| PDF: | |
| Time: | 2016 |
| Journal: | Acta Petrolei Sinica |
| Pages: | |
| Type: | EI |
| Author: | Huafeng Tang ,Tan Kong ,Xiang Liu,Di Yang ,Hongyu Huo,Yulong Huang |
Abstract: | The prolific gas pool of volcaniclastic sedimentary rocks of Early Cretaceous of Wangfu Faulted Depression (WFD) in Songliao Basin (SB) was found in 2011. However, the characteristics and formation mechanisms of high quality reservoirs in volcaniclastic sedimentary rocks of SB is not well understood. In this paper, volcaniclastic sedimentary rocks of Shahezi Formation of well block CS6 in WFD of SB is taken as an example of high quality reservoirs. The void space, porosity-permeability, pore throat and pore diameter are discussed using the following method; thin sections impregnated with blue epoxy resin, helium (He) injection, mercury (Hg) injection and nuclear magnetic resonance respectively. The formation mechanism and main controlling factors of high quality reservoirs are analyzed based on all the above methods. The result shows that the high quality reservoirs are reworked lapilli and breccia，and exhibits the coarsening-upward successions. Primary and secondary porosity and secondary fracture porosity has been identified. The intragranular vesicular of primary porosity are distinguished void space of high quality reservoirs. It has the characteristics of large pore and small throat. The porosity and permeability of reworked breccia is higher than reworked lapilli, and both display relatively higher porosity and permeability than the sedimentary rocks in Shahezi Formation. The porosity is correlated to burial depth. The formation mechanism of volcaniclastic sedimentary rocks reservoir are gas released in parent rocks，grain-support contacts，alteration by organic acid and tectonic deformation. The main controlling factors of reservoirs formation are gas released in parent rocks and the grain-support. The high quality reservoirs are distributed in the middle part of alluvial fan of volcaniclastic sedimentary rocks. Volcaniclastic sedimentary rocks with grain-support, coarse particle, highly percentage of volcaniclasts with intragranular vesicular and burial depth less than 3000m are the favorable target of exploration. |