RU2163966C2 - Method of oil pool waterflooding - Google Patents

Abstract

FIELD: oil producing industry, particularly, methods of waterflooding of oil pools. SUBSTANCE: injection of displacing agent into injection wells is carried out up to pressure rise in formation for 5-10% of running formation pressure before performance of hydraulic fracturing and during periodic stopping of injection. In so doing, duration of injection of displacing agent is determined with due consideration to distance between injection and producing wells and piezoconductivity of nonwaterflooded formation. EFFECT: higher efficiency of method due to increased sweep of formation waterflooding and development of low-permeable interlayers.

Description

 The invention relates to the oil industry, in particular to methods of flooding oil fields.

 A known method of flooding an oil reservoir, which consists in applying the cyclic injection method, carried out with periodic changes in pressure (flow) of the injected and injected liquid [1].

 The disadvantage of this method is its low efficiency when used in a heterogeneous formation.

 The closest in technical essence and the achieved effect is a method of waterflooding of an oil deposit, including hydraulic fracturing of bottom-hole zones of a formation of injection wells, injection of a displacing agent into injection wells until the pressure in the formation increases, and liquid is taken from production wells [2].

 The disadvantage of this method is a slight increase in oil recovery when used in a flooded reservoir.

 The aim of the invention is to increase the efficiency of the method by increasing the coverage of the formation by water flooding and connecting low-permeability layers to the development.

 This goal is achieved by the fact that in the known method of waterflooding of an oil deposit, which includes hydraulic fracturing of bottom-hole zones of a formation of injection wells, injection of a displacing agent into injection wells until the pressure in the formation increases, fluid is taken from production wells, injection of a displacing agent into injection wells is carried out until increase pressure in the reservoir by 5 - 10% of the current reservoir pressure before hydraulic fracturing and during its periodic shutdown, while the duration of pitching displacing agent is determined taking into account the distance between the injection and production wells and piezoconductivity nezavodnennogo formation.

 The method is as follows.

 First, hydraulic fractures of the bottom-hole zones of all injection wells of the reservoir are carried out. Then injection wells are put into operation and the displacing agent is injected until the pressure in the reservoir rises to 5-10% compared to the pressure that existed before the fracturing.

где t - время полуцикла закачки, сек;
l - расстояние между нагнетательной и добывающей скважинами:
κ - средняя пьезопроводность незаводненного пласта, м²/сек.After that, determine the duration of the half-cycle of injection of the displacing agent according to the known formula [3]:

where t is the injection half-cycle time, sec;
l is the distance between the injection and producing wells:
κ is the average piezoconductivity of an unfilled reservoir, m ² / s.

 Periodically stop and start the injection into all injection wells.

 Hydrofracturing of bottom-hole zones of a formation of injection wells will lead to an increase in their permeability due to the formation of cracks in the formation, as well as to cleaning of the faces from mechanical and organic impurities.

 Subsequent injection of water into injection wells increases their injectivity and the coverage of the formation by water flooding in thickness.

 Water injection is continued until the pressure in the reservoir increases by 5 - 10% compared with the pressure measured before hydraulic fracturing, to ensure sufficient energy resource for periodic shutdown and resumption of flooding.

 Cyclic injection will contribute to the involvement of low permeability layers in the development.

 As a result of the subsequent, the water cut of the produced fluid in the whole reservoir will decrease.

This method was tested on reservoir T ₁ with the following geological and physical characteristics:
formation depth - 1850 m
effective thickness - 7.6 m
porosity - 12%
permeability - 0.015 μm ²
reservoir pressure:
initial - 18.1 MPa
current - 14.0 MPa
oil viscosity in reservoir conditions - 3.1 MPa · s
well stock:
mining - 8 units.

 injection - 4 units.

First, hydraulic fracturing of the bottom-hole zones of the reservoir of all injection wells was carried out. As a result, the average daily injection rate of 1 injection well increased from 51 m ³ / day to 207 m ³ / day. After that, water was injected until the pressure in the reservoir increased by 10% (it became equal to 15.4 MPa). Due to this, the dynamic levels of producing wells increased from 1000 - 1100 m to 700 - 800 m.

Then, the injection half cycle was determined using the well-known formula [3] at l = 500 m, κ = 0.05 m ² / s.

Время полуцикла закачки оказалось равным 30 суткам.

The injection half-cycle turned out to be 30 days.

 In the first half-cycle, equal to 30 days, all the injection wells were stopped. In the second half-cycle, within 30 days, water was pumped into all injection wells.

 The effectiveness of the proposed method amounted to 14.7% of the total annual oil production in the whole reservoir.

Sources of information
1. M. L. Surguchev. Secondary and tertiary methods of increasing oil recovery.- M .: Nedra, 1985, p. 144 - 145.

 2. A.S. USSR N 1082332, 03.23.84, Bull. N 11.

 3. M. L. Surguchev. Secondary and tertiary methods of increasing oil recovery. - M.: Nedra, 1985, p. 146 - 147.

Claims (1)

 The method of waterflooding of an oil reservoir, including hydraulic fracturing of bottom-hole zones of a formation of injection wells, injection of a displacing agent into injection wells until the pressure in the formation increases, fluid selection from production wells, characterized in that injection of a displacing agent into injection wells is carried out until the pressure in the formation increases 5 - 10% of the current reservoir pressure before hydraulic fracturing and during its periodic shutdown, while the duration of injection of the displacing agent determined taking into account the distance between the injection and producing wells and the piezoconductivity of the flooded formation.