中2井良里塔格组礁滩序列及台缘地质结构

中2井为塔中南坡上奥陶统良里塔格组第一口探井，基于岩心、岩石薄片和三维地震资料的礁滩组合序列建立及塔中南坡台缘地质结构的解析，对于探明该区地质特征、指导下一步勘探具有重要意义。中2井良里塔格组垂向上整体表现为7个中—高能粒屑滩与礁丘、灰泥丘，夹薄层滩间的沉积旋回，整体沉积能量较高；发育粒屑滩→灰泥丘→礁丘→粒屑滩（组合A），滩间→粒屑滩→灰泥丘→粒屑滩（组合B），滩间→粒屑滩→礁丘→粒屑滩（组合C），滩间→粒屑滩（组合D）4种典型的礁滩微相组合序列模式，以组合B和组合D为主。塔中南坡台缘地质结构与北坡东段相似，为一典型的沉积陡坡型台地边缘，但其台缘带更宽，为4~6 km，台缘内带礁滩相展布范围大；中2井位于台缘与前缘斜坡的相变部位，礁前或台缘上紧邻台缘斜坡的位置，单个礁/丘发育规模较小，造礁生物破碎较严重，礁（丘）滩相主体位于中2井靠台缘内带一侧，建议后期勘探应转向这一区域。

Reef Flat Sequence and Geological Structure of Platform Margin in Lianglitage Formation in Well Zhong-2, Tarim Basin

Well Zhong-2 is the first exploration well drilled into the upper Ordovician Lianglitage formation on the southern slope of Tazhong area. The establishment of reef-flat combination sequence and the analysis on geological structure of platform margin on the southern slope of Tazhong area based on the data of core, thin section and 3D seismic are of great significance to understand geological features in the area and to guide next exploration. There are 7 medium-high-energy sedimentary cycles of grain shoal, reef knoll, micrite mound and thin interbedded interbanks in Lianglitage formation of Well Zhong-2 vertically with high overall sedimentary energy. 4 typical reef-flat facies combinations are developed in the formation including combination A (grain shoal→micrite mound→reef knoll→grain shoal), combination B (interbank→grain shoal→micrite mound→grain shoal), combination C (interbank→grain shoal→reef knoll→grain shoal) and combination D (interbank→grain shoal), and combinations of B and D are dominant. The geological structure of platform margin on the southern slope of Tazhong area is a typical platform margin of sedimentary steep-slope type which is similar to that of the eastern section of the northern slope and has a broader marginal belt with the width of 4~6 km. The reef flat facies is widely distributed in the inner side of the platform marginal belt. Well Zhong-2 is located at the transitional position from platform margin facies to foreslope facies. The size of a single reef/mount is relatively small and serious crush occurs to reef-building organism in the reef front or the area adjacent to the slope of the platform margin. The main part of reef flat facies is located in the area next to the inner side of the platform marginal belt in the well. It is suggested that the later exploration should revolve around these zones