Study Of Induced Flow By Nitrogen Injection Using Coiled Tubing In Depleted Offshore Gas Field

Induced-flow by nitrogen injection with coiled tubing has characteristic of draining fast,low-risk,wide applicability and so on,which can effectively protect the reservoir and has a significant advantage in ultra-deep gas well completions,especially in the offshore depleted gas field.In this paper,based on the theory of gas liquid two-phase flow,seepage mechanics and string mechanics,and combined with construction technology of induced flow by nitrogen injection with coiled tubing,the critical condition of induced-flow,the pressure distribution in well annulus and its influencing factors,the selection of coiled tube and strength calculations were studied.The results indicate that: within the range of usually used nitrogen injection rates,reasonable injection depth and wellhead back pressure are the most two important factors to facilitate successful induced-flow.When the critical condition is reached,blindly increasing the injection nitrogen rate is not a wise strategy for increase the possibility of successful induced-flow but increases the operating costs.Under the same condition,horizontal wells or directional wells with larger deviation angle need to increase the depth of gas injection appropriately or decrease wellhead back pressure.In order to facilitate engineering applications,software for calculations related to induced-flow by nitrogen injection with coiled tubing is compiled in this paper,which has practical significance for the nitrogen injection operations and design.