渤海海域沙垒田凸起西段花岗岩潜山优质储层形成控制因素及综合预测

Control factors and comprehensive prediction of granite buried hill reservoirs in western segment of Shaleitian bulge, Bohai Sea

为弄清低勘探程度区花岗岩潜山优质储层的分布特征,以地质模式为指导,利用刻画花岗岩风化壳效果明显的灰度能量属性,精细描述了渤海海域沙垒田凸起西段花岗岩优质储层的范围和厚度,综合分析构造活动、风化淋滤及古地温变化等因素对花岗岩储层的控制模式和分布特征的影响,探索了一套地质成因与地球物理相结合的预测方法。利用该方法对沙垒田凸起西段花岗岩潜山优质储层进行预测,研究结果表明:研究区花岗岩潜山长石等脆性矿物含量高,为优质储层的形成奠定了基础;断层两盘地层的错动引发诱导裂缝的发育,褶皱脊部的引张作用力促使高角度裂缝的发育,构造隆升引起的温压变化控制了近水平裂缝的发育;研究区西南缘为3类裂缝的叠加区,裂缝极为发育,且研究区西南缘长期接受风化淋滤作用,是花岗岩优质储层发育带。预测结果与实钻揭示的实际地质情况相符合,这说明地质成因与地球物理相结合研究方法能有效预测研究区优质储层的分布,为低勘探程度区花岗岩潜山优质储层预测提供参考。

To understand the distribution characteristics of less-explored granite buried hill reservoirs, based on the geological models and the effective grey energy to delineate weathering crust of granites, this paper describes the scope and thickness and analyzes the influences of tectonic activities, weathering leaching and paleogeothermal changes on the accumulation model and distribution of high quality granite reservoirs in the western segment of the Shaleitian bulge, the Bohai Sea. Finally, this paper proposes a reservoir prediction method combining geological genesis with geophysics. Application of this method in the study area shows that： 1） high content of brittle minerals, such as feldspar, in the granite buried hill, provides the foundation for the development of high quality reservoir; 2） the displacement of fault walls induced the development of induced fractures, the tensile force of folded ridges promoted the development of high-dip fractures, and the temperature and pressure changes caused by structural uplifting controlled the development of nearly horizontal fractures; and 3） in the southwest margin of the study area, superposition of fractures of three types brought extremely developed fractures, and this zone evolved into good granite reservoir zone after weathering leaching for a long time. The prediction results are consistent with the actual geological conditions revealed by field drilling data, indicating that the geological genesis-geophysics method can effectively predict the distribution of high quality reservoirs in the study area. This provides a reference for prediction of high quality reservoirs in granite buried hills in less explored area.