Sweet spots geological characteristics and key exploration technologies of continental shale oil: a case study of Member 2 of Kongdian Formation in Cangdong sag

doi:10.7623/syxb201908011

Acta Petrolei Sinica ›› 2019, Vol. 40 ›› Issue (8): 997-1012.DOI: 10.7623/syxb201908011

• Typical Oil And Gas Fields • Previous Articles Next Articles

Sweet spots geological characteristics and key exploration technologies of continental shale oil: a case study of Member 2 of Kongdian Formation in Cangdong sag

Pu Xiugang, Jin Fengming, Han Wenzhong, Shi Zhannan, Cai Aibing, Wang Aiguo, Guan Quansheng, Jiang Wenya, Zhang Wei

PetroChina Dagang Oilfield Company, Tianjin 300280, China

Received:2019-06-27 Revised:2019-07-15 Online:2019-08-25 Published:2019-08-28

陆相页岩油甜点地质特征与勘探关键技术——以沧东凹陷孔店组二段为例

蒲秀刚, 金凤鸣, 韩文中, 时战楠, 蔡爱兵, 王爱国, 官全胜, 姜文亚, 张伟

中国石油大港油田公司天津 300280

通讯作者: 蒲秀刚,男,1968年12月生,1990年获长春地质学院学士学位,2004年获中国矿业大学(北京)博士学位,现为中国石油大港油田公司教授级高级工程师,主要从事油气勘探领域中的地质研究与管理工作。Email:puxgang@petrochina.com.cn
作者简介:蒲秀刚,男,1968年12月生,1990年获长春地质学院学士学位,2004年获中国矿业大学(北京)博士学位,现为中国石油大港油田公司教授级高级工程师,主要从事油气勘探领域中的地质研究与管理工作。Email:puxgang@petrochina.com.cn
基金资助:
中国石油天然气集团公司科技重大专项"大港油区效益增储稳产关键技术研究与应用"（2018E-11）资助。

Abstract

Abstract:

Under the general trend of stepping-up oil and gas exploration and development in China, the unconventional oil and gas resources such as shale oil and gas have become an important alternative. Abundant continental shale oil resources are developed in Member 2 of Kongdian Formation (Ek₂) of the Cangdong sag in the Huanghua depression of the Bohai Bay Basin which has complex structure, strong heterogeneity, and large buried depth, thus, the geological characteristic of shale oil accumulation and key exploration technologies are investigated on base of the system coring of 635.8 m, centimeter-level fine description and analysis of over ten thousand samples, therefore, the "four accurate" technologies have been developed, including the accurate selection of sweet spot areas, accurate drilling of sweet spot layers, accurate fracturing of sweet spot layers and accurate measure of fracture-rich sections. The results show that the continental shale strata in Member 2 of Kongdian Formation can be divided into three types:felsic shale, limy dolomitic shale and mixed shale. The Member 2 of Kongdian Formation is characterized by diverse mineral components, abundant laminae, good source rocks and medium thermal evolution degree, tight reservoir with rich micropore and microfractures, high oil saturation and brittle mineral content, indicating good prospect of shale oil exploration. Through sedimentological study, TOC and R_o evaluation, brittle mineral calculation, and seismic fusion inversion, a total of 126 km² of Class I sweet spots in Member 2 of Kongdian Formation was delineated comprehensively, which guides horizontal well deployment (Well GD1701H and Well GD1702H). The drilling rate of sweet spot of these two horizontal wells is up to 96% by tracing thin layer through fine calibration, locating compartment through fine inversion, ensuring window entry through precise positioning, and tracking sweet spot through adjustment. The "one-excellent and five-highs" criterion is used to select perforation points to realize differential designs of fracturing intervals and clusters. Micro-seismic and potentiometry monitoring show that the artificial fractures formed by volumetric fracturing are 300-400 m long and 120 m high, and control a volume of about 0.07 km³. The maximum daily oil production of two horizontal wells is 66 t and 53 t respectively to realize the economic exploitation of shale oil reserves controlled by fractures. The shale oil exploration in Member 2 of Kongdian Formation shows that the continental shale oil has great potential of exploration and development, and the above technologies are critical and effective for shale oil efficient recovery.

Key words: shale oil, sweet spot evaluation, fracturing intervals and perforation clusters, Member 2 of Kongdian Formation, Cangdong sag, Bohai Bay Basin

摘要：

页岩油气等非常规油气资源已成为油气勘探开发的重要接替领域。渤海湾盆地沧东凹陷孔店组二段（孔二段）陆相页岩油十分丰富，但面临着构造复杂、储层非均质性强、埋深大等难题。在进行635.8 m系统取心、厘米级精细描述和上万块次分析联测的基础上，开展了页岩油成藏地质特征与勘探关键技术的攻关研究，形成了"选准甜点区、打准甜点段、压准甜点层、测准裂缝区"的"四准"技术。研究结果表明，孔二段陆相页岩层系可划分为长英质页岩、含灰白云质页岩和混合质页岩，矿物成分多样，层理结构发育，源岩品质好，热演化程度中等，储层致密但微孔缝发育，含油饱和度高，脆性矿物含量高，展示了孔二段页岩油具有良好的勘探前景。通过沉积学研究、总有机碳含量及镜质体反射率评价、脆性矿物计算、地震融合反演等综合评价确定了孔二段I类甜点面积为126 km²，指导了GD1701H井和GD1702H井的水平井井位部署；通过"精细标定追小层、精细反演定箱体、精细落实保入窗、实施调整追甜点"等措施确保了两口水平井96%的甜点钻遇率；通过"一优五高"选点实现了压裂段簇的差异设计；微地震及电位法监测结果表明，体积压裂改造形成的压裂缝长300~400 m、高120 m，缝控体积约0.07 km³，两口水平井最高产油量分别达66 t/d和53 t/d，实现了页岩油缝控储量的有效动用。孔二段页岩油勘探实践表明陆相页岩油效益勘探开发潜力大，"四准"技术是页岩油高效动用的关键。

关键词: 页岩油, 甜点评价, 压裂段簇, 孔二段, 沧东凹陷, 渤海湾盆地

CLC Number:

TE122

Pu Xiugang, Jin Fengming, Han Wenzhong, Shi Zhannan, Cai Aibing, Wang Aiguo, Guan Quansheng, Jiang Wenya, Zhang Wei. Sweet spots geological characteristics and key exploration technologies of continental shale oil: a case study of Member 2 of Kongdian Formation in Cangdong sag[J]. Acta Petrolei Sinica, 2019, 40(8): 997-1012.

蒲秀刚, 金凤鸣, 韩文中, 时战楠, 蔡爱兵, 王爱国, 官全胜, 姜文亚, 张伟. 陆相页岩油甜点地质特征与勘探关键技术——以沧东凹陷孔店组二段为例[J]. 石油学报, 2019, 40(8): 997-1012.

References

[1] 邓运华,薛永安,于水,等.浅层油气运聚理论与渤海大油田群的发现[J].石油学报,2017,38(1):1-8.
DENG Yunhua,XUE Yong'an,YU Shui,et al.Shallow hydrocarbon migration and accumulation theory and discovery of giant oilfield group in Bohai Sea[J].Acta Petrolei Sinica,2017,38(1):1-8.
[2] 谢玉洪,张功成,沈朴,等.渤海湾盆地渤中凹陷大气田形成条件与勘探方向[J].石油学报,2018,39(11):1199-1210.
XIE Yuhong,ZHANG Gongcheng,SHEN Pu,et al.Formation conditions and exploration direction of large gas field in Bozhong sag of Bohai Bay Basin[J].Acta Petrolei Sinica,2018,39(11):1199-1210.
[3] 刘惠民,于炳松,谢忠怀,等.陆相湖盆富有机质页岩微相特征及对页岩油富集的指示意义——以渤海湾盆地济阳坳陷为例[J].石油学报,2018,39(12):1328-1343.
LIU Huimin,YU Bingsong,XIE Zhonghuai,et al.Characteristics and implications of micro-lithofacies in lacustrine-basin organic-rich shale:a case study of Jiyang depression,Bohai Bay Basin[J].Acta Petrolei Sinica,2018,39(12):1328-1343.
[4] 张顺,刘惠民,王敏,等.东营凹陷页岩油储层孔隙演化[J].石油学报,2018,39(7):754-766.
ZHANG Shun,LIU Huimin,WANG Min,et al.Pore evolution of shale oil reservoirs in Dongying sag[J].Acta Petrolei Sinica,2018,39(7):754-766.
[5] 宋岩,李卓,姜振学,等.非常规油气地质研究进展与发展趋势[J].石油勘探与开发,2017,44(4):638-648.
SONG Yan,LI Zhuo,JIANG Zhenxue,et al.Progress and development trend of unconventional oil and gas geological research[J].Petroleum Exploration and Development,2017,44(4):638-648.
[6] 王红军,马锋,童晓光,等.全球非常规油气资源评价[J].石油勘探与开发,2016,43(6):850-862.
WANG Hongjun,MA Feng,TONG Xiaoguang,et al.Assessment of global unconventional oil and gas resources[J].Petroleum Exploration and Development,2016,43(6):850-862.
[7] 张廷山,彭志,杨巍,等.美国页岩油研究对我国的启示[J].岩性油气藏,2015,27(3):1-10.
ZHANG Tingshan,PENG Zhi,YANG Wei,et al.Enlightenments of American shale oil research towards China[J].Lithologic Reservoirs,2015,27(3):1-10.
[8] 杨华,李士祥,刘显阳.鄂尔多斯盆地致密油、页岩油特征及资源潜力[J].石油学报,2013,34(1):1-11.
YANG Hua,LI Shixiang,LIU Xianyang.Characteristics and resource prospects of tight oil and shale oil in Ordos Basin[J].Acta Petrolei Sinica,2013,34(1):1-11.
[9] 蒲秀刚,周立宏,韩文中,等.歧口凹陷沙一下亚段斜坡区重力流沉积与致密油勘探[J].石油勘探与开发,2014,41(2):138-149.
PU Xiugang,ZHOU Lihong,HAN Wenzhong,et al.Gravity flow sedimentation and tight oil exploration in lower first Member of Shahejie Formation in slope area of Qikou sag,Bohai Bay Basin[J].Petroleum Exploration and Development,2014,41(2):138-149.
[10] 刘成林,李冰,吴林强,等.松辽盆地上白垩统页岩油地质条件评价[M].北京:地质出版社,2016.
LIU Chenglin,LI Bing,WU Linqiang,et al.Evaluation on Cretaceous geological conditions of oil shale in Songliao Basin[M].Beijing:Geological Publishing House,2016.
[11] 金之均,胡宗全,高波,等.川东南地区五峰组-龙马溪组页岩气富集与高产控制因素[J].地学前缘,2016,23(1):1-10.
JIN Zhijun,HU Zongquan,GAO Bo,et al.Controlling factors on the enrichment and high productivity of shale gas in the Wufeng-Longmaxi formations,southeastern Sichuan Basin[J].Earth Science Frontiers,2016,23(1):1-10.
[12] 孙焕泉.济阳坳陷页岩油勘探实践与认识[J].中国石油勘探,2017,22(4):1-14.
SUN Huanquan.Exploration practice and cognitions of shale oil in Jiyang depression[J].China Petroleum Exploration,2017,22(4):1-14.
[13] 蒲秀刚,韩文中,周立宏,等.黄骅坳陷沧东凹陷孔二段高位体系域细粒相区岩性特征及地质意义[J]. 中国石油勘探,2015,20(5):30-40.
PU Xiugang,HAN Wenzhong,ZHOU Lihong,et al.Lithologic characteristics and geological implication of fine-grained sedimentation in Ek2 high stand system tract of Cangdong sag,Huanghua depression[J].China Petroleum Exploration,2015,20(5):30-40.
[14] 周立宏,蒲秀刚,肖敦清,等.渤海湾盆地沧东凹陷孔二段页岩油形成条件及富集主控因素[J].天然气地球科学,2018,29(9):1323-1332.
ZHOU Lihong,PU Xiugang,XIAO Dunqing,et al.Geological conditions for shale oil formation and the main controlling factors for the enrichment of the 2nd Member of Kongdian Formation in the Cangdong sag,Bohai Bay Basin[J].Natural Gas Geoscience,2018,29(9):1323-1332.
[15] 刘刚,周东升.微量元素分析在判别沉积环境中的应用——以江汉盆地潜江组为例[J].石油实验地质,2007,29(3):307-310.
LIU Gang,ZHOU Dongsheng.Application of microelements analysis in identifying sedimentary environment:taking Qianjiang Formation in the Jianghan Basin as an example[J].Petroleum Geology & Experiment,2007,29(3):307-310.
[16] 孟潇,李春霞,归榕.延安地区上古生界山2段-盒8段微量元素揭示的古沉积环境意义[J].非常规油气,2014,1(2):26-30.
MENG Xiao,LI Chunxia,GUI Rong.Ancient sedimentary environment significance revealed by the trace elements of Shan 2 to He 8 Member of Upper Paleozoic in Yanan[J].Unconventonal Oil & Gas,2014,1(2):26-30.
[17] 蔡观强,郭锋,刘显太,等.东营凹陷沙河街组沉积岩碳氧同位素组成的古环境记录[J].地球与环境,2009,37(4):347-354.
CAI Guanqiang,GUO Feng,LIU Xiantai,et al.Carbon and oxygen isotope characteristics and palaeoenvironmental implications of lacustrine carbonate rocks from the Shahejie Formation in the Dongying sag[J].Earth and Environment,2009,37(4):347-354.
[18] 王冠民.古气候变化对湖相高频旋回泥岩和页岩的沉积控制——以济阳坳陷古近系为例[D].广州:中国科学院,2005.
WANG Guanmin.The sedimentary control to mudstone and shale in lacustrine high-frequency cycle by paleoclimate change:taking the Eogene in Jiyang depression as an example[D].Guangzhou:Chinese Academy of Sciences,2005.
[19] 鄢继华,蒲秀刚,周立宏,等.基于X射线衍射数据的细粒沉积岩岩石定名方法与应用[J].中国石油勘探,2015,20(1):48-54.
YAN Jihua,PU Xiugang,ZHOU Lihong,et al.Naming method of fine-grained sedimentary rocks on basis of X-ray diffraction data[J].China Petroleum Exploration,2015,20(1):48-54.
[20] 蒲秀刚,周立宏,韩文中,等.细粒相沉积地质特征与致密油勘探——以渤海湾盆地沧东凹陷孔店组二段为例[J].石油勘探与开发,2016,43(1):24-33.
PU Xiugang,ZHOU Lihong,HAN Wenzhong,et al.Geologic features of fine-grained facies sedimentation and tight oil exploration:a case from the second Member of Paleogene Kongdian Formation of Cangdong sag,Bohai Bay Basin[J].Petroleum Exploration and Development,2016,43(1):24-33.
[21] 赵贤正,周立宏,蒲秀刚,等.陆相湖盆页岩层系基本地质特征与页岩油勘探突破:以渤海湾盆地沧东凹陷古近系孔店组二段一亚段为例[J].石油勘探与开发,2018,45(3):361-372.
ZHAO Xianzheng,ZHOU Lihong,PU Xiugang,et al.Geological characteristics of shale rock system and shale oil exploration in a lacustrine basin:a case study from the Paleogene 1st sub-member of Kong 2 Member in Cangdong sag,Bohai Bay Basin,China[J].Petroleum Exploration and Development,2018,45(3):361-372.
[22] 高辉,何梦卿,赵鹏云,等.鄂尔多斯盆地长7页岩油与北美地区典型页岩油地质特征对比[J].石油实验地质,2018,40(2):133-140.
GAO Hui,HE Mengqing,ZHANG Pengyun,et al.Comparison of geological characteristics of Chang 7 shale oil in Ordos Basin and typical shale oil in North America[J].Petroleum Geology & Experiment,2018,40(2):133-140.
[23] 蒲秀刚,陈长伟,周立宏,等.整体-局部-整体沉积体系分析在歧口凹陷沙三段的应用[J].西安石油大学学报:自然科学版,2011,26(2):8-12.
PU Xiugang,CHEN Changwei,ZHOU Lihong,et al.Application of a new sedimentary system analysis method in Es3 of Qikou sag[J].Journal of Xi'an Shiyou University:Natural Science Edition,2011,26(2):8-12.
[24] 赵贤正,蒲秀刚,周立宏,等.渤海湾盆地歧口凹陷古近系沉积体系重建与储集层评价[J].成都理工大学学报:自然科学版,2017,44(5):565-578.
ZHAO Xianzheng,PU Xiugang,ZHOU Lihong,et al.Reconstruction of Paleogene sedimentary system and reservoir evaluation in Qikou sag,Bohai Bay Basin,China[J].Journal of Chengdu University of Technology:Science & Technology Edition,2017,44(5):565-578.
[25] 周立宏,蒲秀刚,韩文中,等.一种确定细粒沉积岩中总有机碳的方法:中国,201510419628.X[P].2018-05-04.
ZHOU Lihong,PU Xiugang,HAN Wenzhong,et al.A method for determining total organic carbon in fine sedimentary rocks:CN,201510419628.X[P].2018-05-04.
[26] 周立宏,蒲秀刚,王文革,等.一种岩性识别方法:中国,20151040 4879.0[P].2018-01-02.
ZHOU Lihong,PU Xiugang,WANG Wenge,et al.A lithology recognition method:CN,201510404879.0[P].2018-01-02.
[27] 刘建中,王春耘,刘继民,等.用微地震法监测油田生产动态[J].石油勘探与开发,2004,31(2):71-73.
LU Jianzhong,WANG Chunyun,LIU Jimin,et al.Micro-seismic monitor on the operation of oil fields[J].Petroleum Exploration and Development,2004,31(2):71-73.
[28] 宋维琪,陈泽东,毛中华.水力压裂裂缝微地震监测技术[M].东营:中国石油大学出版社,2008.
SONG Weiqi,CHEN Zedong,MAO Zhonghua.Hydro-fracturing break microseismic monitoring technology[M].Dongying:China University of Petroleum Press,2008.
[29] 董文轩,张永军,谢慧萍,等.微震监测技术在濮城油田的研究与应用[J].断块油气田,2004,11(6):55-56.
DONG Wenxuan,ZHANG Yongjun,XIE Huiping,et al.Study and application of the microseism watch technique in the super Es35-10 reservoir of the Pucheng oilfield[J].Fault-Block Oil & Gas Field,2004,11(6):55-56.
[30] 王佳.油田水力压裂裂缝监测的井地电阻率法研究与应用[D].长春:吉林大学,2013.
WANG Jia.Research and application of borehole-surface electrical resistively method of monitoring hydraulic fracturing in the oilfield[D].Changchun:Jilin University,2013.
[31] 杜浩.稳定电磁场中移入一块介质的互作用能[J].大学物理,1989(1):16-19.
DU Hao.The interaction energy of moving to a medium in a stable electromagnetic field[J].College Physics,1989(1):16-19.
[32] 郭晓林.分布式井-地电位测量仪通信系统及主控软件的设计[D].北京:中国石油大学,2008.
GUO Xiaolin.The design of communication system and main control software of distributed well ground potential measuring instrument[D].Beijing:China University of Petroleum,2008.
[33] 吕超.分布式井-地电位测量仪接收机的研究与设计[D].长春:吉林大学,2006.
LV Chao.Research and design of distributed well ground potential measurement instrument[D].Changchun:Jilin University,2006.

Sweet spots geological characteristics and key exploration technologies of continental shale oil: a case study of Member 2 of Kongdian Formation in Cangdong sag

陆相页岩油甜点地质特征与勘探关键技术——以沧东凹陷孔店组二段为例

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