Due to the poor physical properties of tight reservoirs,CO_(2) huff-n-puff(HNP)is considered a potential enhanced oil recovery(EOR)method after primary depletion.Optimization plays a critical role in the effective imp...Due to the poor physical properties of tight reservoirs,CO_(2) huff-n-puff(HNP)is considered a potential enhanced oil recovery(EOR)method after primary depletion.Optimization plays a critical role in the effective implementation of CO_(2) huff-n-puff.But the optimization requires a good understanding of the EOR mechanisms.In this work,the spatial distribution of oil saturation under different experimental conditions was analyzed by the NMR method to further discuss the HNP mechanisms.According to the variation of 1D frequency signal amplitude,we divided the core into the hardly movable area and movable area,the region with the obvious signal decline was defined as the movable area,and the hardly movable area was the region with limited signal decline.Based on that the recovery characteristics of different scenarios were evaluated.Firstly,the necessity of the soaking stage was studied,where three scenarios with different soaking times were carried out.Secondly,the injection pressure was adjusted to investigate the effect of the pressure gradient.The T_(2) spectra show that soaking has significantly improved the production of crude oil in small pores,and higher oil recovery in a single cycle is observed,but it is lower when the elapsed time(total operation time)is the same.31.03% of oil can be recovered after 3 cycles HNP,which increases to 33.8% and 37.06% for the 4 cycles and 6 cycles cases.As the pressure gradient increases,more oil is removed out of the matrix,and the oil in the deep part of the reservoir can be effectively recovered.During the CO_(2) huff-n-puff process,the oil distributions are similar to the solution gas drive,the residual oil is distributed at the close end of the core and the range that the oil can be efficiently recovered is limited.展开更多
The intricate distribution of oil and water in tight rocks makes pinpointing oil layers challenging.While conventional identification methods offer potential solutions,their limited accuracy precludes them from being ...The intricate distribution of oil and water in tight rocks makes pinpointing oil layers challenging.While conventional identification methods offer potential solutions,their limited accuracy precludes them from being effective in their applications to unconventional reservoirs.This study employed nuclear magnetic resonance(NMR)spectrum decomposition to dissect the NMR T_(2)spectrum into multiple subspectra.Furthermore,it employed laboratory NMR experiments to ascertain the fluid properties of these sub-spectra,aiming to enhance identification accuracy.The findings indicate that fluids of distinct properties overlap in the T_(2)spectra,with bound water,movable water,bound oil,and movable oil appearing sequentially from the low-value zone to the high-value zone.Consequently,an oil layer classification scheme was proposed,which considers the physical properties of reservoirs,oil-bearing capacity,and the characteristics of both mobility and the oil-water two-phase flow.When applied to tight oil layer identification,the scheme's outcomes align closely with actual test results.A horizontal well,deployed based on these findings,has produced high-yield industrial oil flow,underscoring the precision and dependability of this new approach.展开更多
建立了核磁共振氟谱法测定氰化物的氟化衍生化合物1-氰基-2,2,2-三氟-1-苯乙基乙酸酯(CTPA)含量的方法。以乙酸3-氟苄酯为内标,采用5mm Auto XBB探头,探头温度298.2K,考察了不同浓度化合物的定量条件;通过比较化合物样品定量峰与内标物...建立了核磁共振氟谱法测定氰化物的氟化衍生化合物1-氰基-2,2,2-三氟-1-苯乙基乙酸酯(CTPA)含量的方法。以乙酸3-氟苄酯为内标,采用5mm Auto XBB探头,探头温度298.2K,考察了不同浓度化合物的定量条件;通过比较化合物样品定量峰与内标物质响应峰面积,计算化合物的含量。结果该化合物的19 F-NMR检测方法在0.5~50μg/mL具有良好的线性(r2=0.9966),该方法的定量限0.5μg/mL,检出限0.2μg/mL;同时考察了该化合物在不同浓度下的测量准确度。展开更多
The resistivity experimental measurements of core samples drilled from low permeability reservoirs of Ordos Basin, Northwest China, illustrate that the cementation factors are not agminate, but vary from 1.335 to 1.74...The resistivity experimental measurements of core samples drilled from low permeability reservoirs of Ordos Basin, Northwest China, illustrate that the cementation factors are not agminate, but vary from 1.335 to 1.749. This leads to a challenge for the estimation of water and hydrocarbon sa- turation. Based on the analysis of Purcell equation and assumption that rock resistivity is determined by the parallel connection of numerous capillary resistances, a theoretical expression of cementation factor in terms of porosity and permeability is established. Then, cementation factor can be calculated if the parameters of porosity and permeability are determined. In the field application, porosity can be easily obtained by conventional logs. However, it is a tough challenge to estimate permeability due to the strong heterogeneity of low permeability reservoirs. Thus, the Schlumberger Doll Research （SDR） model derived from NMR logs has been proposed to estimate permeability. Based on the analysis of the theoretical expressions of cementation factor and SDR model, a novel cementation factor prediction model, which is relevant to porosity and logarithmic mean of NMR T2 spectrum （T21m）, is derived. The advantage of this model is that all the input information can be acquired from NMR logs accurately. In order to confirm the credibility of the novel model, the resistivity and corresponding laboratory NMR measurements of 27 core samples are conducted. The credibility of the model is confirmed by compar- ing the predicted cementation factors with the core analyzed results. The absolute errors for all core samples are lower than 0.071. Once this model is extended to field application, the accuracy of water and hydrocarbon saturation estimation will be significantly improved.展开更多
为解决T_(2)谱成像精度低,影响检测结果的准确性的问题,对基于贝叶斯的核磁共振T_(2)谱成像方法进行了研究。首先给出了NMR(Nuclear Magnetic Resonance)信号的基本特征,并基于贝叶斯原理,推导了NMR信号的似然函数,构建了T_(2)谱成像框...为解决T_(2)谱成像精度低,影响检测结果的准确性的问题,对基于贝叶斯的核磁共振T_(2)谱成像方法进行了研究。首先给出了NMR(Nuclear Magnetic Resonance)信号的基本特征,并基于贝叶斯原理,推导了NMR信号的似然函数,构建了T_(2)谱成像框架。其次,采用改进的马尔科夫链蒙特卡洛策略,得到T_(2)谱及其不确定度。最后,通过随机构造服从多峰的混合高斯概率密度函数的T_(2)谱模型,验证了基于贝叶斯的核磁共振T_(2)谱成像方法的有效性。该方法可应用于通信原理综合实验内容,也可用于创新性训练实验。展开更多
基金The work is supported by the Strategic Cooperation Technology Projects of CNPC and CUPB(ZLZX2020)by the Fundamental Research Funds for the Central Universities of China.
文摘Due to the poor physical properties of tight reservoirs,CO_(2) huff-n-puff(HNP)is considered a potential enhanced oil recovery(EOR)method after primary depletion.Optimization plays a critical role in the effective implementation of CO_(2) huff-n-puff.But the optimization requires a good understanding of the EOR mechanisms.In this work,the spatial distribution of oil saturation under different experimental conditions was analyzed by the NMR method to further discuss the HNP mechanisms.According to the variation of 1D frequency signal amplitude,we divided the core into the hardly movable area and movable area,the region with the obvious signal decline was defined as the movable area,and the hardly movable area was the region with limited signal decline.Based on that the recovery characteristics of different scenarios were evaluated.Firstly,the necessity of the soaking stage was studied,where three scenarios with different soaking times were carried out.Secondly,the injection pressure was adjusted to investigate the effect of the pressure gradient.The T_(2) spectra show that soaking has significantly improved the production of crude oil in small pores,and higher oil recovery in a single cycle is observed,but it is lower when the elapsed time(total operation time)is the same.31.03% of oil can be recovered after 3 cycles HNP,which increases to 33.8% and 37.06% for the 4 cycles and 6 cycles cases.As the pressure gradient increases,more oil is removed out of the matrix,and the oil in the deep part of the reservoir can be effectively recovered.During the CO_(2) huff-n-puff process,the oil distributions are similar to the solution gas drive,the residual oil is distributed at the close end of the core and the range that the oil can be efficiently recovered is limited.
基金funded by a major special project of PetroChina Company Limited(No.2021DJ1003No.2023ZZ2).
文摘The intricate distribution of oil and water in tight rocks makes pinpointing oil layers challenging.While conventional identification methods offer potential solutions,their limited accuracy precludes them from being effective in their applications to unconventional reservoirs.This study employed nuclear magnetic resonance(NMR)spectrum decomposition to dissect the NMR T_(2)spectrum into multiple subspectra.Furthermore,it employed laboratory NMR experiments to ascertain the fluid properties of these sub-spectra,aiming to enhance identification accuracy.The findings indicate that fluids of distinct properties overlap in the T_(2)spectra,with bound water,movable water,bound oil,and movable oil appearing sequentially from the low-value zone to the high-value zone.Consequently,an oil layer classification scheme was proposed,which considers the physical properties of reservoirs,oil-bearing capacity,and the characteristics of both mobility and the oil-water two-phase flow.When applied to tight oil layer identification,the scheme's outcomes align closely with actual test results.A horizontal well,deployed based on these findings,has produced high-yield industrial oil flow,underscoring the precision and dependability of this new approach.
文摘建立了核磁共振氟谱法测定氰化物的氟化衍生化合物1-氰基-2,2,2-三氟-1-苯乙基乙酸酯(CTPA)含量的方法。以乙酸3-氟苄酯为内标,采用5mm Auto XBB探头,探头温度298.2K,考察了不同浓度化合物的定量条件;通过比较化合物样品定量峰与内标物质响应峰面积,计算化合物的含量。结果该化合物的19 F-NMR检测方法在0.5~50μg/mL具有良好的线性(r2=0.9966),该方法的定量限0.5μg/mL,检出限0.2μg/mL;同时考察了该化合物在不同浓度下的测量准确度。
基金supported by the Major National Oil&Gas Specific Project of China(No.2011ZX05044)
文摘The resistivity experimental measurements of core samples drilled from low permeability reservoirs of Ordos Basin, Northwest China, illustrate that the cementation factors are not agminate, but vary from 1.335 to 1.749. This leads to a challenge for the estimation of water and hydrocarbon sa- turation. Based on the analysis of Purcell equation and assumption that rock resistivity is determined by the parallel connection of numerous capillary resistances, a theoretical expression of cementation factor in terms of porosity and permeability is established. Then, cementation factor can be calculated if the parameters of porosity and permeability are determined. In the field application, porosity can be easily obtained by conventional logs. However, it is a tough challenge to estimate permeability due to the strong heterogeneity of low permeability reservoirs. Thus, the Schlumberger Doll Research （SDR） model derived from NMR logs has been proposed to estimate permeability. Based on the analysis of the theoretical expressions of cementation factor and SDR model, a novel cementation factor prediction model, which is relevant to porosity and logarithmic mean of NMR T2 spectrum （T21m）, is derived. The advantage of this model is that all the input information can be acquired from NMR logs accurately. In order to confirm the credibility of the novel model, the resistivity and corresponding laboratory NMR measurements of 27 core samples are conducted. The credibility of the model is confirmed by compar- ing the predicted cementation factors with the core analyzed results. The absolute errors for all core samples are lower than 0.071. Once this model is extended to field application, the accuracy of water and hydrocarbon saturation estimation will be significantly improved.
文摘为解决T_(2)谱成像精度低,影响检测结果的准确性的问题,对基于贝叶斯的核磁共振T_(2)谱成像方法进行了研究。首先给出了NMR(Nuclear Magnetic Resonance)信号的基本特征,并基于贝叶斯原理,推导了NMR信号的似然函数,构建了T_(2)谱成像框架。其次,采用改进的马尔科夫链蒙特卡洛策略,得到T_(2)谱及其不确定度。最后,通过随机构造服从多峰的混合高斯概率密度函数的T_(2)谱模型,验证了基于贝叶斯的核磁共振T_(2)谱成像方法的有效性。该方法可应用于通信原理综合实验内容,也可用于创新性训练实验。
