平凉北延长组长8段油层地质工程一体化评价

Evaluation method of geology-engineering integration for the 8th Member of Yanchang Formation in northern Pingliang

平凉北处于天环坳陷与西缘冲断带两大构造单元结合部,其地层、构造、烃源岩、成藏控制因素等较盆地内部更加复杂。主力目的层延长组长8段储集层总体具有厚度大、物性较好的特点。由于勘探早期对油层的认识不够充分,改造工艺的选择和规模难以准确把握,导致油层经改造后,或单井产液量较低,或单井油产量较低而水产量较高,制约了勘探成效。按照地质工程一体化思路,通过开展长8段油藏的构造解剖、饱和烃色谱分析、试油及投产数据分析,综合油层结构、含油水饱和度、油层物性、地面原油物性等分析,并考虑试油方案和工艺的合理性,对油层进行综合评价分类。结果表明生储圈配置和油气在系列古构造圈闭内的差异聚集控制了油、水的原生空间分布,自晚侏罗世末成藏开始经历了多次构造反转,导致油气调整、再聚集和油气显示普遍,引起局部生物降解并使流体性质进一步复杂化。油藏受古今构造共同控制,古构造控制油藏大致范围,今构造严格限定了油藏的发育部位。延长组长8段油层可分为2大类5小类。地质工程一体化有助于实现复杂油水层的准确判识和油层的精细评价,弥补常规测录井手段难以精细评价油层的不足,从而为差异化油层改造方案的制定提供了依据,提高了油层改造方案的针对性。

Located at the junction of two major structural units,Tianhuan Depression and western margin thrust belt,Northern Pingliang has more complex stratigraphy,structure,source rocks,and control factors of hydrocarbon accumulation than those inside the basin.The reservoir of the 8th Member of Yanchang Formation,the main target formation,is of large thickness and good physical properties.The insufficient understanding of reservoirs in the early stage of exploration and difficulties in accurate selection and scale of reformation techniques bring about low fluid production of a single well or low oil production but high water production of a single well after oil formation improvement,which restricts the effectiveness of exploration.According to the idea of geology-engineering integration,through analyses of the construction of the 8th Member of Yanchang Formation,saturated hydrocarbon chromatography,formation test and production data,combined with formation structure,oil-water saturation,formation physical properties and ground crude oil physical properties,and considering the rationality of oil test scheme and processes,oil layers are comprehensively evaluated and classified.Results show that differential accumulation of source-reserve cycle in serial paleotectonics controls the primary oil-water spatial distribution.The multiple structural reversals since late Jurassic accumulation cause general oil-gas adjustment,re-accumulation and oil-gas shows,causing local biodegradation and further complicating fluid properties.The reservoir is jointly controlled by ancient structure,controlling reservoir general scope,and current structures,limiting reservoir location.The 8th Member of Yanchang Formation reservoir can be divided into two categories and 5 subclasses.Geology-engineering integration conduces to accurate identification of complex oil-water layers and fine evaluation of oil layers which is hard with conventional logging means,providing a basis for differential modification schemes of oil layer,and improving the pertinence of them.