基于古—今应力场耦合的变质岩潜山有效裂缝储层预测——以渤海湾盆地渤中19-6气田为例

Prediction of effective fractured reservoirs in metamorphic buried hills based on paleo-present stress field coupling: a case study of Bozhong 19-6 Gas Field, Bohai Bay Basin

  • 摘要: 渤海湾盆地渤中19-6气田太古界变质岩潜山埋藏深,裂缝储层形成机理及分布规律复杂,有效裂缝储层研究及预测方法尚属空白,严重制约了该气田的高效开发。基于地震、岩心、测井等资料,通过多期次古构造应力场分析, 明确了储层裂缝发育机制和分布特征,利用有限元法模拟了研究区现今应力分布特征,最终建立了基于古—今应力场耦合的潜山有效裂缝储层预测方法。研究表明:(1)研究区裂缝发育受多期构造运动控制,印支—燕山期挤压作用形成初始裂缝,喜马拉雅期拉张和走滑作用对早期裂缝进行了活化与改造;(2)从构造成因上研究区可划分为西部挤压带和东部走滑带,其中挤压带核部及走滑带是裂缝发育的优势区域;(3)现今应力场特征显示,研究区现今水平最大主应力方向总体为NEE75°—SEE105°,受区域右旋走滑断层影响,自西向东现今水平最大主应力出现SEE—E—NEE向变化;(4)基于古—今应力场耦合预测,将有效裂缝储层划分为三类,即Ⅰ类区分布于挤压带核部及走滑带附近,有效裂缝储层最发育;Ⅱ类区位于井区东部的高部位靠近走滑带附近;Ⅲ类区位于构造较低部位,有效裂缝储层发育较差。

     

    Abstract: The Archean metamorphic buried-hill reservoirs in Bozhong 19-6 Gas Field, Bohai Bay Basin are deeply buried, with complex fracture formation mechanisms and distribution patterns. Research and prediction methods for effective fractured reservoirs are still lacking, seriously restricting the efficient development of this gas field. Based on seismic, core, well logging, and other data, fracture development mechanisms and distribution characteristics of reservoirs were clarified through multi-stage paleo-tectonic stress field analysis. The current stress distribution characteristics in the study area were simulated using the finite element method. Finally, a prediction method for effective buried-hill fractured reservoirs was established based on the coupling of paleo-present stress fields. The results showed that: (1) Fracture development in the study area was controlled by multi-stage tectonic movements. Indosinian-Yanshanian compression formed the initial fractures, and Himalayan extension and strike-slip movements reactivated and modified the early fractures. (2) Structurally, the study area could be divided into western compression and eastern strike-slip zones, with the core of the compression zone and the strike-slip zone being favorable areas for fracture development. (3) The current stress field characteristics showed that current maximum horizontal principal stress direction in the study area was generally NEE75°-SEE105°. Influenced by regional dextral strike-slip faults, the current maximum horizontal principal stress direction showed a SEE-E-NEE directional change from west to east. (4) Based on the prediction using paleo-present stress field coupling, effective fractured reservoirs were classified into three categories. Class Ⅰ area, distributed near the core of the compression zone and the strike-slip zone, showed the most developed effective fractured reservoirs. Class Ⅱ area was located in high positions of eastern well area near the strike-slip zone. Class Ⅲ area, situated in structurally lower positions, exhibited relatively poor development of effective fractured reservoirs.

     

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