基于分形理论的致密砂岩储层微观孔隙结构表征——以冀中坳陷致密砂岩储层为例
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摘要
为了评价致密砂岩储层类型,为致密油气的勘探与开发提供理论依据,利用分形理论和高压压汞方法,结合储层物性资料,通过对11个致密砂岩样品的压汞实验,研究了冀中坳陷致密砂岩储层微观孔隙结构。结果表明:根据进汞曲线拐点,将致密砂岩储层孔隙系统按直径大小划分为裂隙(>10μm)、大孔(1~10 μm)、中孔(0.1~1.0 μm)和微孔(<0.1 μm)。依据分形理论,分别求取各尺度孔隙分形维数,验证了孔隙系统划分的正确性。根据不同尺度孔隙的分布频率,结合样品孔渗、排驱压力和退汞效率等参数将致密砂岩储层分为3类:Ⅰ类储层微孔分布频率高,但几乎无连通孔隙,具有较低的渗透率;Ⅱ类储层连通孔隙发育,但微孔较少;Ⅲ类储层不仅有大量微孔,同时有丰富的连通孔隙,渗透率也较高。通过分析得出,微孔分布频率越高,退汞效率越高,孔隙结构越简单,均质性越好;裂隙和大孔均决定了储层的渗流能力。因此,Ⅲ类致密砂岩储层为最优质的储层,可作为致密油气勘探与开采的首选目标。
To evaluate the type of tight sandstone reservoir and provide theoretical basis for the exploration and development of tight oil and gas,the fractal theory,mercury intrusion capillary pressure analyses,as well as reservoir physical properties,were used to discuss the pore structure characteristics of tight sandstone reservoir in Jizhong Depression,by analyzing 11 tight sandstone samples.The results show that an evaluation method for frac-ture(>10 μm,in diameter),macropores(1-10 μm),mesopores(0.1-1.0 μm)and micropores(<0.1 μm)within tight sandstone reservoir was established by mercury intrusion curves.This method was verified using fractal geometry theory.Based on the above classification,the volume contents of pores and fractures were estimated by mercury intrusion curves.Morever,three types(Ⅰ,Ⅱ and Ⅲ)of tight sandstone reservoir in Jizhong Depression were analyzed based on the distribution of pore volume,porosity,permeability,displacement pressure and mercury withdrawal efficiency.Type I tight sandstone reservoir is characterized by abundant micropores and rarely open fractures,which leads to a low permeability.Type Ⅱ tight sandstone reservoir has high open fractures but a few micropores.Type Ⅲ tight sandstone reservoir not only has abundant micropores but also has high open fractures.Two main parameters obtained from the mercury porosimetry analysis,the mercury withdrawal efficiency and permeability,reflect the totally minable potential and production rate of tight oil and gas,respectively.The more the micropores develop,the higher the mercury withdrawl efficiency is,and the simpler and more homogeneous the pore structure is.The flowing capacity is controlled by fractures and macropores.Therefore,the typeⅢ tight sandstone reservoir in Jizhong Depression is the most appropriate to exploit.
To evaluate the type of tight sandstone reservoir and provide theoretical basis for the exploration and development of tight oil and gas,the fractal theory,mercury intrusion capillary pressure analyses,as well as reservoir physical properties,were used to discuss the pore structure characteristics of tight sandstone reservoir in Jizhong Depression,by analyzing 11 tight sandstone samples.The results show that an evaluation method for frac-ture(>10 μm,in diameter),macropores(1-10 μm),mesopores(0.1-1.0 μm)and micropores(<0.1 μm)within tight sandstone reservoir was established by mercury intrusion curves.This method was verified using fractal geometry theory.Based on the above classification,the volume contents of pores and fractures were estimated by mercury intrusion curves.Morever,three types(Ⅰ,Ⅱ and Ⅲ)of tight sandstone reservoir in Jizhong Depression were analyzed based on the distribution of pore volume,porosity,permeability,displacement pressure and mercury withdrawal efficiency.Type I tight sandstone reservoir is characterized by abundant micropores and rarely open fractures,which leads to a low permeability.Type Ⅱ tight sandstone reservoir has high open fractures but a few micropores.Type Ⅲ tight sandstone reservoir not only has abundant micropores but also has high open fractures.Two main parameters obtained from the mercury porosimetry analysis,the mercury withdrawal efficiency and permeability,reflect the totally minable potential and production rate of tight oil and gas,respectively.The more the micropores develop,the higher the mercury withdrawl efficiency is,and the simpler and more homogeneous the pore structure is.The flowing capacity is controlled by fractures and macropores.Therefore,the typeⅢ tight sandstone reservoir in Jizhong Depression is the most appropriate to exploit.
引文
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[7]李润泽,王长江,李伟,等.基于铸体薄片的致密岩心孔隙结构多重分形特征研究.西安石油大学学报(自然科学版),2016,31(6):66-71.LI R Z,WANG C J,LI W,et al.Multifractal properties of tight rock pore structure based on thin section.Journal of Xi’an Shiyou University(Natural Science Edition),2016,31(6):66-71.
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[12]刘义坤,王永平,唐慧敏,等.毛管压力曲线和分形理论在储层分类中的应用.岩性油气藏,2014,26(3):89-92.LIU Y K,WANG Y P,TANG H M,et al.Application of capillary pressure curves and fractal theory to reservoir classification.Lithologic Reservoirs,2014,26(3):89-92.
[13]白斌,朱如凯,吴松涛,等.非常规油气致密储层微观孔喉结构表征新技术及意义.中国石油勘探,2014,19(3):78-86.BAI B,ZHU R K,WU S T,et al.New micro-throat structural characterization techniques for unconventional tight hydrocarbon reservoir.China Petroleum Exploration,2014,19(3):78-86.
[14]LI P,ZHENG M,BI H,et al.Pore throat structure and fractal characteristics of tight oil sandstone:a case study in the Ordos Basin,China.Journal of Petroleum Science and Engineering,2016,149:1-10.
[15]徐守余,王淑萍.砂岩储层微观结构分形特征研究--以胜坨油田古近系沙河街组储层为例.天然气地球科学,2013,24(5):886-893.XU S Y,WANG S P.Fractal feature about the micro-structure in sandstone reservoir:taking the Paleogene Shahejie Formation in Shengtuo Oilfield as an example.Natural Gas Geoscience,2013,24(5):886-893.
[16]李留仁,赵艳艳,李忠兴,等.多孔介质微观孔隙结构分形特征及分形系数的意义.石油大学学报(自然科学版),2004,28(3):105-107.LI L R,ZHAO Y Y,LI Z X,et al.Fractal characteristics of micropore structure of porous medium and the meaning of fractal coefficient.Journal of the University of Petroleum,China(Edition of Natural Science),2004,28(3):105-107.
[17]张立强,纪友亮,马文杰,等.博格达山前带砂岩孔隙结构分形几何学特征与储层评价.石油大学学报(自然科学版),1998,22(5):31-33.ZHANG L Q,JI Y L,MA W J,et al.Characteristics of fractional geometry and reservoir evaluation of fore mountain belt at begedashan.Journal of the University of Petroleum,China(Edition of Natural Science),1998,22(5):31-33.
[18]张宪国,张涛,林承焰.基于孔隙分形特征的低渗透储层孔隙结构评价.岩性油气藏,2013,25(6):40-45.ZHANG X G,ZHANG T,LIN C Y.Pore structure evaluation of low permeability reservoir based on pore fractal features.Lithologic Reservoirs,2013,25(6):40-45.
[19]张文朝,杨德相,陈彦均,等.冀中坳陷古近系沉积构造特征与油气分布规律.地质学报,2008,82(8):1103.ZHANG W C,YANG D X,CHEN Y J,et al.Sedimentary structural characteristics and hydrocarbon distributed rules of Jizhong Depression.Acta Geologica Sinica,2008,82(8):1103.
[20]杨飞.利用分形模拟研究储层微观孔隙结构-以胜坨油田为例.青岛:中国石油大学(华东),2011.YANG F.Microscopic pore structure using fractal simulationa case study of Shengtuo Oilfield.Qingdao:China University of Petroleum(East China),2011.
[21]赵玉集.三江-穆棱河含煤区煤层气富集规律及开发潜力评价.北京:中国地质大学(北京),2012.ZHAO Y J.Preliminary evaluation of gas enrichment and exploitation potential of coalbed methane in Sanjing-Mulinghe coal-bearing area.Beijing:China University of Geosciences in Beijing,2012.
[22]EVERETT D H.Manual of symbols and terminology for physicochemical quantities and units,appendixⅡ:definitions,terminology and symbols in colloid and surface chemistry.Pure and Applied Chemistry.1972,31(4):585.
[23]陈程,孙义梅.砂岩孔隙结构分维及其应用.沉积学报,1996,14(4):112.CHEN C,SUN Y M.Fractional dimension of the pore-texture in sandstones and its application.Acta Sedimentologica Sinica,1996,14(4):112.
[24]LI J Q,LIU D M,YAO Y B,et al.Physical characterization of the pore-fracture system in coals,northeastern China.Energy Exploration&Exploitation,2013,31(2):276.
[2]李丹,董春梅,林承焰,等.松南让字井斜坡带源下致密砂岩储集层控制因素.石油勘探与开发,2013,40(6):692-700.LI D,DONG C M,LIN C Y,et al.Control factors on tight sandstone reservoirs below source rocks in the Rangzijing slope zone of southern Songliao Basin,East China.Petroleum Exploration and Development,2013,40(6):692-700.
[3]李易隆,贾爱林,何东博.致密砂岩有效储层形成的控制因素.石油学报,2013,34(1):71-82.LI Y L,JIA A L,HE D B.Control factors on the formation of effective reservoirs in tight sands:examples from Guang’an and Sulige gasfields.Acta Petrolei Sinica,2013,34(1):71-82.
[4]孙红华,李旭平,钟建华,等.辽河西部凹陷南段沙三段致密砂岩储层物性特征及主控因素分析.岩性油气藏,2013,25(6):53-61.SUN H H,LI X P,ZHONG J H,et al.Characteristics and controlling factors of tight sandstone reservoir of the third member of Shahejie Formation in the southern West Depression,Liaohe Basin.Lithologic Reservoirs,2013,25(6):53-61.
[5]宋涛,李建忠,姜晓宇,等.冀中坳陷束鹿凹陷致密油成藏特征探讨.复杂油气藏,2014,7(1):4-8.SONG T,LI J Z,JIANG X Y,et al.Accumulation features of tight oil reservoir in Shulu Sag of Central Hebei.Complex Hydrocarbon Reservoirs,2014,7(1):4-8.
[6]贾芬淑,沈平平,李克文.砂岩孔隙结构的分形特征及应用研究.断块油气田,1995,2(1):16-21.JIA F S,SHEN P P,LI K W.Study on the fractal characteristics of sandstone pore structure and its application.Fault-Block Oil&Gas Field,1995,2(1):16-21.
[7]李润泽,王长江,李伟,等.基于铸体薄片的致密岩心孔隙结构多重分形特征研究.西安石油大学学报(自然科学版),2016,31(6):66-71.LI R Z,WANG C J,LI W,et al.Multifractal properties of tight rock pore structure based on thin section.Journal of Xi’an Shiyou University(Natural Science Edition),2016,31(6):66-71.
[8]ZHAO H W,NING Z F,ZHAO T Y,et al.Effects of mineralogy on petrophysical properties and permeability estimation of the Upper Triassic Yanchang tight oil sandstones in Ordos Basin,Northern China.Fuel,2016,186:328-338.
[9]ZHANG P F,LU S F,LI J Q,et al.Characterization of shale pore system:a case study of Paleogene Xin gouzui Formation in the Jianghan Basin,China.Marine and Petroleum Geology,2016,79(1):1-14.
[10]XIAO D S,LU Z Y,JIANG S,et al.Comparison and integration of experimental methods to characterize the full-range pore features of tight gas sandstone-a case study in Songliao Basin of China.Journal of Natural Gas Science and Engineering,2016,34:1412-1421.
[11]李成,郑庆华,张三,等.鄂尔多斯盆地镇北地区长4+5储层微观孔隙结构研究.石油实验地质,2015,37(6):729-736.LI C,ZHENG Q H,ZHANG S,et al.Microscopic pore structure of the fourth and fifth members of the Yanchang Formation in Zhenbei area of the Ordos Basin.Petroleum Geology&Experiment,2015,37(6):729-736.
[12]刘义坤,王永平,唐慧敏,等.毛管压力曲线和分形理论在储层分类中的应用.岩性油气藏,2014,26(3):89-92.LIU Y K,WANG Y P,TANG H M,et al.Application of capillary pressure curves and fractal theory to reservoir classification.Lithologic Reservoirs,2014,26(3):89-92.
[13]白斌,朱如凯,吴松涛,等.非常规油气致密储层微观孔喉结构表征新技术及意义.中国石油勘探,2014,19(3):78-86.BAI B,ZHU R K,WU S T,et al.New micro-throat structural characterization techniques for unconventional tight hydrocarbon reservoir.China Petroleum Exploration,2014,19(3):78-86.
[14]LI P,ZHENG M,BI H,et al.Pore throat structure and fractal characteristics of tight oil sandstone:a case study in the Ordos Basin,China.Journal of Petroleum Science and Engineering,2016,149:1-10.
[15]徐守余,王淑萍.砂岩储层微观结构分形特征研究--以胜坨油田古近系沙河街组储层为例.天然气地球科学,2013,24(5):886-893.XU S Y,WANG S P.Fractal feature about the micro-structure in sandstone reservoir:taking the Paleogene Shahejie Formation in Shengtuo Oilfield as an example.Natural Gas Geoscience,2013,24(5):886-893.
[16]李留仁,赵艳艳,李忠兴,等.多孔介质微观孔隙结构分形特征及分形系数的意义.石油大学学报(自然科学版),2004,28(3):105-107.LI L R,ZHAO Y Y,LI Z X,et al.Fractal characteristics of micropore structure of porous medium and the meaning of fractal coefficient.Journal of the University of Petroleum,China(Edition of Natural Science),2004,28(3):105-107.
[17]张立强,纪友亮,马文杰,等.博格达山前带砂岩孔隙结构分形几何学特征与储层评价.石油大学学报(自然科学版),1998,22(5):31-33.ZHANG L Q,JI Y L,MA W J,et al.Characteristics of fractional geometry and reservoir evaluation of fore mountain belt at begedashan.Journal of the University of Petroleum,China(Edition of Natural Science),1998,22(5):31-33.
[18]张宪国,张涛,林承焰.基于孔隙分形特征的低渗透储层孔隙结构评价.岩性油气藏,2013,25(6):40-45.ZHANG X G,ZHANG T,LIN C Y.Pore structure evaluation of low permeability reservoir based on pore fractal features.Lithologic Reservoirs,2013,25(6):40-45.
[19]张文朝,杨德相,陈彦均,等.冀中坳陷古近系沉积构造特征与油气分布规律.地质学报,2008,82(8):1103.ZHANG W C,YANG D X,CHEN Y J,et al.Sedimentary structural characteristics and hydrocarbon distributed rules of Jizhong Depression.Acta Geologica Sinica,2008,82(8):1103.
[20]杨飞.利用分形模拟研究储层微观孔隙结构-以胜坨油田为例.青岛:中国石油大学(华东),2011.YANG F.Microscopic pore structure using fractal simulationa case study of Shengtuo Oilfield.Qingdao:China University of Petroleum(East China),2011.
[21]赵玉集.三江-穆棱河含煤区煤层气富集规律及开发潜力评价.北京:中国地质大学(北京),2012.ZHAO Y J.Preliminary evaluation of gas enrichment and exploitation potential of coalbed methane in Sanjing-Mulinghe coal-bearing area.Beijing:China University of Geosciences in Beijing,2012.
[22]EVERETT D H.Manual of symbols and terminology for physicochemical quantities and units,appendixⅡ:definitions,terminology and symbols in colloid and surface chemistry.Pure and Applied Chemistry.1972,31(4):585.
[23]陈程,孙义梅.砂岩孔隙结构分维及其应用.沉积学报,1996,14(4):112.CHEN C,SUN Y M.Fractional dimension of the pore-texture in sandstones and its application.Acta Sedimentologica Sinica,1996,14(4):112.
[24]LI J Q,LIU D M,YAO Y B,et al.Physical characterization of the pore-fracture system in coals,northeastern China.Energy Exploration&Exploitation,2013,31(2):276.