RU2423306C1 - Method to assess impact of geodynamic factors at safety of underground gas storage operation in porous bed - Google Patents

Abstract

FIELD: measurement equipment. ^ SUBSTANCE: invention relates to an underground gas storage and is designed to determine impact of various natural-anthropogenic geodynamic processes at safety of an underground gas storage (UGS). The method includes development of a geodynamic polygon and execution of a comprehensive geodynamic monitoring (CGDM) on it, building a map following the CGDM results and forecasting emergency geodynamic events. The comprehensive geodynamic monitoring is executed both at regional and local stages in monitoring units - aerospace, deformation, geophysical, hydrogeological and fluid-dynamic ones, with application of various space and time detail of measurements. At the regional stage, site research is carried out within the geodynamic polygon in monitoring units - aerospace, deformation, geophysical ones. At the local stage of CGDM, well studies are carried out in monitoring units - hydrogeological, fluid-dynamic and geophysical ones. A refined geodynamic model is created. Classification of criterial indices is developed for each monitoring unit to assess a geodynamic risk, to assign a five-point grading at the regional stage, a three-point grading at the local stage, according to the level of the geodynamic danger. Indices calculated for each monitoring unit are compared with criterial indices, intensity of hazardous geodynamic and anthropogenic-induced processes expression is assessed in all monitoring units, then a single total coefficient of UGS geodynamic condition is calculated using the formula. It is compared with a previously calculated criterial coefficient for each level of geodynamic hazard, a level of geodynamic hazard of UGS is defined, and a final map of area ranging according to extent of geodynamic risk is built. ^ EFFECT: improved reliability and safety of UGS operation. ^ 3 dwg, 4 tbl

Description

The invention relates to the gas industry, in particular to underground gas storage, and can be used to determine the effect of various forms of natural-technogenic geodynamic processes on the safety of underground storage of underground gas storage in a porous reservoir.

Analysis of the current level of technology showed the following:

- there is a known method for identifying areas of potential accident rates of structures (see paragraphs of the Russian Federation No. 2206908, class G01V 9/00, published in OB No. 17, 2003), according to which ground and / or space repeated geodetic observations of the earth’s surface are made observation points with an interval between repeated observations at least twice a year, determine the source parameters of anomalous displacements with the subsequent identification of the accident zones of structures.

The disadvantage of this method is the low reliability and safety of the operation of underground gas storage due to the fact that only space and geodetic observations are involved in the method, which do not reflect the actual picture of the manifestation of various forms of natural-technogenic geodynamic processes. The method does not compare geodetic observations with other types of studies, in particular with geophysical, fluidodynamic, seismic, etc., which may lead to the unawareness of possible precursors of various forms of geodynamic events, such as activation of faults, earthquakes, migration processes, etc. Low the informational content of the research results does not allow to obtain a high reliability assessment of the influence of natural and technogenic factors on the geodynamic state as an underground storage facility in general, and its individual sections.

As a prototype, a method for assessing the influence of geodynamic factors on the safe operation of underground gas storage in a porous reservoir, described in the Concept "Geodynamic safety of the development of the hydrocarbon potential of the bowels of Russia", is taken. M.: Publishing House of the Institute of Geology and Geology, 2000, pp. 23-31, including the creation of a geodynamic test site, conducting complex geodynamic monitoring of the GGDM natural and technogenic processes at the regional and local stages by monitoring units - aerospace, deformation, geophysical, hydrogeological and fluidodynamic, using various spatio-temporal detail of measurements, map building based on the results of QGDM at the regional stage and predicting the occurrence of emergency geodynamic events.

The disadvantage of this method is the insufficiently high reliability and safety of operation of the UGS facility, due to the following reasons:

- the proposed structure of geodynamic monitoring, consisting of interconnected blocks, does not have a clear delineation of these blocks according to the stages of work;

- only regional studies are carried out at the regional and local stages, which do not provide detailed studies in places of active manifestation of natural and technologically induced geodynamic phenomena or in areas of the expected occurrence of emergency geodynamic events within the mining allotment of underground gas storage facilities;

- in each of the blocks the set of methods and types of observations, as well as the frequency of studies, are not specified;

- methods for obtaining quantitative characteristics of indicators of the manifestation of geodynamic activity, which most accurately and comprehensively describe the quantitative and qualitative nature of the manifestation of natural-technogenic geodynamics, have not been defined;

- the lack of criteria indicators does not allow a comparison with indicators calculated for each monitoring unit to determine the intensity of the manifestation of dangerous geodynamic natural and technologically induced processes and phenomena;

- insufficiently high information content of the research results does not provide high reliability in assessing the manifestation of various forms of natural-technogenic geodynamic processes.

The technical result that can be obtained by carrying out the invention provides an increase in the reliability and safety of the operation of underground gas storage due to:

- a clear demarcation of the monitoring units according to the stages of the QGDM, with conducting regional studies at the regional stage, which will reveal the extent of the zones of abnormal development of modern geodynamic processes and their spatial relationship to the location of systems and objects of the oil and gas complex in the regional plan, at the local stage - downhole research, with providing detailed studies in places of active manifestation of natural and technologically-induced geodynamic phenomena or where the expected occurrence of emergency geodynamic events within the mining allotment of underground gas storage facilities;

- increase the reliability of assessing the manifestations of various forms of natural-technogenic geodynamic processes due to the high information content of the research results provided by a set of methods and types of observations, the frequency of studies, as well as the determination of geodynamic activity indicators for all monitoring units that most accurately and comprehensively describe the quantitative and qualitative nature of the manifestation of natural -man-made geodynamics.

The technical result is achieved using a method including the creation of a geodynamic test site, conducting complex geodynamic monitoring on it of the QGDM natural and technogenic processes at the regional and local stages by monitoring units - aerospace, deformation, geophysical, hydrogeological and fluidodynamic, using various spatial and temporal measurements , building a map based on the results of the CGM at the regional stage and predicting the occurrence of emergency x geodynamic events.

According to the claimed method carry out QGDM at the regional stage with a frequency of at least once every five years, and at the local stage - at least twice a year. At the regional stage, the QGDM conducts area studies within the created geodynamic testing ground for monitoring blocks - aerospace, by conducting aerospace observations of the underground surface of the underground gas storage, with the determination of indicators - the dynamics of the lineament network density, the relative surface of the zones of the geodynamic influence of faults and the relative area of the distribution of mesocracks, deformation, by measuring the deformation of the UGS day surface, with the determination of the subsidence rate and surface curvature and settling and horizontal deformations, geophysical, by recording the seismic area UGS and disjunctive disorders UGS tank, with the definition of volume ratio staggered disjunctive disorders UGS reservoir seismicity of UGS and maximum values of the relative amplitude exceeding microfractures. According to the data obtained, a preliminary geodynamic model is created.

At the local stage, KGDM conduct borehole research on monitoring units - hydrogeological, by conducting hydrogeological studies of wells, with the determination of indicators of the dynamics of the levels of static pressure in one season, the dynamics of changes in temperature regime in one season and the dynamics of mineralization of formation water, fluid-dynamic, through gas-dynamic studies of wells , with the determination of the dynamics of reservoir pressure in the well or group of wells, the degree of water cut in the wells during the selection and containing helium Ia, geophysical, by conducting well logging, with the determination of gas saturation of surface deposits, the pressure of annular or annulus and the number of wells with the poor condition, and then create a refined geodynamic model.

For each monitoring unit, a classification of criteria indicators is being developed for assessing geodynamic risk with assigning them a five-point gradation at the regional stage and a three-point gradation at the local stage, according to the level of geodynamic hazard. The indicators calculated for each monitoring unit are compared with the criteria indicators, the intensity of the manifestation of dangerous geodynamic and technogenic-induced processes for all monitoring units is evaluated.

Calculate a single total coefficient of the geodynamic state of underground gas storage by the formula

where R _G is the single total coefficient of the geodynamic state of the underground gas storage facility;

x ₁ -x ₁₈ - weighting factors for each monitoring unit, determined taking into account experimental data;

k ₁ -k ₁₈ - scores of indicators of geodynamic activity according to the level of geodynamic hazard, obtained according to the results of KGDM,

compare it with a pre-calculated criterion coefficient for each level of geodynamic hazard and determine the level of geodynamic hazard of underground gas storage facilities.

Build a final map of the ranking of the territory according to the degree of geodynamic hazard.

Thus, the claimed technical solution meets the condition of novelty.

The geodynamic test site is a complex of special underground and ground facilities designed for the GGDM. When creating a geodynamic test site, the configuration of the measuring network is determined based on the features of the geological structure of the territory and the specifics of the UGS under study, as well as the features of its operation. QGDM is carried out at the geodynamic test site in two stages - regional and local. During both stages of the QGDM, methods are used with different spatio-temporal detail of measurements: discrete (repeated), continuous and their combination.

To increase the reliability of the work performed, at each stage of the QGDM, studies are carried out in three monitoring units. Moreover, at the regional stage, areal studies are carried out, and at the local stage, downhole studies. For each block of work, three indicators of geodynamic activity are determined that most accurately and comprehensively describe the quantitative and qualitative nature of the manifestation of natural-technogenic geodynamics.

At the regional stage, the KGDM conduct areal studies in which observations cover the maximum lateral mining allotment area and the maximum thickness of the geo-object reservoir used for underground storage facilities, as well as the area (ring) around it, on average, 2-3 km wide. Moreover, the geodynamic test site at this stage is created on the condition of constant existence within the described boundaries. At the regional stage, it is recommended that the observing system also cover facilities and settlements that are within the scope of the impact of possible dangerous geodynamic events. The results of the studies allow us to identify extended zones of anomalous development of modern geodynamic processes and their spatial relationship to the location of systems and objects of the oil and gas complex in the regional plan. The periodicity of work at the regional stage is determined by the specifics of the UGS operation mode, the nature and intensity of the ongoing geodynamic processes and is at least once every five years, with possible adjustment depending on the scale of the identified zones of intense manifestation of geodynamic processes or the appearance of their precursors.

At the regional stage, the KGDM conduct field research on three monitoring units: aerospace, deformation and geophysical.

The aerospace monitoring unit conducts aerospace observations of the underground surface of the underground gas storage facility, with information on the potentially stressed state of the operated underground gas storage facility. Photographing is carried out in the entire visible range of the electromagnetic spectrum and in the near infrared range. The shooting scale depends on parameters such as shooting height and focal length of the lens. Recently, photographing from space has been carried out on high-resolution digital cameras, followed by the transfer of images via radio channels. The season of shooting is essential, as the condition of the vegetation cover, the presence of snow and other natural factors determine the decryption conditions. For the production of an aerospace unit for monitoring geodynamic processes in the underground gas storage facilities, images of the following types of work are used:

- multizone space photography, carried out in several ranges of the spectrum, which allows the selection of the most optimal conditions for photographing certain natural objects and obtain their spectral characteristics. The processing of this type of images is carried out in a comprehensive manner, both in various spectral ranges and in their combination in the form of a synthesized image;

- infrared shooting, fixing the heat fluxes emitted by the Earth’s surface, which are determined by temperature, properties of natural formations, heat exchange conditions and heat sources in the bowels, which allows to identify fault zones, fractures and interfaces of tectonic blocks;

- radar survey, which is carried out by side-view radars and does not depend on time and weather conditions. Survey materials make it possible to confidently decipher the geological boundaries of structural-material complexes, details of their internal structure and relationships with framing rocks, disjunctive disturbances, and also geological objects not opened by erosion.

The most informative are space photographs of a scale of 1: 200000, their enlarged prints of 1: 100000, 1: 50000 and aerial photographs of larger scales (1: 36000, 1: 22000, etc.).

Research on the aerospace block is carried out on the basis of the analysis of AKFS materials using data from the Federal Space Agency Roscosmos. They conduct the processing of multi-scale aerospace photographs of the ACFS and, based on the results of decryption, determine the indicators to identify the natural and technogenic activity of the UGS facility territory.

The aerospace monitoring unit determines the indicators:

- the dynamics of the density of the lineament network (ΔО), showing the degree of activity of endogenous surface natural natural and induced technogenic geodynamic processes within the underground gas storage facilities. One of the main indicators characterizing the fragmentation of the geomorphological level of the underground gas storage facilities;

- the relative surface of the zones of geodynamic influence of faults (Z), characterizing the degree of activity of hidden (deep) geodynamic processes. One of the important indicators of geodynamic activity, speaking not only about the natural state of underground gas storage facilities, but also about “hidden” zones, a change in which may occur in the near future, since these zones have increased values of dynamic stresses;

- the relative area of distribution of the zones of mesocracks (M), which describes the activation of endogenous natural and technogenic processes. It characterizes the coverage of UGS facilities by induced geodynamic processes.

Using the deformation monitoring unit, measurements are made of the deformation of the daily surface of the underground gas storage facilities, with information on the current stress-strain state of the underground gas storage and its manifestation at the geomorphological level. Surveying and geodetic observations are carried out with different spatial and temporal details, while instrumental (geodetic) observations and analytical research methods are used. The registration of extensive horizontal deformations of the earth's crust of the study area and the determination of their general orientation is carried out using GPS observations. An astronomical and geodetic network is used, consisting of triangles with side dimensions of 0.5-3 km and including about 20-30 reliably fixed reference points of GPS observations. To confidently monitor the development of geodynamic processes and obtain reliable indicators of geodynamic activity, repeated observations are tied to benchmarks used as initial in previous leveling cycles, as geodynamically dangerous zones are identified, a network of benchmarks can be thickened in these areas. Recommended re-leveling lines are drawn across the zones of the most probable deformations. The configuration of the measuring network is chosen taking into account the geological features and specifics of the underground gas storage facilities. According to the results of the work carried out, indicators are determined.

The deformation monitoring unit determines the indicators:

- subsidence rate (v), characterizing the intensity of vertical tectonodynamic deformations of technogenic genesis;

- the curvature of the subsidence surface (trough) (k), which evaluates the nature and volume of the underground storage area involved in the deformation process;

- horizontal deformations (ε), showing the activation of natural tectonic processes.

The geophysical monitoring unit records the seismic activity of the underground gas storage facility and disjunctive disturbances of the underground gas storage reservoir, with information on variations of various geophysical fields. Work on the geophysical monitoring unit is carried out by conducting seismometric studies at the peak of the maximum or minimum gas volume in the underground gas storage facility, which makes it possible to more clearly recognize the stress fields that have arisen and manifested in the underground gas storage tank. Excite oscillations using non-explosive sources. Methods of exciting oscillations are selected in accordance with the tasks and methods of conducting field work. The choice of the optimal variant of excitation, based on the study of the wave field in the process of experimental work, is carried out at the initial stage of the design of underground gas storage. The studies are carried out using the common depth point method in 3D modification using a surveillance system combining parallel, longitudinal and non-longitudinal profiles. Seismic activity registration points are linked to wells located in or near the research area. In order to clarify the geodynamic situation, more detailed work is carried out in separate areas identified by previous types of studies.

The geophysical monitoring unit determines the indicators:

- volumetric coefficient of the prevalence of disjunctive disorders (micro-fractures) of the underground gas storage tank (K _p ). This indicator estimates the degree of infection of UGS with endogenous geodynamic processes;

- seismicity (induced) of the UGSF (C) territory, which characterizes the degree of environmental response to the operation of UGS facilities or the activity of the geological environment in the UGS facility, as well as the seismic risk of damage to the production units;

- the maximum value of the relative excess of the amplitude of the microfracture (disjunctive) (ΔL), showing the deformation of the reservoir at the macro level. Describes the degree of critical response of the geo-object environment to anthropogenic interference or the degree of occurrence of natural geodynamic processes.

Based on the results of the QGDM conducted at the regional stage, a preliminary geodynamic model of the underground gas storage facilities is created, i.e. make up a geodynamic map on which the patterns of the distribution of zones of development of geodynamic processes are displayed by assessing the dynamics of the geomorphological level and the features of the deep structure of the object under study. The creation of a preliminary geodynamic model helps to identify the stages of relief changes, zones of development of mesocracks, disjunctives, stress-strain zones and complexes. It carries information on the localization of modern dangerous geodynamic events and processes and visualizes them.

An assessment of the preliminary geodynamic model is carried out each time after the end of the regional stage of the QGDM, i.e. at least once every five years.

At the local stage, the QGDM conduct downhole studies, create a system of detailed studies in places of active manifestation of natural and technologically induced geodynamic phenomena or in areas of the expected occurrence of emergency geodynamic events within the mining allotment of underground gas storage. The geodynamic test site at the local stage has a mobile type, and its configuration varies depending on the identified potentially hazardous areas. The landfill area, as well as the detail of the research conducted, may vary depending on the recommendations issued by the results of the previous stage. The frequency of the work carried out at the local stage is at least twice a year, which makes it possible to select the optimal operating mode of the wells and timely determine the nature of changes in the natural environment during the development of geodynamic processes.

At the local stage, the QGDM conduct downhole research in three monitoring units: hydrogeological, fluidodynamic and geophysical.

The hydrogeological monitoring unit conducts hydrogeological studies of wells to obtain information on the geochemical composition and dynamic state of fluid systems. Samples of formation fluid are taken from control and observation wells for a full chemical analysis, natural static groundwater levels are established to determine the spectrum and concentration of pollutants contained in the liquid phases of the UGS process chain; quantitative and qualitative compositions of water-soluble gas are determined, and pressure and temperature dynamics are evaluated. In the course of the research, the degree of stability of the bottom-hole zone of the reservoir is determined, the position of the GWC, gas manifestations and corrosion hazard are monitored.

The hydrogeological monitoring unit determines the indicators:

- the dynamics of static pressure levels in one season (ΔН), which estimates the stress distribution in underground storage facilities generated by the pressure of the underlying water. This indicator characterizes the degree of influence of the hydrogeological environment on the geodynamic features of the formation and redistribution of the tectonodynamic stress field;

- the dynamics of changes in the temperature regime in one season (ΔT), which characterizes the energy situation in the reservoir during the change of gas injection-extraction cycles. Determines the energy regime of the process of redistribution of tectonodynamic stresses;

- the dynamics of mineralization of formation water (ΔMi), evaluating the internal and external dynamics of the hydrogeological environment. It characterizes the material balance and dynamics of mass transfer under the influence of stress redistribution.

Gas dynamic studies of the wells are carried out in the fluid dynamic monitoring unit to obtain information on the field performance of the wells and near-well zones. The objects of research are both individual wells (piezometric and observation), and groups of wells recommended for detailed work on the previous research cycles of the regional stage of the QGDM. In this monitoring unit, standard gas-dynamic research methods are used - barometry, thermometry, flow metering, moisture metering, gas sampling, during which the current reservoir pressure is determined when gas is injected and taken into the storage, the permeability of the reservoir, the parameters of the equation of pressure flow in the well-reservoir system ", The composition of the gas.

The fluid dynamic monitoring unit determines the indicators:

- the dynamics of reservoir pressure in a well or group of wells (ΔP _pl ), evaluating the zones of greatest influence on underground gas storage, both due to changes in geological conditions and from technogenic interference. It characterizes the redistribution of vectors and describes the nature of the change in the pattern of the stress field;

- the degree of water cut of wells during the selection (S _about ), used to highlight geodynamically weakened intervals along the section of wells (group of wells). Describes the formation of geodynamically weakened zones both in area and in section;

- helium content (He), showing the activity of deep faults under the geo object. It characterizes the degree of occurrence and activation of the relationship between the UGS geo-object and the surrounding rock mass.

In the geophysical monitoring unit, geophysical studies of the wells are carried out to obtain information on the physical properties of the rocks and their effect on the production characteristics of production wells. During the work, methods are used that are most sensitive to changes in the stress state of the subsoil: acoustic logging, electric lateral logging, neutron gamma-ray logging, etc. Existing cracks (column defects) and a change in their thickness are detected by magnetic pulse defectoscopy. Casing gas accumulations are detected by monitoring the intensity of induced radioactivity (repeated measurements of NTK). Interstratal and annular gas flows are detected by temperature and pressure anomalies, which are recorded by thermometry, barometry, flow metering and moisture metering of wells under various operating conditions. Research is conducted in observational and geophysical wells throughout the entire section uncovered by drilling. The frequency of the work is determined by the mode of gas injection and gas extraction in the underground gas storage facility; it has an annual cycle.

According to the results of the geophysical monitoring unit, indicators are determined:

- gas saturation of near-surface deposits (G), indicating the intensity of technogenic gas migration. The indicator is quantified on the basis of ongoing work to monitor the tightness of the tire and the possible formation of man-made deposits;

- annular or annular (P _k ) pressures characterizing the degree of damage to the underground working units of the underground gas storage station. Assesses the negative impact of technogenic-induced and natural geodynamic processes on underground gas storage wells;

- the number of wells with unsatisfactory technical condition (N), which estimates the paths of gas migration from the storage facility and the greatest geodynamic impact based on the diagnostics of the technical condition of the production well stock.

Based on the results of the QGDM, a refined geodynamic model is created at the local stage with the allocation of wells (or a group of wells) by the UGS area, as well as intervals in the section of wells that are subject to the negative influence of geodynamic factors. The refined geodynamic model is based on the initial geodynamic model, gives a spatio-temporal description of the mass transfer processes of rock particles, fluids and the redistribution of technogenic tension.

This model is updated annually in accordance with the schedule of the CGDM, at least twice a year.

An increase in information content due to the results of geodynamic modeling of the regional and local stages of the QGDM allows a more reliable assessment of the geodynamic state of underground gas storage facilities. Moreover, this assessment is of a qualitative nature and is aimed, first of all, at identifying areas with a negative influence of geodynamic forces on technological processes occurring in the deposits, the technical condition of the well stock and the geological change in the entire storehouse as a whole.

For a quantitative characteristic of the intensity of the manifestation of geodynamic processes for each stage of the QGDM, a classification of criteria indicators has been developed that most comprehensively reflect the natural and technogenic state of underground gas storage facilities (table 1, 2). The classification is structured so that each indicator has initiating forces inherent in its numerical value. Based on a comprehensive comparison of these indicators, they conclude that there is a general trend in the development of underground gas storage geodynamics.

This classification is based on the analysis of field data and the experience of geodynamic modeling of underground gas storage facilities in a porous reservoir.

The determination of the intensity of manifestations of dangerous geodynamic and technogenic-induced processes is based on a level scale of geodynamic hazard in which criteria are assigned a certain number of points according to the level of geodynamic hazard.

For the criterion indicators of the regional stage, the level of geodynamic hazard is presented in the form of a five-point gradation (table 1):

- “safe” - the level of indicators that do not differ from the background (or initial) values for a certain period of operation, this level is assigned a “1” point;

- “conditionally safe” - the level of values slightly different from the background (or initial), due only to the created technogenic load of the operated facility, this level is assigned a “2” point;

- “abnormal” - the values of this level are clearly (confidently) distinguished from the general data array. At the same time, they are combined with nearby data into zones where each of these values differs from the weighted average (background or initial) component by area by more than 20%. Anomalies of values are due to the reaction of the geological environment to the technogenic impact, this level is assigned a “3” point;

- “critical” - the values of this level significantly differ from previous data and exceed the established indicators for the safe operation of wells and facilities. The overall picture of the distribution of indicators changes completely, this level is assigned “4” points;

- “catastrophic” - indicators of this level speak of “global” changes that have occurred in the underground gas storage facilities. Limit values exceed not only those established for safe operation of underground gas storage facilities, but also for individual technological indicators (reservoir pressures, pressure on the tubing, elastic moduli of rocks, etc.), they assign “5” points to this level.

To assess the criterion indicators of the local stage, a simplified level scale of geodynamic hazard is used, presented in the form of a three-point gradation, without indicators of the levels “conditionally safe” and “catastrophic” (table 2). The “safe” level is assigned a “1” point, the “abnormal” level is “2” points, and the “critical” level is “3” points. This gradation allows a more accurate approach to determining the safe operation of underground gas storage facilities and to prevent emergencies.

The ability to compare the calculated indicators for each block with classified criteria indicators allows you to more reliably assess the intensity of the manifestation of dangerous geodynamic and technogenic-induced processes and, according to the level of geodynamic hazard, assign the appropriate number of points.

Subsequently, a single total coefficient of the geodynamic state of the underground gas storage facilities is calculated taking into account the weight coefficients and scoring values of the geodynamic activity indicators. In this case, the weighting coefficients are determined on the basis of experimental data, depending on the intensity and information content of each monitoring unit (table 3), and the scores of the geodynamic activity indicators are based on the results of the QGDM. A single total coefficient is compared with a pre-calculated criterion coefficient for each level of geodynamic hazard and the level of geodynamic hazard of underground gas storage facilities is determined (table 4). A final map of the ranking of the underground storage facilities by the degree of geodynamic hazard, i.e. distribution map of this coefficient. They analyze the map and make a conclusion about the current geodynamic state of underground gas storage facilities and the development of preventive measures to prevent negative geodynamic phenomena.

Based on the foregoing, we have not identified technical solutions that are based on features that match the distinctive features of the claimed technical solution, i.e. methods for assessing the influence of geodynamic factors on the safe operation of underground gas storage in a porous reservoir, ensuring the achieved technical result. Thus, the technical solution does not explicitly follow from the prior art, i.e. meets the condition of inventive step.

The inventive method is illustrated by the following drawings:

figure 1 presents a diagram of a geodynamic test site;

figure 2 - preliminary geodynamic model of underground gas storage;

figure 3 - the final map of the ranking of the territory of the underground gas storage facility according to the degree of geodynamic hazard.

Legend: 1 - underground gas storage facility, 2 - geodynamic testing ground area, 3 - GPS observation points, 4 - recommended re-leveling lines, 5 - seismic activity registration points; 6 - wellhead; 7 - isohypses of the roof of the reservoir; 8 - predicted tectonic disturbances; 9 - isohypses of the surface of the gas-water contact; 10 - lineaments identified on the basis of aerial photographs and space images; 11 - deformations of the geomorphological level, localized on the basis of materials from aerial photographs and satellite imagery AKFS; 12 - piezometric wells; 13 - observation wells; 14 - geophysical wells; 15 - area of distribution of values of a single total coefficient of the geodynamic state of underground gas storage facilities; 16 - zone of development of abnormal geodynamic activity, identified by the results of the local stage of the QGDM.

In more detail, the essence of the proposed method is illustrated by example.

The proposed method is tested on one of the UGS 1 operated in a porous reservoir. All observations are carried out at geodynamic test site 2, the dimensions of which correspond to the area of the mining allotment and the ring around it, 3 km wide (Fig. 1). At the regional stage, the KGDM conduct field research on three monitoring units: aerospace, deformation and geophysical.

When performing the aerospace monitoring unit, aerospace observations of the underground surface of underground gas storage facilities are carried out, followed by processing of multi-scale AKFS. Based on the results of the decryption of materials in the eastern part of the study area, zone 11 was identified (Fig. 2), characterized by the presence of tangential stresses of a local nature, indicating the heterogeneous geodynamic nature of the studied UGS. Subsequently, these data were confirmed by the results of paleotectonic constructions and by the obtained indicators of geodynamic activity.

According to the data of the aerospace monitoring unit, the following indicators are determined:

Lineament network density dynamics (ΔО):

ΔО = O _i -O _i-1 = 0.1-0.05 = 0.05 km / km ² ,

where O _i is the density of the lineament network at the present stage of measurements, km / km ² ;

O _i-1 is the density of the lineament network at the previous measurement stage, km / km ² .

Wherein

where L _i is the total length of lineaments within the geodynamic range or its section at the present measurement stage, km. It is measured at interpretation of AKFS;

L _i - the area of the geodynamic test site or its site at the present stage of measurement, km ² .

Relative surface of zones of geodynamic influence of faults (Z):

- площадь поверхности зон геодинамического влияния разломов в пределах геодинамического полигона или его участка на текущем этапе измерений (абсолютное значение), км². Замеряется при интерпретации АКФС;Where

- the surface area of the zones of the geodynamic influence of faults within the geodynamic polygon or its section at the current measurement stage (absolute value), km ² . It is measured at interpretation of AKFS;

S _i - the area of the geodynamic test site or its site at the current stage of measurement, km ² .

Relative area of distribution of mesocrack zones (M):

- площадь распространения зон мезотрещиноватости в пределах геодинамического полигона или его участка на текущем этапе измерений (абсолютное значение), км². Замеряется при интерпретации АКФС;Where

- the area of distribution of the zones of mesocracks within the geodynamic range or its section at the current stage of measurement (absolute value), km ² . It is measured at interpretation of AKFS;

S _i - the area of the geodynamic test site or its section at the current stage of measurement.

Surveying-geodetic observations with different spatial and temporal detail are carried out by the deformation monitoring block. Registration of extensive horizontal deformations of the earth's crust of the study area and the determination of their general orientation is carried out using GPS observations 3 (figure 1). To reliably track the development of geodynamic processes and obtain reliable indicators of geodynamic activity, repeated observations are tied to benchmarks used as initial ones in previous leveling cycles. Recommended re-leveling lines 4 (Fig. 1) are drawn across the zones of the most probable deformations.

According to the obtained data of the deformation monitoring unit, indicators are determined:

The drawdown speed (v) is calculated by the formula:

where h _i is the excess obtained in the i-th observation cycle, mm;

h ₀ is the excess obtained in the previous observation cycle, mm;

ΔT is the time interval between the compared cycles (at the time of the creation of the geodynamic test site), year.

The curvature of the surface (trough) settling (k) is calculated by the formula:

where η _max is the maximum subsidence (vertical displacement) of the earth's surface above the underground storage facility, determined by calculation, η _max = 35.1 mm = 0.0351 m;

S (Z) is the tabulated function of influence, S '(Z), S' '(Z), the first and second derivatives of S (Z), obtained by regression analysis methods are presented in table 5.

Table 5 one 2 3 four 5 6 7 8 9 10 Z 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 S (Z) 1.00 0.99 0.98 0.94 0.89 0.83 0.75 0.67 0.59 0.50 S '(Z) 0.00 0.15 0.45 0.82 1.16 1.45 1,64 1.73 1.72 1,63 S '' (Z) 0.00 -4.99 -7.01 -7.30 -6.42 -4.81 -2.84 -0.80 1.09 2.67 Continuation of table 5 eleven 12 13 fourteen fifteen 16 17 eighteen 19 twenty 21 Z 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 S (Z) 0.42 0.35 0.28 0.22 0.17 0.13 0.09 0.06 0,03 0.01 0.00 S '(Z) 1.46 1.25 1.01 0.77 0.55 0.36 0.21 0.11 0.05 0.02 0.00 S '' (Z) 3.85 4,56 4.82 4.66 4.16 3.40 2,51 1,62 0.88 0.43 0.00

Z is the dimensionless coordinate of the point of the edge of the settling trough, equal to X / L _min for the main cross section of the trough, Y / L _max for the main longitudinal section of the trough;

X, Y - coordinates of points in the edge of the trough in its main transverse and longitudinal sections, counted from the inner border of the edge part;

L is the size of the edge of the settling trough, equal in the longitudinal main section - L _min = 1500 m, in the transverse - L _max = 3100 m

The curvature of the subsidence surface at the considered point of the edge of the trough in the direction of the longitudinal section is equal to:

The curvature of the subsidence surface at the considered point of the edge of the trough in the direction of the cross section is:

The value of the curvature of the surface (trough) settling (k) is defined as the arithmetic mean between k _x and k _y , therefore,

k = 1.33 × 10 ^-8 m ^-1 .

Horizontal strain (ε) is calculated by the formula:

where e is the coefficient of transition from curvature to horizontal strains, the value of which is determined by calculation, depending on the magnitude of the curvature k. The data of the dependence of the indicators are presented in table 6.

Horizontal deformations in the direction of the longitudinal section are equal to:

Horizontal deformations in the direction of the cross section are equal to:

The value of horizontal deformations (ε, mm / m) is determined as the arithmetic mean between ε _x and ε _y , therefore,

ε = 0.473 × 10 ^-3 mm / m.

Indicators of geodynamic activity in the geophysical block are obtained as a result of seismometric studies. The studies are carried out using the common depth point method in 3D modification using an observation system combining parallel longitudinal and non-longitudinal profiles. The registration points of seismic activity 5 (Fig. 1) are linked to wells located in or near the research area.

According to the data of the geophysical monitoring unit, indicators are determined:

The volumetric coefficient of the prevalence of disjunctive disturbances (micro-fractures) of the reservoir of the geo-object (K _r ).

where (V _p ) _i is the volume of rocks affected by disjunctive disorders within a single independent geoblock or its section at the current measurement stage, km ³ . Measure when conducting seismometric studies;

(V _s ) _i is the volume of a single independent geoblock within the mining allotment of an underground gas storage facility or its section at the current measurement stage, km ³ .

The seismicity (induced) of the underground storage facilities (C), in points on the Richter scale, is determined by the results of measurements of seismic sensors over the entire area of the geodynamic range.

C = 1;

The maximum value of the relative excess of the amplitude of the microfracture (disjunctive) (ΔL, m):

where (ΔL _i ) _max is the maximum value of the excess of the amplitude of a single microfracture in the rock mass within the geodynamic range or its section at the current measurement stage (absolute value) relative to the previous measurement, m;

L _i-1 - the amplitude of the considered micro-fracture in the previous stage of observations, m

As a result of the QGDM at the regional stage, indicators of the manifestation of geodynamic activity were obtained, the values of which are shown in table 7.

Table 7 Indicators of geodynamic activity at the regional stage Aerospace block Deformation block Geophysical areal monitoring monitoring monitoring unit ΔO, Z M v k · 10 ^-8 ε · 10 ^-3 K _P C ΔL, km / km ² % % mm / year m ^-1 mm / m point m 0.05 1,5 19 8 1.33 0.47 0.02 one 0.01

According to the results of the regional stage, create a preliminary geodynamic model of underground gas storage, presented in the form of a geodynamic map (figure 2). The map is compiled according to the analytical principle, the essence of which is to identify and trace the zones of development of geodynamic (natural-technogenic) processes along the studied territory. The basis of the map is data on the location of wells 6, isohypses of the roof of the formation 7, predicted tectonic disturbances 8, isohypses of the surface of the gas-water contact 9, lineaments 10, revealed by the materials of interpretation of ACFS and deformation of geomorphological level 11, localized during processing of ACFS (figure 2) . Predicted tectonic disturbances and zones of deformation development are shown on the map in different colors, and the lineament network is represented as streamlines. All these elements are displayed on the map as indicators of geodynamic processes; they complement and refine information on the geodynamic state of underground gas storage facilities.

At the local stage, the QGDM conducts research on three monitoring units: hydrogeological, fluidodynamic, and geophysical downhole.

When performing a hydrogeological monitoring unit, reservoir fluid samples are taken from control and observation wells for a full chemical analysis, natural static groundwater levels are established to determine the spectrum and concentration of pollutants contained in the liquid phases of the underground gas storage chain; quantitative and qualitative compositions of water-soluble gas are determined, and pressure and temperature dynamics are evaluated.

According to the data of the hydrogeological monitoring unit, indicators are determined:

The dynamics of the static pressure levels (ΔН) is defined as the modular ratio of the static pressure levels calculated for one UGS operation cycle (in the periods “after injection” and “after selection”). The static pressure in each of the periods is calculated by the formula:

H = 10P- (h-Alt),

where P is the atmospheric pressure, atm, measured at a depth of h, m.

The static pressure during the injection period is:

N _s = 10P- (h-Alt) = 10 × 114.82- (1034-276) = 390.2 m.

The static pressure during the selection period is:

H _from = 10P- (h-Alt) = 10 × 77.95- (1034-276) = 21.49 m.

Therefore, the dynamics of the levels of static heads (ΔН) for one UGS operation cycle is:

ΔH = N _s -H _from = 390.2-21.49 = 368.7 m.

The dynamics of the temperature regime (ΔT) is defined as the difference in temperature measured during one cycle of the UGS facility. Measurement of reservoir temperature in the periods “after injection” and “after selection” is carried out at a depth of the upper perforation holes in both a stopped and a working well. The formation temperature is measured at a depth of the upper perforation holes both in a stopped and in a working well. In order to reduce the influence of factors distorting the temperature distribution in the well, thermometric measurements are carried out before all other types of research in the well are carried out.

ΔT = T _from -T _Zak = 94-39 = 55 ° C.

The dynamics of changes in the salinity of formation water (ΔMi) is determined after sampling water through certain depths. The sampling interval is indicated in the research plan.

According to the results of sampling, the dynamics of changes in the salinity of formation water for one cycle of underground gas storage is:

ΔMi = Mi _from -Mi _Coll = 56-4,1 = 51.9 g / ^cm3.

The objects of the study of the fluidodynamic block are both individual piezometric wells 12 and observation 13 (Fig. 3), as well as groups of wells recommended for detailed work on previous studies of the regional stage of the QGDM. In the process of performing the work of this unit, gas-dynamic methods are used to determine: the current reservoir pressure during gas injection and withdrawal into the storage, the permeability of the reservoir, the parameters of the equation for the pressure influx in the well-reservoir system, and the gas composition. The analysis of the obtained data allowed us to identify areas of abnormal manifestations of the fluid dynamic regime and zones of varying degrees of subsoil tension.

According to the data of the fluid dynamic monitoring unit, the following indicators are determined:

The dynamics of reservoir pressure in the reservoir (ΔP _PL )

ΔP _pl = (P _pl ) _i - (P _pl ) _i-1 = 10.8-4.4 = 6.4 MPa,

P _grp = 20 MPa, therefore ΔP _pl <P _grp ,

where (R _pl ) _i is the reservoir pressure within the local geodynamic test site or a portion of it at the current stage of observations, MPa;

(R _pl ) _i-1 — reservoir pressure within the local geodynamic test site or a portion of it at the previous observation stage, MPa;

P _fracturing - hydraulic fracturing pressure, MPa.

The degree of _{water cut} in the wells during the selection (S _about ),

where (S _bore ) _about - the number of wells watered during the selection or injection of gas within the local geodynamic range or its section, pcs .;

S ^_ _rms total number of wells disposed within a local geodynamic polygon or a portion thereof, pieces.

Helium content (He,% of MPC),

therefore, Not = 7 MAC

where m (He) is the mass of helium in 1 DM ³ samples of reservoir gas, DM ³ ,

MPC - maximum permissible concentration, MPC = 0.002 dm ³ .

To conduct work on the geophysical block, methods are used that are most sensitive to changes in the stress state of the subsoil: acoustic logging, electric lateral logging, neutron gamma-ray logging, etc. Studies are carried out in observation 13 and geophysical 14 wells (Fig. 3) throughout the open section by drilling. Based on the results obtained, conclusions are drawn: on the nature of changes in the physicomechanical and filtration-capacitive parameters of UGS rocks, on the state (tightness and deformation) of casing wells and annular gas accumulations, on the dynamics of changes in the current position of GWCs and gas saturation of reservoirs.

According to the data of the geophysical monitoring unit, indicators are determined:

Gas saturation of near-surface deposits (G,% of MPC) according to the results of sampling was:

G = 420 ppm, MPC = 70 ppm,

Therefore, G = 6 MAC,

The annular pressure (P _to ) according to the measurement results was:

P _to = P _PL = 10.8 MPa.

The number of wells with unsatisfactory technical condition (N) was

where (N _t ) _i is the number of wells with unsatisfactory technical condition determined by the results of technical surveys within the local geodynamic test site or its section, pcs .;

N _wells - total number of wells located within the local geodynamic polygon or a portion thereof, pieces.

To assess the geodynamic activity of underground gas storage facilities at the local stage, indicators were determined for the three monitoring units, the values of which are given in table 8.

Table 8 Indicators of geodynamic activity at the local stage Hydrogeological monitoring unit Fluidodynamic monitoring unit Geophysical downhole monitoring unit Not, G ΔH ΔT, ΔMi ΔP _PL S _about % % P _to N m ° C g / cm ³ MPa % from from MPa % MPC MPC 368.7 55 51.9 ΔР _pl <P _grp 12 7 MAC 6 maximum concentration limits P _to = P _PD 35

After carrying out the work at the local stage, an updated geodynamic model is compiled, which allows one to identify the wells and intervals of the wells that are most susceptible to the negative effects of geodynamic forces on the studied area.

For completeness and reliability of the information received and processed during the QGDM, the technology of combining various research methods of both the local and regional stages is used. This allows you to timely identify abnormally stressed areas and zones at the studied object and, subsequently, choose a safer and more rational mode of operation of underground gas storage facilities.

Comparison of the simulation results of the two stages allows a more reliable assessment of the influence of natural and technogenic processes on the UGS facility as a whole and to locate geodynamically stressed sections at a qualitative level.

To obtain a quantitative assessment of the intensity of the manifestation of geodynamic forces, the indicators obtained for each block for monitoring the regional stage (table 7) are compared with classified criteria indicators (table 1). At the local stage, the indicators obtained for each monitoring unit (table 8) are compared with the classified criteria indicators (table 2). At the regional stage, according to the developed level scale of geodynamic hazard, indicators for the aerospace monitoring unit correspond to:

- the dynamics of the density of the lineament network (ΔО) to the “safe” level, assign a “1” point;

- the relative surface of the zones of the geodynamic influence of faults (Z) to the "conditionally safe" level, assign "2" points;

- the relative area of distribution of the zones of mesocracking (M) is “safe” level, assign a “1” point.

The indicators of the geodynamic activity of the deformation and geophysical areal monitoring units correspond to the "safe" level, with each indicator assigned a "1" point.

Indicators of geodynamic activity at the local stage of the QGDM are somewhat different from the background ones, which is due to the arising reaction of the geological environment to the anthropogenic impact. The values of all indicators for the three monitoring units correspond to the “critical” hazard level, with each indicator assigned a “3” point, with the exception of the dynamics indicator of the static pressure levels in one season (ΔН) for the hydrogeological monitoring unit, the value of which corresponds to the “anomalous” level, with assigning him "2" points.

The obtained point values of the indicators of geodynamic activity, taking into account the corresponding weight coefficients (table 3), are substituted into the formula for calculating a single total coefficient of the geodynamic state of underground gas storage at the regional and local stages.

R _G = x ₁ · k ₁ + x ₂ · k ₂ + ... + x ₁₈ · k ₁₈ = 3 · 1 + 3 · 2 + 3 · 1 + 5 · 1 + 5 · 1 + 5 · 1 + 3 · 1 + 3 · 1 + 3 · 1 + 4 · 2 + 4 · 3 + 4 · 3 + 4 · 3 + 4 · 3 + 4 · 3 + 5 · 3 + 5 · 3 + 5 · 3 = 149

Therefore, the unified total coefficient characterizing the current geodynamic state of the underground gas storage facilities as a whole is 149. The obtained value of the unified total coefficient is compared with the values of the criterion coefficient presented in Table 4. The level of geodynamic hazard of the UGS facilities is determined. The obtained value of a single total coefficient corresponds to a “conditionally safe” level of geodynamic hazard.

On the basis of the data obtained, a final map of the territory ranking according to the degree of geodynamic hazard is constructed, on which the areas of the distribution of the values of the single total coefficient are displayed (Fig. 3). To increase the reliability of the results obtained, the final map is combined with the map of the updated geodynamic model. This allows you to more clearly assess the influence of natural and technogenic factors on the geodynamic state of both the UGS facility as a whole and its individual sections - zones of development of anomalous geodynamic activity 16 (Fig. 3).

From the given example it follows that the increase in the reliability and safety of operation of underground gas storage is ensured by the high reliability of the assessment of the manifestation of various forms of natural-technogenic geodynamic processes of underground gas storage by increasing the information content of the research results.

Thus, we can conclude that the proposed technical solution meets the criterion of industrial applicability.

The claimed technical solution meets the criterion of patentability, namely the condition of novelty, inventive step and industrial applicability.

Table 1 Scoring Monitoring units Criteria of geodynamic activity at the regional stage Aerospace Deformation Geophysical Hazard level ΔО, km / km ² Z,% M% v, mm / year k · 10 ^-3 m ^-1 ε · 10 ^-3 mm / m K _p C, point ΔL, m one Safe <0.5 0-1.0 <20 <10 <0.10 <1 <0.05 0,0-3,0 <0.05 2 Relatively safe 0.5-1.0 1.1-5.0 20-30 10th 0.10-0.20 1.0-2.0 0.05-0.20 3.1-4.0 0.05-0.10 3 Abnormal 1.1-2.0 5.1-8.0 31-40 21-30 0.21-0.50 2.1-5.0 0.21-0.25 4.1-4.5 0.11-0.50 four Critical 2.1-2.5 8.1-10.0 41-50 31-50 0.51-1.00 5.1-10.0 0.26-0.30 4.6-5.0 0.51-1.00 5 Catastrophe > 2.5 > 10.0 > 50 > 50 > 1.00 > 10.0 > 0.30 > 5.0 > 1.00

table 2 Scoring Monitoring units Criteria of geodynamic activity at the local stage Hydrogeological Fluid dynamic Geophysical Hazard level ΔН, m ΔТ, ° С ΔMi, g / cm ³ ΔP _pl , MPa S _about ,% Not,% of MAC G,% of MAC P _k , MPa N% Safe <350 <30 <40 P ₀ > P _tech 0 <MPC <MPC 0 0-10 Abnormal 350-650 30-50 40-50 P ₀ > P _tech 1-10 up to 5 maximum concentration limits up to 5 maximum concentration limits 0 <P _to <P _pd 11-30 Critical <650 > 50 > 50 P _tech <P _group > 10 5-10 MAC 5-10 MAC P _to ≥P _PD 31-40

Table 3 KGDM stage Monitoring unit Weight value Regional stage Aerospace 3 Deformation 5 Geophysical areal 3 Local stage Hydrogeological four Fluid dynamic four Geophysical downhole 5

Table 4 UGS geodynamic hazard level The value of the criterion coefficient Note Safe 72-114 - Conditionally Safe 115-150 UGS normal operation Abnormal 151-197 Identification of environmental reactions. Enhanced monitoring of underground gas storage Critical 198-239 Activation of geodynamic processes. Development of a set of preventive measures Catastrophe 240-282 The activation of geodynamic processes and the appearance of failures in the operation of field equipment. Application of risk reduction measures

Claims (1)

A method for assessing the influence of geodynamic factors on the safety of operating an underground gas storage (UGS) in a porous reservoir, including the creation of a geodynamic test site, conducting complex geodynamic monitoring (QGDM) of natural and technogenic processes at the regional and local stages by monitoring blocks - aerospace, deformation, geophysical , hydrogeological and fluidodynamic, using different spatio-temporal detail of measurements, building a map based on the result AMGGM at the regional stage and predicting the occurrence of emergency geodynamic events, characterized in that they conductGGDM at the regional stage with a frequency of at least once every five years, and at the local stage - at least twice a year, and at the regional stage of the GGDM conduct area studies within the created geodynamic test site for monitoring units - aerospace, by conducting aerospace observations of the underground surface of the underground gas storage, with the determination of the dynamics of the density of the lineament network, rel the relative surface of the zones of the geodynamic influence of faults and the relative area of the distribution of mesofracture zones, the deformation, by measuring the deformation of the UGS day surface, with the determination of the subsidence rate, the curvature of the subsidence surface and horizontal deformations, the geophysical, by recording the seismic activity of the UGS territory and disjunctive disturbances of the UGS reservoir, s determination of the volumetric coefficient of the prevalence of disjunctive violations of the underground gas storage tank, seismicity of the underground gas storage area and the maximum value of the relative excess of the amplitude of the microfracture, and according to the data obtained, a preliminary geodynamic model is created, and at the local stage of the well test, borehole studies are carried out on monitoring units - hydrogeological, by conducting hydrogeological studies of the wells with the determination of indicators - dynamics of static head levels in one season, dynamics of change temperature regime in one season and dynamics of formation water mineralization, fluid dynamic, by conducting gas dynamic their well studies with the determination of the dynamics of reservoir pressure in the well or group of wells, the degree of water cut of wells during the selection and helium content, geophysical, by conducting geophysical research of wells with determination of gas saturation of near-surface deposits, intercolumn or annular pressures and the number of wells with unsatisfactory technical condition, then create a refined geodynamic model, and a classification of criteria indicators is developed for each monitoring unit to assess the geodynamic risk with assigning them a five-point gradation at the regional stage, a three-point gradation at the local stage according to the level of geodynamic hazard, compare the indicators calculated for each monitoring unit with criteria indicators, evaluate the intensity of the manifestation of dangerous geodynamic and technogenic-induced processes for all monitoring units, then calculate the single total coefficient of the geodynamic state of the underground gas storage facility according to the formula
R _G = x ₁ · k ₁ + x ₂ · k ₂ + ... + x ₁₈ · k ₁₈ ,
where R _G is the single total coefficient of the geodynamic state of the underground gas storage facility;
x ₁ -x ₁₈ - weighting factors for each monitoring unit, determined taking into account experimental data;
k ₁ -k ₁₈ - scores of indicators of geodynamic activity according to the level of geodynamic hazard, obtained from the results of the KGDM, compare it with a pre-calculated criterion coefficient for each level of geodynamic hazard, determine the level of geodynamic hazard of the underground gas storage facilities and build a final map of the territory ranking according to the degree of geodynamic hazard.

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