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Palaeogeomorphology plays a crucial role in the development of sedimentary facies and the reservoir distribution in the late period of basin evolution, and to a certain extent, controls the assemblage of the late hydrocarbon reservoirs and caprock formations. Therefore, it has a function in controlling the enrichment of oil and gas. Caledonian orogeny uplifted the Ordovician Majiagou Formation in the Ordos basin and thus led to the formation of the weathering crust reservoirs in the process of weathering, erosion and leaching for over 130 Ma. Such palaeogeomorphology represents the background of the palaeokarst, which has an essential influence on the formation of reservoir rocks. Based on Precarboniferous paleogeologic map plotted by 305 wells, and the thickness of bauxite in 272 wells, methods of residual thickness and moulage are applied to reconstruct the palaeogeomorphology in the studied area. In combination with the thickness of horizon to the weathering crust, the criteria for the second order palaeogeomorphologic units were proposed. They are karst highland, karst slope and karst basin, which can be further subdivided into the third order palaeogeomorphologic units of remnant hill, depression, gentle hill, shallow depression and erosional grooves. According to the criteria and refined identify results of ancient grooves using geological data of 272 wells, palaeogeomorphology of the Ordovician weathering crust in the northern Jingbian gas field has been restored accurately. The results show that karst highland developed in the northwest part of the studied area, with remnant hill and depression occurring locally. Karst slope was present in the central and east, predominatly in the form of gentle hills and shallow depressions, with 5 nearly EW-trending ancient erosional grooves developed locally. Finally, integrated data of reservoir property with gas production test implied that the remnant hill in the karst highland, the gentle hill in the karst slope and the two sides of the erosional grooves were favorable positions for gas accumulation.

Sesame seed hull is the major by-product of sesame seed processing and is rich in polysaccharides. In this work, sesame hull polysaccharides (SHP) were extracted by ultrasound-assisted alkali extraction methods with a yield of 6.49%. Three purified polysaccharide fractions were obtained after decolorization, deproteinization, and column chromatography. Then, their main composition and antioxidant activity were investigated. The dominant fraction was SHP-2 with a yield of 3.78%. It was composed of galacturonic acid (51.3%), glucuronic acid (13.8%), rhamnose (8.9%), glucose (8.4%), and others. The linkage types of SHP-2 have the α-D-GalpA-(1,4)-linked, α-D-GlcpA-(1,2)-linked, β-T-D-Rhap-linked, β-D-Glcp-(1,6)-linked, β-T-D-Galp-linked, α-L-Xylp-(1,4)-linked, α-L-Araf-(1,3,5)-linked, and β-D-Manp-(1,4)-linked. This study might provide some useful basic data for developing applications for sesame seed hull polysaccharides in the food and pharmaceutical industries.

Objectives/Scope A low-permeability lithological reservoir was successfully put into operation in 2015 as a gas storage system. The field S2 Underground Gas Storage (UGS) is located in the Ordos Basin and is primarily alithological trap, with low permeability, high heterogeneity, and no obvious seal boundaries. Based on low permeability, low abundance, low vertical wells productivity, low pressure coefficient, serious skin damage in the bottomhole during drilling and completion, strong heterogeneity and unclear lithological boundaries, low control of injection-withdrawal well patterns, the working gas volume and operating efficiency of S2 UGS underperformed relative to modeled expectations. The technical solutions to improve the working gas volume of S2 USG focused upon: well pattern optimization, well placement, stimulation treatment, infillings, and increasing of operating maximum pressure. The results demonstrate that if reasonable technical solutions are adopted, even poor and low-quality storage reservoirs with low permeability, and strong heterogeneity, can be utilized as natural gas storage targets. This discussion provides an overview of approaches used in the Ordos Basin to make operation of S2 UGS more efficient. The development of this project, particularly regarding the operation processes and the resulting adjustments, are noteworthy. The development of such UGS reservoirs require new insights into the performance criteria which can be applied to other reservoirs in the future.

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