一种物性参数可控的人造长岩心制作技术与影响因素分析

Experimental Research on Artificial Long Core Technology with Predesigned Physical Parameters

在天然气水合物等非常规能源勘探过程中,获取不同地层和不同岩性的完整天然岩心不仅存在一定的技术难题,同时还需要较高的经济成本。因此,利用人造岩心模拟已知物性参数的原位地层来替代天然岩心已成为非常规能源领域内的一种研究趋势。针对现有人造岩心技术存在的长度较小、难以满足特殊实验需求,长岩心均匀压实较难以及对原位地层物性参数模拟的准确性不足等问题,研发了一种人造长岩心制作仪器与工艺。根据均匀性试验和正交试验等测试结果,得出一种可靠的均匀人造长岩心制作方法,提出了一种准确模拟目标地层物性参数的试验思路,同时从微观角度分析了多种因素对岩心物性参数的影响机理,并量化研究了多因素及交互作用对岩心渗透率的影响规律。研究结果表明,研发出的岩心制作仪器与工艺的可靠性与可重复性较高,所制岩心均匀密实。密度、渗透率和孔隙度随长度的变化均控制在3.3%以内,且可制作物性参数分段差异的岩心,既简单实用又成本低廉,而且,该人造岩心制作方法能准确模拟冻土区水合物地层的孔隙度和渗透率,孔隙尺寸空间分布也与天然岩心较为相近,仿真程度较高。

In the research of unconventional oil and gas drilling, gas hydrate exploitation and geotechnical investigation, natural core samples are all needed to be used in the related physical simulation test. However, due to the complex formations and different lithologies, there are still many technical difficulties and the costs are high to obtain natural and complete core samples. Therefore, as a replacement, the usage of artificial core samples with physical parameters close to in-situ natural cores has become a trend and has an important research value. This paper presents the design and manufacture of super long artificial core and instrument to solved the problems that the existing small size artificial cores are difficult to meet the needs of special experiments and that the long size cores are too hard for compaction as well as the insufficient simulating accuracy of artificial cores on natural formation parameters. After the uniformity experiments, orthogonal experiments and core compression tests, a reliable large size artificial core sample production technology was developed. Besides, the quantitative research about the effect of factors interaction on permeability was carried out during this process. At the same time, an idea of accurate simulating natural formation physical parameters was put forward, as well as analysis of the effect mechanism about main factors on physical parameters on a micro perspective. The results indicate that this long artificial core sample production method has high reliability, repeatability and high uniformed compaction. The value of core density, permeability and porosity are controlled within the range of 3.3 %. Besides, the artificial cores with different physical parameter sections can be made. What is more, this artificial core sample production method can accurately simulate permafrost hydrate formation permeability, porosity and mechanical strength with high matching degree, the pore size distribution is also similar to the natural cores.