鄂尔多斯盆地Y区块长6致密油层裂缝特征

Fracture Characteristics of Chang 6 Tight Oil Reservoir in Block Y in Ordos Basin

长6致密油层是鄂尔多斯盆地Y区块的主力产层,裂缝发育。目前单井产能低,水淹和水窜现象严重,部分水井注水困难,严重影响了开发效果。为了解决影响开发效果较为严重的裂缝问题,本文通过野外露头和岩心宏观、微观观察,注水指示曲线和压力降落试井资料分析,应力测定,停泵压力梯度与上覆应力梯度关系研究,结合沉积环境,对天然裂缝、人工裂缝发育特征,人工裂缝影响因素,天然裂缝对人工裂缝性质的影响、人工裂缝形态及分布规律等方面进行研究。结果表明:研究区长6油层宏观裂缝主要是以垂直缝为主的区域性构造裂缝,微裂缝主要是以水平缝为主的成岩缝;人工裂缝主要受控于天然裂缝,天然裂缝主要受控于砂体厚度与泥质体积分数,砂体厚度越薄越易形成天然裂缝,泥质体积分数越高越易形成变形构造。

Chang 6is the main producing layer of Y block in Ordos basin,and cracks are developed.At present,the productivity of single well is low,water flooding and water channeling are serious,and some wells are seriously affected.In order to solve the fracture problem,the authors studied the development characteristics of natural fractures and artificial fractures,the influencing factors of artificial fractures,and the influencing factors of natural fractures on artificial fractures through the macroscopic and microcosmic observation of outcrops and cores in the field,the analysis of water injection indication curve,the analysis of pressure drop test data,the measurement of stress,and the analysis of the relationship between the pressure gradient of pump stop and the overlying stress gradient.Combined with the sedimentary environment,the influence of artificial fracture properties,artificial fracture form,and distribution law were studied.The results show that the macro-fractures of Chang 6 oil reservoir are mainly vertical regional structures,while the micro-fractures are mainly horizontal diagenetic fractures.The artificial fractures are mainly controlled by natural fractures,and the natural fractures are mainly controlled by the thickness and shale content of sand body.The thinner the sand body is,the easier the natural fracture is to form,the higher the shale content is,the easier the deformation structure is to form.