ANALYSIS OF THE RESULTS OF GAS HYDRODYNAMIC STUDIES OF WELLS AT ALAN GAS CONDENSATE FIELDS

ABSTRACT

The main method for determining reservoir parameters is gas-hydrodynamic research methods. The article discusses the analysis of the results of gas-hydrodynamic studies on the state of the well, the productive formation at the Alan gas condensate fields, as well as the determination of the value of the filtration resistance coefficients of the average well of the field, including the filtration resistance coefficients determined by the test results, characterize the state of the reservoir and fluid at the time of the well study.

АННОТАЦИЯ

Основным способом определения параметров пласта являются газогидродинамические методы исследования. В статье рассматривается анализ результатов газогидродинамических исследований о состоянии скважины, продуктивного пласта на газоконденсатных месторождения Алан, а также определение значения коэффициентов фильтрационных сопротивлений средней скважины месторождения, в том числе коэффициенты фильтрационного сопротивления, определяемые по результатам испытания, характеризуют состояние коллектора и флюида в момент исследования скважины.

Keywords: Gas and gas condensate fields (GCF), gas-hydrodynamic studies (GDT), filtration resistance coefficient.

Ключевые слова: Газовые и газоконденсатные месторождения (ГКМ), газогидродинамические исследования (ГДИ), коэффициент фильтрационных сопротивлений.

The development of a gas and gas condensate field is understood as the control of the processes of movement of gas and condensate in the reservoir to wells in order to produce gas and condensate [1]. With full and unconditional observance of the principles of establishing the technological mode of operation, rational development of gas and gas condensate fields will be achieved [2]. Studying the nature of the operation of each well, examining the state of the wellhead and columns during underground repairs, as well as when performing work on the impact on the bottomhole zone, provide valuable information that is taken into account when establishing the technological mode of operation of individual wells and the entire deposit as a whole [3]. Gas-hydrodynamic studies of wells allow obtaining the necessary information about the state of the well and the reservoir [4]. Well preparation for gas-hydrodynamic testing is shown in fig. [5].

Figure 1. Scheme of well preparation for gas-hydrodynamic studies

One of the main tasks of the development analysis is to prepare a technological basis for making adjustments to the approved design indicators. The reliability of the forecast for the development of a gas field is largely due to the representativeness of the initial information used for forecasting and, first of all, information about the filtration and hydraulic characteristics of wells [6]. The experience of operating wells in the fields of hydrogen sulfide-containing gas shows that typical well designs can be used in single-layer fields [7].

During the exploration period at the Alan field [8-9], 17 exploration wells were tested in 73 sites. At the same time, gas inflows of more than 100 thousand m3/day were obtained in 37 cases, weak gas inflows - in 9 cases, weak gas inflows with water - in 7 cases, water inflows - in 11 cases and in 3 objects were obtained gas inflows, but have not been measured. In 6 cases, formation fluid inflows were absent. Based on the results of these tests, the Alan deposit under consideration can be characterized as highly productive. Thus, the maximum working gas flow rate in well 13 with an 18 mm choke was 1246 thousand m³/day. Gas-hydrodynamic studies (GDT) of productive intervals over the past development period were performed at 60 wells. At the same time, the maximum gas flow rate of 1280,1 thousand m³/day (with a drawdown of 30 kgf/sm²) took place in well № 136.

At present, the main method for determining reservoir parameters is gas-hydrodynamic research methods. The need to establish these parameters exists at all stages of the field. The tasks and volumes of these studies at various stages of field development are different. During the periods of exploration and pilot operation of the field, gas-hydrodynamic studies are considered a prerequisite. In the process of deposit development, gas-hydrodynamic studies of wells are also carried out in order to control the development. During this period, the volume of research work carried out in order to analyze the development and control the development depends on the change in reservoir parameters over time.

As a rule, filtration resistance coefficients are determined based on the results of well testing using the steady-state extraction method or using a modification of this method with long-term stabilization of bottomhole pressure and flow rate. The duration of testing gas wells by the method of steady-state extractions in six to eight modes, depending on the reservoir properties of the formation, ranges from several hours to several weeks. Conducting research for such a period is methodically justified, since during this time some parameters of the reservoir and the properties of the liquids and gases saturating it practically do not change. Based on this, it can be argued that the filtration resistance coefficients determined by the test results characterize the state of the reservoir and fluid at the time of the well test.

On fig. 2. presents the results of averaging the values of the coefficients of filtration resistance (FFR) by the graphical-analytical method, based on the well testing data of the wells of the current operating fund. Thus obtained average values of the coefficients under consideration are A=4.94; B=0.0249.

Figure 2. Determination of the value of the filtration resistance coefficients of the average well of the GCF Alan

In view of the fact that the last representative hydrodynamic tests of the Alan wells were carried out using modern innovative technologies, the updating of the FSC was carried out taking into account the parameters of the current technological mode of operation of gas producing wells. In this regard, the values of the current FSC are A=4.94; B = 0.0249 and are taken in this work to predict the further development of the Alan GCF using the material balance method.At the Alan gas condensate field, in this paper, the following restrictions on the technological mode of operation of gas producing wells are adopted: drawdown ≤ 15 kgf/sm², gas flow rate in the flow pipes 4–10 m/s. At the same time, the lower limit of the gas flow rate 4 m/s was adopted to ensure the conditions for the removal of liquid from the bottomhole of gas producing wells.

In conclusion, we can say that based on the above results of gas-hydrodynamic and corrosion studies of wells, taking into account many years of experience in their operation, it is possible to predict the period of further development of the Alan gas condensate field. The lower limit of the gas flow rate 4 m/s was adopted to ensure the conditions for the removal of liquid from the bottomhole of gas producing wells.

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