重庆地区页岩气钻井井壁稳定主控因素研究

摘要/Abstract

摘要： 四川盆地及其周缘发育的大套海相页岩是当前中国页岩气开发的突破口之一。该区域页岩气钻井数据显示，在页岩中钻井经常会遇到井眼垮塌、钻具遇阻遇卡、井喷井漏等井壁失稳复杂情况，这些复杂情况是页岩气勘探开发，特别是水平井、丛式井钻井经常需要面对的挑战。重庆市位于四川盆地东部边缘，地跨扬子准地台和秦岭地槽褶皱系两大构造单元，地质构造复杂，地形地貌多样，在页岩气井钻探开发过程中，去除工程影响因素后，可以发现钻井复杂情况在一些区域内呈现出一定的规律性，即井壁失稳与该地区的地质构造、地应力场分布和岩石物理力学性质等有较大的相关性。根据重庆地区不同的沉积、构造演化史和地质条件将重庆市分为4个区域，综合各个区域页岩气藏的地质特征和储集特征，结合钻井数据和实验数据，分析各区域页岩储层段钻井井壁失稳的主要控制因素。研究显示，渝中渝西地区影响井壁稳定的主要因素是地层压力，渝东南地区钻井在避开天然断层后发生井壁失稳的风险较小，渝东北的两个区域受高陡地层和应力偏转的影响，易发生沿断层、节理弱面的剪切滑移破坏。

关键词: 重庆地区, 井壁稳定, 龙马溪组, 牛蹄塘组, 页岩气, 高压气藏

Abstract: The massive marine shales in the Sichuan Basin and its periphery are one of the key targets for shale gas development in China. According to the drilling data of this region, many complexities often occur during the drilling of shale gas wells to cause wellbore instabilities. Such complexities include borehole collapse, drillpipe blocking/sticking, blowout and lost circulation, which are great challenges for shale gas exploration and development, especially for drilling of horizontal wells and cluster wells. Chongqing area in the east margin of the Sichuan Basin extends across two tectonic units (i.e. the Yangtze paraplatform and the Qinling geosyncline fold system), with complicated geological structures and diverse topography. Regardless of the engineering factors, the complexities occurred during drilling of shale gas wells in this region are found with certain regularity, namely, the wellbore instabilities are closely attributable to geological structures, in-situ stress field distribution, and physical-mechanical properties of rocks, etc. Depending on sedimentary and tectonic evolution histories, and geological conditions, the Chongqing area is divided into four zones (I, II, III, and IV). Shale gas reservoirs in these zones are analyzed for the major factors controlling wellbore instabilities, with considerations to the geological and accumulation characteristics of the reservoirs, as well as the drilling and laboratory data. The results indicate that formation pressure is the major factor for wellbore stability in the central and western Chongqing areas, the risk of wellbore instability is lower in the southeastern Chongqing area if the drilling is conducted away from natural faults, and two zones in the northeastern Chongqing area are susceptible to shear sliding along faults, joints and weak planes as a result of high dip-angle formations and stress deflection.

Key words: Chongqing area, wellbore stability, Longmaxi Formation, Niutitang Formation, shale gas, high pressure gas reservoir

姜逸明, 张定宇, 李大华, 陈朝刚, 成俊, 邱以钢, 朱瑜. 重庆地区页岩气钻井井壁稳定主控因素研究[J]. 中国石油勘探, 2016, 21(5): 19-25.

Jiang Yiming, Zhang Dingyu, Li Dahua, Chen Chaogang, Cheng Jun, Qiu Yigang, Zhu Yu. Major factors for wellbore stabilities of shale gas wells in Chongqing area[J]. China Petroleum Exploration, 2016, 21(5): 19-25.

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