Research Of Plug-release Techniques Of Gas Well In Jingbian Gas Filed

Jingbian gas field is a typical field of the low voltage、low permeability and low gas field.The output water of gas well in Jingbian gas filed is in high salinity which also has large scale of scale-forming ions,and there are a certain amount of CO1 and H2S simultaneously.There exists serious corrosion and scaling phenomenon in the gas production strings in this complex environment.The corrosion and scaling products lead to the wellbore pressure loss and Oil-casing pressure differential increased which blocks and throttles the gas wellbore affecting the gas production seriously.The pertinence of plug-release agent selection is not strong and the plug-release technology is short of adaptation on account of the reason of oil-casing pressure differential increased and undefined composition of wellbore plug in Jingbian gas field.Therefore,there is an urgent need to carry out researches of plug-release technique of gas well combining with the in-situ practice in Jingbian gas field.This paper has a study on the identify method of wellbore plug degree to Jingbian gas field firstly based on the theoretical basis of single-phase flow and multiphase flow in gas well,and also has evaluations to well plug degree of different gas wells.Then secondly,detailed analyses to composition properties of wellbore plug in Jingbian gas field have been studied by adopting analytical means such as chemical volumetric method and X-ray diffraction,and the source and formation mechanism of wellbore plug have also been studied simultaneously.Finally,the broken down efficiency of acid and alkaline plug-release agent on wellbore plug in Jingbian gas field have been studied with dissolution as index,and the residue composition after corrosion have also been analyzed.Ultimately,plug-release techniques applied to break down wellbore plug in Jingbian gas field have been worked out.Through the above study the conclusions are as follows:(1)Establishing and verifying identification method of wellbore plug degree in Jingbian gas field,and having analysised on the wellbore plug degree of gas wells because of the wellbore plugging caused by the additional pressure loss is about 1～2MPa(accounting for about 70%of the oil pressure differential)which indicates that wellbore plugging is the main reason of Oil-casing pressure differential increased in Jingbian gas field.(2)The wellbore plug of gas wells in Jingbian gas field mainly have been accumulated and gathered with corrosion and scaling products,clay and organic matters.The corrosion and scaling products are accounting for about 60%which consist of scaling products with CaCO3 and corrosion products with FexSy and FeCO3.The organic matters are accounting for about 60%which are the vital composition of corrosion inhibitor.(3)The efficiency of acid plug-release agent is better than alkaline plug-release agent on condition of wellbore plug of gas wells in Jingbian gas field.However,it’s recommended to add acid plug-release agent firstly and then alkaline plug-release agent to wells plugged by organic matters and the interval period is 1 hour.(4)The broken down solution takes plug-release agents with cyclic adding technique.The dosage of plug-release agents is 10%of wellbore volume for the first operation and the broken down time is controlled with about 10 hours.