四川盆地泸州区块深层页岩气地质力学研究及应用

doi:10.3969/j.issn.1672-7703.2023.05.006

摘要/Abstract

摘要： 四川盆地泸州区块志留系龙马溪组深层页岩气藏（3500～5000m）是中国页岩气开发的重要接替领域，储层岩石力学特性及地应力的变化导致开发过程中存在钻井周期长、单井产量差异大等难题。开展地质力学研究有助于深化对区块内地应力场的认识，为页岩气水平井的井位、钻井工程及压裂设计优化提供依据。基于声波测井、诊断性压裂注入测试（DFIT）、成像测井和实验室应力测量数据，利用Petrel软件构建了高精度地质力学模型，明确了区块储层地质力学特征，并探讨了地质力学成果在工程方面的应用。研究结果表明，泸州区块内随着沉积深度变大，杨氏模量逐渐增大，泊松比逐渐减小。龙马溪组储层为异常高压，孔隙压力梯度范围为16.7～21.7kPa/m。泸州区块应力机制以走滑型为主，上覆岩层压力梯度为25.5kPa/m，最小水平主应力梯度范围为18.8～24.5kPa/m，最大水平主应力与最小水平主应力之比的平均值为1.165，储层水平主应力随着杨氏模量和孔隙压力的增大而增大。利用地质力学研究成果，对井位设计、钻井工程中的钻井液密度优化、压裂设计中的分段分簇和施工参数优化进行了指导，Y65-X井实钻钻井液密度优化至1.85g/cm³，实现了造斜—水平段“一趟钻”完钻，钻井周期较邻井缩短67%；指导了Y2-X井精细分段分簇和压裂施工参数优化，测试日产量达到50.69×10⁴m³。研究认为，高精度的地质力学模型和成果可以有效为提高钻井作业效率、提高单井产量和效益开发服务。

关键词: 深层页岩气, 龙马溪组, 地质力学模型, 孔隙压力, 效益开发, 泸州区块

Abstract: The deep shale gas reservoir (3500-5000m) in the Silurian Longmaxi Formation in Luzhou block in Sichuan Basin is an important replacement field for shale gas development in China. However, the geomechanical properties of reservoir rock and variation in in-situ stress lead to difficulties in the development process, such as the long drilling cycle and large difference in gas rate of a single well. The geomechanical study enables to deepen the understanding of in-situ stress field in the block and provides basis for optimizing well location placement, drilling engineering and fracturing design of horizontal shale gas wells. The acoustic logging, diagnostic fracture injection testing (DFIT), imaging logging, and laboratory stress measurement data are combined to construct a high-precision geomechanical model in Petrel software, which supports to identify the reservoir geomechanical property in the study area, and the application of geomechanical study results in engineering is discussed. The results show that Young’s modulus gradually increases and Poisson’s ratio decreases with the increasing burial depth in Luzhou block. The shale reservoir in Longmaxi Formation is characterized by abnormally high pressure, with pore pressure gradient ranging in 16.7-21.7 kPa/m. The strike-slip type stress regime is dominant in Luzhou block, with an overlying rock pressure gradient of 25.5 kPa/m, a minimum horizontal principal stress gradient ranging in 18.8-24.5 kPa/m, and the average ratio of the maximum horizontal principal stress to the minimum horizontal principal stress of 1.165, and the reservoir horizontal principal stress increases with the increase of Young’s modulus and pore pressure. The geomechanical study results are used to guide the well location placement, optimization of drilling fluid density in drilling engineering, and optimization of fracturing stages and clusters and engineering parameters in fracturing design. For example, the drilling fluid density was optimized to 1.85 g/cm³ in Well Y65-X, achieving “one trip drilling” of the deviated-horizontal section and a 67% reduction in drilling cycle compared to adjacent wells; The fine fracturing stages and clusters and engineering parameters were optimized for Well Y2-X, and a gas flow rate of 50.69×10⁴m³/d was tested. The study concludes that the high-precision geomechanical model and achievements enable to effectively improve the drilling operation efficiency and gas flow rate of a single well, and serve for the benefit development.

中图分类号:

TE122.1

王元, 杨恒林, 黄浩勇, 付利, 陈刚, 张恒, 王子昕, 郭凯杰. 四川盆地泸州区块深层页岩气地质力学研究及应用[J]. 中国石油勘探, 2023, 28(5): 68-83.

Wang Yuan, Yang Henglin, Huang Haoyong, Fu Li, Chen Gang, Zhang Heng, Wang Zixin, Guo Kaijie. Geomechanical study of deep shale gas and application in Luzhou block, Sichuan Basin[J]. China Petroleum Exploration, 2023, 28(5): 68-83.

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