«Oilfield engineering»

Duration of measurements and periodicity of well testing

UDC: 622.276.5.001.5
DOI: 10.33285/0207-2351-2022-6(642)-35-40

Authors:

¹ TatNIPIneft, Bugulma, Russia

Keywords: study frequency, measurement duration, flow rate, water cut, formation pressure, standard deviation

Annotation:

The effectiveness of various technological solutions when designing, controlling and managing oil fields development processes largely depends on the initial information on pressures, flow rates and water cut. Particular attention should be paid to the frequency of studies, which should ensure the reliability of the parameters for single measurements. One of the important parameters is the ratio of the duration of measurements to the frequency of studies Δt/T.

To determine the optimal ratio Δt/T, a method is proposed based on mixing of the initial sampling of high-frequency data and determining of the average value and standard deviation depending on Δt/T. While studying, it was found that for various volumetric samples of flow rate, injectivity, pressure and water cut, the curves for the standard deviation, referred to the maximum value, practically overlap each other with the accuracy acceptable for oilfield practice.

The resulting dependence is close to the Pareto distribution.

With Δt/T equal to 0,1...0,2, a significant reduction in the relative standard deviation is achieved, and therefore in most cases it is sufficient to use this range as the optimal one.

The conclusion obtained is of great practical importance. In particular, the current practice of two-hour production rate measurements within two days leads to Δt/T = 0,042, which is below the recommended range of Δt/T = 0,1...0,2, i. e. clearly not enough. Measurements of flow rate and water cut with a frequency of 1 time per month are even more distant from the optimal ratio Δt/T. At the same time, according to the industry RD 153-39.0-109-01, the frequency of formation pressure measurements once a quarter is excessive for low-productivity reservoirs.

The optimal approach is considered to be the direct determination of the required frequency of pressure, flow rate and water cut measurements, according to the proposed approach for each development object or well.

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