The ability of a novel nonionic CO2 -soluble surfactant to propagate foam in porous media was compared with that of a conventional anionic surfactant（aqueous soluble only）through core floods with Berea sandstone cor...The ability of a novel nonionic CO2 -soluble surfactant to propagate foam in porous media was compared with that of a conventional anionic surfactant（aqueous soluble only）through core floods with Berea sandstone cores.Both simultaneous and alternating injections have been tested.The novel foam outperforms the conventional one with respect to faster foam propagation and higher desaturation rate.Furthermore,the novel injection strategy,CO2 continuous injection with dissolved CO2 -soluble surfactant,has been tested in the laboratory.Strong foam presented without delay.It is the first time the measured surfactant properties have been used to model foam transport on a field scale to extend our findings with the presence of gravity segregation.Different injection strategies have been tested under both constant rate and pressure constraints.It was showed that novel foam outperforms the conventional one in every scenario with much higher sweep efficiency and injectivity as well as more even pressure redistribution.Also,for this novel foam,it is not necessary that constant pressure injection is better,which has been concluded in previous literature for conventional foam.Furthermore,the novel injection strategy,CO2 continuous injection with dissolved CO2 -soluble surfactant,gave the best performance,which could lower the injection and water treatment cost.展开更多
Fluid and effective fracture identification in reservoirs is a crucial part of reservoir prediction.The frequency-dependent AVO inversion algorithms have proven to be effective for identifying fluid through its disper...Fluid and effective fracture identification in reservoirs is a crucial part of reservoir prediction.The frequency-dependent AVO inversion algorithms have proven to be effective for identifying fluid through its dispersion property.However,the conventional frequency-dependent AVO inversion algorithms based on Smith&Gidlow and Aki&Richards approximations do not consider the acquisition azimuth of seismic data and neglect the effect of seismic anisotropic dispersion in the actual medium.The aligned fractures in the subsurface medium induce anisotropy.The seismic anisotropy should be considered while accounting for the seismic dispersion properties through fluid-saturated fractured reservoirs.Anisotropy in such reservoirs is frequency-related due to wave-induced fluid-flow(WIFF)between interconnected fractures and pores.It can be used to identify fluid and effective fractures(fluid-saturated)by using azimuthal seismic data via anisotropic dispersion properties.In this paper,based on Rüger’s equation,we derived an analytical expression in the frequency domain for the frequencydependent AVOAz inversion in terms of fracture orientation,dispersion gradient of isotropic background rock,anisotropic dispersion gradient,and the dispersion at a normal incident angle.The frequency-dependent AVOAz equation utilizes azimuthal seismic data and considers the effect of both isotropic and anisotropic dispersion.Reassigned Gabor Transform(RGT)is used to achieve highresolution frequency division data.We then propose the frequency-dependent AVOAz inversion method to identify fluid and characterize effective fractures in fractured porous reservoirs.Through application to high-qualified seismic data of dolomite and carbonate reservoirs,the results show that the method is useful for identifying fluid and effective fractures in fluid-saturated fractured rocks.展开更多
The size of pores and throats is at the nano- meter scale in tight oil and shale gas zones, and the resistivity of these reservoirs is very high, so the reservoirs show more dielectric properties than conductivity pro...The size of pores and throats is at the nano- meter scale in tight oil and shale gas zones, and the resistivity of these reservoirs is very high, so the reservoirs show more dielectric properties than conductivity proper- ties. The conductive and dielectric characteristics of a parallel plate capacitor full of fresh water, NaCl solutions, and solid dielectrics, for example, sands are investigated in this paper, and the capacitance data of the non-gas capacitor are measured at different salinities and frequencies by a spectrum analyzer. The experimental results illustrate that the capacitance of this kind of capacitor is directly pro- portional to the salinity of the solutions and inversely proportional to the measuring frequency, the same as a vacuum parallel plate capacitor. The remarkable phenom- enon, however, is that the capacitance is inversely pro- portional to the square of the distance between two plates. The specific characteristic of this capacitor is different from the conventional parallel plate capacitor. In order to explain this phenomenon, the paper proposed a new concept, named ＂single micro ion capacitor＂, and established a novel model to describe the characteristics of this particular capacitor. Based on this new model, the theoretical capacitance value of the single micro ion capacitor is calculated, and its polarization and relaxation mechanisms are analyzed.展开更多
Based on the investigation of tight oil exploration and development in North America, the successful cases of tight oil exploration and development in North America are summarized. The geological differences between c...Based on the investigation of tight oil exploration and development in North America, the successful cases of tight oil exploration and development in North America are summarized. The geological differences between continental tight oil in China and marine tight oil in North America is analyzed to explore the technical strategies for the industrial development of continental tight oil in China. The experiences of large-scale exploration and profitable development of tight oil in North America can be taken as references from the following 6 perspectives, namely exploring new profitable strata in mature exploration areas, strengthening the economic evaluation of sweet spots and focusing on the investment for high-profitability sweet spots, optimizing the producing of tight oil reserves by means of repetitive fracturing and 3 D fracturing, optimizing drilling and completion technologies to reduce the cost, adopting commodity hedging to ensure the sustainable profit, and strengthening other resources exploration to improve the profit of whole project. In light of the high abundance of tight oil in China, we can draw on successful experience from North America, four suggestions are proposed in sight of the geological setting of China's lacustrine tight oil:(1) Evaluating the potential of tight oil resources and optimizing the strategic area for tight oil exploration;(2) selecting "sweet spot zone" and "sweet spot interval" accurately for precise and high efficient development;(3) adopting advanced tight oil fracturing technology to realize economic development;(4) innovating management system to promote the large-scale profitable development of tight oil.展开更多
To improve the design and management of an integrated production system(IPS),a set of mathematical models and workflows are developed for evaluating the capacity of an IPS at steady-state conditions.Combining the cons...To improve the design and management of an integrated production system(IPS),a set of mathematical models and workflows are developed for evaluating the capacity of an IPS at steady-state conditions.Combining the conservation laws with applicable multiphase fluid and choke models,these mathematical models are solved to characterize the hydraulics of an integrated system of reservoir,wells,chokes,flowlines,and separator at steady state.The controllable variables such as well count,choke size and separator pressure are adjusted to optimize the performance of the IPs at a specific time.It is found that increasing the well count can increase the bulk flow rate of the production network,but too many wells may increase the manifold pressure,leading to decline of single-well production.Increasing the choke size can improve the capacity of the IPs.The production of the IPs is negatively correlated with the separator pressure.With increasing separator pressure and decreasing choke size,the increment of total fluid production(the capacity of IPS)induced by increasing well count decreases.Validation tests with field examples show a maximum absolute deviation is 1.5%,demonstrating the robustness and validity of the proposed mathematical models and workflows.展开更多
High-resolution 3D seismic data analysis was integrated with a calibrated well and biostratigraphy data to present the first overview of a buried Pleistocene canyon system on the upper slope of the eastern Niger Delta...High-resolution 3D seismic data analysis was integrated with a calibrated well and biostratigraphy data to present the first overview of a buried Pleistocene canyon system on the upper slope of the eastern Niger Delta,the Galabor Canyon.Attribute maps of specific horizons allow documenting the changing morphologies and infill lithologies of two main branches of the canyon through two stages of activity separated by a reference horizon dated at 0.99 Ma based on well calibration.At the upper slope,growth faults dissect the canyon heads,the catchment of which encroaches a network of valleys incised on the outer shelf.The canyon fill is composed of muddy channels and mass-transport deposits,largely derived from the collapse of canyon walls and sand-rich bodies forming a tract sourced by shelf-edge deltas at the outlet of the incised valleys.High-density turbiditic processes likely control the distribution of sand bodies along the canyon,ranging from tributary fans on the upper slope to 6 km-wide meander belts on the middle slope.The sandy deposits accumulate in minibasins formed along the canyon path,downstream of the subsiding hanging wall of the growth faults and upstream of shale ridges that damp the flow in the canyon.These results show that canyons can be major targets for sand reservoir exploration on the upper slope of large muddy deltas.展开更多
The toxicity of benzene is well known, and its leukemia effect has established. It is a natural constituent of crude oil and the diseases related to its exposure are recognized as occupational diseases. <strong>...The toxicity of benzene is well known, and its leukemia effect has established. It is a natural constituent of crude oil and the diseases related to its exposure are recognized as occupational diseases. <strong>Objective:</strong> To assess occupational exposure of benzene to workers in an oil and gas production company. <strong>Materials and Methods:</strong> Firstly, it was a descriptive, cross-sectional study which consisted of benzene atmospheric quantification in a sample individual measurement of a homogeneous exposure group of workers. Secondly, urinary assays of S-phenylmercapturic acid have been performed at the end of the shift in the selected workers.<strong> Results:</strong> The study has included 79 (47.88%) workers, 17 atmospheric samples were usable and 79 urinary assays at the end of the shift were performed. The average benzene concentration for all sites was 10 times lower than the regulatory average exposure value (1 ppm = 3.2 mg/m<sup>3</sup>): average: 0.122 pp, median: 0.053 ppm and range: 0.019 - 1.448 ppm. All 79 urinary assays of S-phenylmercapturic acid with a biological exposure index of less than 25 μg/g creatinine: mean: 0.70 μg/g creatinine, median: 0.52 μg/g creatinine and extends: 0.23 to 6.7 μg/g creatinine. <strong>Conclusion:</strong> Exposure was below to the limit value for benzene in both atmospheric metrology and biometrology. Therefore it is an occupational group with low exposure to benzene. Thus, the medical supervision will be adapted according to the potentially exposing tasks.展开更多
Introduction: Occupational stress is a significant health concern in the work-place, constituting a prevalent psychosocial risk. Due to its specific nature, the oil industry is perceived as a high psychosocial risk zo...Introduction: Occupational stress is a significant health concern in the work-place, constituting a prevalent psychosocial risk. Due to its specific nature, the oil industry is perceived as a high psychosocial risk zone. This study aimed to correlate the perceived stress level with the identified psychosocial risk factors (PSRFs) among employees of an oil company in Congo-Brazzaville. Materials and Methods: This was an analytical cross-sectional study conducted between July and September 2021 among employees of an oil company. They were recruited during their routine medical check-ups. Data were collected using the Perceived Stress Scale (PSS10) and the Copenhagen Psychosocial Questionnaire (COPSOQ), respectively to assess stress and identify PSRFs. Results: Out of the sample, 203 workers were included. The majorities were males (81.3%), and the average age of participants was 39.5 ± 9.62 years. The frequency of perceived stress was 39.4%, and 40% of the workers were exposed to at least 3 PSRFs. A positive correlation was observed between perceived stress and workload (r = 0.37, p Conclusion: The study revealed that employees of this company exhibited a high level of stress. The detrimental impact of certain PSRFs was highlighted. A multidisciplinary intervention appears imperative to address these inherent risks in their professional environment.展开更多
The double-network prepared with an in-situ monomer gel and a fast-crosslinked Cr(III) gel is introduced to develop a thixotropic and high-strength gel (THSG), which is found to have many advantages over the tradition...The double-network prepared with an in-situ monomer gel and a fast-crosslinked Cr(III) gel is introduced to develop a thixotropic and high-strength gel (THSG), which is found to have many advantages over the traditional gels. The THSG gel demonstrates remarkable thermal stability, and no syneresis is observed after 12 months with high salinity brine (95,500 mg/L). Moreover, the SEM and XRD results indicate that the gel is intercalated into the lamellar structures of Na-MMT, where the gel can form a uniform and compact structure. In addition, the THSG gel has an excellent swelling behavior, even in the high salinity brine. In the slim tube experiments, the THSG gel exhibits high rupture pressure and improves blocking capacity after being ruptured. The core flooding results show that a layer of gel filter cake is formed on the face of the fracture, which may be promoted by a high matrix permeability, a small aperture fracture, and a high injection rate. After the gel treatment, the fracture can be completely blocked by the THSG gel. It is found that a high incremental oil recovery (65.3%) can be achieved when the fracture was completely blocked, compared to 40.2% if the gel is ruptured. Although the swelling of ruptured gel can improve oil recovery, part of the injected brine may be channeled through the gel-filled fractures, resulting in a decrease in the sweep efficiency. Therefore, the improved blocking ability by gel swelling (e.g., in fresh water) may be less efficient to contribute to an enhancement of oil recovery. It is also found that the pressure gradient and residual resistance factor to water (Frrw) are higher if the matrix is less permeable, indicating that the fractured reservoir with lower matrix permeability may require a higher gel strength for treatment. The findings of this study may provide novel insights on designing robust double network gels for water shutoff in fractured reservoirs.展开更多
Pore volume compressibility is an essential parameter in reservoir studies,as it plays a major role in recovery mechanisms.Over the past decades,many attempts have been made to establish a link between the pore compre...Pore volume compressibility is an essential parameter in reservoir studies,as it plays a major role in recovery mechanisms.Over the past decades,many attempts have been made to establish a link between the pore compressibility and the porosity and other mechanical properties of the rock.Some scholars introduced analytical correlations between pore compressibility and rock mechanical properties,while others developed empirical formulas for estimating pore compressibility based on a porosity calculated by comparing nonlinear models to laboratory data.In this study,pore volume compressibility is measured on 55 carbonate samples and then applied to derive an empirical relationship between pore compressibility and porosity at each stress step,which is useful for predicting pore compressibility based on initial porosity.We take the net stress effect into account and derive an empirical correlation based on net effective stress and initial porosity to predict pore compressibility.In the end,we compare the measured pore compressibility with that predicted by the derived correlation and other non-leaner models,which indicates that the newly proposed non-linear equation outperforms those available in literature。展开更多
This work presents the design of a robust foam formulation that tolerates harsh reservoir conditions(high salinity,high divalent ion concentration,high temperature,light oil,and hydrocarbon injection gas)in a sandston...This work presents the design of a robust foam formulation that tolerates harsh reservoir conditions(high salinity,high divalent ion concentration,high temperature,light oil,and hydrocarbon injection gas)in a sandstone reservoir.For this,we selected anionic Alpha Olefin Sulfonate(AOS)surfactants and studied their synergistic effects in mixtures with zwitterionic betaines to enhance foam performance.The laboratory workflow used to define the best formulation followed a de-risking approach in three consecutive phases.First,(phase 1)the main surfactant(AOS)was selected among a series of commercial candidates in static conditions.Then,(phase 2)the betaine booster to be combined with the previously selected AOS was chosen and their ratio optimized in static conditions.Subsequently,(phase 3)the surfactant/booster ratio was optimized under dynamic conditions in a porous medium in the absence and the presence of oil.As a result of this study,a mixture of an AOS C14-C16 and cocamidopropyl hydroxysultaine(CAPHS)was selected as the one having the best performance.The designed formulation was proven to be robust in a wide range of conditions.It generated a strong and stable foam at reservoir conditions,overcoming variations in salinity and foam quality,and tolerated the presence of oil.展开更多
文摘The ability of a novel nonionic CO2 -soluble surfactant to propagate foam in porous media was compared with that of a conventional anionic surfactant（aqueous soluble only）through core floods with Berea sandstone cores.Both simultaneous and alternating injections have been tested.The novel foam outperforms the conventional one with respect to faster foam propagation and higher desaturation rate.Furthermore,the novel injection strategy,CO2 continuous injection with dissolved CO2 -soluble surfactant,has been tested in the laboratory.Strong foam presented without delay.It is the first time the measured surfactant properties have been used to model foam transport on a field scale to extend our findings with the presence of gravity segregation.Different injection strategies have been tested under both constant rate and pressure constraints.It was showed that novel foam outperforms the conventional one in every scenario with much higher sweep efficiency and injectivity as well as more even pressure redistribution.Also,for this novel foam,it is not necessary that constant pressure injection is better,which has been concluded in previous literature for conventional foam.Furthermore,the novel injection strategy,CO2 continuous injection with dissolved CO2 -soluble surfactant,gave the best performance,which could lower the injection and water treatment cost.
基金supported by the National Major Science and Technology Project of China(2016ZX05004003)the National Natural Science Foundation of China(41574103,41974120,U20B2015)Open Fund of State Key Laboratory of Coal Resources and Safe Mining(Grant No.SKLCRSM19KFA08)。
文摘Fluid and effective fracture identification in reservoirs is a crucial part of reservoir prediction.The frequency-dependent AVO inversion algorithms have proven to be effective for identifying fluid through its dispersion property.However,the conventional frequency-dependent AVO inversion algorithms based on Smith&Gidlow and Aki&Richards approximations do not consider the acquisition azimuth of seismic data and neglect the effect of seismic anisotropic dispersion in the actual medium.The aligned fractures in the subsurface medium induce anisotropy.The seismic anisotropy should be considered while accounting for the seismic dispersion properties through fluid-saturated fractured reservoirs.Anisotropy in such reservoirs is frequency-related due to wave-induced fluid-flow(WIFF)between interconnected fractures and pores.It can be used to identify fluid and effective fractures(fluid-saturated)by using azimuthal seismic data via anisotropic dispersion properties.In this paper,based on Rüger’s equation,we derived an analytical expression in the frequency domain for the frequencydependent AVOAz inversion in terms of fracture orientation,dispersion gradient of isotropic background rock,anisotropic dispersion gradient,and the dispersion at a normal incident angle.The frequency-dependent AVOAz equation utilizes azimuthal seismic data and considers the effect of both isotropic and anisotropic dispersion.Reassigned Gabor Transform(RGT)is used to achieve highresolution frequency division data.We then propose the frequency-dependent AVOAz inversion method to identify fluid and characterize effective fractures in fractured porous reservoirs.Through application to high-qualified seismic data of dolomite and carbonate reservoirs,the results show that the method is useful for identifying fluid and effective fractures in fluid-saturated fractured rocks.
基金Basic Science Program of Advanced Well Logging Technology of CNPC (2014A-2319)the Science and Technology Program (G12-3) of State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation of SWPU (Southwest Petroleum University)
文摘The size of pores and throats is at the nano- meter scale in tight oil and shale gas zones, and the resistivity of these reservoirs is very high, so the reservoirs show more dielectric properties than conductivity proper- ties. The conductive and dielectric characteristics of a parallel plate capacitor full of fresh water, NaCl solutions, and solid dielectrics, for example, sands are investigated in this paper, and the capacitance data of the non-gas capacitor are measured at different salinities and frequencies by a spectrum analyzer. The experimental results illustrate that the capacitance of this kind of capacitor is directly pro- portional to the salinity of the solutions and inversely proportional to the measuring frequency, the same as a vacuum parallel plate capacitor. The remarkable phenom- enon, however, is that the capacitance is inversely pro- portional to the square of the distance between two plates. The specific characteristic of this capacitor is different from the conventional parallel plate capacitor. In order to explain this phenomenon, the paper proposed a new concept, named ＂single micro ion capacitor＂, and established a novel model to describe the characteristics of this particular capacitor. Based on this new model, the theoretical capacitance value of the single micro ion capacitor is calculated, and its polarization and relaxation mechanisms are analyzed.
基金Supported by the China National Science and Technology Major Project(2016ZX05046,2017ZX05001)the National Key Basic Research and Development Program(973 Program),China(2014CB239000)
文摘Based on the investigation of tight oil exploration and development in North America, the successful cases of tight oil exploration and development in North America are summarized. The geological differences between continental tight oil in China and marine tight oil in North America is analyzed to explore the technical strategies for the industrial development of continental tight oil in China. The experiences of large-scale exploration and profitable development of tight oil in North America can be taken as references from the following 6 perspectives, namely exploring new profitable strata in mature exploration areas, strengthening the economic evaluation of sweet spots and focusing on the investment for high-profitability sweet spots, optimizing the producing of tight oil reserves by means of repetitive fracturing and 3 D fracturing, optimizing drilling and completion technologies to reduce the cost, adopting commodity hedging to ensure the sustainable profit, and strengthening other resources exploration to improve the profit of whole project. In light of the high abundance of tight oil in China, we can draw on successful experience from North America, four suggestions are proposed in sight of the geological setting of China's lacustrine tight oil:(1) Evaluating the potential of tight oil resources and optimizing the strategic area for tight oil exploration;(2) selecting "sweet spot zone" and "sweet spot interval" accurately for precise and high efficient development;(3) adopting advanced tight oil fracturing technology to realize economic development;(4) innovating management system to promote the large-scale profitable development of tight oil.
文摘To improve the design and management of an integrated production system(IPS),a set of mathematical models and workflows are developed for evaluating the capacity of an IPS at steady-state conditions.Combining the conservation laws with applicable multiphase fluid and choke models,these mathematical models are solved to characterize the hydraulics of an integrated system of reservoir,wells,chokes,flowlines,and separator at steady state.The controllable variables such as well count,choke size and separator pressure are adjusted to optimize the performance of the IPs at a specific time.It is found that increasing the well count can increase the bulk flow rate of the production network,but too many wells may increase the manifold pressure,leading to decline of single-well production.Increasing the choke size can improve the capacity of the IPs.The production of the IPs is negatively correlated with the separator pressure.With increasing separator pressure and decreasing choke size,the increment of total fluid production(the capacity of IPS)induced by increasing well count decreases.Validation tests with field examples show a maximum absolute deviation is 1.5%,demonstrating the robustness and validity of the proposed mathematical models and workflows.
基金supported by the Petroleum Technology Develop-ment Fund,Nigeria,TotalEnergies Exploration and Production department,France,and the Society of Exploration Geophysicists。
文摘High-resolution 3D seismic data analysis was integrated with a calibrated well and biostratigraphy data to present the first overview of a buried Pleistocene canyon system on the upper slope of the eastern Niger Delta,the Galabor Canyon.Attribute maps of specific horizons allow documenting the changing morphologies and infill lithologies of two main branches of the canyon through two stages of activity separated by a reference horizon dated at 0.99 Ma based on well calibration.At the upper slope,growth faults dissect the canyon heads,the catchment of which encroaches a network of valleys incised on the outer shelf.The canyon fill is composed of muddy channels and mass-transport deposits,largely derived from the collapse of canyon walls and sand-rich bodies forming a tract sourced by shelf-edge deltas at the outlet of the incised valleys.High-density turbiditic processes likely control the distribution of sand bodies along the canyon,ranging from tributary fans on the upper slope to 6 km-wide meander belts on the middle slope.The sandy deposits accumulate in minibasins formed along the canyon path,downstream of the subsiding hanging wall of the growth faults and upstream of shale ridges that damp the flow in the canyon.These results show that canyons can be major targets for sand reservoir exploration on the upper slope of large muddy deltas.
文摘The toxicity of benzene is well known, and its leukemia effect has established. It is a natural constituent of crude oil and the diseases related to its exposure are recognized as occupational diseases. <strong>Objective:</strong> To assess occupational exposure of benzene to workers in an oil and gas production company. <strong>Materials and Methods:</strong> Firstly, it was a descriptive, cross-sectional study which consisted of benzene atmospheric quantification in a sample individual measurement of a homogeneous exposure group of workers. Secondly, urinary assays of S-phenylmercapturic acid have been performed at the end of the shift in the selected workers.<strong> Results:</strong> The study has included 79 (47.88%) workers, 17 atmospheric samples were usable and 79 urinary assays at the end of the shift were performed. The average benzene concentration for all sites was 10 times lower than the regulatory average exposure value (1 ppm = 3.2 mg/m<sup>3</sup>): average: 0.122 pp, median: 0.053 ppm and range: 0.019 - 1.448 ppm. All 79 urinary assays of S-phenylmercapturic acid with a biological exposure index of less than 25 μg/g creatinine: mean: 0.70 μg/g creatinine, median: 0.52 μg/g creatinine and extends: 0.23 to 6.7 μg/g creatinine. <strong>Conclusion:</strong> Exposure was below to the limit value for benzene in both atmospheric metrology and biometrology. Therefore it is an occupational group with low exposure to benzene. Thus, the medical supervision will be adapted according to the potentially exposing tasks.
文摘Introduction: Occupational stress is a significant health concern in the work-place, constituting a prevalent psychosocial risk. Due to its specific nature, the oil industry is perceived as a high psychosocial risk zone. This study aimed to correlate the perceived stress level with the identified psychosocial risk factors (PSRFs) among employees of an oil company in Congo-Brazzaville. Materials and Methods: This was an analytical cross-sectional study conducted between July and September 2021 among employees of an oil company. They were recruited during their routine medical check-ups. Data were collected using the Perceived Stress Scale (PSS10) and the Copenhagen Psychosocial Questionnaire (COPSOQ), respectively to assess stress and identify PSRFs. Results: Out of the sample, 203 workers were included. The majorities were males (81.3%), and the average age of participants was 39.5 ± 9.62 years. The frequency of perceived stress was 39.4%, and 40% of the workers were exposed to at least 3 PSRFs. A positive correlation was observed between perceived stress and workload (r = 0.37, p Conclusion: The study revealed that employees of this company exhibited a high level of stress. The detrimental impact of certain PSRFs was highlighted. A multidisciplinary intervention appears imperative to address these inherent risks in their professional environment.
基金financial support from the Major Scientific and Technological Projects of CNPC under Grant(ZD2019-183-007)is gratefully acknowledge.
文摘The double-network prepared with an in-situ monomer gel and a fast-crosslinked Cr(III) gel is introduced to develop a thixotropic and high-strength gel (THSG), which is found to have many advantages over the traditional gels. The THSG gel demonstrates remarkable thermal stability, and no syneresis is observed after 12 months with high salinity brine (95,500 mg/L). Moreover, the SEM and XRD results indicate that the gel is intercalated into the lamellar structures of Na-MMT, where the gel can form a uniform and compact structure. In addition, the THSG gel has an excellent swelling behavior, even in the high salinity brine. In the slim tube experiments, the THSG gel exhibits high rupture pressure and improves blocking capacity after being ruptured. The core flooding results show that a layer of gel filter cake is formed on the face of the fracture, which may be promoted by a high matrix permeability, a small aperture fracture, and a high injection rate. After the gel treatment, the fracture can be completely blocked by the THSG gel. It is found that a high incremental oil recovery (65.3%) can be achieved when the fracture was completely blocked, compared to 40.2% if the gel is ruptured. Although the swelling of ruptured gel can improve oil recovery, part of the injected brine may be channeled through the gel-filled fractures, resulting in a decrease in the sweep efficiency. Therefore, the improved blocking ability by gel swelling (e.g., in fresh water) may be less efficient to contribute to an enhancement of oil recovery. It is also found that the pressure gradient and residual resistance factor to water (Frrw) are higher if the matrix is less permeable, indicating that the fractured reservoir with lower matrix permeability may require a higher gel strength for treatment. The findings of this study may provide novel insights on designing robust double network gels for water shutoff in fractured reservoirs.
文摘Pore volume compressibility is an essential parameter in reservoir studies,as it plays a major role in recovery mechanisms.Over the past decades,many attempts have been made to establish a link between the pore compressibility and the porosity and other mechanical properties of the rock.Some scholars introduced analytical correlations between pore compressibility and rock mechanical properties,while others developed empirical formulas for estimating pore compressibility based on a porosity calculated by comparing nonlinear models to laboratory data.In this study,pore volume compressibility is measured on 55 carbonate samples and then applied to derive an empirical relationship between pore compressibility and porosity at each stress step,which is useful for predicting pore compressibility based on initial porosity.We take the net stress effect into account and derive an empirical correlation based on net effective stress and initial porosity to predict pore compressibility.In the end,we compare the measured pore compressibility with that predicted by the derived correlation and other non-leaner models,which indicates that the newly proposed non-linear equation outperforms those available in literature。
基金funded by the Centro para el Desarrollo Tecnologico Industrial(CDTI)of the Spanish Ministry of Science and Innovation(IDI-20170503)the Fundacion Cepsa with the Escuela Tecnica Superior de Ingenieros de Minas y Energia of the Universidad Politecnica de Madrid(UPM)。
文摘This work presents the design of a robust foam formulation that tolerates harsh reservoir conditions(high salinity,high divalent ion concentration,high temperature,light oil,and hydrocarbon injection gas)in a sandstone reservoir.For this,we selected anionic Alpha Olefin Sulfonate(AOS)surfactants and studied their synergistic effects in mixtures with zwitterionic betaines to enhance foam performance.The laboratory workflow used to define the best formulation followed a de-risking approach in three consecutive phases.First,(phase 1)the main surfactant(AOS)was selected among a series of commercial candidates in static conditions.Then,(phase 2)the betaine booster to be combined with the previously selected AOS was chosen and their ratio optimized in static conditions.Subsequently,(phase 3)the surfactant/booster ratio was optimized under dynamic conditions in a porous medium in the absence and the presence of oil.As a result of this study,a mixture of an AOS C14-C16 and cocamidopropyl hydroxysultaine(CAPHS)was selected as the one having the best performance.The designed formulation was proven to be robust in a wide range of conditions.It generated a strong and stable foam at reservoir conditions,overcoming variations in salinity and foam quality,and tolerated the presence of oil.
