Characteristics Of Upper Paleozoic Gas Reservoir And Its Main Controlling Factors In Linxing Area,East Margin Of Ordos Basin

This paper has conducted in-depth and meticulous research on the characteristics of gas reservoirs in the study area.Firstly,the main controlling factors were revealed,then the types and distribution rules of gas reservoirs were summarized,favorable exploration areas were predicted eventually.The district can provide an important reference for the next exploration.The conditions of natural gas reservoir formation are good in the Carboniferous-Permian of the Linxing area.The source rocks are widely distributed,with large thickness and high abundance of organic matter.They are in the stage of mature or over-mature thermal evolution and have reached the peak of anger.The reservoirs in the study area are mainly Gray and gray medium fine grained sandstones,and the main components of rock debris are quartz and rock debris.The reservoir space is dominated by secondary pores,followed by primary pores and fractures.The thickness of sand layer in the study area is large in thickness and widely distributed.Although most of the pores have poor permeability,they are well developed reservoirs.The regional caprock is usually fluvial mudstone with a thickness of 60 to 110 m and a stable distribution.The faults are not well developed in the Linxing area.Except for the eastern margin affected by the uplift of the Zijin Mountain,other areas have better preservation conditions.The gas layer interpretation was performed on the study area by using the three-porosity curve superposition method,acoustic time difference method,cross plot and other methods,explaining a total of 47 layers of gas layers,16 layers of differential gas layers,and 2 layers of gas-bearing water layers.The mudstone content of tight sandstone in this area is high,and the parameters of the Indonesian formula are optimized,which improves the accuracy of sandstone gas content calculation in this area.The calculation results show that the gas content of the Linxing area shows a pattern of“West high East low,North high South low".The gas content of the eastern sandstone is distributed in a circular belt around the Zijinshan rock masses.Partial correlation analysis and grey correlation analysis were used to analyze the main controlling factors of gas content.It was found that the most important factor of gas content was sandstone porosity,followed by gas saturation,and direct cover displacing pressure as well.Through detailed gas reservoir anatomy,gas reservoirs are mainly composed of lithologic gas reservoirs and structural-lithologic gas reservoirs,followed by structural gas reservoirs.The distribution laws of gas reservoirs are as follows:1.The sand-body with good reservoir properties determines the distribution of lithologic gas reservoirs;2.The anticline and nose structures control the distribution of structural gas reservoirs;3.The degree of development of fractures and structural microcracks determines the upper part gas reservoir distribution horizons.The resources of the entire region are predicted to be 1645.36×108 m3 by using the area abundance method,of which the lithologic trap resources are 1044.15×10 m3 and the structural trap resources are 601.11 ×108 m3.According to the main controlling factors of gas distribution,we optimized 3 blocks of one type of favorable areas and 2 blocks of two types of favorable areas for gas accumulation,the one type of favorable areas are respectively LX4-LX7 well area in Zhaojiaping village;the LX2-LX8 well area in the west of Gedashang village and the LX I-TB05 well area in the Surrounding of Tuban town,the two types of favorable areas are located in the north of the He Jiahui Township in the northeast of the study area,the west of the LX-3 well in the western part of the study area and the east of the Eighth Fort township.