Methods To Evaluate The Formation Pressure In Sulige Gas Field

The formation pressure of gas well is an essential parameter in gas reservoir dynamicanalysis.At present, there are a variety of methods to calculate the current formation pressure,butvarious inadequacies still exist. In this paper, as Su6block of Sulige gas field for study objects,with the eight gas wells with actual shut-in testing pressures for reference standard,fourmethods，including the simplified formula method of vertical pipe flow, the iterative method bydensity,the method under the condition of flow controller and the production uncertainty analysismethod,are used to calculate the bottomhole flowing pressure.The calculating bottomholeflowing pressure values are compared with actual shut-in testing pressures.The results show thatthe errors of all kinds of methods are all within the allowed error extent of calculating in the gasfield and the precision of the iterative method by density is the highest and is applicable in theearly and late production stage of wells.Six methods，including the three methods of pressure fallcurve, the surface casing pressure conversion method, the flowing material balance method andthe production uncertainty analysis method,are used to calculate the current formation pressure.The calculating current formation pressure values are compared with actual shut-in testingpressures.The results show that the errors of all kinds of methods are basically within theallowed error extent of calculating in the gas field and only the material balance methodconsidering water production and formation pressure recovery of gas wells does not appear thesituation that the bottomhole flowing pressure values are greater than the formation pressurevalues when wells produces water and frequently shut during the production process and accordswith the actual situation of formation.All methods are applied to270wells of Su6blocks in Sulige gas field and used to calculatethe bottomhole flowing pressure and the formation pressure.The applicability conditions areobtained.These research results can provide a reasonable basis for the productivity andproduction dynamic analysis of gas fields and a beneficial guide for the next stage production.