基于原油黏度的浅层超重油储层非均质性定量表征方法

Quantitative characterization of heterogeneity of shallow super heavyoil reservoirs based on crude oil viscosity

超重油油藏具有埋藏浅,高孔、高渗,岩石结构复杂,原油黏度大,层内、层间差异明显,非均质强等特点,储层刻画难度大,导致井位部署不合理,采收率低。采用传统单一因素表征储层非均质性的方法,难以取得较好的预测效果。针对委内瑞拉奥里诺科重油带X区块超重油储层特点,首次将原油黏度参数引入到储层非均质定量评价当中,将储层岩石的非均质性和流体的非均质性相结合,基于熵权法计算储层非均质综合指数,为储层非均质的定量评价提供了一种新思路。通过对大量超重油油样核磁共振与黏度实验测量结果进行分析,建立了原油黏度与校正T_(2)(横向弛豫时间)几何平均值的关系,从而产生连续、精确的黏度曲线;进而分析了原油黏度的变化规律以及对剩余油分布的影响,揭示了流体的非均质性(特别是黏度的非均质性)对剩余油的分布具有明显的控制作用。研究结果表明,该方法对超重油储层非均质性定量评价精度有明显改进,为剩余油分布预测及水平井井网部署提供了可靠的理论和方法依据。

Characterized by shallow burial depth,high porosity,high permeability,complicated rock structure,large viscosity of crude oil,obvious differences between intra-layers and inter-layers,strong heterogeneity,etc.,super heavy oil reservoirs are difficult to be depicted,leading to unreasonable well placement and low recovery ratio.It is difficult to obtain better prediction results by using traditional single factor to characterize reservoir heterogeneity.With respect to the characteristics of super heavy oil reservoirs in X Block of the Orinoco heavy oil belt in Venezuela,crude oil viscosity parameters were introduced into the quantitative evaluation of reservoir heterogeneity for the first time by combining the heterogeneity of reservoir rocks with the heterogeneity of fluids and calculating the comprehensive index of reservoir heterogeneity based on entropy weight method to provide a new idea for quantitative evaluation of reservoir heterogeneity.By analyzing the results of NMR and viscosity experimental measurements of amounts of super heavy oil samples,relationship between the viscosity of crude oil and the corrected T_(2)geometric mean value(transverse relaxation time)was established,so as to generate continuous and mathematical viscosity curves.Furthermore,the variation of crude oil viscosity and its influence on the distribution of remaining oil were also analyzed,which reveals that the heterogeneity of fluid,especially the heterogeneity of viscosity has a significant control over the distribution of remaining oil.The results show that this method can significantly improve the accuracy of quantitative evaluation for super heavy oil reservoir heterogeneity,and thus provide a reliable theoretical and methodological evidence for remaining oil distribution prediction and horizontal well pattern deployment.