摘要
裂缝发育程度与类型是影响致密砂岩储层能否获得油气高产稳产的重要因素。目前,鄂尔多斯盆地延长组致密砂岩储层勘探开发高度重视构造裂缝,而对层理缝的关注甚微。近期勘探开发实践表明,致密砂岩储层层理缝发育对油气富集具重要影响。综合利用野外露头观察、岩心描述分析与薄片观测,系统表征鄂尔多斯盆地延长组长7油层组致密砂岩储层层理缝特征,并分析其成因机理。结果显示:鄂尔多斯盆地延长组长7油层组致密砂岩储层层理缝多近水平或低角度发育,裂缝开度较小;横向上常断续分布,延伸不远;垂向上彼此独立,基本无联系,其发育分布具强非均质性,可被构造裂缝切割;岩心中发育的层理缝多存在油浸或油迹显示。分析认为:自晚燕山期,长7油层组致密砂岩储层内层理缝开始大规模形成,其发育分布受流体压力、构造应力以及溶蚀作用等多种地质因素综合控制。延长组长7油层组致密砂岩储层层理缝对鄂尔多斯盆地致密油勘探开发的地质意义主要体现在其储集效应,层理缝差异发育是造成鄂尔多斯盆地致密油非均质分布及影响单井产能的重要因素,其发育区可能是致密油勘探开发的"甜点区"。
The development degree and type of natural fractures are key to obtaining high and stable yield in tight sandstone reservoirs.Currently,tectonic fractures have been highlighted in exploration and development of tight sandstone reservoirs in the Yanchang Formation,Ordos Basin,whereas researches on bedding-parallel fractures are rarely seen.However,recent exploration and development practices indicate that bedding-parallel fractures widely developed in tight reservoirs have great effects on hydrocarbon accumulation.In this study,characteristics and genetic mechanism of bedding-parallel fractures in Chang 7 oil layer,Ordos Basin are intensively analyzed based on outcrop,core and thin section observation.The results indicate that the bedding-parallel fractures are commonly in low dip angles or sub-horizontal with small aperture.They are mostly discontinuous and short horizontally and isolated vertically,featuring strong heterogeneity in distribution,but can be cut by tectonic fractures.Oil immersion and stains are common within bedding-parallel fractures of drill cores.It is considered that the bedding-parallel fractures of high density in Chang 7 oil layer were generated in large scale since the Late Yanshanian Movement,and their distribution is jointly controlled by multiple geological factors,including fluid pressure,tectonic stress and dissolution.The accumulation effect of bedding-parallel fractures therein is of geological implication to tight oil exploration and development in the Ordos Basin.The differential development of bedding-parallel fractures is an important factor for the heterogeneity of tight oil distribution and large variability of single well productivity in the Ordos Basin.In all,regions of well-developed bedding-parallel fractures may be the“sweet spots”for tight oil exploration and development.
作者
鞠玮
尤源
冯胜斌
徐浩然
张晓丽
王胜宇
Ju Wei;You Yuan;Feng Shengbin;Xu Haoran;Zhang Xiaoli;Wang Shengyu(Key Laboratory of Coalbed Methane Resources&Reservoir Formation Process,Ministry of Education,Xuzhou,Jiangsu 221008,China;School of Resources and Geosciences,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China;Exploration and Development Research Institute of Changqing Oilfield Branch Company Ltd.,PetroChina,Xi’an,Shaanxi 710018,China)
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2020年第3期596-605,共10页
Oil & Gas Geology
基金
国家自然科学基金青年科学基金项目(41702130)
中国博士后科学基金特别资助项目(2017T100419)。
关键词
层理缝
长7油层组
致密砂岩储层
延长组
鄂尔多斯盆地
bedding-parallel fracture
Chang 7 oil layer
tight sandstone reservoir
Yanchang Formation
Ordos Basin
