RU2235864C1 - Method for extracting multi-bed deposit at later stage with rentable well debit - Google Patents

Abstract

FIELD: oil extractive industry.

SUBSTANCE: method includes drilling of force-pumping and extracting wells, pumping of pushing liquid into force-pumping well and extraction of bed product through extracting well. Portion of non-rentable extracting and force-pumping wells from highly permeable highly watered beds is converted to extraction of less-watered higher beds with forming of system of extraction on basis of thickened mesh. Oil extraction from highly permeable highly watered beds is continued according to dispersed mesh by remaining extracting wells left in hypsometrically lowered portions of deposit. Product extraction from extracting wells is performed while performing operations on providing for rentable debit due to prevention of forming of water cone.

EFFECT: possible extraction of oil deposits with rentable well debit.

4 dwg

Description

The invention relates to the field of oil and gas industry, and in particular to methods of developing multilayer oil fields at a late stage of development. The late stage of development is characterized by a high water cut in the production of wells perforated into highly permeable formations, an increase in the share of reserves in low-permeable reservoirs, an increase in the shutdown of water-cut interlayers, and a decrease in the efficiency of measures to increase oil recovery.

In the development of multilayer deposits, a basic high-permeability layer is primarily involved. At the same time, the well placement system is designed to ensure high rates of selection from the base formation. After the selection of more than 85-90% of the recoverable reserves from the base formation, due to the high water cut of the production, the wells begin to be transferred to other categories or to the overlying return formation. But at the same time, in most cases, the creation of an optimal development system for a return facility is not achieved due to the non-simultaneous transfer of wells from a highly permeable flooded formation.

A known method of developing a multilayer oil field [1], including drilling injection and production wells, injection of displacing fluid into injection wells and selection of products from several reservoirs combined into one production facility.

The disadvantage of this method, as the authors of the source of information [1] correctly point out, is that it does not allow involving oil reserves of all layers in active development, since only highly permeable layers or its sections that extend onto the cutting lines are developed. In addition, due to the heterogeneity of the reservoirs, it is impossible to master all the reservoirs uncovered by injection wells for water injection.

These disadvantages are eliminated in the method of developing a multilayer oil field [2], which includes drilling injection and production wells, the joint development of several reservoirs with a common filter, which provides for the injection of displacing fluid separately into each reservoir through one injection well and separate selection of oil by several sucker rod pumps from each formation through one production well.

Without begging the merits of this method, we note that it also has a number of disadvantages. This consists in the fact that it requires the descent of two parallel columns, with their subsequent descent there is a danger of jamming and tightening. And in a 5 "production casing, the use of parallel rows of pipes is impossible, this leads to a complication of the surface equipment of the well due to the need to install 2 sets of wellhead fittings at the mouth at a short distance. Launching operations of a number of parallel pipes increase the risk of injury.

Due to the lack of reliable packing devices, as well as reliable ground and underground downhole equipment, the method has limited application.

This method is by technical nature closer to the proposed one and can be adopted as a prototype.

The disadvantage of the prototype is that at a late stage in the development of highly permeable formations, well production rates are unprofitable due to the high water cut of the product. Although the residual recoverable reserves in general per site are sufficient even for the payback of drilling a new well.

The objective of the present invention is to ensure the development of reserves with a profitable flow rate of wells.

The problem is solved by the described method, including the drilling of injection and production wells, injection of displacing fluid into the injection and selection of formation products through the production well.

What is new is that in the deposit area along highly flooded high-permeability formations, the mesh is decompressed by transferring part of unprofitable producing and injection wells to the operation of overlying less flooded low-permeable formations. Production wells left on a highly permeable formation are selected hypsometrically in the most elevated section of the reservoir from among the wells with maximum oil production rates. Injection wells left over a flooded highly permeable formation are selected from those that are hypsometrically located in the most submerged parts of the reservoir area. Transfer to the overlying low-permeability formations is carried out with the creation of an optimal development system to ensure the maintenance of reservoir pressure and uniform contraction of the oil content contour.

In the abandoned wells in the lower high-water reservoir, measures are taken to ensure a profitable flow rate due to:

1. Prevention of water cone formation.

1.1 According to the technology of creating a reversed cone in the oil-saturated part of the reservoir.

In the case when the suction part of the pump is lowered below the perforation interval, the accumulation of water against the perforation interval is excluded. This is achieved by the fact that the suction part of the pump is lowered below the perforated interval.

In the case when in the production wells the suction part of the pump is above the interval of perforation of the formation, the movement of production of the formation is from the bottom up. In this case, the separation of products into oil and water phases occurs. Water begins to accumulate opposite the perforation interval. During the down time of the well, this water, penetrating the oil-saturated part of the reservoir, reduces the phase permeability of the oil. And when the well is put into operation, there is an increase in water cut of the product due to the expansion of the perforation interval saturated with water, and in the future this contributes to the formation of a water cone, thereby eliminating a decrease in the phase permeability of oil.

1.2 According to the technology of operation of wells perforated in the oil-saturated and water-saturated parts of the reservoir.

In the case of the operation of wells with perforation of the oil-saturated interval of the formation along the lower part, and the water-saturated interval in the upper part of the formation, the oil phase and the water phase occur at separate intervals. Water accumulates below the suction part of the pump and, due to the lack of perforation opposite the oil-saturated part of the formation, does not penetrate into the formation. This preserves the phase permeability of the oil to the non-perforated part of the oil-saturated formation.

2. Providing filtration flows of oil to the elevated sections of the reservoir, which is carried out by softening the grid and introducing new injection wells in the lower parts of the reservoir of a highly flooded highly permeable reservoir.

The above drawings explain the essence of the formation of the water cone and the inverted cone due to the descent of the shank 3.

Figure 1 shows a well 1 without installing a liner 3 below the downhole pump 2. When the pump is in operation, oil 4 and water 5 come from the formation into the wellbore. Moreover, in the wellbore below the pump 2 there is water with bubbles of pop-up oil 4, which due to its lower density occupies the upper part of the liquid column of the well located behind the tubing. Oil, accumulating in the annulus, gradually occupies the entire volume from the surface of the dynamic level 6 to the suction hole 7 of pump 2. With this method of operation, when the pump 2 is above the perforation intervals, there is water in the well table opposite the oil-saturated part of the formation. Water during the idle time of the well penetrates the oil-saturated part of the reservoir and leads to its saturation with water. This in turn reduces the phase permeability of oil and leads to the formation of a water cone during operation. If the pump 2 is placed below the perforation interval or the bottom of the pump is equipped with a shank lowered below the perforation intervals (see Fig. 2), the oil accumulating in the annulus is also opposite the perforated part of the formation. This preserves the phase permeability of the formation in oil and prevents cone formation.

Figure 2 shows a well in which the formation of a reversed cone is carried out by lowering the shank from the tubing below the pump. The formation of a reversed cone can be carried out in other ways [3].

Prevention of the formation of a water cone by the measures of paragraph 1.2 is achieved as follows:

- in the case of simultaneous perforation in the oil-saturated and water-saturated parts of the formation, the formation of a water cone is limited and applies only to part of the perforated interval of the oil-saturated formation.

To clarify the essence of the proposed development method as a whole according to the invention, before and after implementation, FIGS. 3 and 4 are shown.

Figure 3 shows the geological section of the site before the activities of the proposed development method. In the geological section of the site shown in figure 3, low-permeability layers 1 and high-permeability layers 2 are distinguished.

In low-permeability formations, due to low reservoir properties (porosity, permeability), depletion is 50-60% of the initial recoverable reserves [NCD]. In highly permeable formations, depletion is more than 90% of NCDs.

Wells 1, 3, 4, 5, 7 are perforated in highly permeable formations, and wells 2 and 6 in permeable formations.

Figure 4 shows the geological section of the site after the activities of the proposed method:

- cement bridges 3 were installed in wells 3 and 5 and production cores 4 were perforated in these wells with the aim of introducing low-permeability formations into the development;

- in wells 1 and 7, left for operation of highly permeable high-flooded formations, shanks 5 are lowered to create an inverted cone;

 - well 4 is mastered for injection.

Wells 3 and 5, transferred to overlying low-water formations, allow for the creation of a development system for a compacted grid. Moreover, the creation of foci of water injection will allow for intensive development with cost-effective rates.

Sources of information

1. R.Kh. Muslimova, A.M. Shavalieva, RBB.Hisamova and others. “Geology, development and operation of the Romashkinskoye oil field”, Moscow, VNIIOENG, 1995, p.243-244, 2 vol.

2. “Simultaneous separate exploitation of multilayer oil fields”. M .: Nedra, 1974, p. 83, authors: R.A. Maksutov, B.E. Dobroskok, Yu.V. Zaitsev.

3. RF patent No. 2173770 from 09.20.01.

Claims (1)

A method of developing an oil multilayer field at a late stage of development, including drilling injection and producing wells, injecting displacing fluid into the injection and selecting formation products through the producing well, characterized in that a part of unprofitable producing and injection wells from highly permeable high-water formations are transferred to the development of low-flooded overlying with the creation of a development system for compacted mesh, and the selection of oil from highly permeable highly watered x seams are carried out on a decompressed grid by abandoned production wells located in hypsometrically elevated parts of the reservoir, and displacement fluid is pumped by abandoned injection wells located in hypsometrically elevated parts of the reservoir, while production from abandoned production wells is carried out with measures to ensure a profitable production rate by preventing the formation of a cone of water.

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