Distinct sedimentary environments and their influences on carbonate reservoir evolution of the Lianglitag Formation in the Tarim Basin, Northwest China
Distinct sedimentary environments and their influences on carbonate reservoir evolution of the Lianglitag Formation in the Tarim Basin, Northwest China
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DOI：
10.1007/s11430-012-4457-5
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发表时间：
2012-07
期刊：
影响因子：
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通讯作者：
Jiaqing Liu;Zhong Li;JunCou Huang;Liu Yang
中科院分区：
文献类型：
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作者：
Jiaqing Liu;Zhong Li;JunCou Huang;Liu Yang
上奥陶统良里塔组碳酸盐岩是中国西北部塔里木盆地重要的油气储集层，不同油田储集性明显不同。以塔河油田和塔中油田为例，通过生物地层等时格架、岩心、薄片、测井、锶同位素等方面的综合分析，进行了碳酸盐岩储层对比。研究表明，这两个地区在梁里塔组沉积阶段分别属于不同的碳酸盐台地。对于两里塔格组，塔中可以划分出5个四级层序，而塔河地区仅保存了4个与塔中发现的下部层序相对应的四级层序。塔河梁里塔组碳酸盐岩台地以缓坡和/或弱边缘类型为特征，沉积速率低(37μm/a)，全岩碎屑含量高，碳酸盐基质的87Sr/86Sr同位素比值高，显示出较深的水环境和明显的陆源碳酸盐沉积输入。塔中发育强边缘碳酸盐岩台地，沉积速率高达2 5 0μm/a，全岩碎屑含量少，为高能沉积环境。由于上述沉积环境的差异，塔河地区碳酸盐岩发育较少的高能相，但同沉积(早成岩)海水胶结作用较强，塔中碳酸盐岩普遍发育高能礁滩相，出露频繁，同沉积海水胶结作用较弱。因此，塔河梁里塔组碳酸盐岩中的原生孔隙较少，而塔中(1号断裂带)同一岩石地层单元中保存的原生孔隙较多。可利用的高能礁滩相和早期成岩作用，保存了较多的原生孔隙，为塔中地区主要发育的梁里塔组碳酸盐岩储层提供了重要的物质基础。
The Upper Ordovician Lianglitag Formation carbonate rocks are important oil and gas reservoirs in the Tarim Basin, Northwest China, with obviously distinct reservoir properties among different oilfields. As a case area of the above carbonate reservoirs correlation, Tahe and Tazhong oilfields are chosen for the study through an integrated analysis of biostratigraphic isochronous framework, cores, thin sections, logs, and strontium isotopes. The research shows that the two areas were respectively attributed to different carbonate platforms during the Lianglitag Formation depositional phase. For the Lianglitag Formation, five fourth-order sequences may be divided in Tazhong, whereas only four fourth-order sequences are preserved in Tahe that correspond to the lower ones observed in Tazhong. The Lianglitag Formation carbonate platform in Tahe was characterized by ramp and/or weak rimmed types, with low depositional rates (37 μm/a), higher whole-rock clastic contents, and higher87Sr/86Sr isotope ratios of carbonate matrix, showing relatively deep-water environment and evident terrigenous input for carbonate deposition. However, a strongly rimmed carbonate platform was developed in Tazhong, with high depositional rates of 250 μm/a and less whole-rock clastic contents, indicating a high-energy depositional environment. Because of the sedimentary environment differences mentioned above, less high-energy facies but relatively intense syndepositional (early diagenetic) sea-water cementation of carbonates were developed in Tahe, and ubiquitous high-energy reef and shoal facies, with a frequent exposure to subaerial, and weak syndepositional sea-water cementation of carbonates in Tazhong. Therefore, fewer primary pores occurred in the Lianglitag Formation carbonate rocks of Tahe, whereas more primary pores were preserved in the same lithostratigraphic unit of the Tazhong (No. 1 fault zone). Available high-energy reef-shoal facies and early diagenesis, with more primary pores preserved, provided a key material basis for the Lianglitag Formation carbonate reservoirs that largely occurred in Tazhong.