RU2187620C2 - Method of water shut-off in porous-fractured oil reservoirs - Google Patents

Abstract

FIELD: methods of water shut-off in porous-fractured oil reservoirs. SUBSTANCE: method is realized by injection of selective waterproofing polymer composition with subsequent additional injection of polymer with initial size of particles smaller than transverse sizes of fractures. Polymer is used in form of water-swelling polymer- hydroxyethylcellulose. EFFECT: higher efficiency of method of water shutoff due to provision of continuous screen in water-bearing part of formation with preserved permeability of oil interval of formation. 1 dwg, 1 tbl, 1ex

Description

 The invention relates to the oil industry and can be used to isolate the water entering the oil producing wells from pore-fractured reservoirs (limestone, fractured sandstones and siltstones).

 A known method of isolating the influx of formation water from pore-fractured formations into the well by pumping a suspension of rubber crumb (1).

 The disadvantage of this method is the low efficiency of the water isolation method due to the lack of selectivity in selective isolation, since along with the aquifer part of the formation, particles of rubber crumb may penetrate into the oil interval, where the subsequent swelling of rubber particles in a hydrocarbon medium may block oil-saturated channels, which leads to to reduce the productivity of oil producing wells.

 The aim of the invention is to increase the efficiency of the method of isolating the water of pore-fractured formations by creating a continuous screen in the aquifer of the formation, which prevents the penetration of water into the well while supplying bottomhole pressure during long-term operation of the well and while maintaining the permeability of the oil interval of the formation.

 This goal is achieved due to the fact that in the method of isolating water in pore-fractured reservoirs of an oil reservoir by injection of a selective water-insulating polymer composition followed by an additional injection of a polymer with an initial particle size smaller than the transverse sizes of the cracks, a suspension of a water-swelling polymer, hydroxyethyl cellulose, is pumped as said polymer .

 A known method of isolating the influx of water into a well by injecting a polymer clay solution (2).

 The disadvantage of this method is the low stability of the insulating material, and the presence of a clay component that penetrates deep into the formation, in the absence of selectivity of the method, can overlap the oil-saturated pores to a greater depth along the strike of the formation and prevent the subsequent recovery of residual oil reserves.

 The closest of the analogues is a method of isolating water in pore-fractured reservoirs of an oil reservoir by injection of a selective water-insulating polymer composition with subsequent additional injection of a polymer with a particle size smaller than the transverse size of the cracks (3).

 The use of a suspension of water-swelling polymer with an initial particle size of 70-50 microns allows it to be pumped to the calculated value deep into the reservoir, depending on the specific geological conditions, and to form a continuous water-tight borehole with a mass and volume of 10-15 times swelling in water screen independent of crack size and degree of openness. When polymer particles can enter the oil interval of the formation, polymer swelling does not occur due to inertness to hydrocarbon media.

 As a selective water-insulating composition, formulations based on sodium silicate or hydrolyzed polyacrylonitrile and polyacrylamide can be used.

 High viscosity grades of hydroxyethyl cellulose (OEC) with a specific start time of swelling in formation water can be used as a high molecular weight compound (IUD) of a water swellable polymer. The swelling time of the OEC in water of various salinity and, accordingly, density is shown in the graph of FIG. 1. The effectiveness of the proposed method was determined in laboratory conditions at the installation, the technical scheme of which is shown in FIG. 2.

 The IUD suspension was pumped in the forward direction, and its hydraulic breakthrough strength was checked by pumping wastewater in the opposite direction.

 Example.

A 1.5-2% suspension of highly viscous OEC in wastewater with a density of 1.04-1.12 g / cm ^{3 was} pumped into a steel, vertically installed pipe with a diameter of 50 mm, filled at regular intervals with quartz sand with a particle size of 0.1-0, 15 mm and packages of glass rods, the diameter of an individual rod was 2 mm. The length of each cork made of quartz sand was 10 cm; likewise, the length of one packet of glass rods was 10 cm. The total assembly length was 200 cm.

 After maintaining a certain time in accordance with the data of the graph in figure 1, the injection of waste water was resumed. Through the bends located on the pipe and led to the high pressure gauge, a pressure measurement was carried out, the measurement data are given in the table. From the obtained results of laboratory tests it is seen that the use of a water-swelling polymer is much more effective than the use of rubber crumb under the same experimental conditions. The hydraulic fracture pressure for a layer with a swollen Navy is much higher than for a crumb rubber screen. Moreover, the screen of the Navy, unlike rubber crumb, is firmly held when changing the direction of flow, which is important when operating the well.

 In field conditions, the method is implemented in the following sequence.

After carrying out geological and technical measures in the well, the interval of water inflow, injectivity is determined. Tubing pipes with a packer or open end are lowered into the well and the calculated volume of the waterproofing solution is injected. The injection is carried out using existing standard equipment with registration of the flow rate of the solution and discharge pressure. At the wells of the Romashkinskoye oil field, the water-insulating composition is pumped at a flow rate of not more than 15 m ³ / h at a pressure of 8-12 MPa.

 After completion of the injection of the water-insulating composition, they proceed to pump the suspension of the water-swellable polymer. The polymer powder is poured directly into a stream of water directed into a small chunk of the CA-320 M pumping unit using a hydraulic metering device at a concentration of 1.5-2% while pumping into the well.

Sewage or produced water with a density of 1.05-1.18 g / cm ³ and mineralization of 90-240 g / l is used as the carrier fluid of the polymer suspension. The consumption of water-swelling polymer is 20-25 kg per linear meter of the insulated formation.

 After the calculated volume of water-swelling polymer is pumped and pushed into the formation, the injection is stopped, and after the set time required for swelling, a control measurement of the inflow profile is performed in the well when the level drops to the calculated bottomhole pressure.

List of references
1. Tosunov E.M. and others. Isolation of water inflows and chemical treatment of low-permeability zones of the reservoir // RNTS "Oil field business", 7. M .: VNIIOENG, 1974, p. 34.

 2. Amelin B. A. et al. New methods for non-metallic fastening of boreholes. M .: Nedra, 1964, p. 73-74.

 3. RF patent 2095555 C1, publ. 09/27/1995.

Claims (1)

 A method of isolating water in pore-fractured reservoirs of an oil reservoir by injection of a selective water-insulating polymer composition followed by an additional injection of a polymer with an initial particle size smaller than the transverse sizes of the cracks, characterized in that a suspension of a water-swelling polymer, hydroxyethyl cellulose, is pumped as said polymer.

Images