摘要
以钻井资料为基础,依据笔石生物地层、地球化学特征、岩石矿物组成、储集层微观特征、构造条件等数据,研究渝东北地区巫溪2井页岩气富集模式。巫溪2井上奥陶统五峰组—下志留统龙马溪组富有机质页岩厚达89.8 m,笔石带发育齐全,富有机质页岩段从奥陶系凯迪阶上部上延到下志留统特列奇阶下部,沉积厚度及时间远超四川盆地其他区域。页岩最高实测含气量超8 m3/t,含气性主要受TOC大小控制,有机质纳米孔为主要储集空间,无机矿物对储集空间的贡献较小;其中孔径大于50 nm的有机质孔隙较常见,小于10 nm的有机质孔为吸附气的主要赋存场所。巫溪2井目的层段处于挤压型背斜(田坝背斜)核部中性面以下,在脆性较强层段形成了2个垂向裂缝(劈理)发育带,利于页岩气的储集及后期压裂改造形成复杂缝网;田坝背斜两翼断层属挤压性断层,断层两侧为非渗透性的页岩,且预测断层面有泥岩涂抹现象,具有良好的封堵性,有利于页岩气的保存。上述诸多有利条件的良好匹配最终形成了研究区"构造型甜点"。
The shale gas enrichment pattern of Well Wuxi-2 in northeast Chongqing was studied, based on the data of the drilling, graptolite biostratigraphy, geochemistry, rock minerals, microscopic characteristics of reservoir beds and tectonic conditions, etc. The organic-rich shale of Upper Ordovician Wufeng Formation—Lower Silurian Longmaxi Formation is 89.8 m thick in Well WX-2. The graptolite biozonations are completely developed in this well, and the organic-rich shale intervals extend upward from the late Katian of the Ordovician to the early Telychian of the Lower Silurian. The deposition time of the organic-rich shale is far longer and the thickness is larger than those in other areas of the Sichuan Basin. The highest measured gas content exceeded 8 m3/t in Well WX-2, and the gas content is mainly controlled by TOC. The organic nano-pores are the main storage space, and the minerals contribute less to the storage space. The organic pores larger than 50 nm are well-developed and those less than 10 nm are the main reservoir space of adsorbed gas. The target intervals of Well WX-2 are located under the neutral surface of compressional Tianba anticline. Two vertical fracture（cleavage） development zones, which are beneficial for shale gas storage and complex fracture network formation during later fracturing, were formed in brittle layers of this organic-rich shale. Compressional faults existed in two limbs of the Tianba anticline, with non-permeable shale developing on both sides of fault planes and development of clay smear, which shows that the faults have good sealing properties, and are favorable for shale gas preservation. Thus the good match between the above various accumulation conditions forms the ＂tectonic sweet-spot＂ of shale gas in this study area.
出处
《石油勘探与开发》
SCIE
EI
CAS
CSCD
北大核心
2016年第3期350-358,共9页
Petroleum Exploration and Development
基金
国家重点基础研究发展计划(973)项目(2013CB228000)
国家科技重大专项(2011ZX05018)
关键词
巫溪2井
页岩气
笔石生物地层
有机质孔
构造型甜点
富集模式
Well WX-2
shale gas
graptolite biostratigraphy
organic pore
tectonic sweet-spot
enrichment pattern
