Sedimentary characteristics and development model of Cambrian gypsum-salt rocks, Tarim Basin
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摘要: 塔里木盆地寒武系膏盐岩是塔里木盐下—盐间勘探领域的基本地质要素,也是典型海相蒸发岩沉积序列,但目前对这套蒸发岩的关注较少。通过野外勘测、最新二维地震解释、中央隆起16口探井资料综合分析,以“点—线—面”思路开展了膏盐岩沉积特征研究,编制了中—下寒武统盖层、膏盐岩层等厚图和阿瓦塔格组沉积相图,建立了中—下寒武统膏盐岩“干热古气候+持续海退过程+礁体障壁背景”发育成因模式。中—下寒武统吾松格尔组和阿瓦塔格组纵向稳定发育4种岩相组合的4套膏盐岩盖层,海退期膏盐岩具有“内盐—中膏—外红层”的“牛眼”特征;海侵期膏盐岩具有与膏云岩、膏泥岩的互层沉积特征。塔里木盆地中—下寒武统盖层均厚245 m,膏盐岩均厚167 m(最厚达340 m),具有优越的区域封盖能力。分析认为,干旱炎热的古气候、持续海退过程、礁体障壁条件为塔里木早—中寒武世厚层膏盐岩发育提供了有利条件,古气候和海平面变化制约了局限台地和蒸发台地的相带边界,使巴楚隆起、阿瓦提坳陷(膏盐岩稳定厚度300 m以上)成为了当时的聚盐中心。Abstract: The Cambrian gypsum-salt rocks in the Tarim Basin are key geological elements to the pre-salt play typical marine evaporites, yet little attention has been paid to this set of evaporites. Based on a field survey, the latest 2D seismic interpretation and comprehensive analysis of sixteen exploratory wells, a study on the sedimentary characteristics of gypsum-salt rock was carried out in a progression of "point to line, and to plane", and a contour map of the Lower to Middle Cambrian cap rocks, gypsum-salt rocks and the sedimentary facies maps of the Awatag Formation were compiled. A development model of "dry and hot paleoclimate, continuous regression process, reef barrier background" of the Lower to Middle Cambrian gypsum-salt rocks was established. There are four sets of gypsum-salt rocks with four lithofacies combinations developed longitudinally and stably in the Wusongger and Awatag formations. The gypsum-salt rocks in the regression stage are featured by "inner salt, middle gypsum, outer red-layer", while those in the transgression stage are interbedded with gypsum, mudstone and dolomite. The average thickness of the Lower to Middle Cambrian cap rocks in the Tarim Basin is 245 m, and the average thickness of the gypsum-salt rocks is 167 m (340 m maximum), showing good sealing capacity. The arid-hot paleoclimate, continuous regression and reef and reef barrier provided favorable conditions for the development of thick gypsum-salt rocks in the Early to Middle Cambrian of the Tarim Basin. The paleoclimate and sea level change restricted the facies boundary between limited platform and evaporation platform, and made the Bachu Uplift and Awati Sag (the stable thickness of gypsum-salt rocks is over 300 m) become the salt accumulation center at that time.
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Key words:
- gypsum-salt rocks /
- sedimentary characteristics /
- development model /
- Cambrian /
- Tarim Basin
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图 3 塔里木盆地巴楚隆起中—下寒武统膏盐岩地震剖面
剖面位置见图 6a。
Figure 3. Seismic interpretation of Lower to Middle Cambrian gypsum-salt rocks, Bachu Uplift, Tarim Basin
表 1 塔里木盆地寒武系探井膏盐岩盖层厚度—岩性统计
Table 1. Thickness and lithology of Cambrian gypsum-salt rock wells, Tarim Basin
井号 阿瓦塔格组 吾松格尔组 地层厚度/
m膏岩/
m盐岩/
m泥灰岩/
m泥岩/
m盖层累计
厚度/m盖地
比/%地层厚度/
m膏岩/
m盐岩/
m泥灰岩/
m泥岩/
m盖层累计
厚度/m盖地
比/%巴探5井 233 4/7 8/73 7/7 8/38 125 54 199 0 13/79 7/7 7/44 130 65 楚探1井 200 6/42 9/86 5/5 5/12 145 73 280 10/37 31/81 0 5/10 128 46 玛北1井 323 0 15/128 0 12/135 263 81 189 0 11/49 10/26 13/49 124 65 舒探1井 203 5/42 5/16 17/22 9/56 136 67 154 11/48 2/2 0 4/20 70 40 夏河1井 292 14/56 6/20 3/3 4/14 93 32 新和1井 279 0 0 0 15/59 59 21 140 0 0 0 0 0 0 玉龙6井 380 60/73 22/62 0 20/71 207 54 同1井 382 26/138 19/19 0 21/142 299 78 82 22/29 14/20 0 14/33 82 100 和田1井 590(录井) 累计厚度307 累计厚度15 322 55 和4井 332 5/16 19/150 0 6/48 214 64 300 0 33/120 0 13/13 133 44 方1井 505 累计厚度230 0 0 230 46 208 累计厚度110 0 0 110 53 塔参1井 155 5/13 0 0 4/7 20 13 69 12/23 0 0 2/2 25 36 康2井 320 3/5 14/119 0 12/80 204 64 150 13/37 14/69 0 3/10 116 76 中4井 352 0 15/48 0 40/58 106 30 125 16/27 0 0 5/16 43 35 巴东4井 279 25/45 30/97 0 10/21 163 58 149 12/58 19/59 0 9/23 140 94 中深1井 282 6/27 0 0 0 27 10 119 0 0 0 4/11 11 9 注:表中带“/”的数值意义为:单层最大厚度/累计厚度;空白为:未钻遇。 -
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