利用核磁共振技术确定页岩中游离甲烷气与吸附甲烷气含量
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摘要
在地表标准状态下,页岩储层中游离甲烷气与吸附甲烷气都表现为性质相同的天然气,但在地层孔隙介质条件下具有不同赋存状态和温压响应特征:游离气赋存在较大孔隙中,遵循自由气体状态方程,恒温下其游离气含量随压力变化而呈现线性变化规律;吸附气赋存在微孔隙中,遵循蓝格缪尔方程,恒温下吸附气含量随压力变化呈现非线性变化特征。基于这一原理,利用恒温不同压力下饱和甲烷页岩岩心核磁共振实验,观测核磁共振(NMR)T2谱随压力变化特征,借此分辨出页岩中游离气及吸附气位置,并进行定量评价。在页岩岩心NMR测井T2谱图上,游离气、吸附气分别形成了分离的T2谱峰,分别称为吸附气峰和游离气峰,借此识别出游离气和吸附气。吸附气T2时间较小,分布在0.1~1ms,主峰位置为0.2ms,表明吸附气分布在孔径小的微孔隙中;游离气分布在1~10ms,主峰位置3ms,表明游离气存在大孔隙中。游离气峰面积随压力呈现线性变化规律,符合自由气体状态方程描述的规律;吸附峰面积随压力呈现非线性变化规律,符合蓝格缪尔方程所描述的规律。游离气峰面积与标准状态下游离气体积存在定量转换关系,借此计算页岩中游离气、吸附气含量及其比例。这一技术具有易测量、成本低的优势,具有推广价值。
Adsorption and free methane in shale reservoirs under formation porous media condition would present different occurrence and responses to temperature and pressure.The free gas exists in macropores and follows the ideal gas law(IGL)and varies linearly with pressure changing.However,the adsorption gas exists in micropores,follows the Langmuir Equation(LE)and varies nonlinearly with pressure changing.Based on these principles,through nuclear magnetic resonance(NMR)experiment on the shale core saturated methane under different pressure with constant temperature,we observe the characteristics of NMR T2 spectra with different pressure,so as to identify the peaks of adsorption and free gas and evaluate their volume content.Conclusions are as follows:1)On the NMR T2 spectrum the adsorption and free gas have its own peaks,called as adsorption gas peak and free gas peak respectively.2)The T2 of adsorption gas is distributed in 0.1~1 ms,with a peak of 0.2 ms,indicating that the adsorptiongas exists in micropores.The free gas is 1~10 ms,peaked at 3 ms,indicating that it exists in macropores.3)The T2 spectrum area size of free gas also follows the IGL and varies linearly with pressure changing.The T2 spectrum area size of adsorption gas follows the LE and varies nonlinearly with pressure changing.4)The T2 area size of free gas can be transferred to the volume content of free gas in standard condition.The proposed technique in this paper is easily operated and the cost is low,so that it can be widely applied in shale gas prospecting industry.
Adsorption and free methane in shale reservoirs under formation porous media condition would present different occurrence and responses to temperature and pressure.The free gas exists in macropores and follows the ideal gas law(IGL)and varies linearly with pressure changing.However,the adsorption gas exists in micropores,follows the Langmuir Equation(LE)and varies nonlinearly with pressure changing.Based on these principles,through nuclear magnetic resonance(NMR)experiment on the shale core saturated methane under different pressure with constant temperature,we observe the characteristics of NMR T2 spectra with different pressure,so as to identify the peaks of adsorption and free gas and evaluate their volume content.Conclusions are as follows:1)On the NMR T2 spectrum the adsorption and free gas have its own peaks,called as adsorption gas peak and free gas peak respectively.2)The T2 of adsorption gas is distributed in 0.1~1 ms,with a peak of 0.2 ms,indicating that the adsorptiongas exists in micropores.The free gas is 1~10 ms,peaked at 3 ms,indicating that it exists in macropores.3)The T2 spectrum area size of free gas also follows the IGL and varies linearly with pressure changing.The T2 spectrum area size of adsorption gas follows the LE and varies nonlinearly with pressure changing.4)The T2 area size of free gas can be transferred to the volume content of free gas in standard condition.The proposed technique in this paper is easily operated and the cost is low,so that it can be widely applied in shale gas prospecting industry.
引文
[1]陈康,张金川,唐玄,等.湘鄂西地区下志留统龙马溪组页岩吸附能力主控因素[J].石油与天然气地质,2016,37(1):23-29.
[2]聂海宽,张金川,包书景,等.四川盆地及其周缘上奥陶统下志留统页岩气聚集条件[J].石油与天然气地质,2012,33(3):335-345.
[3]薛冰,张金川,唐玄,等.黔西北龙马溪组页岩微观孔隙结构及储气特征[J].石油学报,2015,36(2):138-149,173.
[4]王秀平,牟传龙,葛祥英,等.川南及邻区龙马溪组黑色岩系矿物组分特征及评价[J].石油学报,2015,36(2):150-162.
[5]王志刚.涪陵焦石坝地区页岩气水平井压裂改造实践与认识[J].石油与天然气地质,2014,35(3):425-430.
[6]孟志勇.四川盆地涪陵地区五峰组龙马溪组含气页岩段纵向非均质性及其发育主控因素[J].石油与天然气地质,2016,37(6):838-846.
[7]李军,路菁,李争,等.页岩气储层“四孔隙”模型建立及测井定量表征方法[J].石油与天然气地质,2014,35(2):266-271.
[8]刘天定,赵太平,李高仁,等.利用核磁共振评价致密砂岩储层孔径分布的改进方法[J].测井技术,2012,36(2):119-123.
[9]薛苗苗,章海宁,刘堂宴,等.定量评价储层孔隙结构新方法[J].测井技术,2014,38(1):59-64.
[10]陈国军.核磁共振测井在致密油孔隙结构及储层综合评价中的应用[J].测井技术,2015,39(1):57-61.
[11]SONDERGELD C H,AMBROSE R J,RAI C S,et al.Micro-structural Studies of Gas Shale[J].2010,SPE 131771.
[12]TINNI A,ODUSINA E,SULUCARNAIN I,et al.NMR Response of Brine,Oil,and Methane in Organic Rich Shales[J].2014,SPE-168971-MS.
[13]李军,金武军,王亮,等.页岩气岩心核磁共振T2与孔径尺寸定量关系[J].测井技术,2016,40(4):460-464.
[14]李军,金武军,王亮,等.利用核磁共振技术确定有机孔与无机孔孔径分布——以四川盆地涪陵地区志留系龙马溪组页岩气储层为例[J].石油与天然气地质,2016,37(1):129-134.
[15]周尚文,刘洪林,闫刚,等.中国南方海相页岩储层可动流体及T2截止值核磁共振研究[J].石油与天然气地质,2016,37(4):612-616.
[16]焦堃,姚素平,吴浩,等.页岩气储层孔隙系统表征方法研究进展[J].高校地质学报,2014,20(1):151-161.
[2]聂海宽,张金川,包书景,等.四川盆地及其周缘上奥陶统下志留统页岩气聚集条件[J].石油与天然气地质,2012,33(3):335-345.
[3]薛冰,张金川,唐玄,等.黔西北龙马溪组页岩微观孔隙结构及储气特征[J].石油学报,2015,36(2):138-149,173.
[4]王秀平,牟传龙,葛祥英,等.川南及邻区龙马溪组黑色岩系矿物组分特征及评价[J].石油学报,2015,36(2):150-162.
[5]王志刚.涪陵焦石坝地区页岩气水平井压裂改造实践与认识[J].石油与天然气地质,2014,35(3):425-430.
[6]孟志勇.四川盆地涪陵地区五峰组龙马溪组含气页岩段纵向非均质性及其发育主控因素[J].石油与天然气地质,2016,37(6):838-846.
[7]李军,路菁,李争,等.页岩气储层“四孔隙”模型建立及测井定量表征方法[J].石油与天然气地质,2014,35(2):266-271.
[8]刘天定,赵太平,李高仁,等.利用核磁共振评价致密砂岩储层孔径分布的改进方法[J].测井技术,2012,36(2):119-123.
[9]薛苗苗,章海宁,刘堂宴,等.定量评价储层孔隙结构新方法[J].测井技术,2014,38(1):59-64.
[10]陈国军.核磁共振测井在致密油孔隙结构及储层综合评价中的应用[J].测井技术,2015,39(1):57-61.
[11]SONDERGELD C H,AMBROSE R J,RAI C S,et al.Micro-structural Studies of Gas Shale[J].2010,SPE 131771.
[12]TINNI A,ODUSINA E,SULUCARNAIN I,et al.NMR Response of Brine,Oil,and Methane in Organic Rich Shales[J].2014,SPE-168971-MS.
[13]李军,金武军,王亮,等.页岩气岩心核磁共振T2与孔径尺寸定量关系[J].测井技术,2016,40(4):460-464.
[14]李军,金武军,王亮,等.利用核磁共振技术确定有机孔与无机孔孔径分布——以四川盆地涪陵地区志留系龙马溪组页岩气储层为例[J].石油与天然气地质,2016,37(1):129-134.
[15]周尚文,刘洪林,闫刚,等.中国南方海相页岩储层可动流体及T2截止值核磁共振研究[J].石油与天然气地质,2016,37(4):612-616.
[16]焦堃,姚素平,吴浩,等.页岩气储层孔隙系统表征方法研究进展[J].高校地质学报,2014,20(1):151-161.