RU2202689C2 - Way to insulate water in creviced formations - Google Patents

Abstract

FIELD: oil production. SUBSTANCE: invention deals with ways insulating water in creviced formations and of lost circulation zones both in terrigenous and carbonate collectors. Way to insulate water in creviced formations includes injection of suspension of rubber crumbs in oil. Suspension is supplemented with organic flour and polymer with following proportion of components, per cent by weight: rubber crumbs 2.0-15.0; organic flour 1.0-20.0, polymer 0.1-0.5; oil being the balance. EFFECT: enhanced efficiency of water insulation in creviced formations and in lost circulation zones both in terrigenous and carbonate collectors. 1 dwg, 1 tbl

Description

 The invention relates to the oil industry, in particular to methods of isolating water in fractured formations and absorption zones in both terrigenous and carbonate reservoirs.

 A known method for isolating the influx of water into a well by injecting a polymer-clay suspension into the formation [1].

 The disadvantage of this method is the low efficiency of isolating the influx of water into the well due to the fact that the injected suspension does not have sufficient structural and mechanical properties.

 The closest in technical essence to the claimed method is a method of isolating the influx of water in fractured reservoirs, which involves the injection of a suspension of rubber crumb in oil [2].

 This method is as follows. The composition is prepared on the surface by mixing rubber crumb (RC) and oil, pumped into the well and crushed into the reservoir. When injected, the particles of rubber crumb are compressed and deformed, which ensures the flow of the suspension into the fractures of the formation and the closure of the channels of water flow into the well due to pinching and compaction of the particles of rubber crumbs in the fractures of the formation.

 However, this method does not have sufficient reliability of isolating the influx of water (plugging properties), because the oil used to prepare the suspension is gradually displaced by water from the space between the particles (granules) of the rubber crumb, and is also washed off from the walls of the cracks, which ultimately leads to water breakthrough.

 The proposed invention solves the problem of increasing the efficiency of water isolation in fractured formations and absorption zones in both terrigenous and carbonate reservoirs.

The problem is solved in that in the method of isolating water in fractured reservoirs, including the injection of a suspension of rubber crumb in oil, it additionally contains organic flour and polymer in the following ratio, wt.%:
Rubber crumb - 2.0 - 15.0
Organic Flour - 1.0 - 20.0
Polymer - 0.1 - 0.5
Oil - Else
Improving the efficiency of isolation is achieved through the following interaction of the components of the suspension.

 In the process of pumping the suspension into the well in the fractures of the formation, the rubber crumb is compacted to form a trellised framework. In this case, at the same time, the pore space of the lattice frame is filled with solid, oil-soaked particles of organic flour, which leads to a significant reduction in the volume of gaps between solid particles. Also, at the same time, these gaps between the solid particles are filled with a polymer that swells due to the absorption of water available in the near-wellbore zone of the well in the fractures and pores of the formation, and provides sealing of micro-gaps between the solid particles and between them and the wall of cracks. The result is a sealed waterproof barrier - a blocking screen that reliably blocks the flow and movement of water through cracks.

 The role of organic flour lies in the fact that, while allowing some deformation of the particles upon application of pressure and being in suspension, it increases the elastic-mechanical properties of the suspension. Due to the fact that the particle density of organic flour is close to the density of oil, they are not susceptible to sedimentation, are in suspension and are easily pumped into cracks and absorption zones, while maintaining the stability of the suspension. In addition, each particle of organic flour is a porous hydrophobic micro-capacity, and when pumped into the well, it is saturated with oil, swelling. Moreover, due to these properties, organic flour particles become oil storage facilities and provide the duration of hydrophobization of the suspension itself and the walls of cracks and near-crack micropores in the formation. The effect of hydrophobization is reflected in the fact that in the cracks, the walls of which are hydrophobized, when water is introduced into them, capillary forces appear, acting in the opposite direction of its movement and during blocking, water does not filter into the well.

 The role of the high molecular weight polymer is that it forms an adhesive-oriented coating of the surface of solid elastic (crumb rubber) and inelastic (organic flour) particles and crack walls, creating a bond between them. In addition, the polymer flocculates the filler particles and maintains the particles in suspension when the suspension is pumped into the well. Subsequently, under the influence of water coming from the reservoir, the polymer particles swell, dissolve and form a highly viscous gel-like mass containing solid elastic and inelastic fillers, which ultimately ensures the reliability of the insulation.

 The suspension pumped into the well by the proposed method is a pulp-like mass having hydrophobic-insulating properties. The suspension does not contain chemically active components and is neutral with respect to fluids in the well, which provides it with high stability and preservation of rheological and filtration properties. Oilfield experience shows that when using plugging materials containing solid fillers for water insulation, the best results are obtained when the solid fillers are polydisperse. Organic flour and crumb rubber used in the proposed method have this quality. The polydispersity of the solid elastic and inelastic phases allows you to "adapt" to the specific geological and physical conditions of the well by combining their fractions with different particle sizes.

 This ability increases the range of the method, depending on the injection pressure and the injectivity of the wells during insulation work. The method can be carried out at any stage of the development of an oil field: in producing wells with intensive formation water supply, it is used to stop the flow of water into the bottomhole formation zone and in injection wells when annular water flows appear - to isolate absorption zones and prevent unproductive leaving of water injected into well according to the reservoir pressure maintenance system (RPM).

 Analysis of the known similar solutions allows us to conclude that there are no signs in them that are similar to the distinguishing features in the claimed method, and that the claimed solution meets the criteria of the invention of "novelty" and "inventive step".

Technical characteristics of the materials used
Rubber crumb is obtained by grinding worn-out tires and tubes, as well as waste rubber products (RTI). For use according to the proposed method, the brands RD 0.5-RD 10 TU 38.108035-97 are used.

Organic flour is a product of grinding agricultural waste, light and wood processing industries. As organic flour can be used:
- buckwheat husk flour (TU 39-0147585-056-99);
- wood flour (GOST 16361-87);
- breaker - a product of grinding decorative paper-laminated plastics (TU 6-19-181 -150-87) and others.

As the polymer, water-swellable and water-soluble polymers can be used, such as:
- domestic polyacrylamide (PAA) according to TU 6-16-2531-81, TU 6-01-1049-81, TU 14-6-121-75;
- PAA imported with a molecular weight of (3-15) (10 ⁶ grades of Kem-Tron, Alcoflood, etc.;
- Polymers of the brand "Terposkrin" and AK-639;
- hydroxyethyl cellulose brand "Sulfacell 30" and others.

 Oil - commercial, crude. Oil substitutes can also be used - liquid hydrocarbons, for example, used oils, etc.

 The amount of suspension, the concentration of its components and the particle size for injection into the formation in accordance with the proposed method are determined from experimental data depending on the geological and physical parameters of the formations (fracture dimensions, permeability of the formation, injectivity of the well, etc.), as well as the technical capabilities of the equipment fisheries.

The optimal concentration of crumb rubber in suspension is 2.0-15.0 wt. %, organic flour - 1.0-20.0 wt.%, polymer - 0.1-0.5 wt.%. The lower concentration limit of the suspension ingredients is limited by the low efficiency of the process. The upper limit is limited by the filtering ability of the suspension in cracks and the technical capabilities of the pumping unit, which is not able to pump too thick highly concentrated suspension. Field experience shows that to create a reliable waterproofing screen, it is necessary to pump 3-10 m ^{3 of} suspension per 1 m of the thickness of the reservoir, but not less than 20 m ³ per 1 well. The particle sizes of the components in the suspension depend on the specific geological and physical conditions of the formation and are 0.3–10.0 mm for crumb rubber and 0.001–5.0 mm for organic flour.

 The effectiveness of the proposed method for isolating the influx of water was tested in laboratory conditions. The experiments were carried out on the installation for the study of core permeability (UIPK), which is widely used in the oil field. Studied the plugging ability of the known and proposed methods on a model that allows you to create crimping pressure. The model was a perforated metal tube filled with the test compound and placed in a rubber cuff through which the crimping pressure was transmitted to the model. Model dimensions: length 20 cm, diameter 3 cm. During the experiments, the crimping pressure was 50 MPa, which made it possible to simulate the composition being in reservoir conditions: to maintain the rubber crumb in a stressed state and to ensure compaction of the whole composition.

For testing, formulations were prepared containing the following components:
- rubber crumb obtained at the Leninogorsk plant RTI of the Republic of Tatarstan (RT) (fraction with particle sizes of 0.3-5.0 mm);
- organic flour - buckwheat husk flour - waste of the mill of Bugulma RT (fraction with particle sizes of 0.001-3.0 mm);
- polymer - PAA Kem-Tron brand manufactured in the USA;
- oil - anhydrous oil of the Bobrikov horizon of the Romashkinskoye field (viscosity 50 mPa • s).

 The plugging ability was determined by filtering water under pressure through a model filled with the composition. During the experiments, the ratio between the crimping pressure and the differential pressure of water filtration was assumed to be comparable with that in reservoir conditions. The results of the experiments are shown in the table. As can be seen from the table, when conducting experiments with the suspension according to the known method with a content of rubber crumb of 15 wt.% In it, water filtration began after a pressure drop of 0.1 MPa was created in the model, and with a maximum content of crumb rubber of 35 wt.%, Water filtration after creating a pressure drop of 0.3 MPa in the model (experiment 4). According to the proposed method, even with a minimum content of components in the suspension, water filtration began after creating a pressure differential of 0.8 MPa in the model (experiment 7), i.e., the insulation efficiency increased by 2.66 (0.8: 0.3) times. Analysis of the data obtained by testing suspensions according to the proposed method for various combinations of component concentrations showed that reliable isolation was achieved with a higher pressure drop in the model (experiments 9-12). Thus, the experimental results presented in the table allow us to conclude that the use of the proposed method will increase the insulation efficiency by more than two times in comparison with the known method (0.8 MPa: 0.3 MPa).

 Under field conditions, the suspension is prepared and pumped into the well using existing oilfield equipment in the following sequence.

 In the selected well, a set of standard geophysical surveys is carried out to determine the height of the cement behind the column, the quality of cementing, the total injectivity of the well, the profile of injectivity in the reservoir, the zone of water inflow, etc.

 Ground equipment and a well are prepared for the injection process of the suspension: the production string is tested for leaks, the well reinforcement is inspected, the face is cleaned, the lower end of the tubing is installed opposite the lower perforation holes, and if necessary, the packer is installed above the formation roof. The necessary materials and equipment are delivered to the well: cementing units, oil and water tank trucks, a sand mixer and a jet pump (ejector) with a funnel.

 The suspension is pumped into the well according to an individual work plan, which includes data on the well, the procedure for the work, and the volumes of materials used.

 The technological scheme of strapping of ground equipment during the injection of the suspension according to the proposed method is presented in the drawing.

 Oil from the tank or tanker 1 is fed by the first pumping unit 2 through the pressure pipe with the ejector 3 to the mixer 4 of the sand mixer 5. On the way through the ejector 3, organic flour 6 and polymer 7 are dosed into the oil. The rubber crumb from the hopper 8 of the sand mixer is fed directly into the oil mixer 4. The resulting suspension from the mixer 4 through the intermediate tank 9 of the second unit 10 through the valve 11 is pumped into the well 12.

 Examples of specific implementation.

 Example 1. Water isolation of a formation in well 6603 of the Novo-Elkhovsky field of the Republic of Tatarstan.

 The reservoir is represented by a fractured-pore oil-saturated reservoir of the Tournaisian layer, which lies at a depth of 1260-1273 m. Below the reservoir is lined with a reservoir with bottom water at a depth of 1273-1309 m. The interval of the reservoir is perforated in the range of 1260-1267 m. Oil is produced using a deep pump , lowered at tubing to a depth of 800 m. After commissioning, the well stably produced 3.5 tons of oil per day with a water cut of 17%. After three years of operation, the well drastically (within a month) was flooded to 99.2%, while oil production was 0.1 tons per day. Hydrodynamic studies and analysis of water samples showed that a breakthrough of water into the well occurred along a crack from the bottom zone of the formation.

Insulation work was carried out in accordance with the proposed method. To do this, the deep pump was removed from the well, the tubing was lowered to the lower perforation holes. Then a suspension was pumped into the well, consisting of 1.5 tons of rubber crumb, 2 tons of organic flour, 80 kg of polyacrylamide and 28 m ^{3 of} oil, which amounted to, respectively, wt.%: RK - 5.3; organic flour - 7.4; polyacrylamide - 0.3. The fractions of rubber crumb produced by the Leninogorsk plant RTI grades A, B and C with sizes of 0.3-1.0 mm were used; 1.0-3.0 mm and 3.0-5.0 mm in a ratio of 1.5: 1.5: 2, as well as a fraction of buckwheat husk flour - waste from a mill in Bugulma with a particle size of 0.001-3.0 mm with a ratio of rubber crumb and flour 1: 1.3.

The suspension was pumped at a volumetric flow rate of 10 m ³ / h; injection pressure: initial - 3.0 MPa, final - 10.5 MPa. The suspension was pushed into the reservoir with salt water with a volume of 4 m ³ . The well was washed with water to the bottom, lowered the pump and put into operation. After conducting insulating works, the well stably produces 3.9 tons of oil per day with a water cut of 11%.

 The data obtained show that the application of the proposed method allowed to reliably eliminate the flow of water into the well and increase oil production.

 Example 2. The proposed method is used to eliminate annular circulation in the injection well 1723A Romashkinskoye field of the Republic of Tatarstan.

Two interlayers of horizon D _{1 were} opened and perforated in the intervals of 1808.5-1810 m and 1814.5-1817 m. The depth of the bottom was 1837 m, the diameter of the production string was 146 mm. For a long time (more than 10 years), water was injected into the well in order to maintain reservoir pressure and displace oil to production wells. Geophysical studies in 2000 established the flow of water into the annulus through the lower perforation interval. In this case, all injected water entered the lower interval of perforation, but did not accept the upper interval. According to studies, the injectivity of the well was 286 m ³ / day at a wellhead pressure of 1.0 MPa.

To eliminate the annular flow of water in accordance with the proposed method, a suspension was pumped, including 1 ton of RK, 1.5 ton of organic flour, 100 kg of PAA, 50 m ^{3 of} oil. The concentration of components was, wt.%: RK - 2, organic flour - 3, PAA - 0.2. The fractions of rubber crumb of grades A, B and C in a ratio of 2: 2: 1 and the fraction of husk flour with sizes of 0.001-3.0 mm were used with a ratio of rubber crumb and flour of 1: 1.5. Suspension injection was stopped when the pressure at the mouth was 13.5 MPa. The suspension was squeezed with a volume of water equal to the volume of the well pipes. The well was washed with water and conducted research.

Geophysical studies have shown that there is no annular flow of water. The well receives 480 m ³ / day at a wellhead pressure of 8.0 MPa, and water flows into both layers: in the upper layer with a flow rate of 120 m ³ / day, in the lower layer with a flow rate of 360 m ³ / day. This means that the upper layer has "earned", that is, the injectivity of the upper layer has been restored without additional perforation work.

 Thus, as a result of the work carried out in accordance with the proposed method, the goal of eliminating the annular flow of water has been achieved. Water injected into the well began to flow as intended to both oil reservoirs to perform useful work to displace oil into production wells.

 The above examples show that the use of the proposed method will improve the efficiency of work to isolate the influx of water in producing wells and eliminate the unproductive flow of injected water in injection wells by creating a more tight reliable insulating screen on the ways of moving water.

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

 2. Tosunov E.M., Shatalov E.G. Isolation of formation water in fractured reservoirs. Oilfield development and reservoir physics. Proceedings of SevKav NIPI oil, vol. XI, Terrible, 1973, p. 296-301.

Claims (1)

A method of isolating water in fractured formations, including the injection of a suspension of rubber crumb in oil, characterized in that the suspension additionally contains organic flour and polymer in the following ratio, wt.%:
Rubber crumb - 2.0-15.0
Organic Flour - 1.0-20.0
Polymer - 0.1-0.5
Oil - Else

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