| The water production of gas wells in the west of Sulige gas field in Ordos Basin has seriously restricted the production capacity of gas wells,which is a prominent contradiction in the effective development of gas reservoirs.In view of this problem,this paper selects the reservoir of He8 member in the typical block?s area?of Western Jiangsu Province as the research object,based on the macroscopic basic geological knowledge,and takes the casting slice,scanning electron microscope,high pressure mercury injection,phase permeability test and real sandstone model gas-water displacement as the experimental method,analyzes the pore structure and fluid seepage characteristics of the target layer,and clarifies the water production mechanism of the reservoir and the water production of the gas well Control factors,and put forward targeted measures to reduce the risk of water,water-proof and water control development.Through the research,we have got the following understanding:?1?There are more quartz in the framework of He8 reservoir in the study area,so quartz sandstone and lithic quartz sandstone are the main types.Compaction,cementation and dissolution are the main types of diagenesis in the study area.Compaction reduces the pore space by 26.19%,which is the main reason for the reservoir densification;cementation reduces the pore space by 9.08%,which increases the reservoir densification;dissolution increases the reservoir permeability space by 3.01%,which inhibits the development of densification.?2?The statistical results of physical properties show that the porosity of He8 reservoir is mainly distributed in 5%-9%,with an average of 6.91%;the permeability of reservoir is mainly distributed in 0.1-0.6×10-3?m2,with an average of 0.41×10-3?m2.The change of sedimentary environment and the difference of rock composition make the physical properties of lower He8 reservoir better than the upper one.?3?The statistical results of pore types show that the pore types are dominated by secondary dissolved pores,and primary pores occupy secondary seats in all kinds of compositions;the throat is dominated by flaky and tube bundle shape,including some point shapes.The pore structure of the target layer in the study area can be divided into four types according to the casting image and mercury injection curve shape,corresponding to four pore combinations of solution pore intergranular pore type,intergranular pore solution pore type,solution pore intergranular pore type and micropore type,and the pore structure of the first to the fourth type gradually becomes worse.?4?The visual displacement simulation experiment shows that:after the simulation of gas drive water reservoir formation,the water in the reservoir exists in three states:membrane residual water,isolated corner residual water and cluster residual water formed by bypass flow,and the proportion of pore structure changes from?to?corner residual water and bypass residual water increases gradually;the simulation process of pressure relief production shows that the reservoir with better pore type has a short pressure relief time,including The change of water saturation is small and the simulated oil recovery is high with more pressure drop.?5?The pore structure of He8 reservoir in the study area controls the gas-water percolation.Different pore structure types correspond to four different micro gas-water percolation characteristics.From class I to class IV,the gas-water two-phase co percolation area is becoming narrow,the bound water saturation is gradually increasing,the isotonic point is decreasing,the gas-water relative permeability curve is shifted to the lower right as a whole,and the micro model gas drive water type Type A is from uniform to reticular to finger displacement.?6?Based on the analysis of micro water production mechanism by micro visualization experiment of gas and water,it is concluded that the main reason for water production is the expansion force caused by large production pressure difference and the shear force caused by high-speed air flow,which makes part of the bound water body change into movable water.According to the test of mercury injection and gas water permeability,the node pressure difference of free water and movable water flow is 2.11mpa and 4.71mpa respectively.Controlling the pressure difference and reasonable production allocation can reduce the water production of the gas well. |
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