裂缝的发育对特低渗透砂岩储层有重要影响。基于室内实验数据,从孔渗关系、微观孔隙结构、应力敏感性及油水两相渗流等角度对裂缝发育储层的特征进行了分析,结果表明:与裂缝不发育的储层相比,相同孔隙度下裂缝发育储层的渗透率更高,孔隙度10%~20%时,裂缝发育储层渗透率约为裂缝不发育储层的3~5 倍;渗透率相同时,裂缝发育储层喉道半径分布范围更宽,大尺寸的喉道比例更高,主流喉道半径更大,渗透率主要由大喉道贡献;裂缝发育储层应力敏感性更强,有效应力增大引起的渗透率损失约为裂缝不发育储层的2~3 倍;裂缝发育储层束缚水饱和度和残余油饱和度均较高,两相共渗区范围窄,随着含水饱和度的增大,油相曲线急剧下降,水相曲线上凸型快速抬升,且幅度很大,无水采油期很短且期内采出程度低,见水后含水率急剧上升,最终采收率很低。
Ultra-low permeability sandstone reservoirs are significantly influenced by development of natural fractures. Based on laboratory experiments, fractured ultra- low permeability sandstone reservoirs were detailedly characterized in terms of porositypermeability relationship, micro-pore structure, stress sensitivity, and oil-water two-phase flow. The results show that permeability of fractured reservoir was higher than that of non-fractured one under equal reservoir porosity. When the reservoir porosity ranged from 10% to 20%, the permeability of fractured reservoir was approximately 2-4 times higher than that of non-fractured one. Compared with experiments on non-fractured reservoir, fractured reservoir is featured by larger throat radius span, higher proportion of largeradius throats, larger radius of dominant throats, and major contribution of large-radius throats to permeability under equal permeability. Fractured reservoir is more stress-sensitive, and the corresponding permeability loss of effective stress increase was 1-2 times higher than that of non-fractured one. Oil-water two-phase flow in fractured reservoir is featured by higher bound water and residual oil saturations, shorter common-flow interval, rapid oil relative permeability decline and water relative permeability increase with the increase of water saturation, short water-free production period, rapid water-cut increase after water break-through and low ultimate recovery factor.
[1] 胡文瑞. 中国低渗透油气的现在与未来[J]. 中国工程科学, 2009, 11 (8): 29-37. Hu Wenrui. The present and future of low permeability oil and gas in China[J]. Engineering Sciences, 2009, 11(8): 29-37.
[2] 王瑞飞, 陈明强, 孙卫. 特低渗透砂岩储层微裂缝特征及微裂缝参数的定量研究——以鄂尔多斯盆地沿25区块、庄40区块为例[J]. 矿物学报, 2008, 28(2): 215-220. Wang Ruifei, Cheng Mingqiang, Sun Wei. Quantitative research on the characterisirics of and parameters for micro cracks in ultra- low permeability sandstone reservoirs: Taking Yan25 and Zhuang40 areas in the Ordos Basin for example[J]. Acta Mineralogica Sinica, 2008, 28 (2): 215-220.
[3] 王景, 凌升阶, 南中虎. 特低渗透砂岩微裂缝分布研究方法探索[J]. 石油勘探与开发, 2003, 30(2): 51-53. Wang Jing, Ling Shengjie, Nan Zhonghu. Micro-fractures distribution in extremely lower permeable sandstone reservoirs of Yanchang Formation and its geologic significance, Ordos Basin, Northwest China[J]. Petroleum Exploration and Development, 2003, 30(2): 51-53.
[4] 王拥军, 李治平, 冉启全, 等. 火山岩储层微裂缝研究[J]. 国外测井技术, 2006, 21(3): 27-29. Wang Yongjun, Li Zhiping, Ran Qiquan, et al. Study on microfractures in volcanic reservoirs[J]. World Well Logging Technology, 2006, 21(3): 27-29.
[5] 齐亚东, 战剑飞, 李晓明, 等. 特低渗透砂岩储层应力敏感性实验[J]. 科技导报, 2012, 30(3): 49-52. Qi Yadong, Zhan Jianfei, Li Xiaoming, et al. Experiments on the stress sensitivity of ultra- low permeability sandstone reservoirs[J]. Science and Technology Review, 2012, 30(3): 49-52.
[6] 郝明强, 杨正明, 刘学伟, 等. 裂缝性低渗透油藏应力敏感性研究[J]. 新疆石油地质, 2006, 27(4): 471-473. Hao Mingqiang, Yang Zhengming, Liu Xuewei, et al. A study on pressure sensitivity of fractured low permeability reservoirs[J]. Xinjiang Petroleum Geology, 2006, 27(4): 471-473.
[7] 张莉, 杨亚娟, 岳乐平, 等. 哈南阿尔善油藏微裂缝特征及其对开发的影响[J]. 石油与天然气地质, 2001, 22(2): 158-160, 193. Zhang Li, Yang Yajuan, Yue Leping, et al. Characteristics of microfractures and their influence on waterflooding in Aershan Reservoir, Hanan Oilfield[J]. Oil & Gas Geology, 2001, 22(2): 158-160, 193.
[8] 张国辉, 任晓娟, 张宁生. 微裂缝对低渗储层水驱油渗流规律的影响[J]. 西安石油大学学报: 自然科学版, 2007, 22(5): 44-47, 51. Zhang Guohui, Ren Xiaojuan, Zhang Ningsheng. Experimental study on the effect of micro- fracture on the water displacing oil law in lowpermeability reservoir[J]. Journal of Xi'an Shiyou University: Natural Science Edition, 2007, 22(5): 44-47, 51.
