RU2347897C1 - Method of controlling profile log of injection well and restricting water influx in production well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is applicable to the oil and gas industry and particularly to biotechnological methods of developing water-flooded oil reservoirs and can become widely used to enhance oil recovery in heterogeneously permeable reservoirs. Technical result is done by improving flow properties of a gelling compound, strengthening gel based on such a compound, increasing stability over time, and decreasing gelling time. The method of controlling the profile log of an injection well and restricting the water influx in a production well includes injecting a gelling compound consisting of the following elements, wt %: xanthan - 0.05-0.5, polyacrylamide or cellulose ester - 0.025-2.0, alkali - 0.005-0.1, bactericide - 0.03-0.3, chromium acetate - 0.005-0.2, water - balance. The xanthan to polyacrylamide or cellulose ester ratio varies from 1:0.25 to 1:10 and alkali solution slug is injected both before and after injecting a gelling compound into the reservoir. The invention is further explicated in subsidiary claims.

EFFECT: enhanced oil recovery enhanced oil recovery as a result of improving water isolation with a solid waterproof screen in heterogeneous reservoirs and adding oil-saturated zones previously not in use to the development process and water-flooding them subsequently.

5 cl, 3 tbl, 1 dwg

Description

The proposal relates to the oil industry, in particular, to biotechnological methods for developing an irrigated oil reservoir, and can be used to increase oil recovery of heterogeneous permeability formations.

In the process of developing oil deposits by water flooding, one of the main methods for increasing oil recovery is the physicochemical methods for regulating the filtration water flows. Under various geological and physical conditions of the formation, an increase in the production of flooded heterogeneous permeability productive formations by increasing the coverage of the formation by flooding is achieved by preliminary complete or partial blocking of the highly permeable flooded zones of the reservoir and the subsequent change in the direction and redistribution of the filtration flows with the involvement of previously unexposed low-permeable productive ones in the development formation zones. To do this, use viscoelastic compositions, gels based on polymers, alkaline-polymer compositions, etc. One of the most important indicators of the successful development of oil deposits in various geological and physical conditions of the formation is the injection of a gel-forming composition, which is distinguished by manufacturability, high and stable rheological properties.

A known method of regulating the development of oil fields, including the injection of an aqueous solution of an anionic polymer of 0.01-5.0%, salts of the polyvalent cation of 0.003-0.2% (AS No. 1645472, IPC EV 43/22, publ. BI No. 16 , 1991). The disadvantage of this method is the low efficiency due to the low waterproofing properties of an aqueous polymer solution.

A known method of regulating the injectivity profile of an oil deposit, including injecting into the formation a composition based on a polysaccharide and a bactericidal additive (patent SU No. 1001866, IPC ЕВВ 43/22, publ. BI No. 8, 1983). As a polysaccharide solution, a culture fluid filtrate of the Xanthomonas campestris microorganism producing the polysaccharide is used, and a bactericidal agent is used as an additive, in the following quantitative ratio by weight: culture fluid filtrate 100, bactericidal agent 0.001-0.2. Sodium azide, a mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one are used as a bactericidal agent. However, the method is not effective enough due to the low strength of the crosslinked polymer.

A known method of regulating the injectivity of an oil deposit, including injecting into the formation a gel-forming composition based on a biopolysaccharide, a compound of a polyvalent metal, alkali and water in the following ratio of components wt.%: Biopolysaccharide 0.1-0.4, polyvalent metal compound 0.001-0.1, alkali 0.0001-0.05, water - the rest (US patent No. 4977960, IPC С09К 8/08, 8/90, 8/588, ЕВВ 43/22, publ. 12/18/1990). As the biopolysaccharide, xanthan is used, produced by microorganisms of the Xanthomonas type. Polyvalent metal compounds are used from the group of trivalent phosphorus, scandium, titanium, vanadium, chromium, manganese, iron, etc. or mixtures thereof, which contribute to the rapid formation of a gel. Potassium, calcium, sodium hydroxide are used as alkali. The method allows you to adjust the injectivity profile of a heterogeneous formation having a low pH of the medium. Xanthan is a slowly soluble reagent, which leads to an increase in the induction period of gelation. In addition, due to the lack of bactericide in the known composition, the resulting gel will undergo rapid biodegradation, therefore, this method is suitable for short-term isolation of waterlogged layers. As a result, oil recovery remains low.

The technical objective of the proposal is to increase oil recovery by increasing the efficiency of water isolation in heterogeneous formations by creating a durable waterproofing screen and connecting oil-saturated, previously unused zones to the development by subsequent flooding, by improving the rheological properties of the gel-forming composition, increasing the strength of the gel based on it, and increasing stability during time, reduce gelation time. The method also allows you to expand the technical means that contribute to the regulation of the injectivity profile of the injection well and the limitation of water inflow in the producing well.

The technical problem is solved by controlling the injectivity profile of the injection well and limiting water inflow in the producing well, including injecting a gel-forming composition based on xanthan, chromium acetate, alkali and water into the formation.

New is that the gelling composition additionally contains polyacrylamide or cellulose ether and a bactericide in the following ratio of components wt.%: Xanthan 0.05-0.5, polyacrylamide or cellulose ether 0.025-2.0, alkali 0.005-0.1, bactericide 0.03-0.3, chromium acetate 0.005-0.2, water - the rest, the ratio of xanthan gum to polyacrylamide or cellulose ether is from 1: 0.25 to 1:10, and before and after injection of the gelling composition into the formation is pumped rims of alkaline solution.

It is also new that, for example, a 40% formaldehyde solution, or the SNPCH-1002 bactericide, or the SNPCH-1004 bactericide, or the SNPCH-1200 bactericide, or the FLEK IK-200 bactericide, are used as a bactericide.

Also new is that sodium or potassium hydroxide is used as alkali.

It is also new that before and after injection of the gelling composition, an alkaline solution is pumped with the following ratio of components wt.%: Alkali 0.01-0.1, water with a density of 1.00 g / cm ³ - the rest.

Also new is that the ratio of injected rims of the alkaline solution, gelling composition and alkaline solution is from 1: 5: 1 to 1: 100: 1, respectively.

The injection volume of the rims of alkaline solutions and gel-forming composition depends on the physicochemical and geological features of the formation, and can range from several tens to several hundred cubic meters.

The injection of the first rim of the alkaline solution, including fresh water and alkali, acts as a buffer that blocks the inhibitory effect of excess salts on the gelation process, precipitating them (primarily Ca ²⁺ and Mg ²⁺ ), and creates an alkaline environment in the pore space, providing the formation more durable gel in a shorter time.

The introduction of a bactericide in the solution of the composition allows to increase the duration of preservation of the properties of both the injected solution and the resulting gel under reservoir conditions. The introduction of alkali can reduce the gelation time and increase the strength of the resulting gel. When polyacrylamide or cellulose ether is introduced into the xanthan gum in a ratio of 1: 0.25 to 1:10, a crosslinked structure of the elastic gel is formed. Crosslinking occurs between adjacent xanthan chains on the carboxyl groups of mannose, polyacrylamide or cellulose ether and through metal ions of variable valency, such as chromium.

The complexation of xanthan gum and polyacrylamide or cellulose ether with chromium depends on the pH of the medium. The tribasic hydroxyl complex of chromium is formed at a pH of 8.5-9.0. Improving the rheological properties of the gelling composition, increasing stability over time, reducing the time of gelation is ensured by the appropriate ratio of components, selected experimentally. The second rim of the alkaline solution acts as an additional buffer and at the same time contributes to the hardening of the waterproofing screen, reinforcing the gel at the interface. The ratio of injected rims of the alkaline solution, gelling composition and alkaline solution is from 1: 5: 1 to 1: 100: 1, respectively, and depends on the injectivity of the well. As a result, the efficiency of water isolation in heterogeneous reservoirs is increased and oil-saturated, previously unused zones are subsequently connected to the development by subsequent flooding, and, consequently, the oil recovery is also increased. The method also allows you to expand the technical means that contribute to the regulation of the injectivity profile of the injection well and the limitation of water inflow in the producing well.

The analysis of patent and scientific and technical literature allowed us to conclude that there are no technical solutions containing essential features of the proposed method that perform a similar task, therefore, the proposed method meets the criteria of "novelty" and "inventive step".

The following reagents are used to prepare the formulations:

- Xanthan is a polymer of imported or domestic production according to TU 2458-002-50635131-2003;

- cellulose ether, for example, hydroxyethyl cellulose (OEC) of the Sulfacell brand according to TU 2231-013-32957739-01 of JSC "Policell", Vladimir, Policell SK-1, grade 600;

- polyacrylamide (PAA) - domestic according to TU 6-16-2531-81, TU 6-01-1049-81, TU 14-6-121-75, imported with a molecular weight of (3-15) -10 ⁶ , for example, Alkoflood 935, Alko-flood 1175;

- chromium acetate according to TU 6-0200209912-7000, tanning agent of the brand “Aqueous solution of chromium acetate” TU 2499-001-50635131-00;

- alkali - sodium or potassium hydroxide (GOST 2263-79);

- as a bactericide, bactericide SNPCH-1002 according to TU 39-1412-89, or bactericide SNPCH-1004 according to TU 39-12966038-OP-001-92, or bactericide SNPCH-1200 according to TU 2458-294-05765670-2003, or formalin technical GOST 1625-89, or FLEK IK-200 bactericide according to TU 2483-015-24084384-2005.

The drawing shows the dependence of gelation time on pH in compositions with a mass fraction of%: xanthan 0.2, PAA 0.025, alkali 0.08-0.1, chromium acetate 0.05, bactericide 0.2. The dependence of the pH of the composition and gelation time are shown in table 1.

Table 1 PH Gelation time, h 7.83 80 8 72 8.99 48 9.5 36 10.69 0.25

In laboratory conditions, gel formation time, strength and viscosity of gel-forming compositions were determined by standard methods. The results of the study of the influence of the mass ratio of the components of the proposed and known compositions are shown in table 2. The results indicate improved rheological properties of the gel-forming composition.

table 2 Experience Number No. Gel-forming composition, wt.% Initial viscosity, MPa · s The strength of the gel, PA Gelation time, h Xanthan PAA OEC Alkali Bactericide Chromium acetate Water NaOH Koh Four raspberries SNPCH-1002 one 0.05 0.1 - 0.008 0.2 0.05 99,592 7.6 130 48 2 0.1 0.1 - 0.008 0.2 0.05 99,542 10.0 180 96 3 0.2 0.1 - 0.008 0.2 0.05 99,442 13.0 260 72 four 0.5 - 0.5 0.008 0.2 0.05 98,742 159.0 780 48-72 5 0.6 - 0.5 0.008 0.2 0.05 98,642 186.0 990 48-72 6 0.2 0.005 - 0.01 0.3 0.05 99,435 6.0 80 168 7 0.2 0.05 - 0.01 - 0.2 - 0.05 99.49 12.0 105 72 8 0.2 0.1 - 0.01 0.3 0.05 99.34 13.0 280 48 9 0.2 0.3 - 0.01 0.3 0.05 99.14 16,0 540 48 10 0.2 1,0 - 0.01 0.3 0.05 98.44 145.2 920 72 eleven 0.2 - 0.05 0.01 0.3 0.05 99.39 16.7 150 72 12 0.2 - 0.75 0.01 0.3 0.05 98.69 83.0 283 48 13 0.2 - 1,0 0.01 0.3 0.05 98.44 116.0 310 72 fourteen 0.2 - 2.0 0.01 0.3 0.05 97.44 927.0 - weak gel fifteen 0.2 - 2.5 0.01 0.3 0.05 96.94 1133.0 - no gel 16 0.2 0.1 - 0.005 0.2 0.05 99,445 12.0 210 96-120 17 0.2 0.1 - 0.002 0.2 0.05 99,448 12.6 228 96.0 eighteen 0.2 0.1 - 0.005 0.2 0.05 99,445 13.0 240 48-72 19 0.2 - 0.75 0.01 0.2 0.05 98.79 83.0 290 48-72 twenty 0.2 0.1 - 0.15 0.2 0.05 99.30 13,4 390 0.15-0.5 21 0.2 0.1 - 0.1 0.2 0.05 99.35 13.3 378 0.5-1.0 22 0.2 - 0.5 0.15 0.2 0.05 98.90 50,0 220 1,0 23 0.2 0.1 - 0.008 - 0.05 99,642 13,2 340 72 24 0.2 0.1 - 0.008 0.02 0.05 99,622 13.0 347 72 25 0.2 - 0.75 0.008 0,03 0.05 98,962 76.0 320 48-72 26 0.2 - 0.75 0.008 0.1 0.05 98,892 100.0 290 48-72 27 0.2 0.1 - 0.008 0.3 0.05 99,342 13,2 340 48-72

Continuation of table 2 Experience Number No. Composition, mass fraction,% Initial viscosity, MPa · s The strength of the gel, PA Gelation time, h Xanthan PAA OEC Alkali Bactericide Chromium acetate Water NaOH Koh Four raspberries SNPCH-1002 28 0.2 0.1 - 0.008 0.35 0.05 99,292 13.3 280 48 29th 0.2 0.1 - - 0.008 0.2 0.005 99,487 13,2 - no gel thirty 0.2 0.1 - 0.008 0.2 0.01 98,482 13,2 160 72 31 0.2 - 0.75 0.008 0.2 0.1 98,742 100.6 447 96 32 0.2 0.1 - - 0.008 0.2 0.2 99,292 13,2 504 72 33 0.2 0.1 - 0.008 0.2 0.25 99,242 13,2 529 72 34 0.2 - - - 0.2 0.05 99.55 7.6 76 168-192 35 0.2 - - 0.008 0.2 0.05 99,542 7.1 144 120-144 36 0.2 - - 0.008 0.2 - 99,592 8.0 - no gel 37 0.4 - - 0.001 - 0.05 99,549 76.0 291 120 38 0.4 - - 0.005 - 0.05 99,545 88.0 420 120 39 - 0.1 - - - 0.05 99.85 4.0 fragile gel 168 SNPCH -1200 40 0.2 - - - - - 0.015 0.05 99,735 7.5 162 168-192 41 0.05 0,025 - 0.005 - - 0,03 0.005 99,885 7.8 gel clots 96 42 0.2 - 2.0 - 0.1 - 0.15 0.05 97.50 7.7 268 84 43 0.5 0.1 - 0.008 - - 0.3 0.2 99,892 13.3 518 72 SNPCH -1004 44 0.2 - - - - - 0.015 0.05 99,735 8.6 140 168-192 45 0.05 0,025 - 0.005 - - 0,03 0.005 99,885 8.9 gel clots 96 46 0.2 - 2.0 - 0.008 - 0.15 0.05 97,592 8.7 248 84 47 0.5 0.1 - 0.1 - - 0.3 0.2 98.8 13.6 480 72

Continuation of table 2 Experience Number No. Composition, mass fraction,% Initial viscosity, MPa · s The strength of the gel, PA Gelation time, h Xanthan PAA OEC Alkali Bactericide Chromium acetate Water NaOH Koh Four raspberries FLEK IR-200 48 0.2 - - - - - 0.015 0.05 99,735 8.6 160 168-192 49 0.05 0,025 - 0.005 - - 0,03 0.005 99,885 8.9 gel clots 96 fifty 0.2 - 2.0 - 0.008 - 0.15 0.05 97,592 8.7 265 84 51 0.5 0.1 - 0.1 - - 0.3 0.2 98.8 13.6 437 72

In order to determine the optimal concentration and sequence of injection of rims, to evaluate the effectiveness of increasing oil recovery in heterogeneous formations, tests were performed in laboratory conditions. Tests of the known and proposed methods were carried out on linear reservoir models filled with a sand mixture (50 cm long, 6.4 cm ² cross-sectional area). By selecting the size of quartz sand grains, the necessary channel permeability of linear reservoir models was created.

The studies were carried out in the following sequence:

- after evacuation, the model was successively saturated with waste water and oil from the Romashkinskoye field. Characteristics of the used oil: density 0.814-0.896 g / cm ³ , viscosity from 7 to 45 MPa · s. The following parameters were determined: pore volume, initial water saturation, water permeability and oil saturation;

- oil was displaced by wastewater with a density of 1.07 g / cm ³ with measurement of oil and water volumes at the outlet. Primary water displacement was carried out to a total water cut of oil at a yield of 100%;

- a gel-forming composition is prepared by successively mixing and mixing the components: first, an alkaline reagent NaOH or KOH is added to water with a density of 1.00 g / cm ³ and mixed, and then bactericide, xanthan, PAA or OEC, chromium acetate are introduced sequentially.

- the rim of the alkaline solution, the second rim of the gel-like composition and the third rim of the alkaline solution were sequentially pumped into the model with a volume ratio of 1: (5-100): 1. The injection pressure was recorded. The reservoir model was squeezed with waste water with a density of 1.07 g / cm ³ . The model was left at the time of reaction and completion of the process of interaction with the breed;

- after which the oil was replaced by wastewater by injecting water by measuring the output of oil and water.

Thus, simulated the process of starting wells and oil production from the reservoir after the implementation of the proposed method.

The analysis of the research results was carried out on the example of the main filtration parameter - residual resistance factor (OFS) according to table 3, which characterizes the filtration resistance during water filtration after injection of rims compared to the initial filtration resistance during filtration of water before injection of rims.

As can be seen from table 3, OFS of the proposed method for regulating the injectivity profile of the injection well and limiting the water inflow in the producing well increases from 31 to 79.

Thus, the proposed method for regulating the injectivity profile of the injection well and limiting water inflow in the producing well can increase the residual resistance factor while maintaining the permeability of low permeability layers and, therefore, increase oil recovery of heterogeneous permeability formations of flooded fields having highly permeable washed zones with low oil displacement of the formations by changing and aligning the filtration flows. The method is simple to implement, technologically advanced. No additional costs for the arrangement of fisheries are required.

The gel-forming composition in the proposed method is not susceptible to syneresis in the reservoir, as a result of which it has a high duration of action.

The application of the proposed method allows to increase oil recovery by increasing the efficiency of water isolation in heterogeneous reservoirs by creating a durable waterproofing screen and connecting oil-saturated, previously unused zones to the development by subsequent flooding, by improving the rheological properties of the gel-forming composition, increasing the strength of the gel based on it, and increasing stability during time, reduce gelation time. The method also allows you to expand the technical means that contribute to the regulation of the injectivity profile of the injection well and the limitation of water inflow in the producing well.

Table 3 Experience number The initial permeability, μm ² The ratio of components, wt.% Technological mode of injection The final permeability, μm ² Residual Resistance Factor, R _ost xanthan PAA OEC alkali bactericide chromium acetate water rim number ratio of rim volumes technological exposure, days NaOH Koh formalin SNPCH -1002 one 0.63 - - - 0.01 - - - - 99,99 First 1: 5: 1 3 0.008 79 0.2 0.3 - 0.01 - 0.2 - 0.05 99.24 Second - - - 0.01 - - - - 99,99 Third 2 1,1 - - - 0.1 - - - - 99.9 First 1: 10: 1 3 0.015 73 0.2 - 0.05 - 0.01 0.3 - 0.05 97.4 Second - - - 0.01 - - - - 99,99 Third 3 1,2 - - - 0.05 - - - - 99.95 First 1: 20: 1 one 0.018 67 0.2 0.1 - - 0.1 - 0.2 0.05 99.35 Second - - - 0.1 - - - - 99.9 Third four 1.28 - - - 0.05 - - - - 99.95 First 1: 40: 1 3 0,027 44 0.2 - 0.75 0.05 - 0.3 - 0.05 98.65 Second - - - 0.05 - - - - 99.95 Third 5 3.42 - - - 0.01 - - - - 99,99 First 1: 50: 1 one 0.106 32 0.2 0.1 - 0.1 - - 0.3 0.05 99.25 Second - - - 0.1 - - - - 99.9 Third 6 7.1 - - - 0.01 - - - - 99,99 First 1: 100: 1 3 0.23 31 0.2 - 1,0 0.01 - 0.2 - 0.05 98.54 Second - - - 0.01 - - - - 99,99 Third 7 1,0 0.2 - - 0.001 - - - 0.05 99,749 - - 7 0,076 13 8 1.9 0.2 - - 0.005 - - - 0.05 99,745 - - 7 0.19 10

Claims (5)

1. The method of regulating the injectivity profile of the injection well and limiting water inflow in the producing well, comprising injecting a gel-forming composition based on xanthan, chromium acetate, alkali and water into the formation, characterized in that the gel-forming composition additionally contains polyacrylamide or cellulose ether and a bactericide in the following ratio of components , wt.%: xanthan 0.05-0.5, polyacrylamide or cellulose ether 0.025-2.0, alkali 0.005-0.1, bactericide 0.03-0.3, chromium acetate 0.005-0.2, water - the rest, the ratio of xanthan to polyacrylamide or to cellulose ether is from 1: 0.25 to 1:10, and before and after injection of the gelling composition, the edges of the alkaline solution are pumped into the formation. 2. The method according to claim 1, characterized in that, for example, a 40% solution of formaldehyde or a bactericide SNPCH-1002, or a bactericide SNPCH-1004, or a bactericide SNPCH-1200, or a bactericide FLEK IK-200, are used as a bactericide. 3. The method according to claim 1, characterized in that the alkali is sodium or potassium hydroxide. 4. The method according to claim 1, characterized in that before and after injection of the gelling composition, an alkaline solution is pumped in the following ratio of components, wt.%: Alkali 0.01-0.1, water with a density of 1.00 g / cm ³ - the rest . 5. The method according to claim 1, characterized in that the ratio of the injected rims of the alkaline solution, gelling composition and alkaline solution is from 1: 5: 1 to 1: 100: 1, respectively.