted hydrates impede or enhance it remains ambiguous.This study probes the permeability response of hydrate-bearing sands to cyclic loading through isotropic compression/swelling and water flow tests.Results reveal that methane hydrate presence curbs the void-ratio decline yet amplifies the effective-void-ratio reduction during isotropic loading.The effective absolute permeability of hydrate-bearing sands declines with rising hydrate saturation and increasing mean effective stress,and permeability stress sensitivity intensifies at higher hydrate saturations and lower mean effective stresses.The introduced model accurately predicts void-ratio changes during isotropic loading and unloading.Coefficients for strengthening,normal filling,and enhanced filling effects are introduced and quantified to disentangle the positive and negative influences of methane hydrate,with the negative filling effect exceeding the positive strengthening effect by one order of magnitude for quartz sands.
基金Project supported by the Scientific Research and Technology Development Project of PetroChina Company Limited“New Experimental Technology Development of Key Laboratory of Carbonate Reservoir”(No.:2018D-5006-35).
文摘In recent years,a series of major natural gas exploration discoveries and breakthroughs have been achieved in deep and ultra-deep carbonate gas reservoirs in the Sichuan Basin,and all discovered gas reservoirs are characterized by great burial depth,complex pore structures and high formation temperature and pore pressure.In order to accurately predict the gas flow rate of single well in high temperature and high pressure(HTHP)gas reservoirs and clarify the gas flow characteristics under formation conditions,this paper establishes a productivity simulation experimental device and method based on the formation temperature and pore pressure of carbonate gas reservoirs in the Middle Permian Qixia Formation of northwestern Sichuan Basin and the Upper Sinian Dengying Formation of central Sichuan Basin.Then,the cores of above mentioned gas reservoirs are selected to carry out the productivity simulation experiment under HTHP.Finally,the gas flow characteristics are studied.And the following research results are obtained.First,the newly established productivity simulation experimental device and method suitable for the conditions of 160℃ formation temperature and 100 MPa pore pressure is used to predict the natural gas AOF(absolute open flow)of Well S-1 in the Qixia Formation gas reservoir of northwestern Sichuan Basin.And the prediction result is better accordant with the calculation result of theoretical model,with a relative error of only 2.12%.Second,based on the Klinkenberg permeability under surface conditions,the single-well gas flow rate calculated from the productivity simulation experiment is better accordant with the gas flow rate from field completion testing;while based on the Klinkenberg permeability under formation conditions,the single-well gas flow rate calculated from the productivity simulation experiment is better accordant with the AOF.Third,the change of formation temperature and pore pressure has a significant influence on rock permeability,and the permeability is more sensitive to stress than to temperature.Fourth,to carry out the reservoir stress sensitivity experiment and the productivity simulation experiment,it is required that core samples be recovered to the formation conditions for aging,or the experimental results may have characteristics of strong stress sensitivity and cannot be used for reservoir engineering evaluation directly.In conclusion,the production rate and AOF of HTHP gas wells can be predicted accurately by means of productivity simulation experiment,based on drilling core samples.In addition,the Klinkenberg permeability under formation conditions can be evaluated by using the relational expression between surface or Klinkenberg permeability under formation conditions and single-well gas flow rate,combined with gas well testing data.
