Research On Wax Deposition Law And Prevention Countermeasures In Wellbore Of Da’anzhai Condensate Reservoir

The wellbores of the Da’anzhai condensate reservoir in the Fuxing area are frequently blocked by wax.The wax deposition speed is fast and the thickness is large,and the effect of conventional wax removal measures is not ideal.For this problem,it is necessary to study the wax deposition law under the three-phase flow state of oil,gas and water in Da’anzhai condensate gas wellbore and formulate reasonable prevention and control measures.This is of great significance for reviving the efficient development of Da’anzhai condensate reservoirs and the safe production of oil and gas wells.First,after collecting and arranging field data,this paper analyzes the composition of samples from Well FY8-1 in the block.Combined with the domestic and foreign research on the wax deposition mechanism of the wellbore or pipeline of waxy oil and gas wells,the research on the wax deposition mechanism and influencing factors of the Daanzhai wellbore was carried out.Through a simulated wellbore that can observe and measure the internal wax deposition,a wellbore wax deposition simulation experimental device that can operate under high temperature and high pressure is established.This study explores the wax deposition evaluation experiment of oil-gas-water multiphase wellbore flow simulation under different working conditions（such as wellbore temperature,flow rate,pipe wall roughness,water content,gas-oil ratio）.Secondly,according to the wax deposition mechanism and law of Da’anzhai condensate oil and gas wells,the diffusion-shear-erosion aging model was used to predict the wax deposition performance under different production,wellhead pressure,temperature,time,roughness and other working conditions.Finally,based on the wax precipitation law of the wellbore,suggestions for optimizing the production system and the size range of the pipe string are put forward,and the formula of the wax inhibitor suitable for the block is formulated.The research results are as follows:the wax deposition in the Da’anzhai wellbore is the result of the combined effect of molecular diffusion theory,phase equilibrium theory and solubility theory,and the heavy components in the crude oil of oil and gas wells provide conditions for wax deposition.Under basic production conditions,the initial position of wellbore wax deposition is at a vertical depth of 1050m,and the maximum wax deposition depth is at a vertical depth of 90m;The average wax deposition rate of the wax deposition well section is 1.12mm/d,and the thickest wax deposition point is 2.54mm/d.The main controlling factors affecting wax deposition include:temperature,pressure,crude oil composition,gas-oil ratio,flow rate and water cut variation.The main prevention and control measures are:try to control daily oil production<30m³/d,daily gas production<1.5×10⁴m³/d,oil pressure>15MPa production;use oil pipes with a diameter of≥2^7/8in,and at the same time add appropriate concentration to the oil pipes regularly chemical wax inhibitor.The comprehensive application of the above measures can achieve the purpose of preventing and controlling wax deposition.The results of this study will provide important technical support for the prevention and control of wax in the Da’anzhai condensate reservoir in the Fuxing area.