RU2379492C2 - Development method at wells re-entry and oil field in general - Google Patents

Abstract

FIELD: oil-and-gas production.

SUBSTANCE: use flush and mechanised oil production method and create a vertical-lateral water flooding system. For that descend cementing strings into re-entering well above a reservoir roof an cement a borehole under pressure at height greater than the reservoir depth. In the well re-entering as a production ones, bore created cement barrel at depth not more than half of reservoir interval, counting from the roof. Additionally create a dib hole for the perforation equipment descending and execute second perforation in interval not greater than reservoir height, counting from the roof. Then start up the well in to operation with flush or mechanised oil production method. In the well re-entering as a injection ones, bore created cement barrel till the reservoir bottom, create a dib hole for the perforation equipment descending and execute second perforation in interval of the reservoir bottom one third. Then start up the injection well with water injection. For decreasing probability of cement rock sealing failure, over or under the perforation interval create a perforation holes with a hydraulic jet perforation method.

EFFECT: oil field development factors improvement during re-entering of the stand-by wells and the oil field in general because of creating vertical-lateral water flooding system using vertical stand-by production and injection wells, without lateral and horizontal boreholes boring.

2 cl, 2 dwg

Description

The invention relates to the oil industry, and in particular to an effective method of re-preservation of idle wells and the oil reservoir as a whole.

There is a method of developing an oil reservoir based on waterflooding of a reservoir and using a system of vertical producing and injection wells [see Muravyov V.M., Sereda N.G. Basics of oil and gas business. M., Nedra, 1967, p.137-145]. The corresponding waterflooding system in the work Zakirov S.N. and other scientific foundations of vertical flooding. Proceedings of the Int. scientific symposium "Theory and practice of applying enhanced oil recovery methods." Moscow, September 18-19. 2007, p.188-196 is called the lateral flooding system.

This development method has been implemented in most domestic and foreign fields. The actual development data show that the lateral flooding system underlying the known development method is characterized by the following disadvantages.

In lateral waterflooding, the water injected into the reservoir displaces oil to the bottom of production wells along the bed, that is, in the lateral direction. Almost all productive formations are layered-heterogeneous in reservoir properties. This determines the primary displacement of oil by water from highly permeable interlayers. As a result, early retirement of wells occurs due to high water cut of produced products. This explains the ubiquitous low oil recovery factor.

Closest to the proposed is a development method based on the so-called vertical flooding system [see Zakirov S.N., Indrupsky I.M., Zakirov E.S., Mukhametzyanov R.N., Dzhafarov I.S., Nuriev M.F., Semenov V.V. The scientific basis of vertical flooding. Proceedings of the Int. scientific symposium "Theory and practice of applying enhanced oil recovery methods." Moscow, September 18-19. 2007, p. 188-196]. In a later work in print, the authors called this waterflooding system a vertical-lateral waterflooding system. According to this waterflooding system, which underlies an alternative development method,

- horizontal and horizontal wells are used as production and injection wells,

- the faces of production and injection wells are spaced vertically and laterally,

- faces of producing wells are located near the roof, and injection wells are located near the bottom of the formation.

The disadvantages of this development method and the corresponding waterflooding system are as follows.

The method is attractive in relation to introduced into the development of oil deposits. The problem of development during the re-conservation of wells or deposits is generally characteristic of deposits, the development of which was previously carried out on the basis of vertical production and injection wells. Therefore, the use of a system of vertical-lateral waterflooding for development when re-preserving vertical wells and deposits in general today is possible on the basis of drilling horizontal lateral shafts from them. However, this approach is very costly. In addition, the design and technical condition of idle wells may not allow horizontal lateral shafts to be drilled from them.

The aim of the invention is to substantiate a development method for re-preservation of wells and an oil reservoir as a whole based on a vertical-lateral waterflooding system without expensive and time-consuming drilling of horizontal sidetracks.

This goal is achieved by the fact that the proposed development method during the re-conservation of wells and oil deposits as a whole is carried out on the basis of a system of vertical-lateral flooding, as well as a fountain or mechanized method of oil production; it is distinguished by the fact that filling pipes are lowered into unreserved idle wells above the top of the productive formation and cementing the bottom of the well under pressure to a height greater than the thickness of the formation; in wells mothballed as producing, the resulting cement cup is drilled to a depth of not more than half of the interval of the reservoir, counting from the roof, an additional sump is created to lower the perforating equipment and repeated perforation in the interval of not more than half of the reservoir, counting from the roof, is then launched wells for oil production in a fountain or mechanized way; in wells that are being mothballed as injection wells, the resulting cement cup is drilled to the bottom of the formation and a sump for perforating equipment is created, repeated perforation is performed in the interval of the lower one third of the formation, then the wells are launched under water injection. And also by the fact that to reduce the likelihood of loss of tightness of cement stone above or below the perforation interval, the creation of perforations is performed by the method of hydro-sandblasting.

The method is implemented as follows.

There is a group of mothballed (idle) wells in the considered oil reservoir, or the entire oil reservoir is in conservation due to high water cut of produced products or low oil production rates and overall recovery from the reservoir. Moreover, by the time of conservation, for example, of an oil deposit, the achieved value of the oil recovery coefficient (CIN) is noticeably lower than the value approved by the State Commission for Mineral Reserves (GKZ MPR).

All or almost all of the production and injection wells are vertical. Therefore, the implemented water flooding system can be regarded as a lateral water flooding system. Provided that the productive section is represented by interbedded interlayers with different values of the permeability coefficient.

Field geophysical research data confirms the selective nature of watering wells in the thickness of the reservoir.

These factors usually allow us to conclude that the lateral waterflooding system has exhausted itself in this area or the oil reservoir as a whole. An effective withdrawal from the conservation of a group of wells or an oil reservoir as a whole can be carried out by switching to an alternative system of vertical-lateral flooding. To do this, perform the following technological operations.

- In all the wells to be deconsolidated, cementing is carried out under bottomhole pressure above the top of the reservoir and thereby a cement cup is formed in the interval of the reservoir.

- According to a previously formed or other designed system for the placement of production and injection wells, re-wells are divided into production or injection wells.

- In each well, which was re-preserved for the purpose of oil production, the created cement cup is drilled to a depth of not more than half the interval of the reservoir, counting from the roof. An additional sump is drilled to lower perforating equipment with the possibility of perforation in the upper half of the reservoir. Then perform repeated perforation in the interval of not more than half of the reservoir, counting from the roof.

- In each well, re-preserving to inject water, the created cement cup is drilled to the bottom of the formation. An additional sump is drilled to lower perforating equipment with the possibility of perforation in the interval of the reservoir. Then perform repeated perforation in the interval of the lower one third of the reservoir, counting from the bottom or from the bottom mark of the original oil-saturated interval.

- The most preferred method of perforation from the point of view of maintaining the integrity of the cement stone above or below the perforated interval is the sandblasting method.

- After completion of the preparatory operations listed above, injection wells begin to pump water into the lower part of the reservoir through the tubing string.

- In production wells, oil begins to be taken from the upper part of the reservoir based on a fountain or mechanized method of operation.

An example implementation of the proposed method.

In the oil reservoir, the next production and injection wells are considered, which are subject to re-commissioning on the basis of a vertical-lateral water flooding system. They are supposed to implement the technological operations provided for by the method.

The scheme of de-preservation of the producing well is presented in figure 1. The entire thickness of a productive formation of 16 m in this well was previously perforated. It is supposed to carry out operations to create a cement cup in the interval of the reservoir, to drill it in the upper half of the reservoir and to perform repeated perforation in this interval. The lower half (8 m) of the reservoir remains isolated from the well with a cement cup; in this interval, perforation is not performed. Upon completion of the perforation work, it is planned to lower the tubing string with a deep pump into the well and start the mechanized production of oil.

Figure 2 shows a diagram of the re-preservation of the injection well. This scheme provides for the creation of a cement cup in the entire interval of the reservoir (14 m), its drilling to the bottom of the reservoir and repeated perforation in the bottom about one third of the reservoir (5 m), counting from the bottom mark of the initial oil-saturated interval. This mark is determined according to the data of geophysical studies of the well in the open hole at the time of its initial completion. Next, it is planned to lower the tubing string into the injection well and pump water through it into the lower part of the reservoir.

The figures in figures 1 and 2 correspond to the real two wells of the same problem deposits in Western Siberia. They were estimated using information on the features of the geological structure of the reservoir in the area of these wells. By the time of conservation, the achieved oil recovery coefficient in this deposit is several times lower than the MPR approved by the State Reserves Committee. By the time of conservation, all producing wells were heavily watered (up to 98%) and were characterized by low, unprofitable oil production rates (about 1 ton / day).

The subsoil user at its scientific and technical meeting approved the implementation of the proposed development method for the sequential re-commissioning of all wells in a given problem deposit. For no one could offer other acceptable alternatives.

The aforesaid allows us to state that the proposed development method for the re-conservation of wells and the oil reservoir as a whole based on a system of vertical-lateral water flooding will be an important alternative to an insufficiently effective traditional development method based on lateral water flooding.

Claims (2)

1. The development method for re-conservation of wells and the oil reservoir as a whole, including the use of a system of vertical-lateral waterflooding and a fountain or mechanized method of oil production, characterized in that the fill pipes are lowered into the unreserved idle wells above the top of the reservoir and cementing the bottom of the well under pressure to a height greater than the thickness of the reservoir; in wells mothballed as producing, the resulting cement cup is drilled to a depth of not more than half of the interval of the reservoir, counting from the roof, an additional sump is created to lower the perforating equipment and repeated perforation in the interval of not more than half of the reservoir, counting from the roof, is then launched a well in oil production fountain or mechanized way; in wells mothballed as injection wells, the resulting cement cup is drilled to the bottom of the formation and a sump for perforation equipment is created, repeated perforation is performed in the interval of the lower one third of the formation and the well is launched under water injection. 2. The method according to claim 1, characterized in that to reduce the likelihood of loss of tightness of the cement stone above or below the perforation interval, the creation of perforations is performed by the method of hydro-sandblasting.

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