Melut盆地G-H地区古近系层序地层及沉积体系研究

Paleogene sequence stratigraphy and sedimentary system in G-H Area, Melut Basin

 冉怀江 范乐元 胡圣利 孙传宗 戴婉薇 鲍闵慧子

 中国石油长城钻探工程有限公司解释研究中心，北京 100101

 Geosciences Center, Great Wall Drilling Company, CNPC, Beijing 100101, China

 Melut盆地是在中非剪切带右旋走滑构造应力场背景下发育起来的中—新生代陆内裂谷含油气盆地。文中在高分辨率层序地层学原理指导下，利用测井INPEFA旋回分析技术，建立了Melut盆地G￣H地区古近系主要目的层的层序地层格架。结合岩心、测井、录井等资料对其进行沉积体系展布特征研究，指出了研究区的有利储集相带，为该区下一步的油气勘探指明了方向。 研究表明：1）Melut盆地G￣H地区古近系A组、B组和 C组可划分出1个长期旋回（二级层序）和3个中期旋回（三级层序），目的层B组从上到下又可划分为SQ1，SQ2，SQ3及SQ4 4个短期旋回。2） 短期旋回SQ1主要发育干旱气候条件下的曲流河沉积，SQ2以三角洲沉积为主，SQ3和SQ4主要发育辫状河沉积。3）研究区A组的湖相泥岩与下部的B组砂岩可以形成有利的储盖组合，B组的有利储集砂体主要为水下分流河道、河口坝及曲流河道砂岩，研究区北部G井区和中部的H井区为有利的储集相带发育区。

 Melut Basin is an important hydrocarbon accumulation zone, which formed in Cenozoic-Mesozoic that has been related to the central African rift system. Taking the theory and method of high resolution sequence stratigraphy as the guideline, applying the technology of INPEFA logging cycle analysis, the sequence stratigraphic framework of G-H Area in Melut Basin is established. On the basis of the study of cores data, well logging, seismic profile, the characteristics of sedimentary sequence and favorable zones of the Paleogene in G-H Area of Melut Basin are studied, indicating the direction for further exploration in the area. The main results and achievement are as follows: There is a long-term base level cycle (second-order sequence) and three middle-term base level cycles from C to A Formation. The long-term base level cycle can be divided into 3 middle-term base level cycles (third-order sequence), and B Formation can be divided into 4 short-term base level cycles (fourth-order sequence). From top to bottom are SQ1, SQ2, SQ3 and SQ4; meandering river sedimentary systems under acrid climate mainly developed in SQ1, delta sedimentary systems mainly developed in SQ2, and braided river sedimentary systems mainly developed in SQ3 and SQ4; there is a favorable reservoir-cap combination of reservoir, A Formation is the seal, and B Formation is the favorable reservoir; the main reservoir sand bodies are underwater distributary channel and mouth bar sandstone of BⅣ, and meandering river channel sandstone of BⅢ. The favorable reservoir facies zones are mainly distributed in G well-block in the north of study area, and H well-block in the center of the study area.

10.6056/dkyqt201504012