Characteristics of the Basement Weathering Crust in Dongping Area, Qaidam Basin

Abstract

Abstract:

Large-scale distributed gas fields are discovered in frontal slope of the Altun Mountain in Qaidam Basin and the role of the basement weathering crust becomes the concerns. Basing on element analysis, X-ray diffraction analysis, cores and slices observation, conventional logging and image logging, structures of the basement weathering crust are identified and each structure owns different reservoir properties. The result shows that the structure of the basement weathering crust of Dongping area in Qaidam Basin can be divided into three layers, soil layer, completely weathered layer and semi-weathered layer which can be further divided into two zones, dissolution weathered zone and fracture weathered zone. The thickness of soil layer is 0-2 m. The thickness of completely weathered layer is 4-15 m. The thickness of dissolution weathered zone is 36.5-164 m. The thickness of fracture weathered zone is 300-1,000 m. The semi-weathered layer is the reservoir of the basement weathering crust. The reservoir property of the dissolution weathered zone is better than that of fracture weathered zone. The dissolution weathered zone with porosity range from 2%-16% develops dissolved pores and map fractures with high degree of dissolution, and the fracture weathered zone with porosity range from 2%-8% develops tectonic fractures and joint fractures with low degree of dissolution. Large-scale development of the basement weathering crust in Dongping area provides the basis for finding hydrocarbon in the slope area of Qaidam Bain far from the source rock.

Key words: weathering crust, basement weathering crust structure, basement weathering crust reservoir, Qaidam Basin

CLC Number:

TE122.2

WU Jin, GAO Xianzhi, MA Dade, ZHANG Yongshu, ZHOU Wei, NIU Huapeng, KONG Hongxi, WANG Bo. Characteristics of the Basement Weathering Crust in Dongping Area, Qaidam Basin[J]. Geoscience, 2017, 31(01): 129-141.

Figures/Tables 15

Fig.1 Location map of Dongping area

Fig.2 Lithological distribution of the basement in Dongping

Fig.3 Petrologic characteristics of the basement rock in Dongping area

Fig.4 Basement rock weathering crust division of Dongping area

Fig.5 Characteristics of the basement core of the top weathering crust in well Ping1H-2-3

Fig.6 Characteristics of cores and mineral alteration of the completely weathered layer in Dongping area

Fig.7 Characteristics of mineral alteration and reservoir space of the dissolution weathered zone in Dongping area

Fig.8 Characteristics of mineral alteration and reservoir space of the fracture weathered zone in Dongping area

Fig.9 Variation of the oxide percent contents and weathering indices for the gneiss with depth in Dongping 105 well

Fig.10 Histograms of mineral percent contents of bulk rock(a) and clay(b) by X-ray diffraction analysis for weathering crust in Dongping

Fig.11 Reservoir space in cores and slices of basement weathering crust in Dongping

Table 1 Log interpretation of physical property of basement weathering crust in Dongping

风化壳结构	东坪1井区片麻岩风化壳				东坪3井区花岗岩风化壳
风化壳结构	AC/(μs/m)	基质孔隙度/%	裂缝孔隙度/%		AC/(μs/m)		基质孔隙度/%		裂缝孔隙度/%
完全风化层	$175 ~ 233 200$	<0.2	<0.1	$7 ~ 146 37$		<0.2		<0.1
半风化层溶蚀带	$181 ~ 217 195$	$2.14 ~ 11.14 4.35$	$0.17 ~ 5.57 1.87$	$37 ~ 599 180$		$1.3 ~ 7.63 3.96$		$0.05 ~ 2.45 1.27$
半风化层崩解带	$171 ~ 210 190$	$1.9 ~ 6.14 2.97$	$0.05 ~ 2.86 1.12$	$45 ~ 413 199$		$0.45 ~ 4.9 3.39$		$0.05 ~ 1.91 0.84$

Table 1 Log interpretation of physical property of basement weathering crust in Dongping

风化壳结构	东坪1井区片麻岩风化壳				东坪3井区花岗岩风化壳
风化壳结构	AC/(μs/m)	基质孔隙度/%	裂缝孔隙度/%		AC/(μs/m)		基质孔隙度/%		裂缝孔隙度/%
完全风化层	$175 ~ 233 200$	<0.2	<0.1	$7 ~ 146 37$		<0.2		<0.1
半风化层溶蚀带	$181 ~ 217 195$	$2.14 ~ 11.14 4.35$	$0.17 ~ 5.57 1.87$	$37 ~ 599 180$		$1.3 ~ 7.63 3.96$		$0.05 ~ 2.45 1.27$
半风化层崩解带	$171 ~ 210 190$	$1.9 ~ 6.14 2.97$	$0.05 ~ 2.86 1.12$	$45 ~ 413 199$		$0.45 ~ 4.9 3.39$		$0.05 ~ 1.91 0.84$

Fig.12 Conventional logging response of the basement weathering crust in well Ping1H-2-3

Fig.13 Image logging response of the basement weathering crust in well Dongping 9

Fig.14 Weathering crust model of the basement in Dongping area

References 37

[1]	陈发景, 李明诚. 基岩油藏的区域地质背景和特征[M]//中国石油学会石油地质专业委员会.基岩油气藏. 北京: 石油工业出版社, 1987:15-22.
[2]	甘克文. 基岩油藏的成因和分布的与盆地的关系[M]//中国石油学会石油地质专业委员会.基岩油气藏. 北京: 石油工业出版社, 1987:23-31.
[3]	SMITH J E. Basement reservoir of La Paz-Mara oil fields, western Venezuela: Geological Notes[J]. AAPG Bulletin, 1956, 40(2): 380-385.
[4]	CUONG T X, WARREN J K. Bach Ho field, a fractured granitic basement reservoir, Cuu Long Basin, offshore SE Vietanm: A “buried-hill” play[J]. Journal of Petroleum Geology, 2009, 32(2): 129-156. DOI URL
[5]	SALAH M G, ALSHARHAN A S. The Precambrian basement: a major reservoir in the rifted basin, Gulf of Suez[J]. Journal of Petroleum Science and Engineering, 1998, 19(3): 201-222. DOI URL
[6]	TONG X G, HUANG Z. Buried-hill discoveries of the Damintun depression in north China[J]. AAPG Bulletin, 1991, 75(4): 780-794.
[7]	高先志, 陈振岩, 邹志文, 等. 辽河西部凹陷兴隆台高潜山内幕油气藏形成条件和成藏特征[J]. 中国石油大学学报(自然科学版), 2007, 31(6):6-9.
[8]	TAMAGAWA T, POLLARD D D. Fracture permeability created by perturbed stress fields around active faults in a fractured basement reservoir[J]. AAPG Bulletin, 2008, 92(6): 743-764. DOI URL
[9]	谢文彦, 孟卫工, 张占文, 等. 辽河坳陷潜山内幕多期裂缝油藏成藏模式[J]. 石油勘探与开发, 2006, 33(6): 649-652.
[10]	刘乐, 杨明慧, 李春霞, 等. 辽西低凸起变质岩潜山裂缝储层及成藏条件[J]. 石油与天然气地质, 2009, 30(2): 188-194.
[11]	吴智勇, 郭建华, 吴东胜. 大民屯凹陷静安堡西侧低潜山变质岩储层裂缝发育特征[J]. 石油与天然气地质, 2001, 22(4): 322-325.
[12]	马振芳, 周树勋, 于忠平, 等. 鄂尔多斯盆地中东部奥陶系顶部古风化壳特征及其与天然气富集的关系[J]. 石油勘探与开发, 1999, 26(5):21-23.
[13]	邹才能, 侯连华, 陶士振, 等. 新疆北部石炭系大型火山岩风化体结构与地层油气成藏机制[J]. 中国科学:地球科学, 2011, 41(11),1613-1626.
[14]	吴颜雄, 马达德, 刘君林, 等. 柴西地区基岩油藏形成的石油地质条件分析[J]. 天然气地球科学, 2014, 25(11):1689-1696.
[15]	赵卫卫, 查明, 吴孔友, 等. 柴达木盆地东部地区中生界不整合与油气成藏的关系[J]. 中国石油大学学报(自然科学版), 2006, 30(6):1-6.
[16]	LUO Jinglan, SADOON Morad, LIANG Zhigang, et al. Controls on the quality of Archean metamorphic and Jurassic volcanic reservoir rocks from the Xinglongtai buried hill, western depression of Liaohe basin, China[J]. AAPG Bulletin, 2005, 89(10):1319-1346. DOI URL
[17]	吴孔友, 查明, 洪梅. 准噶尔盆地不整合结构模式及半风化岩石的再成岩作用[J]. 大地构造与成矿学, 2003, 27(3): 270-276.
[18]	邹华耀, 赵春明, 尹志军. 辽东湾JZS潜山变质岩风化壳识别及储集特征[J]. 天然气地球科学, 2015, 26(4): 599-607.
[19]	赵乐强, 张金亮, 宋国奇, 等. 济阳坳陷前第三系顶部风化壳结构发育特征及对油气成藏的影响[J]. 地质学报, 2009, 83(4): 570-578.
[20]	李晓燕, 蒋有录, 陈涛. 古风化壳孔隙与裂缝发育特征及其油气地质意义[J]. 地球科学与环境学报, 2010, 32(1):60-64.
[21]	王京红, 靳久强, 朱如凯, 等. 新疆北部石炭系火山岩风化壳有效储层特征及分布规律[J]. 石油学报, 2011, 32(5):757-766. DOI
[22]	侯连华, 罗霞, 王京红, 等. 火山岩风化壳及油气地质意义——以新疆北部石炭系火山岩风化壳为例[J]. 石油勘探与开发, 2013, 40(3): 257-265.
[23]	张吉光, 王金奎, 秦龙卜, 等. 海拉尔盆地贝尔断陷苏德尔特变质岩潜山油藏特征[J]. 石油学报, 2007, 28(4):21-25. DOI
[24]	王玉华, 张吉光, 张海军. 海拉尔盆地贝尔断陷布达特群变质岩储层特征及勘探方法[J]. 大庆石油地质与开发, 2007, 26(2):23-26.
[25]	高先志, 庞雄奇, 李晓光, 等. 断陷盆地潜山构造带油气复式成藏特征及油气藏系列——以辽河西部凹陷兴隆台构造带为例[J]. 中国科学D辑:地球科学, 2008, 38(增刊Ⅰ):95-102.
[26]	IRFAN T Y, DEARMAN W R. The engineering petrography of a weathered granite in Cornwall, England[J]. Quarterly Journal of Engineering Geology and Hydrogeology, 1978, 11(3): 233-244.
[27]	IRFAN T Y. Characterization of weathered volcanic rocks in Hong Kong[J]. Quarterly Journal of Engineering Geology, 1999, 32:317-348. DOI URL
[28]	IRFAN T Y. Aggregate properties and resources of granitic rocks for use in concrete in Hong Kong[J]. Quarterly Journal of Engineering Geology and Hydrogeology, 1994, 27(1): 25-38.
[29]	EHLEN J. Fracture characteristics in weathered granites[J]. Geomorphology, 1999, 31:29-45. DOI URL
[30]	WHITE A F, BULLEN T D, SCHULZ M S, et al. Differential rates of feldspar weathering in granitic regoliths[J]. Geochimica et Cosmochimica Acta, 2001, 65: 847-869. DOI URL
[31]	高先志, 孙蕾, 汪立群, 等. 柴西南昆北断阶带油气运移特点[J]. 地球学报, 2014, 35(1):93-100.
[32]	马英军, 刘丛强. 化学风化作用中的微量元素地球化学——以江西龙南黑云母花岗岩风化壳为例[J]. 科学通报, 1999, 44(22):2433-2437.
[33]	李晓燕, 蒋有录, 陈涛. 风化黏土层-半风化岩石型不整合的矿物学、地球化学特征[J]. 地球科学——中国地质大学学报, 2009, 34(3):428-434.
[34]	陈涛, 蒋有录, 宋国奇, 等. 不整合研究中的化学风化指标[J]. 西南石油大学学报 (自然科学版), 2009, 31(1): 41-44.
[35]	DUZGOREN AYDIN N S, AYDIN A. Chemical heterogeneities of weathered igneous profiles: implications for chemical indices[J]. Environmental & Engineering Geoscience, 2003, 9(4): 363-376.
[36]	IRFAN T Y. Mineralogy, fabric properties and classification of weathered granites in Hong Kong[J]. Quarterly Journal of Engineering Geology and Hydrogeology, 1996, 29(1): 5-35.
[37]	王君, 朱如凯, 郭宏莉, 等. 火山岩风化壳储层发育模式——以三塘湖盆地马朗凹陷石炭系火山岩为例[J]. 岩石学报, 2010, 26(1):217-226.