Abstract
Carboniferous-Permian petroleum resources in the Huanghua Depression of the Bohai Bay Basin, a super petroleum basin, are important exploration successor targets. The reservoir sedimentary environment of coal measures in the Upper Paleozoic buried hills is variable, and the structural evolution process is complicated, which restricts the optimization of targeting sections. Using the analysis and testing results of logging, thin section, porosity, mercury injection, hydrochemistry, and basin simulation, this study revealed the formation mechanism differences of tight sandstones in the Upper Paleozoic period in different buried hills. The results show that the sandstones are mainly feldspathic sandstone, lithic arkose, feldspathic lithic sandstone, and feldspathic lithic quartz sandstone. The quartz content varies between 25% and 70%, averaging 41%. Feldspar and debris are generally high, averaging 31% and 28%, respectively. Secondary dissolution pores are the main reservoir spaces, with 45% of the tested samples showing porosity of 5–10%, and 15% being lower than 5%. The pore radium is generally lower than 100 nm, and the sandstones are determined as small pore with fine throat and medium pore with fine throat sandstones by mercury saturation results. Frequent changing sedimentary environments and complex diagenetic transformation processes both contribute to the reservoir property differences. The former determines the original pore space, and the latter determines whether they can be used as effective reservoirs by controlling the diagenetic sequences. Combining tectonic movement background and different fluid history, the different formation mechanisms of high-porosity reservoirs are recognized, which are atmospheric leaching dominated (Koucun buried hills), atmospheric water and organic acid co-controlled (Wangguantun and Wumaying buried hills), and organic acid dominated (Nandagang buried hills) influences. The results can be beneficial for tight gas exploration and development in coal measures inside clastic buried hills in the Bohai Bay Basin.
Highlights
China is rich in coal-derived tight gas resources, accounting for approximately 60% of the country’s natural gas resources, and is a key area for unconventional natural gas exploration and development [1,2,3]
More system in the study area were subjected to conventional physical property analysis, analysis, X-ray diffraction whole-rock composition analysis, mercury intrusion, scanning electron microobservation,cast cast thin thin section section and and fluorescent fluorescent thin section observation, and groundscope observation, isotope tests
The quartz content is mainly concentrated between 25% and 70%, with an average of 40.77%
Summary
China is rich in coal-derived tight gas resources, accounting for approximately 60% of the country’s natural gas resources, and is a key area for unconventional natural gas exploration and development [1,2,3]. The Bohai Bay Basin is an offshore extension in a series of prolific oil-producing basins in NE China, which is a super basin with huge oil and gas production [5,6]. The Upper Paleozoic tight gas still cannot be commercially produced, even though breakthroughs have been observed in different buried hills, such as Wangguantun, Wumaying, and Chenghai buried hills [7,8]. The Upper Paleozoic period in the Bohai Bay Basin experienced long-term tectonic evolution both in the Mesozoic and Cenozoic periods, with multiple subsidences and uplifts [9,10]. There are limited studies on the mechanisms and distribution of high-quality tight gas reservoirs in different buried hills, as different buried hills generally have different tectonic evolution histories
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
