摘要
为了深入了解湘西北下寒武统牛蹄塘组的页岩气资源潜力,需对该地区牛蹄塘组中下部硅质页岩和碳质页岩层段进行可压裂性评价。通过室内实验等手段分析了影响页岩可压裂性的4类关键物理和力学因素。结果显示:牛蹄塘组中下部硅质页岩的脆性矿物平均含量(51.58%)高于碳质页岩(40.55%),而其黏土矿物平均含量(14.13%)低于碳质页岩(24.49%);硅质页岩的脆性系数(基于泊松比和弹性模量)比碳质页岩高34%;硅质页岩的内摩擦角较大,碳质页岩的黏聚力较小;碳质页岩的孔隙度(平均3.67%)较大,但硅质页岩充填性天然裂缝发育程度较高。结合影响因素分析和前人经验,构建了涉及6项指标的页岩可压裂性评价体系。分别求得硅质页岩、碳质页岩和北美Barnett页岩的可压裂系数为0.59、0.29、0.62~0.64。从可压裂系数可以看出,湘西北牛蹄塘组中下部硅质页岩层段的压裂预期效果与北美Barnett页岩相当,且高出碳质页岩1倍,具有较高的开发潜力。
In order to thoroughly understand the resource potential of shale gas in the Lower Cambrian Niutitang Formation of northwestern Hunan, fracability evaluation was conducted for siliceous and carbonaceous shales from the middlelower part of the Niutitang Formation. Four sets of key physical and mechanical parameters affecting the fracability of the shales were then analyzed experimentally. The results show that the average content of brittle minerals in siliceous shale （51. 58%） is higher than that in carbonaceous shale （40. 55%） while the average content of clay minerals （14. 13 %） is lower than that in carbonaceous shale （24.49 %）. And the brittleness coefficient of siliceous shale （based on Poisson＇s ratio and elastic modulus） is 34% higher than that of carbonaceous shale; Whereas the internal friction angle of siliceous shale is larger and the cohesive strength of carbonaceous shale is smaller; Furthermore, the results show that the porosity of carbonaceous shale （average 3.67 %） is larger, while intrinsic fracture filling for siliceous shale is abundant. In view of the above results, evaluation system of fracability with six indicators has been developed for the shale formation integrating influence factors. The fracability indexes of siliceous, carbonaceous and Barnett shales in North America are found to be 0. 59, 0. 29 and 0. 62 - 0. 64, respectively, by solving the evaluation system. This finding suggests that the expectant fracturing ability of siliceous shale can be equivalent to that of Barnett shale and more than double that of the carbonaceous shale. As a result, one may conclude that siliceous shale of the middlelower part of the Niutitang Formation in northwestern Hunan has a high exploitation potential.
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2017年第6期390-398,共9页
Earth Science Frontiers
基金
国家自然科学基金项目(41302124)
油气藏地质及开发工程国家重点实验室(西南石油大学)资助项目(PLN201609)
中南大学中央高校基本科研业务费专项资金资助项目(2016zzts433)
关键词
湘西北
下寒武统
牛蹄塘组
页岩可压裂性
定量分析
northwestern Hunan
Lower Cambrian
Niutitang Formation
shale fracability
quantitative analysis
