四川盆地志留系龙马溪组泥页岩吸水模拟实验及对孔隙连通性的指示意义

发布时间：2018-10-31 21:30

【摘要】：随着水平钻井和水压裂技术的应用和发展,页岩油、页岩气已成为可有效开发的非常规石油天然气资源,其资源潜力巨大,是未来重要的替代能源,但目前页岩油气开发系数很低,仅为5%-10%。富有机质泥页岩中微米一纳米级孔隙发育,为油气的保存和运移提供了空间和通道,因此,泥页岩孔隙连通性研究是提高页岩油气采收率的关键问题之一。本文采用岩石小柱体吸水实验方法,将岩石柱体置于恒定温度和湿度的条件下,通过称重获得岩石吸水量,并结合N2吸附法对孔隙结构和BET比表面积的测量,以及TOC和粘土矿物含量的分析等,研究了岩石在不同湿度条件下对水的吸收程度,以此来探讨孔隙连通性特征和影响泥页岩吸水的主控因素。初步研究结果表明：(1)泥岩的饱和吸水量与TOC、粘土矿物含量呈现很好的线性关系,吸水量随样品TOC和粘土矿物含量的增加而增大,说明TOC和粘土矿物含量是影响泥页岩吸水性的主控因素。(2)岩石饱和吸水量与其BET比表面积也呈现正相关性,同时吸水过程自发且可逆,岩石吸水过程为物理吸附,连通的孔隙增加了岩石的比表面积,为岩石吸水提供了场所。石柱地区龙马溪组泥页岩的饱和绝对吸水量与样品体积呈线性正相关,由斜率计算样品有效孔隙度为6.23%,柱体样品未经破碎,较N2吸附法测量孔隙度值(9.09%)更加接近真实值。(3)垂直层面方向钻取的柱体吸水结果与平行层面方向柱体相比,吸水趋势更接近一致,达到平衡吸水所需时间前者较后者长,同时,蜡封柱体(底面和周面蜡封,仅暴露顶面)吸水达平衡所需时间(360小时)远大于未蜡封样品(32小时),饱和吸水量相差较小,分别为9.28mg/g岩石、10.99mg/g岩石,表明泥页岩垂直层面方向渗透性较平行层面方向差,其差异性可通过蜡封柱体吸水实验进行量化。(4)泥页岩的吸水过程满足一级动力学方程,通过模型可以对地下岩石的吸水随时间的变化进行模拟和预测,从而为研究压裂液在岩石中的渗透、孔隙结构和矿物组成对页岩气后期开采的影响提供实验手段和研究新思路。
[Abstract]:With the application and development of horizontal drilling and water fracturing technology, shale oil and shale gas have become unconventional oil and gas resources that can be effectively exploited. But at present shale oil and gas development coefficient is very low, only 5-10. The development of micron-nanometer pores in organic shale provides space and channel for the preservation and migration of oil and gas. Therefore, the study of pore connectivity is one of the key problems to improve the oil and gas recovery of shale. In this paper, the water absorption of rock is obtained by weighing the rock column under constant temperature and humidity, and the pore structure and BET specific surface area are measured by N2 adsorption method. The water absorption degree of rock under different moisture conditions was studied by TOC and clay mineral analysis. The characteristics of pore connectivity and the main controlling factors affecting shale water absorption were discussed. The preliminary results show that: (1) the saturated water absorption of mudstone has a good linear relationship with the TOC, clay mineral content, and the water absorption increases with the increase of TOC and clay mineral content. It is concluded that TOC and clay mineral content are the main controlling factors affecting the water absorption of shale. (2) the saturated water absorption of rock is positively correlated with its BET specific surface area, and the water absorption process is spontaneous and reversible, and the water absorption process of rock is physical adsorption. The connected pores increase the specific surface area of the rock and provide a place for the rock to absorb water. The saturated absolute water absorption of the shale of Longmaxi formation in Shizhu area shows a linear positive correlation with the sample volume. The effective porosity of the sample calculated by slope is 6.23, and the column sample is not broken. Compared with the N _ 2 adsorption method, the measured porosity value (9.09%) is closer to the true value. (3) the water absorption trend of the drilled cylinder in the vertical plane is closer to the same as that of the parallel plane cylinder. At the same time, the water absorption time of the wax seal cylinder (bottom and circumference wax seal, only exposed top surface) is much longer than that of the unwaxed sample (32 hours), and the difference of saturated water absorption is small, and the water absorption time of the wax seal cylinder (bottom and circumferential surface wax seal, only exposed top surface) is much longer (360 hours) than that of unwaxed seal sample (32 hours). 9.28mg/g rock and 10.99mg/g rock show that the permeability of shale in vertical direction is worse than that in parallel plane. The difference can be quantified by wax seal column water absorption experiment. (4) the water absorption process of shale meets the first-order dynamic equation, and the model can be used to simulate and predict the water absorption of underground rock with time. Therefore, this paper provides experimental means and new ideas for studying the influence of fracturing fluid permeability, pore structure and mineral composition on shale gas production.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13

【相似文献】