Research And Application Of Well Completion Optimization Of Dengying Formation Marine Carbonate Gas Reservoir In Block G

Carbonate reservoirs play an important role in world's production of oil and gas.Benefited from the deepening of exploration knowledge and technological progress,the exploration and development of carbonate gas reservoirs in Sichuan Basin is developing rapidly.The carbonate gas reservoirs of the G-Block are low-permeability and tight,with various types,strong heterogeneity,uneven development of fractures and cavities,and complex local gas-water relationships.The gas reservoirs are seriously polluted during development,resulting in difficult productivity building of individual wells.Optimization of well completion is confronted with adaptation of following factors:the contribution of fractures to well productivity,acidification results and subsequent water control.Therefore it is in urgent need to establish an optimization method of well completion suitable for different types of reservoirs and well leakage characteristics so as to guide the efficient production building of gas wells.Therefore,this paper collates and analyses the data of more than 30 pilot wells,on the premise of fully grasping the geological background,the difficulties of completion engineering technology are summarized.Based on massive statistical analysis of pilot wells'data,adaptability of different factors such as acidification results,drilling fluid loss degree,permeability capacity,difference ratio of I and II types of reservoirs to the pilot completion methods are quantitatively evaluated in this paper,forming a preferred optimization method for well completion of the fractured-vuggy carbonate gas reservoirs of G-Block.A gas reservoir percolation model considering the effect of fractures is established.Gas reservoir percolation model has coupled with wellbore model and get solution,then the prediction model of gas production profile in open hole horizontal wells(highly deviated wells)is obtained.On this basis,considering perforation and liner parameters with additional surface layer,the parameter evaluation model of perforation and liner completion has been established.Completion method optimization and completion parameter optimization scheme design of three development wells in GM area have been completed and field application has been carried out.Result shows:?Reasonable completion method compatible with both characteristics of well leakage and acidification can ensure the effective acidizing deplugging of serious contaminated gas wells of G-Block.?The productivity of gas wells of G-Block is significantly correlated with the loss of drilling fluid and the permeability capacity.The primary factor of well completion optimization is that the applied completion method should be beneficial for fully playing the contribution of fractures to the productivity,followed by factors of large-scale acidification results,then water control demand and post-process requirements,etc.?For gas wells with small loss of drilling fluid and weak fracture development,perforation completion is conducive to releasing gas well productivity.For gas wells with large loss of drilling fluid,good drilling performance and well developed fractures and caves,open hole or liner completion is more conducive to bringing into play the contribution of fracture to gas well productivity.?The application of the optimization theory of deep carbonate completion in G block in practical wells has proved the correctness of the theoretical system in this paper,which has a good reference for subsequent block completion construction.