威远地区页岩气开发对环境影响的地质因素

发布时间：2017-12-28 00:13

本文关键词：威远地区页岩气开发对环境影响的地质因素　出处：《西南石油大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着国内页岩气的大规模开发,钻井数量的增加,钻井与压裂过程中出现环境污染问题日益严重,受到各方高度关注。本文利用威远地区水文、页岩地质资料及页岩气钻井现场跟踪分析,结合矿物岩石学、储层地质学等相关理论知识,对威远地区页岩气钻井过程中污染环境的地质因素进行了分析与探究。通过收集威远地区水文地质资料及对页岩气开发污染现场水质检测分析,认为在页岩气开发井区内存在钻井液和压裂液污染环境的问题。其次,通过现场收集和分析钻井过程中钻井液漏失的主要层位在须家河组、茅口组、栖霞组以及嘉陵江组,根据随钻数据、测井图像、岩心薄片等数据分析认为威远地区须家河组、嘉陵江组以及栖霞-茅口组地层构造缝、溶蚀缝发育,钻井过程中易造成钻井液的漏失,并结合公式计算对其进行了验证。通过数据分析和样品实验可知威远地区页岩分布广泛,厚度较大,TOC含量普遍超过2mg/g,脆性指数在30%-60%,易于压裂形成大规模网缝。建立页岩脆性指数、杨氏模量及泊松比与压力宽度值预测模型,通过3种神经网络算法算法,在MATLAB R2013B中编程确定压裂宽度与脆性指数、杨氏模量及泊松比的关系的网络算法。由预测结果显示,RBF神经网络算法模型预测精度较高。根据压裂规模表明,页岩脆性指数高,微裂缝发育等,使得压裂规模较大,形成的网缝穿透上覆地层,由实验可知在低粘度压裂液和上覆高孔隙度地层等因素下,压裂液更容易出现渗流和运移。井区内发育的断层可成为压裂液运移和渗流至浅表地层的通道,造成环境污染,现场对水质的分析和压裂微地震监测可知,形成的网缝与断层连通可导致压裂液通过裂缝和断层运移和渗流。基于断层的压裂液运移数值模拟分析了在断层存在的情况下,压裂液渗漏点越靠近断层,压裂液的渗流扩散越明显。
[Abstract]:With the large-scale development of shale gas and the increase of drilling numbers, the problem of environmental pollution during drilling and fracturing is becoming more and more serious. Based on the hydrologic and shale geological data and the field analysis of shale gas drilling in Weiyuan area, combined with mineral and petrology and reservoir geology, the geological factors of shale gas drilling process in Weiyuan area are analyzed and explored. By collecting the hydrogeological data of Weiyuan area and analyzing the water quality of shale gas development, it is considered that there is a problem of drilling fluid and fracturing fluid polluting the environment in shale gas development well area. Secondly, through the collection and analysis of drilling fluid leakage in the main stratum of Xujiahe Formation and Maokou group, Qixia group and Jialingjiang group, according to the drilling data, logging data, core slice image analysis that Weiyuan Xujiahe group, Jialingjiang group and Qixia Maokou group stratigraphic structural fractures and dissolved fractures, the leakage of drilling fluid caused by the drilling process, and combined with the formula to verify. Through data analysis and sample experiments, we can see that shale in Weiyuan area is widely distributed, with large thickness, TOC content is generally more than 2mg/g, and the brittleness index is 30%-60%, which is easy to form large scale mesh joints. A prediction model of shale brittleness index, Young's modulus and Poisson's ratio and pressure width value is established. 3 neural network algorithm is applied to determine the relationship between fracture width and brittleness index, Young's modulus and Poisson's ratio in MATLAB R2013B programming. The prediction results show that the prediction accuracy of the RBF neural network algorithm model is high. According to the scale of fracturing, it shows that the high fragility index of shale and the development of microfracture make the fracture scale larger and the network seams penetrate the overlying strata. The experiment shows that fracturing fluid is more prone to seepage and migration under the factors of low viscosity fracturing fluid and overlying high porosity formation. The fault developed in the well area can become a channel for fracturing fluid migration and seepage to shallow strata, resulting in environmental pollution. The on-site water quality analysis and fracturing microseismic monitoring show that the formation of network gap and fault connectivity can lead to fracturing fluid migration and seepage through fractures and faults. The numerical simulation of fracture fluid migration based on fault shows that the seepage point of the fracturing fluid is closer to the fault when the fault exists, the more obvious the seepage diffusion of the fracturing fluid is.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X741

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