| The Upper Paleozoic Xiashihezi 8 reservoir of Sulige gas field southeast region in Ordos basin is the typical tight sandstone gas reservoir, it's more complex with pore and throat structure compared with conventional reservoir. Characteristics of low porosity, low permeability and low gas saturation The reservoir performance in low porosity and low permeability and low gas saturation, low productivity of a single well, well short stable production period, The contradiction between gas and water is outstanding, and the development of such type reservoir is difficult. The tight sandstone reservoir need to a certain degree of improvement of the reservoir can obtain better economic benefits. At present, the horizontal well technology, staged fracturing in horizontal well, large volume fracturing and other advanced technology have become the economic and rational development key technique of tight sandstone gas of Sulige gas field. Especially the horizontal well drilling technology, increase the single well productivity effect is obvious, it can effectively increase the single well productivity and producing degree of reservoir area of control. In the face of increasing production capacity building tasks and the pressure of stable production, the horizontal well technology will become one of the important means of developing Sulige's tight sandstone gas reservoir.This paper is based on a large number of experiments, to carry out a comprehensive study of reservoir characteristics and classification and evaluation. Through the analysis of the feasibility of horizontal well development in study area, Based on the results of comprehensive evaluation of reservoir, the favorable regional of the horizontal well development has divided.It is provides a theoretical basis for efficient, reasonable and economical development of Upper Paleozoic Xiashihezi 8 reservoir of tight sandstone gas reservoir in Southeast Region of Sulige gas field. The main content of this paper mainly includes:(1) The research of reservoir lithology, property, reservoir diagenesis study of evolution etc. based on the physical analysis test, cast thin section, scanning electron microscope, X-diffraction experiment.(2) Study on micro pore structure of reservoir with high pressure mercury, constant speed mercury injection experiment(3) Study on micro percolation characteristics of reservoir based on the experiment of nuclear magnetic resonance and gas water phase permeability.(4) According to the above experimental basis, carried out the research of reservoir natural gas charging and the main controlling factors of the reservoir productivity.(5) Reservoir comprehensive evaluation of various experiments and flow unit division.(6)The study of the Horizontal well applicability and the division of favorable area of Horizontal well.This paper mainly obtains the following conclusions and understanding:(l)The He 8 tight sandstone reservoir diagenesis stage reached in B stage in the middle diagenetic stage of study area. Mechanical compaction and cementation are the main reasons for the densification of reservoir, especially mechanical compaction is the most strong influence on the density of the reservoir, it caused by porosity reduction rate of up to 69.12%. The dissolution followed is the primary factor to improve the physical property of reservoir, it caused by the increase of porosity porosity is 22.96%.(2)The reservoir pore types are mainly intercrystalline pore, dissolution pore, and the dissolution pore is mainly dominated by debris dissolution. The main pore combination types of the study area are intergranular-dissolution pore type and intercrystalline pore type. The overall fine throat, the pipe bundle is the main throat, and there are some point and lamellar throat.(3)The second small layer of lower part of He 8 with low displacement pressure and median pressure and higher mercury withdrawal efficiency, it shows that this small layer have the largest effective space of reservoir and the connectivity between the pores is better and the seepage ability is stronger compared with orher small layers.(4)Reservoir can be divided into two types of the pore contribution and the throat contribution. And the pore contribution type sample has larger radius range and the final mercury injection saturation than throat contribution type.(5)The pore development degree of reservoir is small, the pore radius and the number of pores are close. The difference of micro pore structure between samples is mainly concentrated in the throat, so caused that the pore throat radius ratios of different types of reservoirs are obviously different.(6)The different pore type reservoir T2 spectrum has the obvious regularity of distribution, and the distribution curve of T2 spectrum is weak double peaks form of the Samples with a single type of pore.(7)For the tight sandstone gas reservoirs, the development degree of throat largely controlled the reservoir's seepage ability.(8)The second small layer of lower part of He 8 has good quality of seepage, but also has strong heterogeneity. The different pore type reservoir samples permeability characteristics difference.(9)Early Cretaceous is main period of the gas filling hydrocarbon accumulation of study area. The study area of pore and throat flow fower limit value is determined by 0.1 ?m by different methods. And the lower limit of physical property of the natural gas charge is calibrated, the lower limit of porosity is 6%, and the lower limit of permeability is 0.1×10-3?m2. In the process of migration of natural gas, the capillary force is the main resistance force, the maximum capillary resistance of gas filling is 1.17MPa in the stage of Early Cretaceous.(10)Fluid excess pressure is the main driving force for the natural gas migration of this research area. Natural gas migration is mainly vertical migration, and the gas filling index is between 0.22-0.90, the average value is 0.42. The overall performance is medium filling strength, strong charging degree accounted for 20% of all.(11)Water lock effect is the main reason for the sharp drop of productivity in gas well production. Reasonable control of gas well production pressure has important significance for delaying gas well to see water, slowing down the production of gas well(12)For tight sandstone gas reservoir development, the irreducible fluid is a relative concept, when the gas phase fluid flow rate exceeds a certain value, it can caused that the drag force of water film in hole wall of the pore and throat bigger than the flowgesistance of water film, Which leads the irreducible fluid change to movable.(13) According to the reservoir evaluation results, the lower part of He 8 had more proportion of the advantages reservoir than the upper part of He 8, and the second small layer-of lower part of He 8 is the advantages layer in the lower part of He 8,it's mainly with I class reservoir, And the proportion reached 67.12%.(14) The difference of diagenesis evolution is the main reason caused the different types of reservoir quality.(15) Through the two aspects of geological and economic analysis of the feasibility of horizontal well, the second small layer of lower part of He 8 is the main target of the research area of conventional horizontal wells, it has the largest proportion coMPared to other small layer, reached to 87.67%. |
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