Research On Unblocking Technology Of Low Permeability Condensate Gas Reservoir In Offshore W Gas Field

The offshore reservoir of group G and group H in W gas field is a kind of condensate gas reservoir characterize by low-middle porosity, low permeability and low pressure. In order to resolve issues of the unexpected pressure of surface casing, workover operations have been done in some wells. However, the situation of workover fluid leak off have occurred in most repaired wells, nearly all repaired wells’ production have dropped strikingly, even down to zero, it is extremely likely that the reservoir have suffered from damage. In order to find reasons of low production after work-over operations, and find the solution, through literature research, lab experiments and theoretical analysis as well as numerical simulation, can the main work and contributions that have achieved in this thesis be summarized as follows.Through the analysis of porosity and permeability, lithology, temperature and pressure system, formation fluid, wetting property, susceptibility of group G and group H in the W gas field, the potential damage factors of the reservoir have been defined.Based on the potential damage factors, combined with the analysis of workover and flowback data, the evaluation of water lock damage and anti-condensate damage have been carried out, the chief damage factors of reservoir damage have been ascertained as liquid phase and solid phase damage. Meanwhile, according to the well conditions and operating environment, the difficulties were identified, and thus a two-step stimulated method of well washing with foam fluid and compound stimulation have been enacted.On the basis of the well washing technology with foam transferred by coiled tubing, a foam fluid system of well washing is developed, and then the FLUENT software is utilized to simulate the influence of particle size, flow rate, foam quality and deviation on effect of well washing, the parameters of well washing have been optimized.Aimed to deep stimulation, a non-acid and acid combination technology was studied. A compound fluid system is developed. The parameters of flow back through gas lift with coiled tubing have been optimized, meanwhile, a set of diagnostic method of liquid accumulated in the bottom of the wells has been introduced.Finally, apply the theory and technology of this thesis into well Z10 stimulation, which have got a obvious effect.This thesis put forward a strong applied compound stimulated technology, which provide strong theoretical and technical support for stimulation of wells with same problems in W gas flied, it is significant for long term development of W gas field.