Ultra-deep naturally fractured tight sandstone gas reservoirs have the characteristics of tight matrix, natural fractures development, strong heterogeneity and complex gas-water relations. There is strong uncertainty of gas reserves estimat

Both complete and uncompleted radiolarian siliceous shells were developed at Wufeng-Longmaxi radiolarian siliceous shale laminae in Sichuan Basin. Micro- and ultra-micropetrological observation suggests that they were successively filled by calcite, pyrite and organic–silicon complex, where pyrite and organic–silicon complex filled dissolved pores associated with calcite during sedimentation. Calcite was derived from calcium carbonate produced by microbial activities at the seawater surface. The environment of radiolarian siliceous shell cavities, which was suitable for sulfate reducing bacterial growth or dissolved hydrogen sulfide reducing Fe³⁺, contributed positively to pyrite development. Organic–silicon complex development was related to microorganism metabolism that was an important silica source. Honeycomb-like organic pores were developed in cavities with complete shells, but were not developed in cavities with uncompleted shells. This is because the latter could not withstand overburden pressure compared with the former. The only approach to figure out organic pore carriers and understand sequences and development processes of minerals and organic matter is to select weakly compacted radiolarian siliceous shale laminae to carry out micro- and ultra-micropetrological observation and geochemical testing via various technologies.

In order to reduce the cost of wellheads, the production rate of the gas wells in the Hechuan Gas Field are mostly measured in groups, which raises a stringent barrier for industries to determine the production rate of each single well. The technique for determining the production of a single well from the production of the well-group can be called the production splitting method (PSM). In this work, we proposed a novel PSM for the multi-well-monitor system (MWMS) on the basis of the Beggs and Brill (BB) correlation. This proposed method can account for the multi-phase flow together with the features of the pipelines. Specifically, we discretize the pipeline into small segments and recognize the flow pattern in each segment. The pressure drop along the pipeline is calculated with the Beggs and Brill correlation, and the production of each well is subsequently determined with a trial method. We also applied this proposed method to a field case, and the calculated results show that the results from this work undergo an excellent agreement with the field data.