Simplified graphical correlation for determining flow rate in tight gas wells in the Sulige gas field

The Sulige tight gas reservoir is characterized by low-pressure,low-permeability and low-abundance.During production,gas flow rate and reservoir pressure decrease sharply;and in the shut in period,reservoir pressure builds up slowly.Many conventional methods,such as the indicative curve method,systematic analysis method and numerical simulation,are not applicable to determining an appropriate gas flow rate.Static data and dynamic performance show permeability capacity,kh is the most sensitive factor influencing well productivity,so criteria based on kh were proposed to classify vertical wells.All gas wells were classified into 4 groups.A multi-objective fuzzy optimization method,in which dimensionless gas flow rate,period of stable production,and recovery at the end of the stable production period were selected as optimizing objectives,was established to determine the reasonable range of gas flow rate.In this method,membership functions of above-mentioned optimizing factors and their weights were given.Moreover,to simplify calculation and facilitate field use,a simplified graphical illustration(or correlation)was given for the four classes of wells.Case study illustrates the applicability of the proposed method and graphical correlation,and an increase in cumulative gas production up to 37% is achieved and the well can produce at a constant flow rate for a long time.