RU2679773C1 - Method of accounting of gas flows on man-made fluid-conducting channels between two gas-condensate formations - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil and gas industry, and in particular to methods for accounting for gas crossflows resulting from a hydraulic fracturing in nearby formations, which are independent objects for calculating reserves. Method of accounting for gas crossflows resulting from hydraulic fracturing in two nearby formations, which are independent objects for calculating reserves, at the same time, the initial information for accounting for gas crossflows is the approved values of the content of components C₅₊ formations and approved formation gas densities and gas condensate studies results, as a result of which the current potential content of condensate and the flow rate of formation gas are determined. At the same time, on the basis of mass conservation law, the flow rate of the formation gas of a formation, from which the flow occurred, is determined according to the expression:

where Q_{form. gas} is the formation gas flow rate according to the results of the gas condensate studies, thousand m³/day; FS^mix ₅₊ is the content of components C₅₊ in the formation gas according to the results of the gas condensate studies, g/m³; Q^A is the flow rate of the formation gas of a formation, from which the flow occurred, thousand m³/day; ρ^A is the approved density of the formation gas from which the flow occurred, kg/m³; ρ^B – the approved density of the formation gas, in which the flow occurs, kg/m³; FS^A ₅₊ is the approved content of C₅₊ components of the formation from which flow was carried out, kg/m³; FS^B ₅₊ is the approved content of components C₅₊ of a the formation, which was carried out flow, g/m³.

EFFECT: technical result is higher accuracy of estimating recoverable reserves, taking into account the amount of formation gas migrating from one formation to another, due to formation of man-made fluid-conducting channel during hydraulic fracturing.

1 cl, 2 dwg

пл газа - form gas

смеси - mixtures

Description

The invention relates to the oil and gas industry, and in particular to methods for accounting for inter-reservoir gas flows generated as a result of hydraulic fracturing measures in nearby formations, which are independent objects for calculating reserves, and can be used to correctly write off reserves in the developed gas condensate formations.

An important element of control over field development is to account for the production of formation gas from each layer developed by one well. By controlling the gas production from each formation, gas reserves are written off from the state balance, and reliable information on the contribution of the layers, which are independent objects of reserves calculation, allows for the most accurate deduction of reserves.

So, in the event that each layer that is re-opened (perforated) in the well is an independent object for calculating reserves, the subsoil user needs to write off the reserves of produced gas based on the determination of the contribution of each layer to the total production rate of the well. In most cases, this is realized by performing mechanical flow metering and similar methods to establish the gas flow rate from each formation. However, in practice, there are cases when the readings of a mechanical flowmeter raise doubts about the reliability of the data, in particular at high values of the water factor in the wells or the impossibility of lowering the flowmeter to the artificial bottom of the well.

In addition to the foregoing, there are difficulties in writing off reserves from multilayer objects in which hydraulic fracturing (hydraulic fracturing) of the formation was carried out. So, in wells that open low-permeability gas condensate deposits, which are independent objects for calculating reserves, cost-effective development of formations without the use of stimulation by the hydraulic fracturing method is impossible. After hydraulic fracturing for each reservoir, there is a risk of the formation of a technogenic fluid-conducting channel through which inter-reservoir gas flow from one object of reserves estimation to another is possible. In this case, according to the data of mechanical flow metering, after the influx from two perforated reservoirs is intensified, only one can work (for reasons of overlapping the formation with a proppant plug or for other reasons), and according to the results of hydraulic fracturing simulation (or according to microseismic fracturing monitoring), one of the fractures breaks into the adjacent layer. In addition, when conducting gas condensate studies (GKI) after intensification of the inflow, an increased content of C ₅₊ components in the produced products of the working formation is observed, which does not correspond to the approved value for the working formation. These factors indicate the possible operation of the formation, which according to mechanical flow metering does not work. These circumstances may make it difficult to correctly evaluate gas production from each independent reserve calculation facility.

Currently, there are many examples of the simultaneous operation of two or more layers of gas fields. To solve the main problems - regulation of the inflow and synchronization of production, many researchers have developed and justified such methods as: simultaneous and separate exploitation of several productive formations (ORREENO) [Yudakov AN Efficiency of using simultaneously separate injection in the South licensed territory of the Priobskoye field / I.B. Dubiv, S.F. Mulyavin // Drilling and oil. - 2009. - No. 5. - S. 36-39; Baryshnikov A.V., Polyakov D.B., Shaimardanov R.F. Implementation and improvement of technology for simultaneous and separate operation of wells in the southern licensed territory of the Priobskoye field // Oil industry. 2010. - No. 5. - S. 121-123; Afanasyev V.A. Optimization of the layout and pumping equipment of the ORE wells / V.A. Afanasyev // Engineering practice. 2012. - No. 2. - S. 36-39]; The use of wells with different completions [Gerasimenko S.A. The results of computational experiments on the design of the development of multi-layer objects (article) / S.A. Gerasimenko, D.N. Glumov, V.V. Zhuravlev, A.S. Samoilov. // Territory of oil and gas. - 2012. - No. 12. - S. 16-23; Samoilov A.S. Development of technological solutions to improve the operational efficiency of a multilayer object of the South Khadyryakhinskoye field (article) / A.S. Samoilov, D.N. Glumov, S.A. Gerasimenko, V.V. Zhuravlev // Oil and gas business. - 2013. - No. 4. - S. 124-149]; Conducting selective methods for increasing component output [Grachev S.I. Justification of the technology for the development of multilayer deposits (article) / S.I. Grachev, A.V. Strekalov, A.B. Rublev, I.V. Zakharov, S.M. Strikun // News of higher educational institutions. Oil and gas. - 2012. - No. 3 - S. 44-49]. However, in the aforementioned works, control over the development of reserves is difficult and had no solution.

There is a method of simultaneous and separate exploration and development of multilayer deposits, including the descent of the underground layout into the injection well, to study the hydrodynamic connection between the layers and the targeted injection of the indicator tracer in it, the bottomhole pressure is measured in the well and the presence of interstratal flows is detected by the appearance of the tracer indicator in producing wells [RU 2371576 C1, IPC ЕВВ 47/10 (2006.01), publ. 10/27/2009].

The known method allows to determine the presence of interstratal flows in the near-wellbore zone, however, it excludes the possibility of assessing the quantitative characteristics of the interstratal flows.

The technical problem is the correct assessment of recoverable reserves, taking into account the determination of the amount of gas condensate mixture (reservoir gas) migrating from one reservoir to another, due to the formation of a technogenic fluid-conducting channel during hydraulic fracturing. Establishing the volume of inter-reservoir flows, in turn, will make it possible to write off reserves from reservoirs in which control over the development of reserves is difficult.

When implementing the claimed technical solution, the problem is solved by achieving a technical result, which consists in increasing the reliability of quantitative determination of produced gas based on determining the contribution of each formation to the total production rate of the well by taking into account the determination of the volume of inter-reservoir flows of formation gas drained by one well.

The proposed invention solves the problem of accounting for the volume of flows through technogenic fluid-conducting channels. The use of this invention will allow a quantitative assessment of inter-reservoir flow from one reservoir to another and thereby provide the most reliable write-off of reserves from the counting objects (layers). The novelty of the proposed method is the use of the potential condensate content, as well as its changes, to estimate the amount of flow from one gas condensate formation to another.

It was established that in wells developing two gas condensate reservoirs in the absence of the contribution of one of them (according to flow measurement data), a change in the potential condensate content (according to the results of gas condensate studies of the well) was observed for the working formation, which indicated that this change was due to inflow from the idle adjacent formation. The probability of hydrodynamic communication between the strata was determined by hydraulic fracturing modeling (where the probability of a fracture breaking into an adjacent formation is estimated) or by microseismic monitoring, where the fixation of acoustic emission sources also allows determining the probability of a fracture breaking into a neighboring formation.

After the fact of flow through technogenic fluid-conducting channels has been established based on the results of hydraulic fracturing simulation, or according to microseismic monitoring of the hydraulic fracturing process, taking into account the geomechanical properties of the rocks, or by other known methods, using the physicochemical properties of the formation fluid saturating each formation approved in the project document, as well as the results of gas condensate studies performed during the operation of the well, on the basis of the law of conservation of mass determine the magnitude of the overflow of technogenic gas channels between the two fluid-gas-condensate reservoirs according to the expression:

where Q _{pl. gas} - reservoir gas production rate according to the results of the gas analysis, thousand m ³ / day;

- содержание компонентов С₅₊ в пластовом газе по результатам ГКИ, г/м³;

- the content of components With ₅₊ in the reservoir gas according to the results of the GKI, g / m ³ ;

Q ^A is the flow rate of formation gas of the formation from which the overflow was carried out (idle formation), thousand m ³ / day;

ρ ^A is the approved density of the gas of the reservoir from which the overflow was carried out, kg / m ³ ;

ρ ^B is the approved density of the gas of the formation into which the overflow is carried out (working formation), kg / m ³ ;

ρ ^mixture - reservoir gas density according to the results of GKI, kg / m ³ ;

- утвержденная величина содержание компонентов С₅₊ пласта, из которого осуществлялся переток, кг/м³;

- the approved value is the content of the components of the C ₅₊ formation from which the overflow was carried out, kg / m ³ ;

- утвержденная величина содержание компонентов С₅₊ пласта, в который осуществлялся переток, кг/м³.

- the approved value is the content of the components of the C ₅₊ formation into which the overflow was carried out, kg / m ³ .

The inventive method of accounting for cross-flow of formation gas between two layers will allow for more accurate accounting of recoverable reserves, while taking into account the well-known physicochemical properties of the formation gas saturating each of the layers, as well as the potential condensate content and density of the formation gas.

The main source of information for the implementation of the method are the results of the State Property Committee (using separation equipment), which determine the following values:

- reservoir gas production rate, thousand m ³ / day ;;

- reservoir gas density (according to the results of laboratory analysis of gas and condensate samples), kg / m ³ ;

- potential content of components C ₅₊ , g / m ³ ;

In addition, according to the reservoir fluid model adopted in the project document for development of the field and the approved properties of the produced fluid, the reservoirs under consideration, the following parameters are used:

- reservoir gas density, kg / m ³ (design value);

- the potential content of the components With ₅₊ , g / m ³ (design value);

The available results of gas condensate studies and the values of the potential condensate content and gas density approved by the project document are used in formula (1), the conclusion of which is presented below.

The known law of conservation of mass [B.M. Yavorsky, A.A. Detlaf. Handbook of physics for engineers and university students / Publishing House "Science". - M. 1979] for gas:

Where

Q ^B - the rate of formation gas of the formation in which the flow was carried out, thousand m ³ / day;

The law of conservation of mass [B.M. Yavorsky, A.A. Detlaf. Handbook of physics for engineers and university students / Publishing House "Science". - M. 1979] for degassed condensate will have the form:

Solving a system of two equations with respect to Q ^A , a ratio is obtained that determines the magnitude of the overflow through technogenic fluid-conducting channels according to formula (1).

The essence of the claimed technical solution is illustrated by example and illustrative materials, where in FIG. 1 schematically shows a possible formation of a technogenic fluid-conducting channel 3 between the counting objects: formation 4 (working) and formation 5 (non-working), indicated: 1 - well bore, 2 - development of hydraulic fractures, 6 - clay bridge, in FIG. Figure 2 shows the visualization of the results of microseismic hydraulic fracturing monitoring of two formations 4 and 5, according to which a fracture break was identified in the adjacent formation, the numbers indicate -7 - the perforation interval, 8 - the source of acoustic emission during hydraulic fracturing. It should be noted that the formation of a technogenic fluid-conducting channel between the counting objects is possible both in the underlying reservoir and above it.

The method is as follows.

In well 1, which operates two formations 4 and 5, separated, for example, by a clay bridge 6, an activity was carried out to intensify the flow of hydraulic fracturing to each formation with the formation of hydraulic fractures 2. Formation 4 was opened a second time (perforated) to form a perforation interval 7. Based on the results mechanical flowmetry development of the underlying reservoir 5 is not observed. Thus, the write-off of reserves is carried out on the basis of the results of mechanical flow measurement, namely for one layer 4 (working). According to the results of the hydraulic fracturing simulation, in particular, in the example we used the data of microseismic hydraulic fracturing monitoring using an acoustic emission source 8, the presence of anthropogenic fluid-conducting channel 3 is predicted. In addition, when conducting the hydraulic fracturing, there is an increased content of C ₅₊ fraction components in the produced product (reservoir gas) working formation 4.

According to the GKI results, wells made using separation equipment determine the rate of formation gas, m ³ / day .; formation gas density, kg / m ³ (according to the results of laboratory analysis of gas and condensate samples); potential content in the reservoir gas of the fraction of C ₅₊ components (according to chromatographic analysis).

According to the reservoir fluid model adopted in the project document and the approved properties of the produced fluid of the reservoirs under consideration, the reservoir gas density and the potential content of the C ₅₊ fraction in the reservoir gas are used.

The value of the overflow is determined by the technogenic fluid-conducting channel — the rate of formation gas of the formation from which the overflow (idle formation) is carried out, thousand m ³ / day according to formula (1).

Example.

According to the results of GKI wells, performed using separation equipment before accounting for the magnitude of the flow of formation gas, the following data are determined:

production gas production rate - 320.0 thousand m ³ / day .;

the density of the reservoir gas is 1.17 kg / m ³ ;

the potential content in the reservoir gas of the fraction of C ₅₊ components is 330.0 g / m ³ ;

определяют величину перетока по техногенному флюидопроводящему каналу - дебит пластового газа пласта, из которого осуществляется переток (неработающий пласт), тыс.м³/сут;Knowing the approved design values corresponding to the adopted model of reservoir fluid (according to the project document for the development of the field): ρ ^A = 1.20 kg / m ³ ; ρ ^B = 1.15 kg / m ³ ;

determine the amount of flow through the technogenic fluid-conducting channel - the rate of formation gas of the formation from which the flow (idle formation) is carried out, thousand m ³ / day;

Thus, the inventive method provides the reliability of the quantitative assessment of inter-reservoir flows during the depletion of reserves of gas condensate reservoirs drained by one well, more accurate adaptation of the digital filtration model and helps to develop recommendations for improving the technological efficiency of hydraulic fracturing.

Claims (10)

The method of accounting for inter-reservoir gas flows generated as a result of the hydraulic fracturing in two nearby reservoirs, which are independent objects for calculating reserves, while the initial information for accounting for inter-reservoir flows is the approved values of the content of components C ₅₊ layers and the approved density of the reservoir gas, results gas condensate studies (GKI), which determine the current potential content of condensate and flow rate of gas, in this case based on the law of conservation of mass flow rate determined by the formation of gas reservoir, from which the flow, according to the expression

, Where Q _{pl. gas} - reservoir gas production rate according to the results of the gas analysis, thousand m ³ / day;

- the content of components With ₅₊ in the reservoir gas according to the results of the GKI, g / m ³ ; Q ^A is the production gas rate of the formation from which the overflow was carried out, thousand m ³ / day; ρ ^A is the approved density of the gas of the reservoir from which the overflow was carried out, kg / m ³ ; ρ ^B is the approved density of the gas of the reservoir into which the overflow is carried out, kg / m ³ ;

- the approved value of the content of the components of the C ₅₊ layer from which the overflow was carried out, kg / m ³ ;

- the approved value of the content of C ₅₊ components of the reservoir into which the overflow was carried out, g / m ³ .

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