RU2826995C1 - Method for conducting gas-dynamic studies of gas and gas condensate wells - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method for conducting gas-dynamic studies of gas and gas condensate wells in the presence of a telemetry system in the wellhead connection and operation of wells without exceeding the maximum allowable specific content of mechanical impurities includes well development for a flare device and further well survey in three modes with gas release into atmosphere: with working flow rate of well, with flow rate of well established by process mode, and with maximum allowable flow rate of well. Content of liquid and mechanical impurities in the gas flow is monitored and stabilization of all measured parameters is monitored. If the content of mechanical impurities does not exceed the established limits, and there is no highly mineralized formation water in the well product, further investigation is carried out without gas releases into atmosphere provided that the well operates into the gas gathering network. At the same time in the process of execution of works there provided is long-term stabilization of thermobaric parameters in n modes and their fixation is performed. Well flow rate is controlled by flow meter assembly from well telemetry with control of pressure in cluster manifold.

EFFECT: increasing the efficiency of gas-dynamic studies of wells.

1 cl, 3 dwg, 2 tbl

Description

The invention relates to the oil and gas industry and can be used in conducting gas-dynamic studies of gas and gas condensate wells in the process of monitoring the development of fields. The method includes measuring the thermobaric parameters of the gas flow in various well study modes, including using stationary telemetry systems.

In the process of industrial development of a field, it is necessary to conduct gas-dynamic studies of gas and gas condensate wells to assess changes in well productivity and the state of the bottomhole formation zone, monitor changes in reservoir energy and the introduction of reservoir water into the deposit, and identify geological and technological limitations.

These studies are conducted in production gas wells, but not less than in seven modes with a gradual increase in the diaphragm diameter and, accordingly, an increase in the well flow rate. Of the seven modes, at least two must be conducted in reverse, i.e. from a higher flow rate to a lower one, in order to verify the measurement data and eliminate the effect of excess hydraulic losses from the accumulation of a liquid plug in the wellbore. Conducting studies by this method entails irretrievable losses of reservoir gas, since the studies are conducted with the release of gas into the atmosphere [Gritsenko A.I. et al. Guide to Well Studies. - M.: Nauka, 1995, pp. 241-256].

A method for studying wells in cluster placement is known from the prior art [RU 2644997 C2, E21B 47/06, published 15.02.2015], including measuring the gas flow rate, formation, bottomhole and wellhead pressures, temperatures at the wellhead of the i-th well, where i = 1, 2, 3, …, n, in each of the modes of wells in the cluster simultaneously operating in a flowline. For each well, the filtration resistance coefficients are determined by sequentially disconnecting one selected well at a time up to (n-1) simultaneously operating wells in the cluster. Curves are plotted for the dependence of quadratic depression on gas flow rate for wells in the cluster in different modes, according to which the filtration resistance coefficients are determined using a graphic-analytical method.

The disadvantage of this method is the need to group wells with different productive characteristics operating in one gas-gathering manifold. Starting and stopping wells leads to a change in pressure in the gas-gathering manifold and requires adjusting the operating modes of individual wells. This method can only be used in fields with wells draining intervals at one operation site and similar in geological and technical condition, since the difference in the filtration characteristics of wells located on one well pad does not allow determining filtration resistance. This method is also effective at an early stage of field operation.

There are various accelerated methods of well research, for example, the express method, which allows to significantly reduce the duration of research modes. The express method technology is as follows: before the start of the research, the well must be stopped to record the reservoir pressure. Then the well is put into operation with a flow rateQ ₁ for a while t _{p 1} =1200–1800 s, by the end of timet _{p 1} the thermobaric parameters of the gas flow are measured and the bottomhole pressure is calculated. Then the well is closed for a certain period of time, while the operating time of the well in the modes and the stop time between modes should be taken as the same. Then the well is put into operation in the second mode with a flow rate ofQ ₂ for a while t _{p 2} =1200–1800 s. Then the well is closed for a certain time. Similar actions are carried out in subsequent well operating modes. The obtained results are processed using the given formulas [Gritsenko A.I. et al. Well Research Guide. - Moscow: Nauka, 1995, pp. 241–256].

The disadvantage of the express method is the lack of stabilization of the thermobaric parameters in the research modes, as well as insufficient time for lifting the particles of the reservoir rock from the bottom of the well, which will lead to an incorrect determination of the boundary conditions. It should also be noted that when using the express method, it is possible to allow an unreliable determination of the filtration resistance coefficients, which will require a repeated study.

The closest method of gas-dynamic well studies [RU 2490449 C2, E21B 47/06, published 20.08.2013]. The known method includes measuring the thermobaric parameters at specified well operating modes, processing the results and determining the coefficient of quadratic resistance. In this case, to reduce the number and time of modes, and, consequently, the volumes of emissions into the atmosphere, the mathematical function "influence function" is used. To determine the coefficients of quadratic resistance, the period of the study is set, divided into N time intervals, the duration of which depends on the characteristics of the well, the known properties of the influence function are set and an equation is written for each interval.

The disadvantage of this method is that research can only be carried out on wells whose output does not contain mechanical impurities or liquid, i.e. it is unacceptable to use this method at the final stage of field development.

The technical problem that the proposed technical solution is aimed at solving is to increase the reliability of obtaining well data, reduce the release of natural gas into the atmosphere, and reduce the time required to conduct the study while ensuring an increase in the operation of the well in the gas collection network.

The technical result that the proposed invention is aimed at achieving is increasing the efficiency of gas-dynamic well studies.

The specified technical result is achieved by the fact that the Method of conducting well research is carried out on wells equipped with a telemetry system, the wells must be operated without exceeding the maximum permissible specific content of mechanical impurities and liquid, the well is developed using a flare device, then the well is researched in three modes with gas released into the atmosphere: with a working gas flow rate established by the technological mode, the maximum permissible well flow rate, while monitoring the content of liquid and mechanical impurities in the gas flow and monitoring the stabilization of all measured parameters. If the content of mechanical impurities does not exceed the established limits and there is no highly mineralized formation water in the well output, further research is carried out in the gas collection network without gas releases with a gradual increase in the well flow rate to the maximum possible; in the process of performing the work, long-term stabilization of the thermobaric parameters in n modes is ensured and they are recorded, while the well flow rate is monitored using a flow meter unit from the well telemetry system with pressure monitoring at the wellhead, in the annular space and in the cluster manifold.

It is proposed to conduct well surveys using a telemetry system in the well piping. Telemetry and telemechanics are a set of technological methods that allow for remote measurements, data collection and control of regulating and locking devices in the well piping.

The proposed Method for conducting gas-dynamic studies of gas and gas condensate wells with a telemetry system in the wellhead piping and well operation without exceeding the maximum permissible specific content of mechanical impurities, including well development on a flare device, then conduct well studies in three modes with gas release into the atmosphere: with the working flow rate of the well, with the well flow rate established by the technological mode and with the maximum permissible flow rate of the well, while monitoring the content of liquid and mechanical impurities in the gas flow and monitoring the stabilization of all measured parameters, with the content of mechanical impurities not exceeding the established limits, and the absence of highly mineralized formation water in the well output, further research is carried out without gas releases into the atmosphere, provided that the well operates in the gas collection network, while in the process of performing work, long-term stabilization of the thermobaric parameters in n modes is ensured and they are recorded, and the well flow rate is monitored using a flow meter unit from the telemetry wells with pressure control in a cluster collector.

The essence of the claimed method is explained by the following figures and description.

Fig. 1 shows a diagram of the wellhead equipment during exploration using a telemetry system.

Fig. 1 shows the following designations and abbreviations:

1 - fountain fittings;

2 - flow meter unit from the well telemetry system;

3 - corner fitting;

4 - control device (CDD);

5 - gas pipeline to the gas treatment facility;

6 - HFC;

7 - diaphragm critical pressure meter (DICP);

8 - pressure gauges.

Fig. 2 shows a block diagram comparing studies using the standard method and the telemetry system.

Fig. 2 shows the following designations and abbreviations:

Qработа - working flow rate of the well;

Qдоп. пром. - established technological mode;

Q additional well - maximum permissible well flow rate;

n - number of research modes.

Fig. 3 shows the indicator curve of a well study using a telemetry system after processing the study.

The essence of the proposed method consists of sequentially performed operations on the well. To perform the study, it is necessary to have a telemetry system in the wellhead piping. Such a piping scheme requires metering devices that allow measuring or calculating the amount of gas passing per unit of time without releasing gas into the atmosphere, also to perform the study, it is necessary to equip the well with portable or use stationary thermometers and pressure sensors, the well must be connected to a gas collection network, or an installation that allows gas to be received during the study (Fig. 1). It should be noted that well studies using this method do not require stopping neighboring wells operating in a single gas collection manifold.

Before conducting research, it is necessary to familiarize yourself with the geological and industrial materials for this well, you need to make sure that the products do not contain liquid and mechanical impurities that do not exceed the permissible values. Next, you need to make sure that the well bottom is clean. To reduce the distortion of readings during research, it is recommended to run the well on a flare device (if the well was operated below the minimum permissible flow rates for liquid removal according to pump and compressor pipes or if the well has been idle for a long time). When performing the study, the first mode is performed Q working on the flare device through the separator and DICT, the flow rate is calculated using formulas (1-3). In the process, the readings of the pressure and temperature devices at the wellhead and before the DICT are constantly recorded. This mode for fields with high filtration characteristics of the formation is sufficient to carry out no more than 20 minutes, however, complete stabilization of the instrument readings should be monitored. After stabilization of the well parameters and reading of data from the devices, the amount of mechanical impurities and liquid in the well output should be estimated. The content of mechanical impurities and liquid in the well output is calculated using formulas (4-5).

where Qр is the working flow rate of the well, thousand ^m3 /day;

P – pressure before the diaphragm, kgf/ ^cm2 ;

k – coefficient for taking into account the change in the gas adiabatic index (≈ 1);

z – coefficient of gas supercompressibility;

T – gas temperature, K;

– relative density of gas;

The coefficient is approximately calculated using the formula:

Dд – diameter of the diaphragm installed in the DICT.

The coefficient of supercompressibility of gas is calculated using the formula:

where: Tcr, Pcr – critical temperature and pressure of gas;

Tpr = Tgas dict/Tcr – reduced gas temperature;

Рпр = Рдикт/Ркр – reduced gas pressure;

Wж - specific liquid content, ^cm3 / ^m3 ;

Wп – specific content of mechanical impurities, ^mm3 / ^m3 ;

Vж – volume of liquid in the cylinders of the Nadym-1 collector, ^cm3 ;

Vп – volume of mechanical impurities in the cylinders of the Nadym-1 collector, ^cm3 ;

t – time of measurements.

Then the second mode of research is carried out Q the established technological mode, this mode is carried out in the same way as the first on the flare device with registration of data from the devices and assessment of the content of mechanical impurities and liquid in the well production, the flow rate is calculated using formulas (1-3). Assessment of the content of mechanical impurities and liquid in the well production is calculated using formulas (4-5). In case of determination of the amount of mechanical impurities or liquid in the well production exceeding the established limits, it is not recommended to continue using this research method since it will be difficult to assess the geological and technical condition of the well due to the lack of the ability to assess the amount of mechanical impurities and liquid in the gas in various operating modes. In this case, the research is continued using the standard method.

Then the third mode of research is carried out Q the maximum permissible flow rate of the well, this mode is carried out in the same way as the first on the flare device with the registration of data from the devices and the assessment of the content of mechanical impurities and liquid in the well product, the calculation of the flow rate is carried out according to formulas (4–5).

After completing three research modes, the well is transferred to work in a single gas cluster collector, then research is carried out with a gradual increase in the well flow rate to the maximum possible, provided that the well operates in the gas collection network. In n research modes, the pressure and temperature at the wellhead are recorded, and instead of data from the DICT, the parameters of the telemetry system installed in the well piping are recorded. The step between the research modes is selected depending on the productive characteristics of the well when working in the gas collection network. The range varies from 20 to 100 thousand ^m3 /day.

In Fig. 2 it is evident that the difference between the studies lies in the method of taking the parameters of pressure, temperature, gas flow rate during the research work on the well with and without gas release into the atmosphere. The process of research using the telemetry system is described above. Research using the standard method is carried out according to the well research manual [Gritsenko A.I. et al. Well Research Manual. - Moscow: Nauka, 1995, pp. 241–256]. The results of the well research using the standard method are presented in Table 1.

An example of implementing the method.

When performing the study, wellhead pressure gauges-thermometers (hereinafter referred to as UMT) and a temperature sensor were used in the first three modes. The gas flow rate was calculated using formula (1) taking into account the pressure value before the DICT. The amount of liquid and mechanical impurities contained in the well output was assessed using the Nadym-1 collector, the data are presented in Table 2. Then the modes were carried out without releasing gas into the atmosphere. The well flow rate was controlled using the HyperFlow telemetry system.

The study was conducted in seven modes using the telemetry system. The operating time in the first, second and third modes was 20, 40 and 60 minutes respectively, the well was stopped between modes for 20 minutes. From the fourth to the seventh mode, the operating time for data stabilization was 40 minutes. Well stopping was not required due to the transition to the next mode using control devices. Well operating parameters in the modes are given in Table 2.

A comparison of the results of studies performed using the standard method [Gritsenko A.I. et al. Well Research Guide. - M.: Nauka, 1995, pp. 241–256] and using a telemetry system is shown in Figure 3. The deviation between the flow curves is comparable to the error in determining the gas flow rate.

When using telemetry systems during gas-hydrodynamic studies, natural gas releases are reduced from seven modes on average 280 minutes to 120 minutes (Table 2). Thus, the total time of gas release during the study of one well is reduced by 160 minutes. Thus, the amount of gas losses when using the proposed method is reduced by more than 2 times, while the operating time of the well in the gas collection network increases. The proposed method ensures an increase in the efficiency of gas-dynamic studies of wells.

Table 1 - Research by standard method

Table 2 - Research using telemetry system

Claims (1)

A method for conducting gas-dynamic studies of gas and gas condensate wells with a telemetry system in the wellhead piping and well operation without exceeding the maximum permissible specific content of mechanical impurities, including well development on a flare device, then conducting well studies in three modes with gas release into the atmosphere: with the working flow rate of the well, with the flow rate of the well established by the process mode, and with the maximum permissible flow rate of the well, while monitoring the content of liquid and mechanical impurities in the gas flow and monitoring the stabilization of all measured parameters, with the content of mechanical impurities not exceeding the established limits, and the absence of highly mineralized formation water in the well output, further research is carried out without gas releases into the atmosphere, provided that the well operates in the gas collection network, while in the process of performing the work, long-term stabilization of the thermobaric parameters in n modes is ensured and they are recorded, and the well flow rate is monitored using a flow meter unit from the well telemetry system with pressure control in the bush collector.