摘要:
文章通过对塔中北坡古隆1井与顺南1井奥陶系碳酸盐岩地层所取161个样品的碳同位素数据综合分析,依据中央隆起区奥陶系碳同位素对比标准,根据2口井的碳同位素变化特征,结合岩电与牙形石化石特征,对2口井奥陶系碳酸盐岩地层进行了准确识别与划分,进而总结了一间房组岩电特征。研究表明,一间房组组岩性为黑灰、灰色泥晶灰岩、砂屑泥晶灰岩与亮晶颗粒灰岩不等厚互层,电阻率曲线呈尖峰状高阻,自然电位曲线平直,自然伽马为小齿状低值且自下而上呈现增大趋势。继而,通过与古隆3井与顺南2井相应层位的岩电特征对比,对古隆3井与顺南2井进行了划分。进而通过连井对比探讨了塔中北坡古城墟隆起西部到顺托果勒低隆东部一间房组厚度变化情况。研究表明,顺托果勒低隆东部一间房组厚度明显大于古城墟隆起西部一间房组厚度,这种厚度差异应该是由一间房组沉积时期两个地区所处沉积环境不同所致。在此基础上,通过对古隆1井一间房组\恰尔巴克组界面上下牙形石动物群演变特征、过顺南1井地震剖面上T74界面上下地震反射终止关系研究,表明至少在塔中北坡古城墟隆起西部到顺托果勒低隆东部地区,靠近或接近塔中隆起的区域,T74界面应该为不整合界面,一间房组顶部地层明显遭受剥蚀。该地区除此之外的其余区域,T74界面应该为整合界面,也即一间房组与上覆恰尔巴克组之间为没有沉积间断的连续沉积。
Abstract:
161 carbon isotope samples of the Ordovician carbonate from well GL1 and SN1 were analyzed. According to the standard of the carbon isotope established for the Central Uplift Zone, the authors divided the Ordovician carbonate layer system according to the features of carbon isotope, lithology and conodont. Based on the summary of lithology and electric features, the authors divided well GL3 and SN2 through correlation of lithology and electric features. On such a basis, the authors further studied the thickness variation of Yijianfang Formation. The results show that the thickness of Yijianfang Formation in the east of the Shuntuogule Uplift is thicker than that of Yijianfang Formation in the Guchengxu Uplift, possibly because of the difference of the sedimentary environment. According to the evolution characteristics of conodont from the interface between the Yijianfang Formation and the Qrebake Formation in well GL1 and the seismic reflection termination of the T74 interface of well SN1, the authors have reached the conclusion that the T74 interface is a unconformity interface near the Tazhong Uplift, because the upper part of the Yijianfang Formation was subjected to obvious erosion. Nevertheless, the T74 interface should be a conformity interface in other areas. In other words, the strata between the Yijianfang Formation and the Qrebake Formation are continuous in other areas.
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