RU2501940C1 - Method for oil production from formation with abnormally low formation pressure - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method provides for extraction of formation liquid by means of a bottom-hole pump from vertical production wells drilled so that a sump is formed. A cavity is created in lower part of a productive formation in each vertical production well. In addition, flat directional production wells are drilled, thus attaching the face of each flat directional well to the cavity of the corresponding production vertical well, and mouths of flat directional production wells are interconnected with atmosphere. Diameter of vertical production wells is larger than diameter of flat directional wells. Mouths of flat directional wells are located for example near mouths of neighbouring vertical production wells. Creation of the cavity is performed for example by water jet washing-out of rock by means of a special adapter with a side water jet nozzle, and filling of the cavity with filler is performed for example by gravel alluviation.

EFFECT: improving oil extraction from formations with high average number of permeable intervals and abnormally low formation pressure owing to enlarging the formation drainage zone and activation of formation liquid runoff by increasing the forces contributing to displacement of formation liquid.

4 cl, 3 tbl, 1 ex, 3 dwg

Description

The invention relates to the oil industry and can be used in the development of oil deposits, represented by layered heterogeneous reservoirs, including formations with high stratification and abnormally low reservoir pressure.

A known method of oil production, including the selection of formation fluid using a deep pump from vertical production wells that open the entire thickness of the reservoir with the formation of a sump (see the book Muravyova IM, Bazlova MN and others. "Technique and technology of oil production and gas. ”- M .: Nedra, 1971, p. 79).

However, the development of oil formations with high stratification and a small effective thickness by vertical wells, ensuring the opening of all layers at the same time, does not provide the required profitability, while under conditions of abnormally low reservoir pressure, a very low inflow of formation fluid into the bottomhole zone of vertical wells is provided.

There is a method of oil production from layered reservoirs by drilling a horizontal wellbore in the middle of the reservoir with horizontal branches above and below the main wellbore (see patent RU No. 2431038, IPC: Е21В 43/16, publ. 10.10.2011).

However, in formations with high stratification under conditions of an abnormally low reservoir pressure, the influx of reservoir fluid from the descending horizontal branches will not be obtained due to the low reservoir energy of the reservoir, as a result, part of the reservoir is not involved in the development.

Also known is a method of producing oil from layered reservoirs by drilling a horizontal wellbore in the middle of the reservoir and a vertical producing well drilled to form a sump and intersecting the end of the horizontal well, adopted by the authors as a prototype. The method is intended for the production of highly viscous oil, while a horizontal well is used to pump coolant into the formation before liquefying oil around the horizontal wellbore, then the well is stopped for soaking, followed by selection of formation fluid from a vertical well (see patent RU No. 2307242, IPC: Е21В 43 / 24, published September 27, 2007).

However, this method cannot be used in the development of formations with high stratification, especially at an abnormally low reservoir pressure, when drilling horizontal wells is unprofitable due to the discontinuity of productive layers, their fragmentation and weak inflow of formation fluid into vertical wells.

The objective of the invention is to increase oil recovery from reservoirs with high stratification and abnormally low reservoir pressure by increasing the drainage zone of the reservoir and activating the flow of reservoir fluid by enhancing the forces that contribute to the displacement of reservoir fluid.

This object is achieved by the fact that in the inventive method of oil production from a reservoir with an abnormally low reservoir pressure, reservoir fluid is sampled using a downhole pump from vertical production wells drilled to form a sump.

Salient features of the claimed invention are:

- create a cavity in each vertical production well in the lower part of the reservoir;

- fill the cavity with filler;

- drill additionally bi-directional production wells;

- connect the bottom of each directional well with a cavern of the corresponding producing vertical well;

- report the mouth of the bi-directional production wells with the atmosphere;

- drill vertical wells with a diameter greater than the diameter of semi-directional wells;

- position the mouths of semi-directional wells, for example, near the mouths of adjacent vertical production wells;

- carry out the creation of a cavity, for example, by hydromonitorial erosion of rocks using a special sub with a lateral nozzle;

- fill the cavity with a filler, for example, with a wash of gravel filler.

The indicated set of essential features ensures the creation of conditions for increasing oil recovery from formations with high stratification and anomalously low reservoir pressure by increasing the drainage zone of the reservoir by additionally drilling an extensive network of hollow directional production wells, which provide maximum coverage of productive layers both in thickness and in area. The connection of the faces of the bi-directional production wells with the cavity created in the lower part of the reservoir in the vertical production well, and communication with the atmosphere of the mouths of all the bi-directional production wells provides activation of forces that contribute to the displacement of the reservoir fluid. It is the strengthening of gravity due to the additional action of atmospheric pressure that contributes to the activation of formation fluid flow into a vertical well from a larger area of the reservoir, while at the same time, due to the collection of formation fluid in the cavity and sump, favorable conditions for the operation of the borehole pump are prevented, which prevent formation disruptions liquid to the surface.

Thus, the proposed method of oil production from reservoirs with high stratification and anomalously low reservoir pressure (20-30% lower than hydrostatic) due to the execution of vertical and semi-directional production wells and their interconnection can significantly increase oil recovery by increasing the drainage zone of the reservoir and activation of forces that contribute to the displacement of reservoir fluid.

The claimed combination of essential features is not known to us from the prior art, therefore, the claimed invention is new. The claimed features of the invention are not obvious to the average person skilled in the art. In this regard, we believe that the claimed invention has an inventive level. The invention is industrially applicable, since the available equipment and technology developed by us, allow us to implement the method in full.

In Fig.1 shows a diagram of the drilling of a deposit (block element), Fig.2 is a schematic diagram of the completion of a vertical production well, when developing a formation with an abnormally low reservoir pressure, Fig.3 is a schematic diagram of the completion of a vertical production well, while operating separately reservoirs with different filtration properties, the upper of which is with abnormally low reservoir pressure.

The development of reservoir 1 with abnormally low reservoir pressure (AAP) is carried out using vertical production wells 2, directional production wells 3 and injection wells 4. Wells are, for example, in a row grid (see figure 1) with four rows of vertical production wells and for each vertical production well, for example, six semi-directional production wells are drilled, i.e., semi-directional wells located between vertical production wells are directed towards each other Yeah, but do not interfere with each other. The option of drilling a larger number of directional wells and another option for drilling a deposit is possible. Vertical production wells 3 are drilled from the surface of the earth. The upper intervals of the rocks in the well overlap direction and conductor. It is possible to install only one conductor 5 (see figure 2). Then open the reservoir 1 with an abnormally low reservoir pressure with the formation of a sump 6. Next, in the lower part of the reservoir 1, a cavity 7 is created, for example, by rock erosion using a special sub with a lateral hydraulic nozzle or by means of a hydraulic sliding expander, or by other methods. After the descent of the production casing 8 carry out its cementing from the mouth to the roof of the cavity. The option of cementing the production string to the top of the reservoir is possible. Then the filter 9 is lowered into the well and the cavity is filled, for example, by pouring gravel filler, crushed stone or other filler (the position on the diagram is not shown), through which the flow of formation fluid into the cavity is ensured and the filter is finally installed to the sole or below the bottom of the reservoir. The filter 9 can be lowered into the well either independently or together with production casing 8. The sump 6 of the vertical well is left open or, if necessary, fixed, for example, with a cement glass.

After drilling vertical production wells 2, an extensive network of semi-directional production wells 3 is drilled, the faces of which reveal an artificial cavity 7 of a vertical well, usually in the lower part of formation 1, i.e., several production directional wells are drilled to each vertical production well. The mouths of shallow wells are located, for example, near the mouths of adjacent vertical production wells, while the mouths of each shallow wells are equipped with shutoff valves and a device for communicating with the atmosphere, for example, a valve assembly (not shown in the diagrams). All work on the preparation and filling of the “window” in the production casing of a vertical production well, the drilling of hollow wells and their fastening is carried out in accordance with a special project for the construction of hollow wells. The proposed design of semi-directional wells consists of a conductor, production casing with a filter section in the interval of the reservoir (not shown in the diagrams).

In parallel, vertical injection wells are drilled and equipped according to generally accepted technology for pumping a displacing agent.

After drilling production vertical wells, directional production wells and vertical injection wells and completion of well construction, all wells are equipped with downhole equipment. As the deep-pumping equipment of vertical production wells, rod-type deep-well pumping units (USGGN) or screw pumps with a surface drive, providing the possibility of changing the flow of formation fluid, are most preferable. The depth of descent of the downhole pumping equipment (GND) and, accordingly, the suspension length of the tubing (tubing) is determined by the design of the well and the required guaranteed immersion at a dynamic level limited by the roof of the reservoir. The GNO suspension depth is calculated for each well individually depending on the length of the wellbore and the level of the formation roof, and, as a rule, the downhole pump 10 is located in the sump 6 of the vertical production well.

Prepared wells are put into operation. Oil production is as follows. The reservoir fluid from reservoir I, through the trunks of half-directed wells 3, under the influence of gravity and atmospheric pressure due to communication with the atmosphere of the mouths of half-directed wells, enters the cavity 7 and flows into the sump 6 of the producing vertical well 2 from where it is pumped to the surface by a deep pump 10 Moreover, due to the possibility of an additional increase in the volume of formation fluid accumulation due to the cavity, favorable conditions are created for the operation of the well pump, which prevent breakdowns under chi formation fluid to the surface.

Together with the commissioning of production wells, the displacing agent is injected into injection wells, while the injection pressure is maintained at the level of the initial reservoir pressure. The volumes of injection of the displacing agent into each injection well are calculated from the condition of compensation for the production of formation fluid from the surrounding production wells. As a displacing agent, for example, water, water with a surfactant and other reagents are used, which are selected according to the results of experimental work. It is possible to transfer production wells to injection wells, while the mouths of half-directional wells are blocked by shutoff valves.

It is possible that, together with oil production from a reservoir with an abnormally low reservoir pressure, oil is produced from lower- or overlying formations with other filtration properties. In this case, the development of reservoirs is carried out by a single grid of wells using well-known technologies for simultaneously separate operation and at the same time separate injection of the displacing agent.

Consider the option of joint development of a reservoir with an abnormally low reservoir pressure and an underlying reservoir with other filtration properties.

Vertical production wells 2 are drilled from the surface of the earth and open reservoirs 1 and 11 with the formation of sump 12 under reservoir 11 (see figure 3). Drilling a vertical well is carried out according to generally accepted technology. Pre-drill a vertical well below the reservoir 1 with an abnormally low reservoir pressure. Further, in the reservoir 1, a cavity 7 is created, for example, by hydromonitorial erosion of the rock using a special sub with a lateral hydromonitor nozzle or by means of a hydraulic sliding expander, or by other methods. Then, production casing 8 with filter 9 is lowered and the cavity is filled, for example, by pouring gravel filler, crushed stone or other filler, through which the flow of formation fluid into the cavity is ensured. After cementing the production cavity from the mouth to the roof of the cavity 7 or to the roof of the reservoir 1, the vertical well is drilled below the reservoir 11 with the formation of a sump 12. Then, a filter 13 with a swellable packer 14 is lowered into the well, which separates the reservoirs and prevents formation water from flowing into well. It is possible that production casing 8 is lowered into the well below the reservoir 1, which, after filling the cavity with filler and installing the filter 13 with the swellable packer, is perforated above the swellable packer 14. The sump 12 of the vertical well is left open or, if necessary, fixed, for example, with cement a glass.

Then, drilling of semi-directional wells is carried out similarly to their drilling during the development of a single formation with ANPD. All work on the preparation and filling of the “window” in the production casing of a vertical producing well, the drilling of half-directional wells, the launching and fastening of the liner is also carried out in accordance with a special project for the construction of half-directed wells. The proposed design of semi-directional wells consists of a conductor, production casing with a filter section in the interval of the reservoir. The mouths of shallow wells are located, for example, near the mouths of adjacent vertical production wells, while the mouths of each shallow wells are equipped with shutoff valves and a device for communicating with the atmosphere, for example, a valve assembly (not shown in the diagrams). In parallel, vertical injection wells are drilled and equipped. After drilling a block of producing vertical wells, half-directed producing wells and vertical injection wells and completing the construction of wells, all wells are equipped with downhole equipment.

As the downhole pumping equipment (not shown by the position in the diagram) of vertical production wells, rod sucker-rod installations (USGN) or screw pumps with a surface drive are most preferable. The depth of descent of the downhole pumping equipment (GND) and, accordingly, the suspension length of the tubing (tubing) is determined by the design of the well and the required guaranteed submersion under a dynamic level limited by the roof of the reservoir. The GNO suspension depth is calculated for each well individually, depending on the length of the wellbore and the level of the formation roof. For vertical well equipment using simultaneously separate operation technology (ORE), given the large diameter of the production string and the insignificant depth of the productive formations, the two-lift layout (parallel lift) for pumping equipment is most preferable. It is possible to pump formation fluids from the formations by mixing them in the cylinder of the upper pump, while the lower pump pumps out the liquid from the lower reservoir, and the liquid coming from the lower pump is simultaneously sucked together with the upper pump along with the liquid of the upper reservoir. In this case, the diameter of the upper pump is selected so as to ensure the production of formation fluids from both layers.

As an equipment for an injection well, when water is injected into two objects using the technology of simultaneously separate injection (ORZ), a two-packer arrangement with a double elevator, consisting of ground and downhole equipment, is recommended.

Prepared wells are put into operation. Together with the commissioning of production wells, the displacing agent is injected into injection wells, while the injection pressure is maintained at the level of the initial reservoir pressure. The volumes of injection of the displacing agent into each injection well are calculated from the condition of compensation for the production of formation fluid from the surrounding production wells. As a displacing agent, for example, water, water with a surfactant and other reagents are used, which are selected according to the results of experimental work. It is possible to transfer production wells to injection wells, while the mouths of half-directional wells are blocked by shutoff valves.

Consider an example of a specific implementation of the method, when a reservoir with an abnormally low reservoir pressure lies above a reservoir with other filtration properties. The method can be carried out in the conditions of the Nizhnechutinsky field, which is located in the Ukhta region of the Komi Republic. It is advisable to introduce two layers into the joint development and develop them by an independent grid with the creation of a system for maintaining reservoir pressure. The reservoir is characterized as a complex pore-fracture, weakly cemented. The upper layer is characterized by high fragmentation (up to 10-12 productive layers), an abnormally low reservoir pressure of 0.325 MPa and low filtration properties compared to the underlying layer.

The parameters of the layers are shown in table 1

Table 1 Formation parameters Upper layer Lower layer The average depth of the roof, m 68.9 138.3 Average total thickness, m 37.8 3.6 Porosity,% 22 24 Permeability, 10 ^-3 μm ² fifty 472 Sandiness coefficient, fractions of units 0.352 0.667 Dissection 9,519 2,240 Initial reservoir temperature, ° C 3,7 7.0

The development of reservoirs of layers 1 and 11 (see figure 3) is carried out by a single grid of wells using technologies of simultaneously separate operation and simultaneous-separate injection of a displacing agent. The design of vertical production wells should provide for the accumulation of formation fluid, the required diameter of the well for subsequent opening at a predetermined depth by semi-directional training wells, for example, six shafts.

The proposed design of the vertical production wells are shown in table 2.

table 2 Name and diameter of the column, mm Departure Depth, m Cementing interval from before Conductor, 426 55 0 55 Operational, 324 180 0 55 Open barrel, 393.7 185 - -

A conductor with a diameter of 426 mm serves to preserve the bulk base of the rig site, to cover unstable deposits. Cementing is carried out, for example, with cement of the PTsT-II-50 brand. The 324 mm production casing is used to accumulate formation fluid and place pumping equipment for pumping fluid to the surface. The cementing of the casing is carried out, for example, with cement of the PTsT-II-50 grade in one step using a cuff cementing packer (the position on the diagram is not indicated) with its installation depth in the interval of the roof of the productive horizon, approximately 55 m. Before the launch of production casing 8 in the interval of the lower parts of the productive horizon (83-103 m) produce a cavity 7, for example, using the hydromonitor method using a special sub with a lateral hydromonitor nozzle. Before the cuff cementing of the production casing 8, an operation is carried out to fix the cavity, for example, by pouring gravel filler. After fixing the production casing, cumulative perforation is performed at a depth of 95-103 m. A swelling packer is provided in the equipment of the production casing to separate productive formations. The swelling occurs under the influence of the reservoir fluid, the swelling time of the packers is set during their production, is regulated by the composition of the elastomer, depending on the characteristics and composition of the reservoir fluid. For the lower reservoir 11 in the equipment of the production casing a filter 13 is provided, which is installed under the swellable packer 14.

The proposed design of semi-directional wells (not shown in the diagrams) is shown in Table 3 and consists of a conductor with a diameter of 178 m, lowered to a depth of 55/226 m (vertical / barrel), a production casing with a diameter of 127 mm and a filter section in the interval of the production horizon 55/226 m - 103/511 m (vertical / trunk).

Table 3 Name and diameter of the column, mm Departure Depth, m Vertical descent depth, m Cementing interval from before Conductor, 178 226 55 0 55/226 Operational, 127 226 55 0 55/226 Filter, 127 511 103 - -

The direction of a semi-directional well is cemented over the entire length, for example, with cement grade PTsT-II-50. The production string above the filter section is also cemented, for example, with cement grade PTs-II-50 by means of lip-cementing.

For vertical well equipment using the technology of simultaneous and separate operation, taking into account the large diameter of the production string and the insignificant depth of the productive formations, the two-lift scheme (parallel lift) for pumping equipment is most preferred

The depth of descent of the downhole pumping equipment (GND) and, accordingly, the suspension length of the tubing (tubing) is determined by the design of the well and the required guaranteed submersion at a dynamic level limited by the roof of the formation and on average it is 1-70 m for vertical wells of the formation, stratum 11-140 m. Pumping equipment is installed below the roof of the strata. Plast 1 is equipped with a short elevator, layer 11 is equipped with a long elevator. Under such conditions, rod-type deep pump units (USGN) are most preferable as GNO. As a drive USHGN it is recommended, for example, the chain drive ЦП-40-2,1-0,5 / 2,5, which according to its characteristics (stroke length up to 2.1 mi the number of swings from 0.5 kach / min to 2, 5 kach / min) will ensure the normal operation of sucker rod pumps for formation 1, for example, type НН2Б-57 and pumps for formation 11, for example НВ2Б-38. To control the operation of the reservoir-pump-well system, it is advisable to equip the pumps with a cable deep complex system, for example, SOYU3-FOTON. Underground telemetry sensors are installed under the pump on each elevator, data are transmitted to the ground side via a geophysical cable mounted on each elevator. As equipment for an injection well, when injecting a displacing agent into two layers (ORZ), a two-packer arrangement with a double elevator, consisting of ground and downhole equipment, is recommended. The supply of a displacing agent, for example water, to formations 1 and 11 is carried out in separate lines equipped with a flow meter and a flow regulator for controlling and regulating the amount of water. The design of downhole equipment allows for the operational accounting and control of parameters (pressure, volume) of the injected displacing agent into each formation. The volumes of injection of the displacing agent into each injection well are calculated from the condition of compensation for the production of formation fluid from the surrounding production wells. It is possible to transfer production wells to injection wells, while the mouths of half-directional wells are blocked by shutoff valves.

Thus, the proposed method for developing oil deposits in stratified heterogeneous reservoirs due to the performance of vertical and semi-directional production wells and their interconnection will create favorable conditions for increasing oil recovery from a reservoir with anomalously low reservoir pressure and ensure oil production from it, as well as economically viable joint development of formations with various filtration properties.

Claims (4)

1. The method of oil production from a reservoir with an abnormally low reservoir pressure, including the selection of reservoir fluid using a deep pump from vertical production wells drilled with the formation of a sump, characterized in that in each vertical production well create a cavity in the lower part of the reservoir, fill the cavity filler and drill additionally bi-directional producing wells, connecting the bottom of each bi-directional well with a cavity of the corresponding producing vertical well, and the mouth hollow directional production wells communicate with the atmosphere, while vertical production wells are drilled with a diameter greater than the diameter of the directional wells. 2. The method according to claim 1, characterized in that the mouths of the directional wells are located, for example, near the mouths of adjacent vertical production wells. 3. The method according to claim 1, characterized in that the creation of a cavity is carried out, for example, by hydromonitorial erosion of the rock using a special sub with a lateral hydromonitor nozzle. 4. The method according to claim 1, characterized in that the filling of the cavity with a filler is carried out, for example, with gravel.

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