RU2536523C1 - Development of multi-zone gas field - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: invention relates to the oil-and-gas industry and can be used for the development of hard-to-extract gas deposits. The proposed method comprises drilling of the main wellbore, running-in of a production string, surveying, drilling of a horizontal section in a productive formation. Note here that the said main wellbore is drilled with a preset inclination angle, encased by the production string with a precut opening in an aluminium shell for drilling and finishing of a smaller-diameter lateral borehole. The wellbore production sections are drilled gently sloping and equipped with appropriate filters. Simultaneously, a dual production string is run-into the main and lateral horizons to be isolated by a packer above the roof of the lower productive horizon to develop separately the horizons by separate production strings. In the well operation, methanol is fed automatically at a preset flow rate in the main wellbore annulus and lateral borehole annulus.

EFFECT: higher efficiency of development.

2 dwg

Description

The invention relates to the field of the gas industry and can be used in the development of hard-to-recover gas deposits represented by unconsolidated, clayed reservoirs with high residual water saturation, for example, Turonian deposits.

A known method of developing gas fields, including the development of two or more reservoirs operated by separate well grids with a single land-based arrangement system and combining gas flows from different reservoirs (Zakirov S.N. et al. Design and development of gas fields. M .: Nedra, 1974 ., p. 312). The disadvantage of this method is the increased capital costs when drilling separate grids for each formation.

A known method for the development of multilayer gas fields (RF No. 2377396 E21B 43/14), including the construction of separate grids of production wells for each development site, connecting wells operating different development facilities to a single pipeline network. Field development begins with the exploitation of lower gas deposits having a higher initial reservoir pressure, and the overlying deposits are included in the development when the current wellhead pressure of the wells draining the lower deposits decreases to the initial wellhead pressure of the wells draining the overlying deposits.

However, the above method does not allow to carry out work on development, research and operation separately for each wellbore, to keep track of products separately for different production facilities.

A known method of drilling wells and the development of multilayer hydrocarbon deposits with heterogeneous geological conditions of occurrence of productive formations (RF Patent 2295632, CL E21B 43/14, E21B 7/04, 03/13/2006). The method is applicable when a low permeable reservoir with anomalous high reservoir pressure 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. Bypass wells are drilled with multi-lateral horizontal endings in both formations, and an impenetrable section, for example, in the form of a cement bridge, is installed above the sidetracking interval in the upper low-permeability formation. Further above it, the sidetrack is drilled onto the lower highly permeable formation and the subsequent drilling of the impermeable section.

The disadvantage of this method is its narrow scope due to the fact that it is applicable only when the combination of the lower high-permeability layer and the upper low-permeability layer with anomalous high reservoir pressure is quite rare in geological practice. In addition, this method does not allow for simultaneous and separate gas production, in which development, research and production operations can be performed separately for each wellbore, without completely stopping the production process.

In addition, all of these methods are applicable only to Cenomanian reservoirs, where the permeability of gas-saturated formations is very high. The gas reserves concentrated in the Turon turned out to be difficult to extract, primarily because the permeability of gas-saturated rocks is ten times lower than in the Cenomanian, and therefore gas inflows are insignificant. And its development using traditional vertical wells for the Cenomanian is impractical due to low flow rates, which do not exceed 10-18 thousand cubic meters per day, and this is below the level of profitability.

The objective of the invention is to increase the efficiency of the development of multilayer deposits, the deposits of which lie in a consistent area and are not hydrodynamically interconnected, reduce capital costs for drilling wells with shallow ends, and reduce adverse environmental effects.

The technical result from the application of the proposed method consists in the possibility of separate exploitation of several productive horizons for individual tubing columns, to carry out work on development, research and geological and technical measures for each wellbore, to minimize the size of well pads, to increase technical and economic gas production indicators, reduce the need for wellhead equipment.

To achieve this technical result in a known method of developing a multi-layer gas field, including:

- drilling the main trunk,

- launching a production casing and conducting geophysical studies,

- drilling a horizontal section in the reservoir,

ACCORDING TO THE INVENTION

- the main barrel is drilled with a given zenith angle,

- casing it with a production casing, in which a window in an aluminum shell is pre-cut for drilling and completion of a sidetrack of a smaller diameter,

- productive sections of the shafts are drilled with shallow subhorizontal layers in two different hydrodynamically unconnected formations and equipped with filters of appropriate diameters,

- produce simultaneous descent of the double lift string of tubing to the main and lateral horizons, isolating them together above the roof of the lower productive horizon with a packer,

- and carry out separate exploitation of horizons for individual columns of tubing,

- at the same time, methanol is supplied in an automatic mode with a fixed flow rate into the pipe space of the main barrel and the annular space of the side barrel.

The method is illustrated by drawings, where in Fig.1 shows a borehole, in Fig.2 - the supply of methanol during operation of the well.

The well consists of two trunks, the main 1 to the horizon T ₂ and side 2 to the horizon T ₁ . The main barrel 1 is cased with a production casing 3, which includes a filter 4. For drilling a sidetrack 2 onto horizon T ₁ , a special pipe 5 with a pre-cut window 6 is used. A shank filter 7 is lowered into sidewall 2. Horizons T ₁ and T ₂ they are isolated from each other by packer 8. In the main 1 and lateral 2 boreholes, the lift columns of tubing 9 and 10 are simultaneously lowered. Methanol pipelines are connected to each of the boreholes for supplying the inhibitor to the pipe and annulus of the well: lateral bore 2 - methanol pipe 11. Methanol pipe 12 is connected to the main trunk 1, methanol tank 13 is supplied to the inhibitor from the tank 13. At the wellhead, double fountain fittings 14 are installed for sealing the wellhead, suspending the lift columns of tubing 9 and 10, monitoring and regulation of the mode of operation of the well, overlapping and direction of the produced products in the gas gathering loop, as well as various technological operations.

The inventive method is as follows as an example of a double-well well No. 174 of the Yuzhno-Russkoye oil and gas field.

The main trunk 1 is drilled through horizon T _{2 of the} double-hole well No. 174 through a reservoir with a zenith angle of 84.2 degrees and cased by production string 3, which includes filter 4. A complex of geophysical surveys is carried out. In production casing 3, in the range of 1010-1470 m, window 6 was cut for drilling and completion of sidetrack 2. A pre-cut window 6 guarantees a more accurate installation of the latter, without turning the metal-intensive production casing 3 in azimuth. A liner-filter 7 is lowered into the lateral wellbore 2 to horizon T _1. Isolation of horizons T ₁ and T _{2 to} each other at a depth of 1509 m (the roof of horizon T ₂ ) is carried out by packer 8. In the main wellbore 1, there is a well completion system designed for separate operating horizons T ₁ and T ₂ for individual columns of tubing 9 and 10 are simultaneously lowered in both barrels 1 and 2 of the well to the filter arrangement 4 and 7. Said system allows to well completion work for the development and research separately to channels on each barrel 1 and 2 multilateral wells, and also allows separate access through tubing 9 and 10 in the main side 1 and the borehole 2 during the subsequent operation. Gas production on both trunks 1 and 2 is independent of each other. Gas horizons T ₁ and T ₂ through a double fountain valve 14 separately through tubing 9 and 10 enters through the corresponding reinforcing blocks in the cluster gas collector (not shown), where gas flows from the Turonian shafts 1 and 2 of well No. 174 are mixed and Cenomanian wells of the South Russian oil and gas field. The thermobaric conditions of the Turonian deposits suggest the formation of hydrates in the gas production process, both in the wellbore and directly in the bottomhole formation zone, which significantly complicates the gas production process. To prevent hydrate formation in the wellhead piping scheme, methanol is fed into the pipe space of the main barrel 1 (into the tubing string) and the annular space of the side wellbore 2. The piping of the well 174 also provides for the supply of methanol to the pipe space of the sidetrack 2.

Inhibition of the main wellbore 1 is carried out by supplying in the required volume of methanol directly to the tubing with a barrel stop 1 for 1 hour. The inhibitor is supplied from the tank - methanol tank 13 with a volume of 5 m ³ under its own hydrostatic pressure through the methanol pipe 12. Operations to open and close valves of the fountain valves, control the injection of the required volume are carried out automatically in accordance with the parameters specified on the main control panel (not shown) . Inhibition occurs once a day. The stopping time of the main wellbore 1 was established based on the conditions of sufficient time for a gravitational decrease in the injected methanol through the wellbore to the bottomhole zone, and was determined on the basis of experimental data when performing similar work on the Cenomanian wells.

Inhibition of the sidetrack 2 is carried out through the annulus of the well also in automatic mode. Methanol injection occurs in a continuous cyclic mode in accordance with a given installation to maintain the required flow rate of methanol supply without stopping gas production by the sidetrack 2.

The use of the gas production method by a double-well production well in comparison with the method of production by a single-well well provides a number of advantages.

1. A double-well borehole can significantly increase the extraction of gas from one well. During the construction of the experimental double-hole well No. 174 of the Yuzhno-Russkoye field, the production rate increased by 3.5 times compared to the single-well well No. 170N located on the same gas well cluster.

2. The zone of formation drainage with a double-well borehole is significantly larger, while the depression created on the formation during gas production is much lower, which increases the efficiency of developing low-permeability gas reservoirs.

3. The use of double-hole wells allows each of the wellbores to be equipped with its own tubing and to separately operate several productive horizons with different characteristics (temperature, pressure). And also allows you to keep track of products separately for different production facilities.

4. Work on the development, research and operation can be carried out separately for each wellbore, without completely stopping the production process.

5. The use of a gas production method with a double-well production well reduces the number of wells required for effective drainage of the reservoir, which leads to time and cost savings. The decrease in the surface area leads to an improvement in the environmental situation. By eliminating the need to drill wells in several places, this technology can reduce the environmental impact of drilling operations by at least 50%. This is especially important in environmentally sensitive areas such as the West Siberian Plain.

6. The benefits also include reduced lead times and, as a result, reduced costs for heating fluids and equipment and lower costs for disposal of sludge.

Claims (1)

A method of developing a multilayer gas field, including drilling the main trunk, launching the production string and conducting geophysical surveys, drilling a horizontal section in the reservoir, characterized in that the main trunk is drilled with a predetermined zenith angle, casing it with a production string in which the window is pre-cut in aluminum shell for drilling and completion of a smaller sidetrack, productive sections of the shafts are drilled with shallow subhorizontal in two different in non-dynamically unconnected formations and equipped with filters of appropriate diameters, simultaneously run the dual lift string of tubing to the main and lateral horizons, isolating them together above the roof of the lower productive horizon with a packer, and separately operate horizons along separate tubing tubing columns, while supplying methanol in an automatic mode with a fixed flow rate into the pipe space of the main barrel and the annular space b shackle barrel.

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