METHOD FOR OPERATION OF GAS-LIFT WELL SYSTEM Russian patent published in 1996 - IPC

FIELD: oil producing industry. SUBSTANCE: method for operation of gas-lift well system includes measurement of parameters of operation of each well, construction of plots of production rate versus flow rate of working agent, determination of optimal flow rate of working agent, change from existent to new mode of operation by wells, comparison of measured parameters with calculated data, and repeated operation of changing the mode of operation when comparable data mismatch, until the moment of attaining the optimal operation of the system. Measured more than once in each well on each mode (at each flow rate of gas), at fixed value of gas working pressure and current water encroachment, is production rate of fluid, and relative measurement error is determined by measured production rate in total. This procedure is repeated under different modes for all wells covered by the given measuring plant. On the basis of experimental data in total, dependence of measurement error on fluid production rate, gas and water content of product. Dependence of the fluid production rate on the gas flow rate is approximated with observation of the requirement of the fact that the approximated error should not exceed the measurement error for the given concrete well under the given operating conditions. Optimal technological modes are determined and established on the basis of obtained dependences. During approximation for each measurement, own weight may be established, with weight value selected inversely proportional to measurement error in the given operating conditions. Number of measurements and their duration may be selected depending on errors in the previous measurements. When relative error of measurements in the given operating conditions exceeds doubled average error for the given type of units at similar parameter values affecting measurement (fluid production rate, gas and water content), the given mode of operation may not be taken into account in construction of plot of error versus affecting factors. Approximation of dependence of fluid production rate on gas flow rate may be accomplished by pieces of parabolas of the second order; in this case, each subsequent piece corresponding to the larger gas flow rate should have value less than ratio of variation of fluid production rate to variation of gas flow rate. Boundaries of pieces may be selected on the basis of abrupt changes of gas working pressure and the number of points of injection of gas process to be not less than the number of pieces of parabolas of approximating curve. When error of measuring device exceeds the average one for the given type of units at the similar parameter values affecting the measurement (fluid production rate, gas and water content) calibration (adjustment) may be undertaken of the given measuring device. The moment of attaining the optimal mode of operation of the well system may be selected on the basis of the requirement that the maximum absolute error in the production rate of the given well group should not exceed the difference of the total product value of this group of wells of the previous and the subsequent stages of optimization. The value of the gas working pressure is considered steady-state when the maximum working pressure deviates from the minimum working pressure during the time of measurement not more than by 10%. In periodic change of the well operating parameters, the time of measurement of the fluid production rate may be taken multiple to the period of change of these parameters. EFFECT: higher efficiency of the method due to higher accuracy in selection of optimal well operating conditions by more accurate determination of the dependence of the fluid production rate on the gas flow rate. 5 cl