| Ordos basin is the second largest sedimentary basin in China with abundant reserves of natural gas,coal and other mineral resources.Sulige gas field contains huge natural gas reserves.In recent years,good exploration and research achievements have been made in the west area of Sulige gas field.The increasing natural gas reserve area indicates that there are abundant untapped resources in this area.However,in the process of exploration in the west area of Sulige gas field,many problems have been found.For example,in the gas wells in the west region,water is seriously generated in the production process,the gas-water distribution relationship is complex,and the law of water production is not clear.The western gas field is a new area and reserve area for rolling exploration and development of Sulige gas field,but the complex gas-water relationship directly affects the production well layout and efficient rolling development process of the gas field,which causes huge resistance to further positive industrial production.Therefore,this article adopts the methods of sedimentology,structural geology,hydrochemical analysis to analyze the distribution of gas and water in this area,looking for distribution rules of gas and water and controlling factors,and providing geological basis for the efficient development of gas fields in this area.This article mainly completes the following work:① Clearly identify the formation water in the study area,analyze its chemical characteristics and genesis,determine the distribution of formation water in the study area,determine the type of formation water and the hydrogeological background at the time of formation;② Based on the current structural characteristics and the distribution relationship between formation water and gas reservoirs in the present study area,the distribution characteristics of formation water and gas reservoirs under the current structural background are determined;③ By means of the restoration method of the denudation thickness,the denudation of strata in each period of this area was calculated,so as to restore the paleotectonic features of this area.By comparing with the current structural characteristics,the stratigraphic background and reservoir condition changes during the gas reservoir formation period can be determined,and the reason for the general low pressure of the current gas reservoir can be determined;④ Through the investigation of previous research results and reports,the sedimentary evolution history and tectonic change trend of the study area are understood in detail,the tectonic movement experienced in the study area and the adjustment of the distribution position of gas reservoirs in the process of tectonic movement are understood,so as to determine the influence of tectonic factors on the distribution of gas reservoirs.Through the above research,the following main results and understandings are obtained:①The formation water in the study area is mainly CaCl2 water with a PH<7,showing weak acidity.The hydrogeological environment in which the formation water is located is mainly a reductive environment and is burial metamorphic water;② The present structural pattern of the study area is high in the east and low in the west,and the distribution of gas reservoirs is high in the northeast and low in the southwest,while the water content is just the opposite;③According to the calculated denudation distribution,the denudation thickness of the study area did not change much before the Jurassic period,the western area had a small amount of denudation,and the eastern area had a large amount of denudation.After the cretaceous period,however,great changes took place,and the amount of erosion in the west increased dramatically compared with that in the east;④ Before the late cretaceous,the geological structure features of the study area are initially high in the west and low in the east,natural gas reservoir in the west and abundant water in the east.The formation of central paleouplift provides conditions for the formation of oil and gas.After the tectonic movement,stratum uplift,cap layer denudation,gas reservoir pressure relief,the overall show the characteristics of low pressure.Since the denudation at the end of cretaceous,the distribution of gas reservoirs has been controlled by the present structural pattern of high east and low west. |
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