应用地层倾角测井资料研究古河流特征

STUDY ON THE CHARACTERISTICS OF PALAEOCURRENTS BY USING DIPMETER LOGGING DATA

鄂尔多斯盆地绥德－榆林地区石炭、二叠系砂岩体大多为点砂坝，通过本区仅有的３口井倾角测井资料的研究，提供了古河流特征参数。这些数据表明石盒子和山西期的河流类型为辫状河－曲流河；太原期为低弯度曲流河。砂体宽度３００－９００ｍ，平均４９６ｍ。经镇川堡气田试采验证，这种认识与客观实际相符。另外，本区地层倾角测井所得垂直于倾向的走向方向才是河流的古流向，为测井数据合理解释古流向提供了理论依据。

Carboniferous and Permian sand bodies in Erdos Basin are the chief reservoir for the exploration and ex,lloitation of natural gas. The present paper interprets the dipmeter logging data of three wells and uses them to study the characteristics of palaeocurrents. It is revealed by detailed study that the flow direction of palaeocurrents is not the dip-orientation of the gentle dipping sand bodies obtained from the dipmeter logging out perpendicular to it. This result has solved the problem of how to explain the flow direction of palaeocurrents according to the dipmeter logging data.Calculated results based on the parameters of palaeocurrents indicate that the rivers were braided-meandering ones during the Shihezi to Shanxi period, and were low-sinuosity meandering rivers during the Taiyuan period. The width of sand bodies ranges from 300 to 900m with an average value of 496m. All these are testified by practical sampling in the Zhenchuanbao gas field.This study provides reliable geologic basis for the exploration and exploitation of natural gas in sand bodi' s.