南川地区龙马溪组页岩气地应力场特征及对产量影响分析
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张培先(1983—),男,山东潍坊人,副研究员,硕士,从事页岩气勘探研究工作。E-mail:zhangpx.hdsj@sinopec.com。

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国家科技重大专项“彭水地区常压页岩气勘探开发示范工程”(2016ZX05061),中国石化科技部项目“华东探区天然气富集规律与目标评价”(P20059-6)。


Characteristics of in-situ stress field and its influence on shale gas production from Longmaxi Formation in Nanchuan area
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    摘要:

    南川地区处于四川盆地盆缘转换带的构造复杂区,龙马溪组以常压页岩气为主,具有较好的页岩气成藏富集条件,但地应力场复杂,单井产量差异较大,成为制约常压页岩气效益开发的关键因素之一。通过野外剖面测量、有限元应力场数值模拟、特殊成像测井分析及区域应力场研究,结合大量页岩气水平井压裂实践,认为:①燕山中期南川地区最大主应力在背斜区呈EW向,在南部单斜区呈NEE向;喜马拉雅期以来,现今水平地应力场在平面上具明显的分区特征,局部存在地应力方位和大小的转换带,纵向上受岩性影响地应力自上而下呈下降趋势,局部粉砂岩及观音桥段介壳灰岩地应力明显增大。②龙马溪组地应力主要受构造改造强度、构造样式、埋深、裂缝发育程度等影响,改造弱、埋深大、背斜核部或向斜核部、天然裂缝发育较少的地区地应力较高。③明确地应力场对页岩气井产量有重要影响,古地应力场控制天然裂缝发育程度,影响储层物性、含气性,现今地应力场影响人工裂缝的复杂程度。地应力适中、水平井轨迹与最小水平主应力夹角越小,越易改造并有利于形成复杂缝网,可提高单井产量,有效指导南川地区页岩气勘探开发。

    Abstract:

    Nanchuan area is located in a complex tectonic area in the basin-margin transition zone of Sichuan Basin,and its Longmaxi Formation dominated by normal-pressure shale gas is endowed with favorable shale gas accumulation and enrichment conditions.However,the complex in-situ stress field and the large difference in single-well production become the key factors restricting the profitable development of the normal-pressure shale gas. Field profile survey,numerical finite-element stress field simulation,and special imaging logging were conducted,and the regional stress field was investigated. Moreover,lots of practices in shale-gas horizontal well fracturing were reviewed. The following three conclusions were thereby obtained:①In the Mid-Yanshanian,the maximum principal stress was in the east-west(EW)direction in the anticline area and in the northeast-east(NEE)direction in the southern monoclinal zone in Nanchuan area;Since the Himalayan period,the current horizontal in-situ stress field has been characterized by marked planar zoning,with local transition zones of in-situ stress direction and magnitude. In the vertical direction,the insitu stress has descended with the increase in depth under the influence of lithology. The in-situ stress in local silty sandstone and that in the local shell limestone in Guanyinqiao Member have increased substantially. ②The in-situ stresses in Longmaxi Formation were mainly affected by the intensity of tectonic reworking,tectonic style,burial depth,and fracture development,and they were high in the weak tectonic reworking,the deep burial depth,the core of anticline or syncline,or the few natural fractures areas. ③The in-situ stress field has a great influence on the production of shale gas wells. Specifically,the paleo-stress field controlled the development of natural fractures and affected the physical properties and gas-bearing properties of reservoirs. In contrast,the current in-situ stress field influenced the complexity of artificial fractures. A smaller angle between the horizontal well trajectory and the minimum horizontal principal stress,on the premise of moderate in-situ stress,corresponds to easier stimulation,which is more beneficial for creating complex fracture networks and further improving single-well production. This research can effectively guide shale gas exploration and development in Nanchuan area.

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张培先,高全芳,何希鹏,高玉巧,刘明,何贵松,张志萍,周頔娜.南川地区龙马溪组页岩气地应力场特征及对产量影响分析[J].油气地质与采收率,2023,30(4):55~65

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  • 在线发布日期: 2023-08-02
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