Optimization Theory For Injection/production Horizontal Wells Completed By Inflow Control Devices

In recent decades,horizontal wells have became the primary design type to develop reservoirs with advances in drilling and production technology.Horizontal wells enable greater well-reservoir contact and can increase productivity/injectivity from conventional wells significantly.However,the increased wellbore length also leads to some problems in production that mainly display imbalanced fluid inflow/injection along the wellbore caused by frictional pressure drop of fluid flow in the wellbore and reservoir permeability heterogeneity.The uneven inflow/injection distribution often leads to early water or gas breakthrough,which will cause reduction in oil recovery and development benefit of horizontal wells.Employment of inflow control devices(ICDs)is an advanced well completion option that provides a practical means to minimize the problem and has achieved widespread commercial application in foreign oilfield(this technology is rarely used in domestic,still in its infancy).The ICDs completion have proved to be of the ability to mitigate the imbalanced influx/injection,to optimize well and field management and to improve oil recovery.However,these is not a complete set of optimization theoretical system of injection/production horizontal wells completed by inflow control devices,which can realize accurate simulation of the completion performance and design-optimization of ICDs completion parameters.Therefore,this thesis systematacially carries out the research work of ICDs completion optimization theory in order to provide reliable theory basis for oilfield staff in designing completion program.First,the ICD types,ICD applications,AICD types,and AFI types at home and abroad are adequately investigated,then based on computational fluid dynamics(CFD)method,the flow characteristics of four types of ICD and fluidic diode AICD are analyzed.As a result,the throttling characteristics of different restriction structures are systematacially revealed.Next,the production horizontal wells completed by inflow control devices in bottom-water reservoirs and the injection horizontal wells completed by inflow control devices in closed reservoirs are selected as research object,then a semi-analytical model that couples the reservoir inflow/injection to the downhole flow is developed for predicting the performance of injection/production horizontal wells completed by inflow control devices based on a 3D volumetric source model and the principle of potential superposition and solved by the iteration approach.The inflow/injection model incorporates reservoir permeability heterogeneity in the near well region,reservoir anisotropy,near-wellbore formation damage and wellbore trajectory,and the downhole flow model includes pressure drops in the tubing,annulus,and ICDs.Meanwhile,a method to simulate the performance of injection/production horizontal wells completed by inflow control devices that combine steady-state model with transient-state model is established.The transient-state simulation is based on the multisegment well model of reservoir simulators Eclipse 2008TM.Then,on the basis of the above method to simulate the performance of injection/production horizontal wells completed by inflow control devices,the ICDs completion performance in high-permeability homogeneous reservoirs,heterogeneous sand reservoirs,and fractured carbonate reservoirs is simulated and predicted.The simulation results indicate that:the horizontal wells with ICDs completion can considerably improve the production performance compared with barefoot completion.Meanwhile,the influence of ICD flow-restriction size,number of openhole packers,and variable ICD flow-restriction size design on the performance of injection/production horizontal wells completed by inflow control devices and the performance of two horizontal wells individually/simultaneously adopting ICDs completion in injection-production pattern are analyzed.The simulation results indicate that:the influence law of ICDs completion parameters on the performance of injection/production horizontal wells completed by inflow control devices in different reservoir types is not the same;the most cost-effective completion solution is to employ ICDs completion only in injection horizontal well for injection-production pattern.Finally,the ICDs completion design-optimization methods of injection/production horizontal wells for different types of reservoirs and ICD arrangement are proposed.At last,the ICDs completion design-optimization of instance well in field using the set of optimization theory is carried out.After that,the reliability of theoretical system is verified by comparing production performance with a adjacent well.The completion optimization theory of injection/production horizontal wells completed by inflow control devices established in this thesis provides technical support for optimal operations of ICDs completion in production/injection system,and lays the foundation for popularization and application of this technology in domestic and forming core service ability of independent intellectual property rights.The study in this thesis has important theoretical and practical value.