鄂尔多斯盆地奥陶系古岩溶发育程度的分形特征

摘要

Oil and gas exploration practice shows that the development degree of paleokarst has influence on reservoir quality.However,there is no means of quantitative description for such a feature.This paper analyzes the development degree of the Ordovician paleokarst in the Ordos basin based on its fractal features.First,the fractal features of paleokarst were studied.Then,fractal algorithm was analyzed and its operation flow was designed.Finally,the paleokarst development degree was quantitatively described by fractal dimension combined with the drilling data,and the relationship between fractal dimension and reservoir was analyzed.Results indicate that the development degree of Ordos paleokarst shows fractal features,which reflect the development degree of paleokarst under certain geological conditions,and the fractal dimension of industrial gas wells is greater than 1.65.Therefore,using fractal dimension to classify the development degrees of paleokarst can improve the objectivity and accuracy of reservoir evaluation in areas with paleokarst.%鄂尔多斯盆地奥陶系天然气勘探实践表明,古岩溶发育程度影响着储层优劣,然而对古岩溶发育程度的描述缺少定量化手段.本文利用分形理论对鄂尔多斯盆地奥陶系古岩溶的发育程度进行定量化研究,首先分析了古岩溶的分形特征,进而研究了分形维数的计算方法与实现流程,最后结合钻探资料利用分形维数对工区内古岩溶发育程度进行了定量化描述并分析了其与储层优劣的关系.结果表明,鄂尔多斯盆地奥陶系古岩溶的发育具有分形特征,分形维数反映了古岩溶在一定地质条件下的发育程度,工区内工业气流井的分形维数大于1.65.因此,将分形维数作为衡量古岩溶发育程度的定量指标,无疑会提高古岩溶储层评价的客观性、科学性.