RU2434124C1 - Procedure for development of oil deposit in carbonate collectors complicated with erosion cut - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: procedure consists in specification of oil bearing deposit circuit, in determination of oil saturated thickness of producing terrigenous beds in erosion cut, in drilling producers, including horizontal ones, in payout terrigenous beds of erosion cut with edge exposure, in drilling pressure wells, in withdrawal of product from well and in pumping working substance into bed. According to the invention there is additionally determined position of the cut edge. Horizontal wells are drilled from oil deposit in carbonate collectors into erosion cut, into near-top section of the terrigenous payout bed. Further, working substance is pumped into the terrigenous payout bed of erosion cut and product is withdrawn from it. If pressure drops, then working substance is periodically pumped into an oil deposit in carbonate collectors till bed pressure in it is equalised with pressure in the terrigenous payout bed of erosion cut. At presence of several payout beds in erosion cut the horizontal well is made stepped successively covering all beds starting from a top one. At production watering the horizontal well is successively stepped insulated starting from the lower step.

EFFECT: raised efficiency of development due to optimal arrangement and operation of horizontal wells.

2 cl, 3 dwg

Description

The proposal relates to the oil industry, namely, to the field of development of an oil deposit represented by low-permeable carbonate reservoirs complicated by an erosion insert.

There is a method of developing oil deposits complicated by an erosive Visean insert (patent RU 2298087, ЕВВ 43/20, ЕВВ 43/30, published on 04/27/2007 Bull. No. 12), including the specification of the contours of the oil content of the deposits and the determination of the oil-saturated thickness of the Bobrikov-Radayev reservoirs erosive Visean insert, drilling production and injection wells in the instrumentation area of the insert, selection of products and injection of the working agent into the formation. Then drill at least one horizontal production well, two injection. The horizontal wellbore of the producing well is placed within the erosion Visean insert on the Bobrikov-Radaev deposit, parallel to the sideline of the erosive Visean insert and perpendicular to the displacing flow of the working agent from a horizontal or oblique directional injection well located outside the erosive Visean insert on the tournai. The horizontal wellbore is directed parallel to the cut-off line and the trunk of the producing horizontal well. The second injection well is placed obliquely directed within the erosion Visean insert into the Bobrikov-Radaev deposit, according to the adjusted design grid.

The disadvantage of this method is that the proposed method is applicable for the development of a single oil reservoir located in the insert and does not provide for the drilling and simultaneous operation of horizontal oil deposits with different types of reservoirs.

The closest in technical essence to the proposed one is a method of developing oil deposits complicated by an erosion insert, including clarifying the oil profile of deposits and determining the oil-saturated thickness of reservoirs in an erosion insert, drilling production and injection wells, selecting production wells and pumping a working agent into the formation (patent RU 2334087 , ЕВВ 43/20, publ. September 20, 2008 Bull. No. 26). In a highly permeable cut-in zone, a branched horizontal production well is drilled with branches extending beyond the cut into the tight-permeable zone of the Tournaisian object to a distance not exceeding two-thirds of the length of one branch. In this case, the branches are placed in the same horizontal plane with the main horizontal trunk or along an ascending or descending path and are directed perpendicular to the displacing flow of the working agent from vertical or directionally directed injection wells.

The disadvantage of this development method is that it can be applied only on deposits with erosion cuts having a channel type, within which you can drill a branched horizontal well. With significant areas of cuts, oil reserves in carbonate reservoirs are produced partly due to limited technical capabilities when drilling wells of this design.

The technical task of the proposed method is to increase the efficiency of development of oil deposits in carbonate reservoirs complicated by erosion insertion, involvement in the development of terrigenous reservoirs located in the insert due to the optimal placement and operation of horizontal wells, contributing to a more complete development of oil reserves.

The technical problem is solved by the method of developing an oil deposit in carbonate reservoirs complicated by an erosion insert, including clarifying the oil contour of the deposit, determining the oil-saturated thickness of productive terrigenous strata in an erosive insert, drilling production wells, including horizontal wells in productive terrigenous strata of erosive cutting and opening and injection wells, product selection from the well and injection of the working agent into the formation.

What is new is that they additionally determine the location of the cut-in side, horizontal wells are drilled from an oil deposit in carbonate reservoirs into an erosion cut, into the side part of a productive terrigenous formation, the working agent is injected into a productive terrigenous formation of an erosive cut and selected from it, while reducing pressure in the oil deposits in carbonate reservoirs, the working agent is periodically pumped into the reservoir until the reservoir pressure in it is equal to the pressure in the productive terrigenous layer of erosive cut.

Also new is the fact that in the presence of several productive formations in an erosion insert, a horizontal well is built in steps, sequentially covering all formations, starting from the top, and when the product is flooded, a horizontal well is isolated in steps, sequentially, starting from the lower stage.

Figure 1 shows a diagram of the implementation of the proposed method for the development of oil deposits.

Figure 2 shows a section aa in figure 1.

Figure 3 shows a section aa of figure 1 in the presence of several productive formations in an erosive incision.

The inventive method is carried out in the following sequence.

Massive oil reservoir 1 (Fig. 1) in carbonate reservoirs is drilled with vertical wells 2-9 on a rare grid. Clarify the geological structure of the reservoir according to deep well drilling and seismic studies in the field.

According to the results of interpretation of well logs, the presence of erosive cut 10 in carbonate reservoirs 11 (Figs. 1, 2, 3) and flange 12 (Fig. 1) of cut 10, effective oil-saturated thicknesses h1 (Figs. 1, 2) of carbonate reservoirs 11 and thickness hi (FIGS. 1, 2) of terrigenous reservoirs 13 of erosive cut 10, filtration-capacitive properties of reservoir rocks. Then, on the structural plan and the map of effective oil-saturated thicknesses of the carbonate reservoirs 11 (Fig. 1), the border of the side 12 of the cut-in 10 and the level of the water-oil contact (WOC) 14 are applied (Figs. 2, 3). Based on the results of hydrodynamic studies and the work of wells, the development process is modeled, the existence of a hydrodynamic connection between the oil reservoir, which is represented by low-permeability carbonate reservoirs 11 (FIGS. 1, 2 and 3), complicated by erosion insert 10 and terrigenous reservoirs 13 (FIG. 2, is established). 3), located in the inset 10. Measure formation pressure.

For the systematic placement of wells 2–9 (Fig. 1), in the immediate vicinity of the side 12 of the erosion cut 10, a section of reservoir 1 is allocated with carbonate reservoirs 11 having oil-saturated thicknesses h (FIGS. 2 and 3) of more than 10 m, and terrigenous reservoirs 13 with an oil saturated thickness hi of more than two meters. In carbonate reservoirs 11 (FIGS. 1, 2, and 3), a well with a horizontal wellbore 15 is additionally drilled towards cut 10 with a portion of the horizontal well 15 entering the highly permeable terrigenous collectors 13 of cut 10 at a distance not exceeding half the length of the horizontal well 15. Trajectory horizontal trunk 15 extends in the bedside of the terrigenous reservoir 13 and has downward or subhorizontal profiles 15a (FIG. 2). In the presence of several reservoir layers 13a, 13b (FIG. 3) with an oil-saturated thickness h1 of more than two meters, each horizontal trunk 15 may have a step-like profile 15b, sequentially covering all layers, starting from the top. Such a trajectory of a horizontal well increases the drainage area of well 15. Oil reserves from cut 10 are more fully developed without the need for additional well drilling.

The length of the upper part of the horizontal wellbore 15 (Figs. 1, 2 and 3) located in the carbonate reservoirs 11 does not exceed the step of the design well grid (250-300 m), and the length of the lower part of the horizontal wellbore 15 can be adjusted taking into account the dimensions of the cut 10 and depends on technical capabilities.

The horizontal well 15 is mastered and put into operation, and the part of the horizontal wellbore 15 located in the cut-in 10 is first in operation. When watering the products, the horizontal well 15 (Fig. 3) with a stepped profile is sequentially isolated, from the bottom up, starting from the bottom stage for exclusion water cut of products extracted from the well 15.

From the number of producing vertical wells 2, 3, 6, 7 (Fig. 1), drilled in cut 10 and located in the immediate vicinity of the horizontal well of the producing well, some of the wells 3 are converted into injection wells when oil production rates are reduced to extremely profitable or as water cuts extracted well products. Injection vertical wells 3 drilled in terrigenous reservoirs 13 (FIGS. 2 and 3) of incision 10 should be located at a distance of not less than the grid pitch from the horizontal wellbore 15 (Fig. 1) and from side 12 of incision 10. With a decrease in pressure in the reservoir oil 1 in carbonate reservoirs 11 (Fig. 1) periodically injects the working agent into the reservoirs 11 until the reservoir pressure in it is equal to the pressure in the productive terrigenous reservoir 13 of erosive incision 10.

If there are two or more cuts 10 within the reservoir (Figs. 1, 2, and 3), the proposed method for placing wells is repeated for each cut 10 separately.

An example of a specific implementation.

The implementation of this method, consider the example of a site characteristic of a massive oil reservoir of the Tournaisian layer. Oil reservoir 1 (Fig. 1) in carbonate reservoirs is drilled with vertical wells 2-9 (Fig. 1) along a 300 × 300 m grid. According to the data of deep well drilling and 2D seismic surveys conducted on the field, the geological structure of the reservoir is specified.

According to the results of the interpretation of logs in wells 2, 3, 6, 7, the presence of erosion cut 10 in the carbonate reservoirs 11 (Figs. 1, 2, 3) of the Tournaisian tier up to 20 m deep is determined. Effective oil-saturated thicknesses of carbonate reservoirs 11 (Fig. 1) average 12 m, and terrigenous reservoirs of Bobrikov-Radaev age 13 in an erosion incision 10-5 meters. The permeability of carbonate reservoirs is 0.75 μm ² , terrigenous - 582 μm ² .

On the structural plan and the map of effective oil-saturated thicknesses of carbonate reservoirs 11, the border of the side 12 of the cut 10, which has a northeast direction, is applied. The absolute mark of the oil-water contact (WOC) 14 (Fig. 2, 3) of the reservoir in carbonate reservoirs is set at an absolute mark of minus 1064 m. In terrigenous reservoirs, the bottom of the lower oil reservoir is defined at an absolute mark of minus 1062 m. Two terrigenous reservoirs were identified in the incision zone -collector 13a and 13b (Fig. 3) with oil-saturated thicknesses h1 of 3.8 and 3.2 m, respectively. The thickness of the clay bridge between them was 1.0 m. Wells 4, 5, 8 and 9 were drilled east of the erosion board cut 12 in the direction of increasing oil-saturated strata n, at 1 site deposits having oil saturated thickness h (2 and 3), more than 5 m.

Based on the results of hydrodynamic studies and the work of the wells, we simulated the development process and revealed the presence of a hydrodynamic connection between the oil reservoir, represented by low-permeable carbonate reservoirs 11 (Figs. 1, 2, and 3), complicated by erosion insert 10 and terrigenous reservoirs 13 (Fig. 2 and 3), located in the inset 10. Measurement of reservoir pressure in the reservoir, which amounted to 11.2 MPa.

In addition, a zone with oil-saturated thicknesses of more than 10 m was identified on the site and a production well was drilled with a horizontal bore 15 in the direction of the cut 10 with the exit of a part of the horizontal bore 15 to the highly permeable terrigenous collectors 13 of the cut 10. The length of the upper part of the horizontal bore 156 (Fig. 3), located in the carbonate reservoirs 11, was 300 m. The trajectory of the horizontal trunk 15b (Fig. 3) in the incision passed along the bedside of the upper terrigenous stratum 13a (Fig. 2) and stepped into the lower terrigenous stratum 136. Its length was 280 m.

The horizontal well 15 was mastered and put into operation the lower part of the horizontal wellbore 15, located in the inset 10. The initial water cut of the well production was 12%.

The producing vertical wells 2, 3, 6, 7 (Fig. 1), drilled in the inset 10, were also put into operation. After a year, well 3, with a decrease in oil production to 1 t / day, was transferred under injection to maintain reservoir pressure in the reservoir. The location of the well provided the flow of the injected agent along the minimum possible distance to the horizontal wellbore.

The work of injection wells performs the task of stabilizing reservoir energy and contributes to a gradual increase in reservoir pressure in the reservoir. Throughout the stabilization period, research was carried out to monitor the operation of both producing and injection wells. Injection well 3 operated in a mode with excess wellhead pressure exceeding the initial reservoir pressure by 10% until the initial reservoir pressure in the reservoir was restored. The injection of the working agent significantly affects the well performance, especially the increase in reservoir and bottomhole pressures, as well as an increase in the proportion of water in the fluid and the flow rate of the fluid.

As a result of the existing hydrodynamic connection between terrigenous and carbonate reservoirs, in the process of pumping a working agent into reservoir layers, a gradual increase in the level of the military-industrial complex is simultaneously observed. After five years of operation of terrigenous reservoirs, water cut increased to 63%. At the horizontal well 15 (Fig. 3) with a stepped profile, the lower part of the wellbore passing in the cut terrigenous reservoirs was isolated.

The reservoir pressure in the oil reservoir 1 in the carbonate reservoirs decreased to 9.8 MPa, therefore, a periodic injection of the working agent into the well 8 (Fig. 1) was introduced until the reservoir pressure was equalized in the reservoir with carbonate reservoirs with a pressure in the terrigenous strata 13 (Fig. 3) erosion cut 10.

An analysis of the technological performance of the wells showed that the sequential stop of the injection of the working agent into the injection well during the month compensates for the selection of the production of the horizontal well of the working agent, therefore the injection well 8 (Fig. 1) worked in a sequential mode on and off the injection of fluid at injection pressures providing reservoir pressure close to the initial one.

Thus, the proposed method allows to increase the production rate of oil from producing wells and oil recovery of reservoirs, to increase the coverage of oil reserves in carbonate reservoirs complicated by erosion insertion, as well as in productive terrigenous reservoirs located in the instrument zone of erosion insertion.

Claims (2)

1. A method of developing an oil deposit in carbonate reservoirs complicated by an erosion insert, including clarifying the oil contour of the deposit, determining the oil-saturated thickness of productive terrigenous strata in an erosive insert, drilling production wells, including horizontal wells in productive terrigenous strata of erosive insert, opening its side injection wells, selection of products from the well and injection of the working agent into the formation, characterized in that it further determines the location of the cut-in side, horizontal Wells are drilled from an oil deposit in carbonate reservoirs into an erosion cut, into the side part of a productive terrigenous formation, the working agent is injected into a productive terrigenous formation of an erosive cut and selected products from it, while the pressure in the oil deposit in carbonate reservoirs is reduced, the working agent is periodically injected into the reservoir until the reservoir pressure in it is equalized with the pressure in the productive terrigenous layer of the erosive cut. 2. The method according to claim 1, characterized in that in the presence of several productive formations in an erosion insert, a horizontal well is built in steps, sequentially covering all formations, starting from the top, and when the product is flooded, a horizontal well is isolated in steps, sequentially, starting from the lower stage.

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