致密油甜点的内涵、评价与优选——以酒泉盆地青西凹陷白垩系下沟组为例

Connotation,evaluation and optimization of tight oil sweet spots:A case study of Cretaceous Xiagou Formation in Qingxi Sag,Jiuquan Basin

致密油甜点是致密油勘探开发的核心领域。通过对酒泉盆地青西凹陷白垩系致密油储层的成藏富集规律研究,揭示了致密油甜点的内涵、评价与优选方法。研究结果表明:(1)致密油甜点是含油气盆地细粒沉积体系中整体低丰度含油背景下的相对高丰度含油区域(或层位),致密油甜点可分为物性甜点、油藏甜点、工程甜点、产能甜点和经济甜点等5类,其中物性甜点和油藏甜点合称为地质甜点。(2)控制致密油甜点的主要地质因素包括岩性组合特征、源储品质、源储组合类型和裂缝发育程度。(3)致密油甜点的评价与优选方法为优质源岩Ro定边界、源储组合定区带、四优(优源、优相、优缝、优配)匹配定甜点、多层联合定井轨迹,该套致密油甜点评价与优选方法对油气田高效勘探开发具有指导意义。

The tight oil sweet spot is a core area for tight oil exploration and development. Through the study on the accumulation and enrichment law of Cretaceous tight oil reservoirs in Qingxi Sag,Jiuquan Basin,the connotation,evaluation and optimization methods of tight oil sweet spots were revealed. The results show that:(1)Tight oil sweet spots are relatively high abundance oil-bearing areas(or strata)under the overall low abundance oil-bearing background in fine-grained sedimentary system of petroliferous basin. Tight oil sweet spots can be divided into five categories:physical sweet spot,reservoir sweet spot,engineering sweet spot,productivity sweet spot and economic sweet spot. Physical sweet spot and reservoir sweet spot are collectively referred to as geological sweet spot.(2)The main geological factors controlling tight oil sweet spots include lithology combination characteristics,source and reservoir quality,source reservoir assemblage and fracture development degree.(3)The evaluation and optimization methods of tight oil sweet spots are:high-quality source rocks and Rodetermining tight oil distribution,source-reservoir assemblage determining favorable tight oil zones,the matching of four excellent factors(high quality source rocks,high quality reservoirs,well-developed fractures and favorable matching of these factors in time and space)determining tight oil sweet spot,and multi-layer superimposition determining tight oil exploration and development well trajectory.