Study On Wax Deposition Mechanism And Plugging Solution In Bozi Dabei Block

Bozi dabei block in China has abundant condensate gas reserves,but its characteristics of high temperature and high pressure and high wax content have always been a problem restricting our effective exploitation.The formation temperature and pressure change greatly with the mining process,which is often accompanied by wax deposition.When deposited in the reservoir or wellbore,it can significantly reduce wellbore productivity.Therefore,it is very important to study the mechanism of wax deposition in Bozi-Dabei block.In this paper,the wax deposition in dabi-14 wellbore was studied.Firstly,the laboratory analysis experiments such as gas permeability measurement device,scanning electron microscope,gas liquid chromatography and differential scanning calorimeter were used to analyze the reservoir wax deposition with PVTsim.Then,PVTsim and OLGA software are used to judge wellbore wax deposition,and the amount,location and thickness of wax deposition are predicted,so as to determine the mechanism of wax deposition,and determine the effects of gas-oil ratio,flow rate,downtime time and pipe wall roughness on wax deposition.Finally,a wax remover suitable for Dabei-14 well was selected.The results show that the dabei-14 reservoir is of low permeability and low porosity.The wax precipitation point of the condensate is 11.4℃,and the crystalline type of the wax sample is mainly microcrystalline wax.The simulated wax precipitation point of PVTsim condensate is 10.56℃,and no wax deposition occurs in the reservoir.The wax deposition occurred during well shutdown at a depth of 980 m or more.The MATZAIN model was the best match for the field conditions.The simulated wax deposition was5.434kg/d,and the thickness of the deposition did not cause wellbore clogging.The process of wax deposition is that condensate oil is produced in the process of cooling and depressing,and then wax deposition occurs in the condensate oil,in which molecular diffusion plays a leading role.The smaller the gas-oil ratio is,the more likely wax deposition occurs.The longer the shut-in time,the more obvious the wax deposition.The lower the flow velocity is,the lower the wax deposition is.The larger the roughness is,the more wax deposition is.The cycloaromatic hydrocarbon type wax inhibitor FL-05 and oil-based wax remover QL-01 have the best wax remover effect on dabei-14 well.