RU2799672C1 - Method for monitoring gas well watering - Google Patents

Abstract

FIELD: gas industry.

SUBSTANCE: invention relates to methods for diagnosing the beginning of flooding of gas wells and preventing their self-damping, and can be used in the development and operation of gas fields. According to the method, an arbitrary packerless well is selected, on which wellhead tubing pressure, wellhead annular pressure and flow rate are measured with a certain frequency. Then, according to the data obtained, a time dependence graph is built and areas are selected on it with a simultaneous drop in wellhead pipe pressure and flow rate with an increase in annulus wellhead pressure. After that, the coefficients of multiple correlation and multiple determination are calculated if the value of the multiple correlation coefficient exceeds the critical value equal to ≥ 0.9, then the beginning of the process of watering the gas well is acknowledged, if the obtained values are less than critical, then the watering of the gas well does not occur.

EFFECT: timely diagnosis of the beginning of watering of gas wells.

1 cl, 2 dwg, 1 tbl

Description

The invention relates to the gas industry, in particular to methods for diagnosing the beginning of flooding of gas wells and preventing their self-damping, and can be used in the development and operation of gas fields.

A known method for controlling the process of flooding gas and gas condensate wells (USSR author's certificate No. 1830413, publ. 07/30/1993), in accordance with which drilling of exploration wells for sampling formation fluid along the entire length of the reservoir. Then the position of the current gas-water contact is determined, the concentration of trace elements in the selected gas samples, and then the dependence of these concentrations on the distances between the reservoir opening zone and the GWC is plotted. After that, periodic sampling of gas from production wells takes place and the change in the concentration of trace elements in them is judged by the change in the position of the GWC and, accordingly, the watering of the wells.

The disadvantage of this method is the unaccounted for the possibility of fluid entering the wellbore before the HWC level rises to the perforation interval, for example, in the form of water vapor condensate in the wellbore, extracted together with gas, or formation fluid filtration along the most drained interlayers with the formation of a water cone.

A known method for controlling the watering of gas and gas condensate wells (Gritsenko A.I. Guidelines for well research. - M.: Nauka, 1995, p. flow meter and tanks for collecting separated impurities.

The disadvantage of this method is the need for chemical analyzes to determine the nature of the separated liquid. In addition, the values of filtration resistance coefficients a and b, which are obtained as a result of processing gas-dynamic studies of wells using the method of steady-state extractions without analyzing the dynamics of these coefficients over time, are not informative from the point of view of formation and bottom waters entering the deposit.

There is a known method for controlling the watering of gas wells (RF patent No. 2202692, publ. 07/13/2000), in the implementation of which standard gas-dynamic studies are carried out at the well by the method of steady-state selections, the determination of the filtration resistance coefficients a and b, the analysis of the dynamics of the filtration resistance coefficients a and b in time, plotting their changes, comparing the values of the filtration resistance coefficients a and b with the previous ones, as well as the conclusion about the presence of formation waters in the bottomhole formation zone by an abrupt increase in the values of the filtration resistance coefficients.

The disadvantage of this method is the relatively large errors in determining the date of receipt of formation waters associated with large intervals between the dates of the study.

A known method for determining the process of watering gas and gas condensate wells (Ermilov O.M. Improvement of systems for the development, production and treatment of gas in the fields of the Far North. M., Nauka, 1996, p. 35), carried out by conducting a complex of field geophysical studies observation and producing gas wells.

The disadvantages of this method are non-operational diagnosis of the process of watering gas wells, due to the duration of the conduct and interpretation of geophysical surveys of wells and the impossibility of conducting studies on the entire operating fund of producing wells for technical reasons.

A known method for controlling the watering process of gas wells (RF patent No. 2604101, publ. 20.10.2015), adopted as a prototype, in which standard measurements of wellhead parameters, pressure and temperature are used to control the watering process, standard deviations of temperature and pressure are determined under different modes well performance and compare them. The beginning of the watering is set by the change in time of the values of the standard deviation of temperature and pressure.

The disadvantage of this method is the possibility of influencing the values of wellhead parameters of environmental factors and, as a result, incorrect registration of changes in values, as well as not taking into account changes in other important parameters, which are used to judge the beginning of the process of flooding a gas well.

The technical result is the timely diagnosis of the beginning of watering of gas wells.

The technical result is achieved by selecting an arbitrary packer-free well, on which wellhead pipe pressure, wellhead annular pressure and flow rate are measured with a certain frequency, and then, according to the data obtained, a time dependence graph is built and areas are selected on it, with a simultaneous drop in wellhead wellhead pressure and flow rate with an increase in the annular wellhead pressure, then the coefficients of multiple correlation and multiple determination are calculated, if the value of the multiple correlation coefficient exceeds the critical value equal to ≥ 0.9, then the beginning of the process of watering the gas well is ascertained, if the obtained values are less than critical, then the watering there is no gas well.

The method is illustrated by the following figures:

fig. 1 - algorithm for applying the proposed method;

fig. 2 – graph of wellhead parameters change in time.

The method is carried out in the following sequence (figure 1). At the field, an arbitrary packer-free well is selected, from which research will be carried out. For the selected well, wellhead parameters are measured, such as wellhead pipe pressure, wellhead annular pressure and flow rate. The pressure at the wellhead is measured by means of a transducer installed on the well, for example, a process parameter recorder RTP-4 or a multi-parameter intelligent sensor MVT 3808-30A. The flow rate of a gas well is determined using a device used to measure gas flow, for example, DICT-50 or DICT-100. Measurements are carried out at least once a week, and from the beginning of the allocated interval for calculating the necessary dependencies - daily.

After measuring the values of pipe wellhead pressure, annular wellhead pressure and well flow rate, according to the data obtained, graphs of the dependence of these parameters over time are built. Next, an area is selected on the graph in which there is a simultaneous drop in wellhead tubing pressure with an increase in wellhead annular pressure, accompanied by a sharp decrease in well flow rate. By simultaneous changes in these wellhead parameters, the beginning of the process of watering gas wells is judged.

Then the relationship between the changing wellhead parameters is established and the multiple correlation coefficient is calculated, which is calculated by the formula:

– множественный коэффициент корреляции величин x, y и z;Where

is the multiple correlation coefficient of x, y, and z values;

– линейный выборочный коэффициент корреляции между устьевым трубным давлением и устьевым затрубным давлением;

– linear sample correlation coefficient between wellhead tubing pressure and wellhead annular pressure;

– линейный выборочный коэффициент корреляции между устьевым трубным давлением и дебитом;

- linear sample correlation coefficient between wellhead pipe pressure and flow rate;

– линейный выборочный коэффициент корреляции между устьевым затрубным давлением и дебитом.

- linear sample correlation coefficient between wellhead annular pressure and flow rate.

The wellhead pipe pressure is taken as x, while the annular wellhead pressure and flow rate are taken as y and z, respectively.

The linear sample correlation coefficient is calculated by the formula:

– i-е значение параметра x;Where

– i-th value of parameter x;

– i-е значение параметра y;

– i-th value of the parameter y;

N is the number of sample elements;

– среднее значение параметра x из выборки;

is the average value of the parameter x from the sample;

– среднее значение параметра y из выборки.

is the average value of the parameter y from the sample.

The i-th value of the indicators is the measured value at the wellhead.

After that, a quantitative assessment of the relationship between the selected values for analysis is given, which is determined using the coefficient of multiple determination, calculated by the formula:

Next, the relationship between changes in wellhead parameters is assessed using the Chaddock scale presented in Table 1.

Table 1 - Chaddock scale

A quantitative measure of the tightness of the connection Qualitative measure of tightness of connection 0.1 - 0.3 Weak 0.3 - 0.5 Moderate 0.5 - 0.7 Noticeable 0.7 - 0.9 high 0.9 - 1 Very high

If the obtained value of the multiple correlation coefficient exceeds the critical value equal to R _{x ( yz )} ≥ 0.9, then the beginning of the process of watering the gas well is ascertained. The critical value of the coefficient of multiple determination is determined by substituting R _{x ( yz )} = 0.9, so it takes the value D ≥ 81%. In this case, measures are taken to periodically or continuously remove fluid from the wellbore, for example, blowing the well or operating with a plunger-lift. In the event that the obtained values are less than critical, the watering of the gas well does not occur: the lower the calculated value of the coefficient, the more significant are the unaccounted factors that affect the change in wellhead pipe pressure, wellhead annular pressure and flow rate, but do not mean the beginning of the well watering process , for example, a change in pressure or temperature in the plume.

The method is explained by the following example.

On the graph of changes in wellhead parameters over time (figure 2) shows the change in wellhead parameters over time for a well gas field, which is characterized by the accumulation of formation water in the wellbore. Two characteristic areas can be clearly seen on the graph: the area to the left of the black vertical line with relatively constant wellhead parameters and the area to the right of the same line, where there is a decrease in flow rate and wellhead pipe pressure and an increase in wellhead annulus pressure. Using the measured values of wellhead parameters, linear sample correlation coefficients were calculated. Their meanings:

= -0,941;

= -0.941;

= 0,967;

= 0.967;

= -0,972.

= -0.972.

The multiple correlation coefficient for this case is:

=

=

=
= 0.967.

=

=

=
= 0.967.

Multiple determination coefficient calculated by formula 3:

=

*100% =

*100% = 93,579 %.

=

*100% =

*100% = 93.579%.

≥ 0,9 и D ≥ 80 %. Based on the calculations for various wells of Western Siberia fields based on this method, it is possible to judge the onset of well watering at the value

≥ 0.9 and D ≥ 80%.

Interpreting the obtained data, we can conclude that the relationship between the change in wellhead parameters on the Chaddock scale is very high, and the influence of external factors is insignificant - 6.421%. The values of the coefficient of multiple correlation and the coefficient of multiple determination exceed the critical values, which means that we can judge the beginning of the process of flooding a gas well in the area of the black line in Fig.2. Indeed, the calculated data coincide with practical studies - the process of watering began in the wellbore around the date that coincides with the black line in Fig.2.

The proposed method for monitoring the watering of gas wells makes it possible to diagnose the beginning of the inflow and accumulation of reservoir fluid in the wellbore, which makes it possible to take timely measures to prevent self-damping of the well.

Claims (1)

A method for monitoring the watering of gas wells, in which the beginning of watering is determined by the change in time of the values of the coefficients calculated from the results of well measurements, characterized in that an arbitrary packer-free well is selected, on which wellhead pipe pressure, wellhead annular pressure and flow rate are measured at a certain frequency , and then, according to the obtained data, a time dependence graph is built and areas are selected on it with a simultaneous drop in wellhead pipe pressure and flow rate with an increase in annular wellhead pressure, after which the coefficients of multiple correlation and multiple determination are calculated if the value of the multiple correlation coefficient exceeds the critical value equal to ≥ 0.9, then the beginning of the process of watering the gas well is stated, if the obtained values are less than critical, then the watering of the gas well does not occur.

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