RU2580671C1 - Procedure for development of multi-pay oil deposits - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: at initial stage the deposit is drilled out with producing wells as per triangle or square grid. Secondary opening is made through one of the pays with large oil-saturated thickness, which is the main formation. Upon the period less than ten years the deposit is compacted by drilling wells with diameter less than the drilled diameter per 1.1-1.5 times. At that for vertical and directional wells density of the well grid is increased 3-5 times. For wells with horizontal ending distance between the boreholes is decreased per 1.5-3.0 times. Simultaneously in less than 20% of wells drilled at the initial stage other formations are engaged by usage of equipment for dual production. Upon decrease in formation pressure in any of the pays more than per 50% of the initial value working agent is injected to less than one half of all operated wells, which were drilled at the initial stage. At that for two and more formations injection of working agent is carried out with equipment for dual injection or dual operation and injection. Waste water or fresh water is used as working agent with alternated injection of banks of water with pH more than 7, which constitute 5-10% of the total volume of injection for the deposit.

EFFECT: improved production rate for multi-pay oil deposits.

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Description

The invention relates to the oil industry and may find application in the development of a multilayer oil reservoir, the layers of which coincide structurally.

A known method of developing an oil deposit, including the development of a deposit by a system of vertical production and injection wells, drilling additional shafts from vertical wells, pumping a working agent through additional shafts of injection wells and selecting products through additional shafts of production wells. According to the known method, in order to engage in the development of low-permeability zones of the reservoir, vertical flows of formation fluids are provided, for which, as vertical shafts from vertical injection wells, half-inclined shafts are drilled in the upper part of the reservoir, from the vertical production wells, half-rising shafts are drilled in the lower part of the reservoir, measures to eliminate the injection of the working agent through the vertical shafts of injection wells and the selection of products through the vertical production wells, for which insulating materials are pumped into the perforation intervals, as a working agent, coolant is pumped into the upper part of the productive layer through the directional wells of the injection well, products are taken from the bottom of the production wells from the bottom of the production well, and the coolant is injected into the mode determined by the degree of heating of the reservoir, and the selection of products is carried out with maximum depression on the reservoir with maintaining the liquid level in the producing wells at a minimum level in such a way that they cause the heated oil to flow along the shallow trunks to the vertical producing wells (RF patent No. 2274741, cl. ЕВВ 43/24, publ. April 20, 2006).

The closest in technical essence to the proposed method is a method of developing a massive type of oil deposits with layer-by-layer heterogeneity, including the development of vertical production and injection wells built on a grid of wells, the construction of additional bi-directional shafts, pumping an agent into production wells and selecting products from production wells. According to the invention, sloping shafts are drilled from additional injection and production wells with a bit diameter of 144 mm, which are drilled from the surface with a mesh seal of 1-4 ha / well. Shallow shafts are drilled across the fracture of the formation with a length of 2-3 formation thicknesses, followed by casing of the trunks and the secondary opening of the reservoir, after which, before launching additional wells in the flooded layers of the reservoir, waterproofing works are carried out from their half-directed trunks, and in tenos - acid treatment (RF patent No. 2439298, CL EV 43/16, publ. 10.01.2012 - prototype).

A common disadvantage of the known methods is the low oil recovery factor (SIF) due to the insufficient coverage of the reservoir both in thickness and area, as well as low waterflooding efficiency.

The proposed invention solves the problem of increasing oil recovery multilayer oil deposits.

The problem is solved in that in a method for the development of multilayer oil deposits, including drilling wells with subsequent densification of a grid of wells, drilling small diameter wells, using equipment for simultaneous and separate operation, pumping a working agent into injection wells and selecting products from production wells, according to the invention, at the initial stage, the deposit is drilled by producing wells on a triangular or square grid, the second opening is carried out in one of the layers with large oil thicknesses - the main formation, after a period of not more than ten years, the reservoir is compacted by drilling wells with a diameter that is 1.1-1.5 times smaller than previously drilled, while for vertical and directional wells, the grid of wells is compacted into 3-5 times, and for wells with horizontal completion, the distance between the wells is reduced by 1.5-3.0 times, while at least 20% of the wells drilled at the initial stage are attached to other layers using equipment for simultaneous and separate production, after lowering pressure on any of the strata, on average, by more than 50% of the initial one, transfer not more than half of the wells operating at the initial stage operating under injection of the working agent, and for two or more strata the working agent is injected using equipment for simultaneous and separate injection or at the same time separate extraction and injection, wastewater or fresh water is used as a working agent with alternating injection of water rims with a pH of more than 7 units of 5-10% of the total volume of injection in the reservoir.

SUMMARY OF THE INVENTION

The oil recovery of a multilayer oil reservoir is significantly affected by the effectiveness of the developed development system aimed at developing reserves of all reservoirs with maximum coverage and displacement factors. Existing technical solutions do not fully allow the effective development of such deposits. The proposed invention solves the problem of increasing oil recovery multilayer oil deposits. The problem is solved as follows.

In FIG. 1 is a schematic representation of an oil reservoir in plan with the placement of wells. In FIG. 2 is a schematic sectional view of an oil reservoir along line AA with the placement of wells. Designations: 1 - oil reservoir, 2 - upper oil-saturated formation, 3 - lower oil-saturated formation, 4-10 - wells drilled at the initial stage of development, 11-16 - compacting wells of small diameter, VNK - water-oil contact.

The method is implemented as follows.

A multilayer oil reservoir, the strata of which coincide structurally, is drilled with vertical and / or directional production wells along a triangular or square grid. Drilling open all the layers, however, the secondary drilling is carried out on one of the layers with large oil-saturated thicknesses (the main layer), which allows to obtain higher flow rates at the initial stage and to reduce the payback period for drilling wells.

After a period of operation of drilled wells, not exceeding 10 years, the reservoir is compacted by drilling wells with a diameter that is 1.1-1.5 times smaller than previously drilled. For vertical and directional wells, the grid of wells is compacted 3-5 times, and for wells with a horizontal end, the distance between the wells is reduced by 1.5-3.0 times. At the same time, in at least 20% of the wells drilled earlier, another layer is attached to the equipment through simultaneous-separate production (ORD).

According to studies for most oil deposits during well operation for more than ten years, subsequent compaction of the grid leads to a lower oil recovery factor than during compaction up to 10 years, which is associated with the development of oil reserves, most often uneven. Compaction of the grid of wells increases the coverage of the reservoir over the area. Calculations show that when compaction of the grid of wells less than 1.5 times, the required coverage of the formation is not achieved, and compaction more than 3.0 times is not economically viable. The smaller diameter of the wells allows you to reduce the cost of capital investments, and the use of oil production methods - to develop reserves for all layers and increase the coverage of the layers in thickness. Moreover, if we transfer to the ARD less than 20% of the previously drilled fund, then according to the calculations, the development of the remaining layers (not the main one) turns out to be low, which leads to low oil recovery factor values. Reducing the diameter of the sealing wells by more than 1.5 times reduces the rate of oil extraction and makes it difficult to carry out repair work in the wellbore.

It should be noted that most multilayer oil deposits have a main reservoir, where a greater number of reserves are concentrated, and from one to three smaller reservoirs. The modern development of technology for simultaneous-separate operation (WEM) allows you to develop separately up to four layers. More than four layers are rare and most often the fifth and subsequent layers have very low thicknesses and worse geological and physical characteristics, or significantly smaller areal sizes, which significantly reduces the economic profitability of joint development with the main reservoir, so their development is left at the very last moment, after development of the main strata, or not carried out at all.

After reducing the reservoir pressure during the development of any of the reservoirs by an average of more than 50% of the initial one, not more than half of the wells operating at the initial stage are transferred under injection of the working agent. For two or more layers, the injection of the working agent is carried out using equipment for simultaneous-separate injection (ORZ) and / or simultaneously-separate production and injection (ORDiZ).

According to studies, if the reservoir pressure on average over the reservoir decreases by more than 50% of the initial one, then the subsequent waterflooding system does not allow achieving the necessary efficiency, which leads to low oil recovery factor. More than half of the stock of wells operating the formation, which provide for flooding, to transfer under injection is impractical, because The oil recovery of the reservoir, according to calculations, is lower. Due to the fact that the wells drilled at the initial stage have a larger diameter than the compacting ones, they are suitable for use with ARI and / or ORDiZ equipment, the use of which is economically attractive for multilayer reservoirs.

As injected use wastewater or fresh water with alternating injection of rims of water with a pH of more than 7 units that make up 5-10% of the total volume of injection in the reservoir. According to studies, more alkaline water with a pH above 7 units. better washes oil from the pores of the reservoir. Moreover, the injection of such water in a continuous mode or with a volume of more than 10% of the total injection volume is not economically justified. Injection with rims followed by pushing with formation, waste or fresh water allows achieving the necessary efficiency. Injection of alkaline water with a volume of less than 5% of the total injection volume does not allow to obtain an increase in oil recovery factor due to an increase in the washing of oil from the pores.

Wells with a small diameter, after their flooding to 98%, or a drop in oil production below a profitable one, are transferred for injection into this reservoir or to develop residual reserves in other reservoirs.

Development is carried out until the full economically viable development of deposits.

The result of the implementation of this method is to increase oil recovery multilayer oil deposits.

Examples of specific performance of the method

Example 1. Oil reservoir 1 (Fig. 1), represented by two layers 2 and 3, coinciding in structural terms, is drilled with seven vertical producing wells 4-10 with a diameter of 168 mm along a triangular grid with a distance between wells of 300 m. The density of the well network is 11.7 ha / well Layers 2 and 3 differ slightly in area. Drilling open all the layers, however, the secondary opening is carried out on the lower layer 3.

The upper terrigenous layer 2 (Fig. 2) has an average effective oil-saturated thickness of 8 m and lies at a depth of 1050 m, the average permeability is 200 mD, porosity is 20%, the initial reservoir pressure is 10 MPa, and the oil viscosity at reservoir conditions is 45 MPa · s. Lower carbonate formation 3 has an average effective oil saturated thickness of 28 m, average permeability of 120 mD, porosity of 16%, initial reservoir pressure of 11 MPa, oil viscosity at reservoir conditions of 30 MPa · s. Water-oil contact (VNK) is located at a depth of 1110 m.

After 10 years of operation of the lower layer with 3 drilled wells 4-10, the reservoir is compacted by drilling vertical production wells 11-16 with a diameter of 114 mm (1.5 times less). Moreover, wells 11-16 are placed in the centers of triangular elements. For example, in the center of an isosceles triangle formed by wells 8, 9, 10, a well 12 with a smaller diameter is placed. Thus, the distance between new wells 11-16 and previously drilled 4-10 is 150 m, and the density of the grid of wells is 2.9 ha / well. (i.e. it is compacted 4 times).

In all previously drilled wells, 4-10 (i.e., 100%) attach the upper layer 2 through the equipment for the open-cast mining operations.

After 12 years from the start of development, reservoir pressure in the lower layer 3 decreases to 5.5 MPa (i.e., 50% of the initial one), and in the upper 2 - up to 8 MPa (i.e. 20% of the initial one). 4, 6, 8 are transferred under injection (i.e. 43% of the wells drilled at the initial stage). The injection is carried out on both layers 2 and 3 using equipment for acute respiratory infections.

As injected use wastewater. The injection is carried out with a constant flow of water. With a period of 3 days. every month (i.e. 10% of the total volume of injection in the reservoir), rims of water with a pH of 7 units are injected.

The development is carried out until the full economically viable development of the site.

Example 2. Perform as example 1. The reservoir has several other geological and physical characteristics, dimensions and three layers. Drill on an uneven quadrangular grid with vertical wells with a diameter of 168 mm of the main layer. After 5 years of operation, the reservoir is compacted 3 times by drilling of directional production wells with a diameter of 146 mm (1.15 times less). In 20% of the previously drilled wells, two other formations are attached by means of the equipment for the production of oil wells. After 10 years from the start of development, reservoir pressure in the main reservoir decreases by 50% from the initial one, and in the rest - by 10%. Half of the wells drilled at the initial stage and operating the main formation are transferred under injection for the same formation, and for other formations in the same wells, selection is made using equipment for OCR.

Example 3. Perform as example 1. The deposit has other geological and physical characteristics and dimensions. The main formation is drilled along an irregular triangular grid with directional wells, and horizontal and multilateral horizontal wells are drilled in areas of maximum thickness. Multilateral horizontal wells reveal both layers. After 7 years of operation, vertical wells are compacted 5 times. By drilling additional horizontal production wells, with a parallel arrangement of trunks, reduce the distance between the trunks by 3 times. By drilling additional multilateral horizontal production wells, the trunks of which are placed in different layers, they achieve a 1.5-fold reduction in the distance between the trunks. Subsequently, after the introduction of flooding in the reservoirs, fresh water is used as injected. The injection is carried out with a constant flow of water. With a period of 1.5 days. every month (i.e. 5% of the total volume of injection in the reservoir), water rims with a pH of 9 units are injected.

As a result of the development, which was limited by the watering of reservoir 1 to 98%, 1062 thousand tons of oil were produced, oil recovery factor amounted to 0.426 units. According to the prototype, ceteris paribus, 964.8 thousand tons of oil was produced, oil recovery factor was 0.387 units. The increase in recovery factor by the proposed method is 0.039 units

The proposed method allows to increase oil recovery multilayer oil deposits by optimizing the development system.

The application of the proposed method will solve the problem of increasing oil recovery multilayer oil deposits.

Claims (1)

A method for developing multilayer oil deposits, including drilling wells with subsequent densification of a grid of wells, drilling small diameter wells, using equipment for simultaneous and separate operation, pumping a working agent into injection wells and selecting products from production wells, characterized in that the deposit is drilled at the initial stage producing wells on a triangular or square grid, the secondary opening is carried out in one of the layers with large oil-saturated thicknesses - the main After a period of not more than ten years, the reservoir is compacted by drilling wells with a diameter that is 1.1-1.5 times smaller than previously drilled, while for vertical and directional wells, the grid of wells is 3-5 times compacted and for wells with horizontal completion, the distance between the wells is reduced by 1.5-3.0 times, while at least 20% of the wells drilled at the initial stage are attached to other layers using equipment for simultaneous and separate production, after reducing the reservoir pressure for any of the formations, on average, more than 50% of the initial one is transferred under injection of the working agent by no more than half of the wells operating from this number of wells drilled at the initial stage, and for two or more formations the working agent is injected using equipment for simultaneous-separate injection or simultaneously - Separate production and injection, waste or fresh water is used as a working agent with alternating injection of rims of water with a pH of more than 7, amounting to 5-10% of the total volume of injection in the hall and.

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