Abstract:

To address the challenges of poor sorting, strong heterogeneity, and unclear overburden pressure-dependent variations in porosity and permeability in glutenite reservoirs, where existing conventional sandstone correction methods are inadequate, this study investigates the Paleogene Kongdian Formation glutenite reservoirs (burial depth: 3800~4100 m) in the BZ area. Using overburden pressure porosity-permeability experiments and rock mechanics test data from 13 core plugs covering the main porosity-permeability range, we reveal the unique variation patterns and establish a targeted correction model. The results show that this is a low-porosity, ultra-low-permeability reservoir, with matrix porosity of 5%~15% and permeability of 0.1~6 mD under ambient conditions. The pore space is dominated by intergranular and intragranular dissolution pores, with occasional microfractures, indicating significant heterogeneity. Unlike conventional sandstone reservoirs, the porosity and permeability of these glutenite reservoirs decrease following a power-law function with increasing overburden pressure. The decline gradient varies with the initial porosity and permeability at ambient pressure. Thus, the overburden pressure-dependent porosity/permeability is a bivariate function of the overburden pressure and its initial value at ambient conditions. By fitting the experimental data, we derived the quantitative relationship between the power-law coefficients and the ambient-pressure porosity/permeability, constructing a triaxial overburden pressure correction model. Incorporating rock mechanics data, a uniaxial overburden pressure bivariate correction model for in-situ conditions was also established. Accuracy verification shows that the triaxial model achieves an MSE of 0.369% for porosity and 0.281 mD for permeability. Compared to the traditional univariate model, accuracy improves by 67% and 43%, respectively, providing reliable characterization across both high and low porosity-permeability ranges. The proposed bivariate correction method fills a gap in overburden pressure porosity-permeability correction for glutenite reservoirs and solves the problem that traditional methods cannot adequately account for their strong heterogeneity. This method provides an essential correction tool for accurate reserve evaluation and productivity prediction, and offers a theoretical basis for designing efficient development strategies.

Key words: glutenite formation, porosity, permeability, overlying pressure correction

摘要：

针对砂砾岩储层分选差、非均质性强，孔、渗覆压变化规律认识不清，现有常规砂岩校正方法难以适用的问题，本文以BZ地区3800~4100 m埋深的古近系孔店组砂砾岩储层为研究对象，基于13块覆盖主要孔渗分布范围的柱塞岩心覆压孔渗实验及岩石力学测试数据，揭示了砂砾岩储层覆压孔渗特殊变化规律并建立针对性校正模型。研究表明，该储层为低孔特低渗型，基质常温常压孔隙度5%~15%、渗透率0.1~6.0 mD，孔隙空间以粒间－粒内溶孔为主，并伴有微裂隙，非均质性显著；与常规砂岩储层不同，砂砾岩储层孔渗随覆压呈幂函数递减、且不同常压孔渗大小的变化梯度不同，孔渗覆压变化是上覆压力和常压孔渗大小的二元函数。基于实验数据拟合得到幂函数系数与常压孔渗的量化关系，构建三轴覆压孔渗校正模型，结合岩石力学实验数据建立了地层条件下的单轴覆压孔渗二元校正模型。精度验证显示，三轴覆压孔隙度校正计算均方误差0.369%，渗透率0.281 mD，较传统一元模型精度分别提升67%和43%，在孔渗高低值区均能精准表征覆压变化规律。本文建立的二元校正方法突破了传统单变量模型局限，能够有效适配砂砾岩强非均质性，为同类储层储量评价、产能预测提供了重要的校正方法，为合理制定高效开发方案提供了规律认识。

关键词: 砂砾岩储层, 孔隙度, 渗透率, 覆压校正

CLC Number: 

• P618.13

• TE135