塔中地区鹰山组岩溶储层表征与古地貌识别——基于电成像测井的解析

针对塔中地区鹰山组顶部风化壳的储层特征,以成像测井为手段,研究了岩溶古地貌表征和识别方法。利用成像测井进行单井岩溶要素表征,可精细识别的要素包括:基岩、古土壤层、裂缝、溶孔以及洞穴等;对岩溶要素进行二维和三维空间配套,综合划分了古土壤层、垂直淋滤带、水平潜流带等结构单元;根据现代岩溶发育知识,以岩溶带划分结果为依据,刻画和解释了古地貌。研究结果表明:研究区内鹰山组顶部发育岩溶高地、岩溶斜坡和岩溶洼地3种地貌单元,整体表现为由sw向NE渐低的古地貌形态,其中十号带的西部单元为高地,垂直淋滤带发育;十号带与一号带之间为斜坡,水平潜流带发育;一号带为洼地,岩溶不发育。基于以上认识构建了塔中地区鹰山组顶部风化壳储层地质模型,进一步研究表明,绝大多数油气井位于岩溶高地及其周边的岩溶斜坡带,水井多位于远离高地的东部斜坡带或洼地,这表明塔中地区鹰山组顶部岩溶古地貌对成藏具有明显的控制作用。

Paleotopographic characterization and reconstruction of karst reservoirs in Yingshan Formation,Tazhong area,Tarim Basin：a research based on borehole image log interpretation

This study characterizes and reconstructs the paleotopography of karst reservoirs in weathering crust at the top of Yingshan Formation in Tazhong area, Tarim Basin, China. characterization and identification methods of karst ancient landform are establi shed. Single-well karst elements are characterized by image logging, and elements that can be finely identified include bedrock,paleosol layer, fractures, dissolution pores, and caves. The above elements are assorted into the two-and three-dimensional spaces and then divided into structural units such as paleosol layer, vertical vadose zone, and horizontal phreatic zone. The paleokarst topography is described and interpreted according to division of karst belts on the basis of modern karstology. In Tazhong area, paleokarst at the top of Yingshan Formation has developed three topographic units, including highland (karst belt No.10, with development of vertical vadose zone), slope (between karst belts No.10 and No.1, with development of horizontal phreatic zone), and depression (karst belt No.1, with poor development of karst reservoir); overall, the paleokarst topography shows a gradually descending tendency from southwest to northeast. Further, a geological model is established for karst reservoirs in weathering curst at the top of Yingshan Formation. The modelling results show that most oil and gas wells are mainly distributed at or around the karst highland, while water wells are mainly located on the eastern slope or the karst depression distant from the karst highland. This finding indicates that paleokarst topography at the top of Yingshan Formation plays a strong role in controlling hydrocarbon accumulation in the adjacent area.