Theoretical Study And Field Application On Quit Flowing Time Prediction Of Horizontal Wells In Carbonate Reservoir

Carbonate reservoir is a very important type of oil and gas resources,its reserves and production ranked the first in the world,especially in the Middle East area.In the early exploitation stage of such reservoirs,natural flowing is the main production way,but with time flows,the formation pressure decreases,and water cut increases.Such factors will lead to well stop flowing.The study of prediction of the stop flowing time is still relatively less.In this paper,on the basis of relevant literature in-depth research,aiming at gaint carbonate reservoir in the Middle East,integrate theoretical analysis and experimental simulation,the stop flow time forecast method were studied.First carbonate reservoir rock and reservoir properties of the system is described,analyzed the carbonate reservoirs important properties like saturation,wettability,capillary forces,capillary pressure and production efficiency;Secondly,for development features of carbonate reservoirs such as widely use horizontal wells,cluster wells,trajectory borehole and complex wellbore structure,high liquid volume and gas-oil ratio,conducted the experimental study of variable mass and multiphase flow in horizontal wellbore.By studying the horizontal wellbore variable mass multiphase flow pattern,established the micro-element method of variable mass flow mathematical model in horizontal well,deduced a new formula to predict horizontal well pressure drop;Then,based on the analysis of the important characteristics of natural flowing wells' production such as oil pressure,casing pressure,water cut,gas-oil ratio,choke size,etc.Designed the fitting and calculation method of pressure from the choke to the vertical to the horizontal wellbore and wellbore system.Combined fluid properties PVT,inflow performance IPR and wellbore multiphase flow,dynamic data integration,fluid parameters,reservoir parameters and wellbore parameters,established flowing well optimal design model.According to the production well characteristics,the reasonable production requirements were given,and then predicted the stop flowing time of natural flowing wells.Using Arps law of decline to calculate the remaining recoverable reserves of single well after stop flowing;Finally,take Halfaya oilfield in Iraq as an example,conducted the field application using the method proposed.The application results show that in the stop flowing time prediction in Halfaya and Ahdeb oilfield,the method greatly reduces the prediction error,and the general error is small.By the study of quit flowing time prediction of horizontal wells in carbonate reservoir,provide important theoretical basis for decision-making in the transformation from flowing to pump,surface construction and subsequent development.Provide important reference for development and production of similar fields both at home and abroad.