RU2342521C1 - Method of development of shallow low-yield oil deposits - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: suggested method refers to oil producing industry and can be employed at development of low-yield deposits. The essence of the invention is as follows: the method of development of shallow low-yield oil deposits in which prospecting wells have been bored incorporates boring producing wells, withdrawal of oil from producing wells and individual water pumping into pressure wells to maintain pressure in oil reservoirs, then displacement of oil into the direction of producing wells. According to the invention before boring of producing wells the map of oil areas with bored prospecting wells is overlaid with a base uniform square well location map. After that wells are bored according to the base map near the existing prospecting wells. Hydrodynamic investigations of bored wells are performed and in case of confirmed productivity of oil reservoirs a rational integration of reservoirs into operational sites is performed under condition of increase of medium well yield. The following wells are bored also according to base uniform square map till forming self contained operating cells of wells from bored and hydrodynamic investigated wells with allocating pressure wells in them. Efficiency of individual pumping water into pressure wells in these cells is determined on base of efficiency of surrounding producing wells.

EFFECT: increased efficiency of low-yield deposits development.

1 ex

Description

The proposed method relates to the oil industry and can be used in the development of unproductive fields.

Unproductive fields very often remain underdeveloped with inaccurate boundaries of oil areas even with increased density of exploratory wells per unit of oil area. Usually, according to the known method, oil fields are first explored, their boundaries and effective thicknesses of oil formations are determined, oil wells are obtained from exploratory wells and oil reserves are calculated. After the exploration and approval of the estimated oil reserves, the fields themselves can be put into commercial development, the development can be designed, the wells can be drilled and developed, and oil can be extracted from the wells. (Rules for the development of oil fields. Minnefteprom. M., 1987. The rules for the preparation of design technological documents for the development of oil and gas and oil fields. RD 153-39-00-96.)

The disadvantage of such methods (analogues) with the standard procedure for first exploration, calculation and approval of oil reserves, and then design and development, as applied to small unproductive oil fields, often consisting of several domes and separated oil areas, is a large proportion of design wells designed in the limits of proven oil areas, but which turned out to be outside the actual oil areas, and part of the actual oil areas, which were without design wells Jin.

These errors - deviations of actual oil areas from explored oil areas - are connected with the fact that small domes have small domes; the amplitude of the emitted domes is comparable to the error of the allocation of these domes according to seismic data, with a maximum error of even 3D seismic.

Closest to the proposed development method, adopted as a prototype, is a method of developing oil reservoirs, called selective water flooding, in which, after drilling, as well as geophysical and hydrodynamic studies of wells, taking into account the established parameters of the wells and oil reservoirs, those wells are selected for water injection, which will best provide the surrounding production wells with water injection, increasing the current oil production and final oil recovery. (A method of developing zonal deposits of oil reservoirs heterogeneous in reservoir properties. A.S. No. 356344. 1966)

The advantage of the known method with selective flooding is the accounting and targeted use of the established geological structure and productivity of oil reservoirs when choosing injection wells from among the already drilled wells.

The disadvantage of this method is the loss of a large number of drilled wells in areas where the actual oil area was less than explored (confirmed by intelligence) oil area, and the absence of drilled wells in areas where the actual oil area was more than explored.

Another disadvantage of this method is the excessive number (excessive density of the grid) of drilled wells in areas where the actual effective oil thickness was much less than according to exploration data; and, conversely, an insufficient number of drilled wells in areas where the actual effective thickness was much larger than according to exploration data.

A common disadvantage of the known methods is the supply of water to injection wells from a common pump station with a common injection pressure. For this reason, at some oil sites, the injection pressure and water injection will be insufficient, which will lead to a decrease in the oil production rate of the surrounding producing wells, a decrease in their bottomhole pressure below the saturation pressure and the possible emergence of a depletion regime with all negative consequences; at other oil sites, the injection pressure and water injection will be excessive, which can lead to an outflow of oil beyond the line of the surrounding production wells and their rapid watering, to an outflow of oil to the aquifer and a loss of some recoverable oil reserves there.

These and other disadvantages are absent in the proposed method for the development of small unproductive oil fields.

The objective of the invention is to increase the efficiency of the development of unproductive deposits.

This problem is solved by the fact that in the method of developing small unproductive oil fields in which exploration wells were drilled, including drilling production wells, oil extraction from production wells and individual injection of water into injection wells to maintain pressure in oil reservoirs, displacing oil towards producing wells, before drilling production wells on the map of oil areas with drilled exploratory wells impose a basic uniform square grid of placement of important, after which, according to the basic grid, wells are drilled near existing exploratory wells, hydrodynamic studies of drilled wells are carried out and, if the productivity of oil reservoirs is confirmed, rational pooling of reservoirs into production facilities is carried out, given the increase in average well production, the following wells are also drilled along the basic uniform square grid to the formation of autonomously working wells cells from drilled and hydrodynamically investigated wells with discharge injection into them wells, while the productivity of individual water injection into injection wells in these cells is determined by the productivity of the surrounding production wells.

The principal difference of the proposed method for the development of small unproductive oil fields is that the possible inaccuracy is initially taken into account - that their geological and recoverable oil reserves are determined inaccurately from the strata of the border of oil areas, with a large error. And they should not, as is usually the case, be taken on faith.

The essence of the proposed development method is to combine industrial oil production from the created wells cells and to continue exploration of oil reservoirs by drilling new wells, their geophysical and hydrodynamic studies and creating new wells cells based on the obtained reliable information from the drilled wells.

Well cells are introduced into the work, which can autonomously exist and act independently of other sections, from other well cells that are already working or not working, that are just being created.

Based on the reliable information obtained from drilled wells, various types of choices are made:

- selectivity of drilling wells when they decide: to drill further wells or not to drill, to thicken the grid of wells or not to thicken;

- selectivity of combining oil reservoirs into production facilities when rational combining of oil reservoirs into facilities is carried out;

- selectivity of injection wells: their selection from those that will best provide the surrounding production wells with water injection, and from those that have drilled into the aquifer;

- the use of individual pumps for water injection with their placement on well bushes near injection wells and matching their performance with the productivity of the surrounding producing wells.

In all cases, uniform square grids of wells are used from the same standard dichotomous row of square grids, which is obtained starting from the thickest grid of 1 hectare per well (100 × 100 m section) by 2 times sequential dilution: 1, 2, 4, 8, 16, 32, 64 and 128 ha per well.

The advantage of square well grids is their actual steady uniformity. So, with a sequential vacuum of 2 times and with a sequential thickening of 2 times, the grids remain uniform. And uniform triangular grids when diluted by 2 times and when condensed by 2 times become uneven grids with a rather large unevenness.

In the process of drilling oil areas, square well grids are most easily cut 2-4-8 times, if necessary, and then thickened back: divide one square grid into two square grids (divide one production facility into two production facilities) and, conversely, two square connect the grids into one square grid (turn two operational facilities into one).

The rational density of the grid of wells is determined on the basis of technological and economic calculations according to the criterion of maximum economic efficiency (according to the maximum discounted net profit). For example, the rational density of the grid of wells is equal to 25 ha per well, i.e. does not coincide with some grid from the standard dichotomous row, it turns out to be intermediate between two grids of the standard dichotomous row 16 ha per well and 32 ha per well, and the grid with 16 ha is twice as thick as the grid with 32 ha. This means that a rational grid from 25 ha per well will be composed of two grids 32 and 16 ha per well: 32 ha per well is the primary rarer grid, and 16 ha per well is the base thicker grid. First, a primary rarer grid is carried out, and then in areas of increased effective oil reservoir thickness, the base is thicker. The thickening of the grid of wells in areas of increased effective oil thickness leads to an increase in the coverage factor by displacement and, accordingly, the oil recovery coefficient.

When two or more production facilities are identified at a multilayer oil field for each of the facilities, on the basis of technological and economic calculations, a rational well grid density, its primary rarer well network and its own base thicker well network are determined. All possible wells of the production facility can only be located at the points of its base grid. The base grids of different production facilities are so evenly shifted that, as a whole, they form the most uniform grid in the field.

This will make it possible to better establish the geological structure of individual formations and the entire field as a whole, therefore, it will increase oil recovery and ensure a more complete, more efficient use of the entire well stock.

An important difference of the proposed method for the development of small unproductive oil fields is the adopted procedure for drilling an oil field and its oil areas.

The direction of drilling goes from known to unknown, from existing exploratory wells to the boundaries of oil fields. With such drilling, simultaneously with industrial oil production, wells are already being explored in geological structure of oil reservoirs in neighboring sections, which is immediately taken into account when creating new wells cells, determining the density of wells in these cells and identifying specific injection wells.

An example implementation of the proposed development method.

In one small unproductive oil field in Western Siberia on its western oil area, according to the existing method, a development system was designed with a uniform square grid for well placement and dispersed water flooding according to a reversed 9-point pattern.

The design grid for well placement was adopted as the base. Drilling went from the center to the periphery, from the known to the unknown. As a result, the actual oil area was significantly less than the explored oil area, taken according to intelligence. Of the 80 design wells, 40 were drilled within the actual oil area, i.e. 40 wells were not drilled in vain.

As a result of the application of the proposed method, based on reliable information on drilled and explored wells, in addition to limiting further drilling, autonomous working well cells with injection and surrounding producing wells have been created that provide industrial oil production that do not interfere with other working well cells, neighboring drilled and created wells wells. Due to the accepted procedure for drilling and well research, there was no delay in oil production. With another standard technology, procrastination can be measured in months and years.

Due to the use of individual water injection, the water injection pressure was close to the hydraulic fracture pressure (10% lower than the hydraulic fracturing pressure), and the bottomhole pressure of the producing wells was reduced to the oil saturation pressure with gas, but not lower than the saturation pressure. The bottomhole pressure difference between injection and production wells was doubled and the possibility of oil outflow beyond the well cells and the loss of part of recoverable oil reserves were excluded.

Thanks to the use of dispersed selective flooding, the total filtration resistance of the system of wells and reservoirs was reduced by 1.5 times.

Due to the rational combination of the two layers into one common production facility, the average well production rate was increased by 1.5 times.

Compared to the usually designed three-row strip of producing wells and the usually designed technology for operating production and injection wells, the production rate per 1 design well was increased by (80/40) · 2 · 1.5 · 1.5 = 9 times, and by 1 drilled well 2 · 1.5 · 1.5 = 4.5 times, specifically from 6 t / day to 27 t / day. Plus, prolonged delays with the start of industrial oil production are excluded.

Thus, thanks to the application of the proposed method, the development of a small unproductive oil field has become cost-effective.

Claims (1)

The method of developing small unproductive oil fields in which exploratory wells were drilled, including drilling production wells, extracting oil from production wells and individually pumping water into injection wells to maintain pressure in the oil reservoirs, displacing oil towards production wells, characterized in that before drilling production wells on the map of oil areas with drilled exploratory wells impose a basic uniform square grid of wells, after which about, according to the basic grid, wells are drilled near existing exploratory wells, hydrodynamic studies of drilled wells are carried out, and if the productivity of oil reservoirs is confirmed, rational pooling of the reservoirs into production facilities is carried out, given the average average production rate of wells, the following wells are also drilled along the basic uniform square grid until drilled and hydrodynamically investigated wells of autonomously operating well cells with the allocation of injection wells in them, at th performance of individual pumping water into injection wells in these cells is determined by the productivity of the surrounding production wells.