RU2135748C1 - Method for development of multiple-bed gas deposits - Google Patents

Abstract

FIELD: gas production industry. SUBSTANCE: according to method, gas is overflown from lower bed to upper lower-pressure bed under regulation of pressure. Producing wells are drilled into higher-pressure bed. Producing wells are drilled in number needed for ensuring preset recovery of gas from entire deposit. Overflow of gas from higher-pressure bed is initially carried out through one pattern of drilled wells into roof of bed with most lower bed pressure with closed wells at their heads and until levelling of bed and bottom-hole pressure within interval of opening of lower-pressure bed. Upon levelling of pressures, performed is simultaneous combined operation of upper and lower beds by using single lifting string. At flooding of lower bed, flooded wells are brought to operation of upper bed. Application of aforesaid method allows for reducing capital cost for drilling of wells together with increasing gas output. EFFECT: higher efficiency. 4 dwg, 1 tbl

Description

 The invention relates to the gas industry and can be used in the development of multilayer gas deposits.

 There is a method of developing gas fields, including the development of two or more layers, operated by separate networks of wells with a single system of land facilities and combining gas flows from different layers [1].

 The disadvantages of this method are: limiting the planned gas extraction from the field and transferring production volumes to the overlying formation, which in the general case can also be low-pressure, which leads to early commissioning of the compressor station (booster compressor station); the worst conditions for the exploitation of deposits, because the grid of wells on various formations are static, drilled based on initial information about the geology of the formations; the need to supply a hydrate inhibitor in the plumes of wells drilled on the upper low-temperature formation.

 The closest technical solution to the proposed method is the "Method for the development of a multilayer gas or gas condensate field," including drilling production wells, bypassing gas from the lower reservoir with pressure adjustment [2].

 The specified method consists in drilling a production grid of wells at the upper object, taking it for the main development object. To slow down the flooding of production wells of the upper layer, bypass wells are constructed on the lower and upper layers. Then, using these bypass wells, gas is transferred from the lower reservoir to the GWC interval (gas-water contact) of the upper main facility. In order for the reservoir pressure in the upper main object to not decrease in the bypass interval in the GWC area, it is necessary to maintain the equality of the volumes of produced and bypassed gas. Based on these considerations, the number of bypass wells is determined. Field development begins immediately from the upper layer.

 The disadvantages of this method are: 1) the limitation of gas production from the upper development object, because it is necessary to maintain the equality of the volumes of gas produced and bypassed, and the lower layer is not actively developed; 2) possible gas losses during bypass into the most permeable layers of the upper object in the GVK area; 3) an increase in capital costs due to an increase in the stock of wells at the upper main facility and their separate operation; 4) the need to feed a hydrate inhibitor into wells drilled on the upper low-pressure and low-temperature formation.

 The technical result of the invention is to reduce the capital cost of drilling.

 The required technical result is achieved by the fact that in the method of developing multilayer gas fields, including drilling production wells, transferring gas from the lower formation to the upper low pressure formation with pressure control, according to the invention, production wells are drilled to the lower high pressure formation in an amount that ensures the planned production of gas from the whole deposits, and gas bypass from the high-pressure formation is carried out previously on a single drilled grid of wells in the roof of the formation with the lowest reservoir pressure at closed wells at the wellhead and before the formation and bottomhole pressures are equal in the interval of opening the low-pressure formation, then, after pressure equalization, the upper and lower reservoirs are simultaneously operated together on a single lift string, and when the lower reservoir is flooded, watered wells are put into operation upper layer.

 Figure 1 shows a diagram of the proposed method in the first stage of the preliminary gas bypass; figure 2 - diagram of the proposed method at the second stage of field operation.

The method includes transferring gas (see Fig. 1) to reservoir 1, where the pressure is P _1pl <P _1ab , from reservoir 2, where R _2pl > P _2ab along a single lift column 3 equipped with a pressure regulator 4, and at the same time, joint development ( see Fig. 2) formation 1, where P _1pl > P _1ab and formation 2, where P _2pl > P _{2ab a} single lift column 3, equipped with a pressure regulator 4.

 In FIG. Figure 3 shows the dynamics of gas production at the same time - the joint development of two reservoirs using the example of the Bovanenkovskoye field, where curve 1 is the annual gas production from the low-pressure reservoir, curve 2 is the total annual gas production from the two reservoirs.

 In FIG. Figure 4 shows the change in current gas reserves and pore volume of a low-pressure formation during gas bypass and development, where curve I is the change in current reserves, curve II is the flooding of the reservoir.

 The method is as follows. Drilling production wells at the lower high-pressure formation in an amount that ensures the planned production of gas from the entire field (i.e., taking into account the simultaneous operation of formations 1 and 2 (Fig. 1) through the same lift string). Then, gas bypass is carried out using the pressure regulator 4 (Fig. 1) from the lower to the upper low-pressure formation with closed wells at the wellhead, i.e., gas production during the bypass is not performed until the formation and bottomhole pressures in the low-pressure formation 1 are equalized.

 During the bypass (from 2 to 5 years), the arrangement of the fishery is carried out.

 At the second stage, they carry out simultaneously - the joint development of both layers through the same production wells, previously drilled to the lower horizon using a single lift string.

The total annual gas production from the field consists of
q _sum = q _n + q _in ,
where q _sum - total gas production from the field, billion m ³ / year; q _n - production from the lower reservoir; q _in - production from the upper low-pressure reservoir, which after bypass became also high-pressure.

 In the prototype, only gas production from a limited by-hole fund is realized, and the resources of the upper formation are essentially temporarily conserved, which leads to limited gas production from the field as a whole.

 Due to the complete and staged gas bypass, the thermodynamic potential of the low-pressure formation 1 increases and the synergetics of the multilayer system is most fully realized.

Example. During exploration of the Bovanenkovo field, two other gas reservoir deposits were discovered, among others. Lower reservoir: 1500 m depth, reservoir pressure 15.0 MPa, reservoir temperature plus 42.5 ^o C. The main gas reserves are concentrated in the lower reservoir (deposits), which amount to 2031 billion m ³ . Upper low-pressure reservoir: depth 620 m, reservoir pressure 6.8 MPa, reservoir temperature plus 16 ^o C. The gas reserves of the upper low-pressure reservoir are 870 billion m ³ .

 When developing the upper deposit (Cenomanian) by an independent grid, it is necessary to immediately introduce a booster compressor station (BCS).

To implement the method, 327 production wells were drilled into the lower reservoir (see table). According to the proposed method, for the first 5 years, gas was transferred from the lower layer to the roof of the upper one according to the already drilled well stock (see figure 3 — shaded area). The total flowing gas volume amounted to 413.2 billion m ³ . During the bypass period, gas production is not carried out until the bottomhole and reservoir pressures are equalized. In this case, the volume of bypass gas is controlled by a pressure regulator 4 installed in the elevator column 3. In addition, additional control of the gas bypass is carried out at the wellhead by a known calculation method.

 After the end of the gas bypass, the wells are put into operation, and at the same time, joint development of both layers along one lift string is carried out.

 As a result of gas bypass, the development conditions of the upper (Cenomanian) reservoir are improved, associated with its watering, which provide a significant increase in the period of water invasion into the reservoir (see Fig. 4 - the beginning of the water invasion in the 18-19th years of development).

The table presents the results of calculations of the technological parameters of the development of the Bovanenkovo field when implementing the proposed method. The planned volume of gas production in the amount of 115 billion m ³ / year is sold by 327 production wells, while production of the same volume of gas from the prototype will require almost twice as many production wells.

 BCS is introduced according to the proposed method for the 9th year from the start of field development.

 Using the proposed method for the development of multi-layer gas fields has the following advantages compared to the methods currently existing: 1) combining the layers into one hydrodynamically coupled, self-regulating system increases its synergetics; 2) as a result of preliminary transfer of gas from a high-pressure formation to a formation with a lower formation pressure and their subsequent joint operation by a single lift string, the well stock is reduced by 30-50%, depending on the initial gas reserves and reservoir properties of the reservoirs; 3) in the case of combining formations of low pressure (less than 7.4 MPa) and high pressure (more than 7.4 MPa), the period of non-compressor operation of the system increases; 4) simultaneous-joint operation of formations with different thermobaric characteristics allows to obtain, in some cases, non-hydrate conditions for the operation of wells by combining flows of more “hot” and “cold” gases in a single lift string; 5) the operating conditions and watering of the reservoir system are improved, which are manifested primarily in the fact that the underlying horizon is initially flooded, while the advance of the GWC of the overlying horizon significantly lags behind the advance of the GWC of the underlying one (due to an increase in the pore volume of the upper reservoir due to gas overflow lower). Thus, in case of critical flooding of the underlying horizon, flooded wells are transferred to the operation of the overlying one.

 Thus, the method allows you to efficiently generate the resources of both operational facilities with significantly lower costs compared to existing development methods at the present time.

Sources of information
1. Zakirov S.N. and others. Design and development of gas fields. -M .: Nedra, 1974, p. 312.

 2. RF patent, 2034131, cl. E 21 B 43/00, 04/30/95.

Claims (1)

 A method of developing multilayer gas fields, including drilling production wells, transferring gas from the lower formation to the upper low-pressure formation with pressure adjustment, characterized in that the producing wells are drilled to the lower high-pressure formation and in an amount that ensures the planned production of gas from the entire field, and gas bypass from a high-pressure formation, preliminary, according to a single drilled grid of wells, to the roof of the formation with the lowest formation pressure with closed wells at the mouth before equalization reservoir and bottomhole pressures in the range of low-pressure opening seam, and then, after the pressure equalization is carried out simultaneously the joint operation of the upper and lower layers at a single tubing, and with a water content lower reservoir Obvodny wells is transferred to the upper layer operation.

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