沁水盆地郑庄区块地应力发育特征及其地质意义

Characteristics and its geological implication of ground stress in Zhengzhuang Block of Qinshui Basin

为研究地应力对煤层气开发的影响,基于水压致裂地应力测量方法,结合煤层气井试井、测井和水力压裂三维微地震监测资料,研究了郑庄区块16井次21层目的层段原位地应力发育规律。结果表明:(1)地应力场为典型的构造应力场类型,浅部以逆断层和走滑断层应力机制组合类型为主,深部以正断层和走滑断层应力机制组合类型为主;(2)最大和最小水平主应力及垂向应力随埋深均呈线性增加趋势;(3)侧压系数位于Hoek-Brown包络线内,随埋深增加而降低且变化幅度逐步缩小;(4)最大水平主应力方位为NE-NEE向。一方面,现今地应力场方位与断裂构造产状的叠加影响了煤层气富集;另一方面,地应力增加导致渗透率呈指数式降低,而储层压力呈线性增加;2方面作用对煤层气高效开发产生了显著影响。

The in-situ ground stress distribution features of 21 target intervalsof 16 wells in Zhengzhuang Block were studied based on the hydraulic fracturing ground stress measuring methods combined with well test analysis,density log and 3D hydraulic fracturing seismic survey. The results showed that the current ground stress was typical tectonic stress field,the shallow region was mainly composed of combination type of thrust fault and strike-slip fault stress mechanism while the deep region was mainly composed of combination type of normal fault and strike-slip fault stress mechanism. The maximum and minimum horizontal principal stress and the vertical principal stress increased linearly as buried depth increased.The lateral pressure coefficient was located in the Hoek-Brown envelope curve and decreased with gradual diminishing variation range as buried depth increased. The orientation of maximum horizontal principal stress was NE-NEE.One side,the enrichment of coalbed methane was influenced by the superposition of current ground stress field and fracture structures. On the other hand,the increasing ground stress led to the exponential reduction of permeability and the linear increment of reservoir pressure.Both sides had significant impact on efficient coalbed methane exploration and development.