RU2383719C1 - Procedure for development of multi-bed gas-condensate deposit implementing transportation of gas via high permeable formation - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention refers to oil and gas industry and can be used for raising efficiency of development of multi-bed gas-condensate deposits, particularly in cases, when there are low-permeable formations with lower gas-condensate characteristics present in geological cross-section together with main operational object - high yield gas-condensate deposit. The essence of the invention is as follows: the procedure consists in drilling production wells to a high permeable gas-condensate formation, in development the high permeable formation with production wells till drop of formation pressure to value exceeding pressure of beginning of hydrocarbon condensate precipitation in this formation. Development of other gas-condensate formations with lower gas-condensate characteristics and initial formation pressure is carried out at continuation of gas withdrawal from the high permeable formation through production wells. Development is performed with cross-flow of gas from low permeable formations and through by-pass wells into depression craters of the high permeable formation thus facilitating maintenance of pressure in this formation above pressure of beginning of hydrocarbon condensation in it for maximally possible time. Further rates of pressure drop in the formation are slowed down and there appears possibility of extraction of condensate precipitated in the main process object with drier by-pass gas.

EFFECT: facilitating raise of final condensate yield of highly productive formation due to maintaining formation pressure above pressure of start of hydrocarbon condensation for long time; more uniform draining of deposit; eliminating formation of sections of entrapped gas and reverse evaporation of precipitated condensate into by-pass gas.

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Description

The invention relates to the oil and gas industry and can be used to increase the efficiency of the development of multilayer gas condensate fields, especially if in the geological section along with the main operational object (highly permeable gas condensate deposit) there are formations with lower gas condensate characteristics (gas condensate factors), including low permeability.

A known method of developing multi-layer gas and gas condensate fields, in which formations with close thermobaric conditions are separated into separate production facilities with their borehole development by drilling individual wells or well clusters at these facilities (Gritsenko A.I., Istomin V.A., etc. The collection and field treatment of gas in the northern fields. M: Nedra, 1999, pp. 71-73). The disadvantage of this method is the increased capital costs associated with drilling separate wells for each production facility and a separate collection system for the production of gas condensate wells.

There is also known a method of developing gas fields, including the development of two or more layers (production facilities) with a single system of ground-based field equipment and combining gas flows from different layers (Zakirov S.N. et al. Design and development of gas fields. M .: Nedra, 1974 , p. 312).

The disadvantages of the above methods are irrational losses of reservoir pressure at the wellheads (when equalizing the pressure at the wellheads operating at different horizons, as with or without the use of ejection devices), as well as significant difficulties in regulating the operation of wells at the late stage of operation of a multilayer field (the appearance of wells with low flow rates, self-pressuring and shutting down of low-productivity wells, the need for reconstruction of gas gathering networks, etc.).

There is a method of developing a multilayer gas or gas condensate field, including drilling production wells and transferring gas from the underlying formation to the upper one with a certain adjustment of pressure in the formations and wells, as well as calculating the volume of gas bypass according to special mathematical relationships. In this case, the upper productive horizon is considered as the main one. To increase the efficiency of this method, it is also possible to operate bypass wells as producing wells in the initial period of development in the presence of excess pressure (RF Patent No. 2034131, CL. EVB 43/00, 04/30/95). The disadvantages of this method are associated both with inefficient losses of reservoir energy, but also with the possibility of additional gas losses due to the transfer of bypassed gas into the most permeable interlayers of the upper horizon.

A known method of developing multilayer gas fields of the field, including drilling production wells on the lower high-pressure formation and bypassing gas into the upper low-pressure formation with pressure control. Production wells are drilled in an amount that ensures the planned production of gas from the entire field, and the transfer from the high-pressure formation is carried out preliminarily by one drilled grid of wells into the roof of the formation with the lowest formation pressure with closed wells at the wellhead and before the formation and bottomhole pressures are equal in the interval of opening of the low-pressure layer. After pressure equalization, simultaneous joint operation of the upper and lower layers along a single lift column is carried out. When watering the lower layer, waterlogged wells are transferred to the operation of the upper layer (RF Patent No. 2135748, Cl. EB21B 43/14, 43/16, 08/27/99). This method is impractical to use if the lower reservoir is a gas condensate reservoir due to premature condensation in the lower reservoir and condensate losses during its extraction in the field during the development of the upper reservoir.

Of the known methods for the development of multi-layer gas and gas condensate fields, the closest to the proposed one is the method of drilling wells and the development of multi-layer hydrocarbon deposits with heterogeneous geological conditions of occurrence of productive formations (RF Patent No. 2295632, Cl. Е21В 43/14, ЕВВ 7/04, 03/13/2006 ) The method is applicable when a low-permeable productive formation with anomalous high reservoir pressure (ARPA) is located above the main production facility in the form of a highly permeable formation. The method includes drilling wells into the lower formation, preliminary, pressure-controlled fluid transfer from the high-pressure formation to the fluid distribution zone in the low-pressure formation, limited by the contact of the fluid with water, with closed wells at the wellhead, and subsequent field operation. Field development is carried out by well clusters.

The disadvantage of this method is its narrow scope due to the fact that it is applicable only when a combination of the lower high-permeability layer and the upper low-permeability layer with the air pressure drop is quite rare in geological practice. In addition, this method, judging by its description, is intended for purely gas multilayer fields and does not imply an increase in the efficiency of hydrocarbon condensate extraction from a highly productive formation.

The objective of the claimed invention is to increase the efficiency of the development of a multilayer field and to increase the degree of extraction of condensate from the deposits of the field with high gas condensate factors.

This problem is solved by the method of borehole development of multilayer gas condensate fields for depletion with heterogeneous geological conditions of occurrence of productive formations that differ in initial pressures and gas condensate characteristics, which includes:

the geological section of the definition of highly productive horizons (gas condensate deposits) with high gas condensate factors and their allocation in the main operational object;

the allocation in the geological section of productive (highly permeable) formations with lower gas condensate factors, a separate (independent) development of which for depletion for any reason is unprofitable or unprofitable;

drilling production wells on a highly permeable gas condensate formation (the main production facility) with a high gas condensate factor (with an initial pressure P and the pressure of the onset of condensation of heavy hydrocarbons in the P _cond deposits, with P> P _cond );

development of a highly permeable (highly productive) formation (reservoir) by production wells (reservoirs of production wells) with a decrease in reservoir pressure up to P ₁ , where P ₁ > P _con (P _{con is the} pressure at which hydrocarbon condensate begins to form in this reservoir);

Moreover, according to the invention, while continuing to take gas from a highly permeable formation by production wells, other gas condensate reservoirs with lower gas condensate characteristics and initial reservoir pressures P _i (P _i > P ₁ ) are developed by the flow of gas from these reservoirs through bypass wells into depression funnels of the highly permeable reservoir with ensuring that the maximum possible pressure time in the main production facility (high permeable formation) is maintained above the start pressure of the condens hydrocarbon content in it and a subsequent reduction in the rate of pressure drop in the reservoir (with the possibility of condensate being drained by the drier gas by the drier gas).

To increase the effectiveness of the proposed method, gas flows from other layers are carried out in the zone of the depression funnel (in the zone with the lowest reservoir pressure). At the same time, in a highly productive reservoir (the main production facility), the reservoir pressure is equalized in area, and if condensate begins to form in it, the bypassed gas dissolves the condensate that has formed (thereby increasing the final condensate yield of the highly productive reservoir). It should be noted that both underlying and overlying strata can be involved in the development, since the initial stage is the development of a highly productive reservoir, which significantly reduces the pressure in it and, thus, provides the possibility of gas bypass from other, including low-permeability formations.

In addition, part of production wells can be used as cross-hole wells, the operation of which is transferred to the gas bypass mode after appropriate conversion (for example, by shooting a formation of interest or by conducting an additional wellbore to the formation of interest).

In addition, to increase the development efficiency, bypass wells are drilled with horizontal sections and with additional wells trimming.

As an option of this method, in the presence of several productive formations, flows to the main production facility are carried out sequentially from formations with ever lower gas-condensate characteristics, i.e. involving in the development (through the transport of gas to production wells in the main production facility) ever thinner gases and, thereby, increasing the condensate recovery and gas recovery of the main productive highly permeable formation (main production facility).

Example. When developing one of the multilayer deposits in the north of the Tyumen region of Russia, two deposits were discovered: gas (Cenomanian) and gas condensate (Valanginian) deposits (Fig. 1).

Reservoir Characteristics

Cenomanian (gas) reservoir

A deposit with a complex occurrence nature, the development of which requires drilling wells with a complex wiring profile.

Depth 1124 m

Depth 85 m

Gas saturation - 0.72

Initial reservoir pressure - 11.2 MPa

Valanginian (gas condensate) reservoir

Depth 2343 m

Deposit height 120 m

Gas saturation - 0.75

Initial reservoir pressure - 24.4 MPa

The initial content of condensate to the reservoir gas is 88 g / m ³

Condensation start pressure in the formation - 23.7 MPa

In figure 1. the contours of the deposits are schematically shown: the upper gas reservoir is Cenomanian, the lower reservoir is Valanginian, bypass wells are shown (position 1 in FIG. 1) (drilled into gas and gas condensate deposits) and production wells (position 2 in FIG. 1).

Figure 2 presents a graph comparing the annual gas production with overflow (the proposed method) and without overflow.

Currently, nine production wells of the Valanginian deposit are being operated. The annual gas withdrawal from the Valanginian reservoir is 2.5% of the initial gas reserves.

Bypass wells 1 are vertical or directional drilled in the domed part of the field and open the Cenomanian and Valanginian deposits simultaneously. These wells were drilled after 14 years of development of the Valanginian reservoir, when the pressure in the gas condensate Valanginian reservoir fell below the reservoir pressure in the Cenomanian gas reservoir. With a decrease in pressure in the Valanginian reservoir below the reservoir pressure in the Cenomanian reservoir, gas is transferred through wells 1. At the same time, dry gas, moving along the Valanginian reservoir and dissolving the precipitated condensate, is advancing to the faces of production gas condensate wells.

The results of the field development are presented in figure 2, which shows a graph comparing the annual gas production with the organization of the gas flow from the Cenomanian deposit to the Valanginian deposit and without such an overflow (time - from the moment the overflow began).

The gas recovery coefficient at the moment of the beginning of the flow is 59.8%. The condensate recovery rate is 45.9%.

Over the course of 20 years, the overflow has amounted to 35.2 billion m ³ or 29.7% of the initial reserves of Cenomanian gas.

Recovery ratios from Valanginian deposits:

The estimated gas recovery coefficient (KIT) without overflow is 87.9%, and the condensate recovery coefficient (KFC) is 58.4%.

The CIG with overflow is 99.1%, and the CFC is 61.5%.

At the same time, additional gas production during development with overflow is 24.1 billion m ³ , condensate - 0.73 million m ³ .

When organizing the overflow, the well stock is reduced by 4 units (i.e., 4 wells with a complex wiring profile), 25.5 km long gas collection lines are not built, and additional facilities for the preparation of Cenomanian gas at the gas treatment facility are not built.

Claims (4)

1. A method of developing a multilayer gas condensate field with heterogeneous geological conditions of occurrence of productive formations that differ in initial pressures and gas condensate characteristics, including drilling production wells on a highly permeable highly productive gas condensate formation with an initial pressure P and development of a highly permeable formation with production wells for depletion to a pressure P ₁ above or above above ₁ or pressure of the beginning of the formation of hydrocarbon condensate in this reservoir, from characterized in that while continuing to take gas from a highly permeable formation by production wells, other gas-condensate formations with initial formation pressures are developed
P _i , higher than P ₁ and lower gas condensate characteristics, the flow of gas from these reservoirs into the depressing funnels of the highly permeable reservoir through the bypass wells to ensure the transportation of gas from other gas condensate reservoirs through the highly permeable reservoir while maintaining the pressure therein above the onset pressure of hydrocarbon condensate in the highly permeable reservoir. 2. The method according to claim 1, characterized in that as cross-hole wells use production wells available in the zone of depression funnels, connecting them to the corresponding reservoir. 3. The method according to claim 1, characterized in that for a more efficient gas flow, additional directional wells are drilled with horizontal sections both in the gas condensate formations being developed and in a highly permeable formation. 4. The method according to claim 1, characterized in that the gas flow is carried out from the formation with low gas condensate characteristics to ensure evaporation of condensate that has precipitated at a late stage of development of a highly permeable formation.

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