Research On Liquid-loading Identification Method Based On Flow Pattern Transition

In the process of gas reservoir development,liquid-loading is one of the main problems restricting the stable and high production of gas wells.When gas well liquid loading,it will increase the bottom hole pressure,aggravate the gas-liquid slippage,reduce the productivity of gas wells,and even cause the well to stop production in serious cases,resulting in high abandonment pressure of reservoirs and low final recovery.Therefore,it is of great significance to objectively evaluate the liquid carrying state of gas well,identify the time of liquid-loading as accurately as possible,formulate reasonable production allocation in advance and select the appropriate drainage method in time,ensure the normal and stable production of gas well.The research on continuous liquid carrying in gas well shows that when continuous liquid carrying is carried out in gas well,the two phases of gas and liquid in wellbore generally present annular flow or annular mist flow,and the liquid phase is carried continuously by the gas phase and continuously moves upward.However,when the continuous liquid carrying fails,the flow will deviate from the annular or annular mist flow to other types,and the production state will change to discontinuous liquid carrying state,and then the production with liquid gradually changes to liquid-loading,serious liquid-loading.Therefore,the occurrence of liquid-loading in gas well is the accumulation of transient change process,liquid-loading and flow pattern transformation occur simultaneously and equivalently,and the two are mutually causal.Compared with the liquid drop model,liquid-loading identification method based on the flow pattern transition can adapt to different actual complex situation,because when both liquid gas well by continuous annular flow into the discontinuous with liquid slug flow,the flow structure will change,thus fluid carrying mechanism will also change,judge the happening of the effusion should be at the same time considering the micro shaft flow characteristics,and the macroscopic dynamic changes of flow pattern,pressure drop and liquid holdup.Therefore,this thesis firstly analyzes the flow pattern change of the actual gas well liquid-loading process,clarifies the flow pattern transition boundary between transition flow and slug flow,clarifies the causal relationship between gas well liquid-loading and flow pattern transition,and gives a new knowledge of gas well liquid-loading.Then,from the perspective of flow pattern transition,based on the transient change process of gas well liquid-loading,transient simulation software OLGA is used as the tool to capture the change characteristics of macro and micro parameters when flow pattern transition occurs,and verify the feasibility of flow pattern transition method to predict liquid-loading.Finally,the flow pattern transition prediction model was established,the corresponding flow pattern chart was drawn,and the liquid-loading identification method based on flow pattern transition was proposed.