RU2786663C1 - Method for identifying interlayer flows in the development of oil and gas condensate or oil fields - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the oil and gas industry, and in particular to the control of the dynamic conditions of oil and gas condensate and oil fields. A method for identifying interlayer flows between at least two reservoirs during the development of oil and gas condensate or oil fields is claimed, which includes the stages at which a) at least one oil sample is taken from the wells of each of the indicated at least two reservoirs, b) the contents of the components are determined oil in selected oil samples using geochemical analysis, c) one or more oil components with the largest differences in contents and one or more oil components with the smallest differences in contents are selected in the selected oil samples from different reservoirs, d) one or more ratios of the oil components with the largest differences in contents to the oil components with the smallest differences in contents are then selected, wherein the number of such ratios is equal to at least the number of reservoirs minus one, and e) monitoring the change in these ratios in the oil of the field over time to obtain information about the change in the composition of the oil in percentage terms, based on which the presence of crossflow between the reservoirs and its volume is determined.

EFFECT: providing the possibility of qualitative and quantitative assessment of interlayer crossflows, which makes it possible to increase the success and optimize the ongoing geological and technical measures in the development of oil and gas condensate and oil fields.

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Description

The field of technology to which the invention belongs

The invention relates to the oil and gas industry, and in particular to the control of dynamic states of oil and gas condensate and oil fields. In particular, the invention relates to a method for identifying cross-flows in the development of oil and gas condensate or oil fields. It can be used to diagnose and prevent uneven development of multi-layer deposits in order to substantiate measures for intensifying and optimizing reservoir development.

State of the art

The development of a multi-layer oil field is very often complicated by inter-layer cross-flows. Qualitative and quantitative assessment of the scale of flows and their dynamics is extremely important for the correct accounting of residual reserves, the construction of adequate geological and hydrodynamic models (GGDM) and the management of ongoing development, in particular, planning of geological and technical measures (GTM) and drilling wells. Cross-flows in developed fields occur due to the difference in reservoir pressures due to different rates of production and injection in reservoirs, and the presence of hydrodynamic communication between reservoirs. The most common and, accordingly, the most studied type of inter-layer cross-flows is the cross-flow through wells that open several layers. This type of cross-flow can occur: during shut-ins of wells operating as a single filter, or through annular/annular cross-flows in case of violations of the tightness of the cement stone or separating packers. This type of flow is quite confidently detected using well logging, and in some cases, geochemical analysis of oil. Another type of interstratal flows is flows through the geological windows of the confluence of layers, erosive washout surfaces, incision channels of sedimentation and other objects of a geological nature. This type of flow is much less studied due to the difficulty of registering it by direct measurement methods. Indirect information indicating the presence of a crossflow can be a change in reservoir pressure, which is difficult to explain by geological causes and the state of development, anomalous behavior of production wells, changes in pressure and / or saturation recorded by 4D seismic, etc. Quantitative assessment of the scale of such crossflows is extremely difficult. This becomes especially difficult when there is a crossflow of the same phase with similar properties (for example, the flow of oil into oil). As a rule, quantitatively, the volumes of flows are estimated using material balance models and / or GGDM, taking into account all available indirect geological and field data.

In the prior art, methods are known for estimating interlayer crossflows in a well based on estimating changes in pressure or temperature in the well. In particular, a method is known for determining interlayer flows in a well (see RU 2361079 C1, 07/10/2009), in which, as a criterion for assessing the presence or absence of fluid flows in a well, the presence or absence of a periodic pressure change in the well under study from work is chosen, respectively. perturbing well, characterized by the amplitude of the first harmonic of the pressure change.

This method cannot be used to determine the presence of an admixture of oil from one reservoir in the oil of another due to the similarity of the physicochemical properties of oil.

A known method for determining the relative flow rates of jointly operated oil reservoirs based on geochemical analysis (see RU 2710574 C1, 12/27/2019). This method consists in determining the most stable component, and based on the ratio of the value of each oil component in each oil sample to the value of the found stable component in the same oil sample, the ratio of the value of each oil component in the oil mixture to the value of the specified stable component in the oil mixture is determined, followed by determining the proportion of each oil sample in a mixture of oils.

However, standard chemical analysis approaches are not suitable for flow detection for a number of reasons, the main ones being:

- Oils in different reservoirs almost always consist of the same set of components. Therefore, as a rule, it is not possible to find a unique component of another formation in oil and identify it.

- You can not use the difference in the concentration of the components. Due to the high volatility of oil and the complexity of component-by-component analysis of oil, it is extremely difficult to obtain reliable data. In other words, the concentration of the components changes when the physical and chemical properties of the field oil change and during the sampling and storage of samples on the surface.

Disclosure of invention

The objective of the invention is to determine interlayer flows in the developed oil and gas condensate and oil fields.

The technical result consists in providing the possibility of a qualitative and quantitative assessment of interstratal flows, which makes it possible to increase the success and optimize the ongoing geological and technical measures in the development of oil and gas condensate and oil fields.

The solution of this problem and the technical result achieved in this case is ensured by the fact that the method for identifying interlayer flows between at least two layers during the development of oil and gas condensate or oil fields includes stages at which

a) taking at least one oil sample from the wells of each of said at least two formations,

b) determine the content of oil components in the selected oil samples using geochemical analysis,

c) selecting one or more oil components with the greatest differences in contents and one or more oil components with the smallest differences in contents in selected oil samples from different reservoirs,

d) compose one or more ratios of oil components with the largest differences in grades to oil components with the smallest differences in grades, and the number of such ratios is equal to at least the number of reservoirs minus one, and

e) monitor the change in the indicated ratios in the oil of the field over time to obtain information about the change in the composition of the oil in percentage terms, on the basis of which the presence of crossflow between the reservoirs and its volume is determined.

In a preferred embodiment of the method according to the present invention, step a) is carried out prior to the commencement of field development.

In a preferred embodiment of the method according to the present invention, in step d), when drawing up the ratios, pairs of components with close boiling points are selected.

In a preferred embodiment of the method according to the present invention, step e) comprises taking at least one oil sample from at least one well in the field and performing a geochemical analysis to determine the content of oil components in the samples taken.

In a preferred embodiment of the method according to the present invention, step e) is repeated one or more times.

In a preferred embodiment of the method according to the present invention, the geochemical analysis is selected from the group consisting of gas chromatography, emission spectrum analysis, atomic absorption analysis, X-ray analysis and mass spectral analysis.

In a preferred embodiment of the method according to the present invention, the geochemical analysis is high resolution gas chromatography.

Brief description of the drawings

Fig. 1 – geological profile of the Astokhsky area of the Piltun-Astokhskoye oil and gas condensate field with indication of the layers XXI-S, XXI-1’, XXI-2;

Fig. 2 - section of the chromatogram of oil from the field with components;

Fig. 3 - Quantification of the reservoir fraction in the sample (2-component system);

Fig. 4 - Sequential change in the ratios of geochemical components towards the formation XXI-S as a result of the flow in well H;

Fig. 5 - Dependence of reservoir pressure in the reservoir XXI-1' on the injection of water into the reservoir XXI-S in wells;

Fig. 6 - Pressure measurements in an open wellbore. Signs of flow between layers;

Fig. 7 - Lack of flow between layers in well C;

Fig. 8 - Sequential change in the ratios of geochemical components towards the reservoir XXI-1' as a result of a change in inflow in well G;

Fig. 9 - Reservoir pressure and flows between reservoirs according to the material balance model.

Implementation of the invention

As an invention, a method is proposed that allows the identification of inter-layer cross-flows between at least two reservoirs in the development of oil and gas condensate or oil fields and, in particular, to monitor the dynamic state of oil reservoirs using geochemical analysis of oil through a qualitative and quantitative assessment of inter-layer cross-flows. This method can be applied to flows of the second kind (through geological objects), which is the subject of this application. The method was tested in the Astokhsky area of the Piltun-Astokhskoye oil and gas condensate field, located on the northeastern shelf of about. Sakhalin.

This development object is shown in Fig. 1 and includes three layers - XXI-S, XXI-1' and XXI-2. The formations are composed of fine-grained, predominantly quartz sandstones, contain light low-viscosity undersaturated oil and have a common oil-water contact. Filtration and capacitance properties vary widely. The most permeable and consistent in terms of area and section layer XXI-S unconformably lies on layers XXI-1’ and XXI-2. Formations XXI-1' and XXI-2 have a clinoform structure and are complicated by internal channels and cones of sedimentary material.

Prior to the start of development, oil deposits were in a state of hydrodynamic equilibrium due to the connection through the erosion surface in the western and partly in the central parts of the area. The grid of production wells is quite rare due to the limited number of drilling windows on the platform, some of the wells develop only the XXI-S layer, some only the XXI-1’ layer, and part of the fund is common to both layers. The lower layer XXI-2, which is of secondary importance in terms of reserves, is operated only in conjunction with other layers. Oil sampling for geochemical analysis has been carried out since the beginning of development (1999), but the coverage of the well stock has been uneven and irregular. The application of this method made it possible to identify the regularities and features of the composition of oils from the XXI-S, XXI-1 ', XXI-2 formations.

As stated above, this invention is based on the geochemical analysis of the oil and the fact that the composition of the oil is different in different formations of the field. Thus, the ability to detect crossflow relies on the ability to clearly identify the presence of an admixture of oil from one reservoir in oil from another.

Due to the inapplicability of standard approaches, it is proposed to use an approach based on the ratio of oil components. If the concentrations of individual oil components can vary significantly, then the ratios of components with similar physical properties are stable and less dependent on the method errors.

As you know, oil contains more than a thousand different components. If you formally iterate over them, then you can come up with more than a million different ratios of components, which makes enumeration a difficult task. There are special programs that cope with finding the most convenient ratios and their quantitative processing using artificial intelligence. Despite the availability of such programs, working with them is complex and time-consuming, and can also lead to erroneous results due to the impossibility of filtering method errors (sampling and analysis) and slight differences in the compositions of similar oils.

The method in accordance with the present invention makes it possible to identify cross-flows between at least two formations in the development of oil and gas condensate or oil fields. The method in accordance with the invention includes taking at least one oil sample from wells of each of said at least two formations, determining the contents of oil components in the selected oil samples using geochemical analysis, selecting one or more oil components with the largest differences in contents and one or more components with the smallest differences in grades in selected oil samples from different reservoirs, drawing up one or more ratios of oil components with the largest differences in contents to components of oil with the smallest differences in contents, and the number of such ratios is equal to at least the number of reservoirs minus one, and tracking changes in these ratios over time to obtain information about the change in the composition of oil in percentage terms, on the basis of which the presence of a crossflow between the reservoirs and its volume is determined.

In more detail, at the initial stage of the method in accordance with the present invention, in order to study the field and determine the geochemical "look" of the oils of each of the reservoirs, at least one oil sample is taken from each of the reservoirs. These oil samples are reference, i.e. characteristic of the oil of the corresponding reservoir. In this application, reference samples are understood to mean such oil samples that are produced from one reservoir, i.e. in the case when one of the layers is involved in production at 100%, and the other at 0%. Preferably, these oil samples are taken prior to field development. Typically, in practice, samples are taken from production wells, however, sampling can also be carried out from any other wells penetrating the reservoir, for example, prospecting, exploration, injection, absorbing, and others. As noted above, in fact, it is sufficient to take one sample of oil from each of the reservoirs, however, in practice it may be preferable for each of the reservoirs to collect as many oil samples as possible, preferably from different wells, in order to take into account the possible variation in the composition of oil within one reservoir, as well as to increase field coverage.

Then the selected oil samples are analyzed using the method of geochemical analysis in order to determine the content of oil components in each of the samples. As an illustrative example of a geochemical analysis method suitable for use in the present invention, an illustrative and convenient gas chromatography method may be mentioned. However, as will be understood by one skilled in the art, the method of the present invention is not limited to the use of gas chromatography as a method for determining the content of oil components in samples, and any method of geochemical analysis of oil that can determine the content of oil components can be used in the present invention. in samples. As other geochemical analysis methods suitable for use in the present invention, there may be mentioned, in particular, emission spectral analysis, atomic absorption analysis, X-ray analysis, mass spectral analysis and others. As noted above, in a preferred embodiment of the present invention, the selected oil samples can be analyzed on a gas chromatograph to determine the concentrations of oil components in the samples. The more oil samples taken from each of the reservoirs and analyzed, the more accurate the results and the easier their interpretation. It should be noted that instead of the obtained concentrations of the components, it can be convenient to use their analytical signals, for example, the height or area of the chromatographic peaks of the corresponding components, as an indicator of the content of the oil component in the sample.

Based on the obtained data on the content of oil components in the samples, one or more components (let's call them K _n ) of oil are selected with the smallest differences in contents, in particular concentrations, in oil samples taken from different reservoirs of the field. In addition, one or more components (let's call them D _N ) of the oil with the largest differences in contents, in particular concentrations, in oil samples taken from different reservoir layers are selected.

Of the selected components, one or more ratios of the form D _N /K _n are formed, preferably pairs of components with close boiling points are selected so that the volatility of the oil does not affect these ratios. The number of such ratios is equal to at least the number of layers minus one. It should be noted that instead of the obtained ratios of component concentrations, it is convenient to use the ratios of their analytical signals, for example, the heights or areas of chromatographic peaks.

After compiling the above pairs of components, you can rely on the following property: since the denominators are very close values, when mixing oils from different reservoirs of the field, these ratios will behave almost linearly, that is, you should use the differences in the ratios A _m = D _N /K _n as differences in component contents. In other words, for a given deposit, the ratios found should be further used as linearly varying grades in the classical approach of chemistry for impurity detection.

In the next step of the method in accordance with the present invention, the change in these ratios in the oil of the field is tracked over time. This step of the method according to the invention may be repeated one or more times at intervals. In particular, in order to monitor the change in these ratios after a certain period of time after the selection of (reference) oil samples, carried out at the initial stage of the method in accordance with the present invention, at least one oil sample can be taken from at least one well of interest in the field (i.e. from any well in the field for which cross-flow identification is required) and geochemical analysis can be performed on it in order to determine the contents of oil components. Suitable methods of geochemical analysis are the same as previously described. Such sampling of oil and their geochemical analysis in order to track changes in these ratios can be repeated one or more times at certain intervals of time. Since the change in the ratios is a linear function of the percentage of oil in each of the reservoirs in the samples, the change in the ratios over time allows obtaining information about the change in the composition of the oil (the contribution of the reservoirs to the well production) and, in the case of a single reservoir in the well, to judge the presence (or absence) flow from other layers. By the percentage ratio of the contribution of the reservoirs to the production of the well, one can judge the volumes of the flow. To unambiguously identify the nature of the flow (in the well or outside it), it is recommended to combine the method in accordance with the present invention with other methods (geophysical survey of wells (GIS), modeling, pressure monitoring, etc.).

EXAMPLES

The implementation of this invention will be shown on the example of the Astokhsky area of the Piltun-Astokhskoye oil and gas condensate field. Various oil samples from the Astokh area were taken and analyzed on a gas chromatograph (see Fig. 2). During the comparison of the obtained results, among all the peaks of the chromatograms, the components D _n were identified and selected, which have the greatest differences in concentration (shown in Fig. 2 in blue and green); as well as components K _N , which have the smallest differences in concentration (shown in red and orange in Fig. 2) among all oil samples from the Astokh area. After that, the ratios D _N /K _n were compiled. It should be noted that the minimum number of required ratios is equal to the number of layers minus one, there is no maximum limit, the data can be averaged in various ways. In our case, there are three reservoirs XXI-S, XXI-1', XXI-2, therefore, two ratios of iso-C15/K_1728 and n-C16/K_1728 were chosen (K_1728 is a symbol used for an unidentified oil component, probably an aromatic hydrocarbon ) on the example of two components of oil, mainly for reasons of clarity of the two-dimensional diagram and good analytical qualities of these peaks on the chromatograph used. After that, the declared linearity of the relationships, found by the method described by us, was confirmed.

Figure 3 shows how laboratory-made mixtures of 25%, 50%, and 75% of reference oil samples from two different reservoirs correspond to their calculated position. From which it is concluded that the ratios obtained based on the two components of oil iso-C15 / K_1728 and n-C16 / K_1728 are suitable for determining the flow and contribution of the reservoirs. Let's follow their change on the example of real wells.

Production well H was drilled in 2000 in the central part of the area. The well was completed in only one layer XXI-1’. Geologically, the well is located in the area of direct unconformity overlapping of XXI-S reservoirs on XXI-1’ reservoirs. Oil samples were taken in 2000, 2008, 2010, 2012, 2015-2019. All samples were analyzed. The ratios of the components are determined. The ratio of n-C16/K_1728 showed a consistent change in values from 2.8 to 1.5, and the ratio of iso-C15/K_1728 from 4.6 to 3.8. Knowing the reference ratios for the end members (oils characterizing the XXI-S and XXI-S formations), it is possible to calculate the fraction of the oil component using the example of iso-C15/K_1728 of each of the two formations using the formula:

To calculate the share of another oil component n-C16, it is necessary to make a similar equation for this ratio. In this application, reference values are those values at which oil is produced from one reservoir, namely, in the case when one of the reservoirs participates in production by 100%, and the other 0%.

The results of the interpretation of the geochemical analysis of oil from well H are summarized in Table 1.

Table 1

Selection date ISO-C15/K_1728 n-C16/K_1728 Share XXI-S % Share XXI-1'% 12/10/2000 3.845 2,770 0.0 100.0 12/09/2008 4.401 2.175 28.3 71.7 13/05/2010 4.295 2.054 22.8 77.2 13/10/2012 4.688 1.792 43.0 57.0 19/01/2015 4,892 1.599 53.4 46.6 19/01/2015 4,833 1.611 50.4 49.6 12/09/2015 4.885 1.505 53.1 46.9 20/02/2016 5.001 1.471 59.0 41.0 09/06/2016 4,887 1.466 53.2 46.8 09/12/2016 4.813 1.522 49.4 50.6 21/02/2017 5,080 1.463 63.1 36.9 07/04/2017 5.001 1.471 59.0 41.0 05/05/2017 4.958 1.466 56.8 43.2 20/06/2017 4.865 1.503 52.1 47.9 20/07/2017 4.777 1.457 47.6 52.4 21/09/2017 4,852 1.487 51.4 48.6 20/10/2017 5.102 1.517 64.2 35.8 20/11/2017 5.064 1.496 62.3 37.7 21/01/2018 5.032 1.525 60.6 39.4 21/01/2018 4.937 1.466 55.8 44.2 21/03/2018 4,894 1.467 53.5 46.5 21/04/2018 4.908 1.469 54.3 45.7 19/05/2018 4.919 1.467 54.8 45.2 19/01/2019 4.931 1.621 55.4 44.6 19/01/2019 4.961 1.623 57.0 43.0 21/04/2019 4.637 1.546 45.0 55.0

Geochemical analysis by high-resolution gas chromatography showed a consistent change in the ratios of the components selected to characterize the oils of the Astokh area, from reservoir XXI-1' towards reservoir XXI-S (see Fig.4). This indicates the successive mixing of oils from two reservoirs in the area of this well as a result of the flow from the upper layer XXI-S to the underlying XXI-1'. In view of the historical significant difference in recovery compensation by injection, a significant pressure drop was created between the two reservoirs, which caused the flow. Another indication of hydrodynamic coupling and crossflow is the behavior of reservoir pressure in well H. In particular, there was an increase in reservoir pressure in response to the injection of water into the reservoir XXI-S (see Fig. layer XXI-1' were insignificant at that time).

This observation is confirmed by the more stable operation of the H well compared to other wells operating the XXI-1 formation, which are located to the east of the overlap zone and which did not show changes in the geochemical composition (see Fig. 5). Later, the presence of crossflow was confirmed by openhole reservoir pressure measurements by a dynamic reservoir tester in an adjacent well (at a distance of 200 m), where the formation pressure increase is clearly visible up the section (see Fig. 6).

One of the discoveries of the developed method was the identification of successive changes in the geochemical appearance of some wells over a long period of time. If a number of wells are characterized by a very stable geochemical appearance for almost two decades, then in a number of other wells a tendency was found to “migrate” the “geochemical fingerprint” from one end member to another. This phenomenon indicates the process of mixing of oil from one reservoir with oil from another reservoir, in particular, about the flow from reservoir XXI-S to reservoir XXI-1’. Recorded changes are systemic, consistent and significantly exceed the uncertainty of the measuring equipment.

The obtained laboratory results were also verified through integration with field information and modeling results, in particular:

Reservoir pressure behavior in production wells;

Well operation data - flow rates, bottom hole pressures, gas-oil ratio (GOR), water cut;

Production logging data (flow metering, temperature logging, pulsed neutron-neutron logging (INNK));

Geological prerequisites for the existence of overflows;

Material balance models and GGDM.

The conclusions drawn can be demonstrated on the example of other wells.

Production well C:

Drilled in 2000. Completed at seam XXI-S. Oil samples were taken in 2010, 2012, 2015-2019. All samples were analyzed by high resolution gas chromatography. The ratios of the components are determined. For both ratios, the analysis showed very low variability. Which indicates the unchanged geochemical appearance of the oil from this well and the absence of overflow from other layers (see Fig.7). This is also supported by geological data. The results of the interpretation of the geochemical analysis of oil from well C are summarized in Table 2.

table 2

Selection date ISO-C15/K_1728 n-C16/K_1728 Share XXI-S % Share XXI-1'% 02/06/2010 5,440 0.689 100.0 0.0 02/06/2010 5.516 0.762 100.0 0.0 04/02/2017 5.634 0.730 100.0 0.0 05/05/2017 5.443 0.728 100.0 0.0 07/04/2017 5.318 0.731 100.0 0.0 11/06/2016 5.421 0.744 100.0 0.0 11/06/2016 5.437 0.718 100.0 0.0 12/06/2015 5.547 0.746 100.0 0.0 12/12/2016 5.418 0.724 100.0 0.0 13/10/2012 5.595 0.713 100.0 0.0 19/01/2015 5.456 0.726 100.0 0.0 20/02/2016 5.481 0.714 100.0 0.0 20/06/2017 5.299 0.707 100.0 0.0 20/07/2017 5.605 0.619 100.0 0.0 21/02/2017 5.637 0.722 100.0 0.0 21/09/2017 5.438 0.671 100.0 0.0 20/11/2017 5.511 0.702 100.0 0.0 21/01/2018 5.428 0.689 100.0 0.0 21/01/2018 5.353 0.687 100.0 0.0 21/03/2018 5.160 0.652 100.0 0.0 21/04/2018 5.499 0.706 100.0 0.0 19/05/2018 5.415 0.676 100.0 0.0 19/01/2019 5.476 0.647 100.0 0.0

Geochemical analysis by high-resolution gas chromatography showed 100% of the XXI-S formation in the production. Thus, there is no flow between the layers.

Production well G:

Production well G was drilled in 1999 in the central part of the area. The well was completed in two formations XXI-S and XXI-1'. Oil samples were taken in 2010, 2012, 2015. All samples were analyzed. Ratios are defined. The change in ratios reflects the proportion of the share of each of the two layers in the production. The results of the interpretation of the geochemical analysis of oil from well G are summarized in Table 3.

Table 3

Selection date ISO-C15/K_1728 n-C16/K_1728 Share XXI-S % Share XXI-1'% 13/05/2010 3.798 2.076 9.4 90.6 13/05/2010 3.834 2.022 11.1 88.9 13/05/2010 3.966 2.101 17.4 82.6 13/05/2010 3.818 1.974 10.4 89.6 13/05/2010 3.818 1.974 10.4 89.6 02/06/2010 3.821 2,050 10.5 89.5 13/10/2012 4,484 1.605 42.1 57.9 13/10/2012 4.491 1.584 42.4 57.6 13/10/2012 4,580 1.574 46.7 53.3 13/10/2012 4.751 1.656 54.8 45.2 09/06/2015 3.859 2.139 12.3 87.7 19/09/2015 3.742 2.026 6.8 93.2 19/04/2016 4.309 1.736 33.7 66.3 19/04/2016 4.192 1,700 28.2 71.8 07/06/2016 3.831 2.031 11.0 89.0 04/11/2016 3.564 2.085 0.0 100.0 07/04/2017 3.616 2.058 0.8 99.2 07/04/2017 3.616 2.131 0.8 99.2 05/05/2017 3.591 2.219 0.0 100.0 05/03/2019 3.362 1.789 0.0 100.0 21/04/2019 3.297 1.927 0.0 100.0

In FIG. Figure 8 shows a sequential change in the ratios of geochemical components towards the formation XXI-1' as a result of a change in the inflow into the well. Thus, in 2010 the XXI-S reservoir was mechanically isolated and the geochemical analysis also showed 90% production of the XXI-1' reservoir (by n-C15 ratio). Further, the XXI-S reservoir was reopened and the values of the ratios changed - the reservoir share in the XXI-1 production decreased to 58%; and then consistently increased to 100% due to water breakthrough and a decrease in inflow from the XXI-S reservoir (confirmed by other indirect data - modeling, chemical analysis of water and tracer studies).

The conclusions made on the basis of the geochemical analysis of oil and geological and field information were fully confirmed by the material balance modeling and HGDM data (see Fig. 9). Moreover, the results of the geochemical method of oil analysis using high-resolution chromatography, provided that it is integrated with geological and field information, core data and 4D seismic surveys, made it possible to significantly revise the correlation of the Astokhsky area reservoirs and update the GGDM. In a number of other wells, geochemical oil analysis data made it possible to optimize planning and increase the success of geological and technical measures. Currently, geochemical analysis of oil is routinely used to monitor the development of the Astokh and Piltun areas, along with other methods.

This method has been tested and gives reliable results for a two-component system (two end members - two reservoirs) at the level of qualitative determination of the crossflow scale and general dynamics (reservoir pressure behavior, reactions to changes in water withdrawals and injection). Also gives a quantitative interpretation for individual wells (% oil of each of the reservoirs) with an error of 10% (determined by the reproducibility of the results and the uncertainty of identifying end members). The functionality of the method can be extended to a 3 or more component system, provided that the third component (the third layer) and, if necessary, subsequent components (layers) are reliably identified geochemically.

Claims (12)

1. A method for identifying interlayer flows between at least two reservoirs in the development of oil and gas condensate or oil fields, which includes the stages at which a) taking at least one oil sample from the wells of each of said at least two formations, b) determine the content of oil components in the selected oil samples using geochemical analysis, c) selecting one or more oil components with the greatest differences in contents and one or more oil components with the smallest differences in contents in selected oil samples from different reservoirs, d) compose one or more ratios of oil components with the largest differences in grades to oil components with the smallest differences in grades, and the number of such ratios is equal to at least the number of reservoirs minus one, and e) monitor the change in the indicated ratios in the oil of the field over time to obtain information about the change in the composition of the oil in percentage terms, on the basis of which the presence of crossflow between the reservoirs and its volume is determined. 2. The method according to claim. 1, in which stage a) is carried out before the development of the field. 3. The method according to claim 1 or 2, in which at stage d) when drawing up the ratios, pairs of components with close boiling points are selected. 4. The method according to any one of paragraphs. 1-3, in which step e) includes taking at least one oil sample from at least one well of the field and performing a geochemical analysis to determine the content of oil components in the collected samples. 5. The method according to any one of paragraphs. 1-4, wherein step e) is repeated one or more times. 6. The method according to any one of paragraphs. 1-5, in which the geochemical analysis is selected from the group including gas chromatography, emission spectral analysis, atomic absorption analysis, X-ray spectral analysis and mass spectral analysis. 7. The method according to any one of paragraphs. 1-6, in which the geochemical analysis is high resolution gas chromatography.

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