RU2378491C1 - Selective water influx insulation method - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: method involves subsequent pumping of acid solution and deposit-forming compound to the bed. After deposit-forming compound is pumped to the bed, there subsequently pumped is gel-forming compound and cement grout bank. As acid solution, there used is hydrolysis acid, as deposit-forming compound there used is composition on the basis of sodium bisulphate, which contains, wt %: sodium bisulphate 3-20; 5-20% solution of techincal lignosulphonate in water with mineralisation of up to 18 g/l 3-20; organic-silicon water-repellent agent is the rest, as gel-forming compound it contains polyacrylamide, sodium bichromate and technical lignosulphonate at the following component ratio, vol %: polyacrylamide - 0.5-1.0; sodium bichromate - 0.1-0.2; techincal lignosulphonate - 0.2-0.4; water - the rest. Cement grout can be modified with anionic surface-active substances plasticising agent addition with volume of 10-20%.

EFFECT: increasing water influx insulation efficiency in beds which are non-homogenous as to permeability.

2 cl, 3 tbl, 2 ex

Description

The invention relates to the oil industry, in particular to the selective isolation of water inflow in heterogeneous permeability formations.

There is a method of isolating the influx of formation water, including the sequential injection into the flooded layer of two substances that interact with the formation of an obstruction sludge, while alkaline waste from the purification of light oil products is taken as one substance, and 10-15% aqueous solution of calcium chloride as the other [ USSR AS No. 962595, 1982]. The method is used on homogeneous permeability layers to completely isolate one of the flooded layers.

The method is not technologically advanced under conditions of heterogeneous permeability of formations at a late stage of their development.

The closest technical solution, taken by us as a prototype, is a method of selective isolation of water inflow, including the sequential injection of an acid solution and a reagent that promotes sedimentation [US Patent No. 3396790, 1968].

The disadvantages of this method are the low efficiency and high cost of the treatments. In addition, the use of such a toxic reagent as ferric chloride during the implementation of the method worsens the environment and promotes the formation of insoluble compounds that reduce the efficiency of subsequent well operation.

The aim of the invention is to increase the efficiency of isolation of water inflow in heterogeneous permeability formations.

This goal is achieved by the fact that in the method of selective isolation of water inflow, which includes sequential injection of an acid solution and a sediment-forming composition into the formation, characterized in that after the injection of the sediment-forming composition, the gel-forming composition and the cement mortar rim are sequentially injected, while the hydrolysis is used as the acid solution sulfuric acid, as a precipitating composition using a composition based on sodium bisulfate, containing, wt.%:

sodium bisulfate 3-20 5-20% solution of technical lignosulfonate 3-20 in water with salinity up to 18 g / l organosilicon water-repellent rest

as a gelling composition contains polyacrylamide, sodium dichromate and technical lignosulfonate in the following ratio of components, vol.%:

polyacrylamide 0.5-1.0 sodium bichromate 0.1-0.2 technical lignosulfonate 0.2-0.4 water rest

and the cement mortar is modified by the addition of plasticizer APAV in the amount of 10-20%.

Analysis of known technical solutions showed that the use of precipitating agents containing lignosulfonate is known. However, the use of known compositions does not provide redistribution of filtration flows, which is achieved using a hydrophobizing, precipitating composition based on sodium bisulfate containing an organosilicon hydrophobizing substance, and technical lignosulfonate as a precipitating reagent. The injection of the indicated solutions into the formation ensures the following processes, sodium bisulfate interacts with the mineralized water and the additionally injected lignosulfonate to form a finely divided precipitate in the water-washed intervals.

The essence of the method, including the injection of a hydrophobizing sediment-forming composition, is as follows, a solution of sodium bisulfate containing an organosilicon hydrophobizing substance is pumped into the formation.

The injection of a hydrophobizing agent into the oil reservoir leads to a change in the wettability of the formation rock fluids and is accompanied by an increase in the phase permeability of the oil and a decrease in the phase permeability in water. In this case, the absolute permeability of the collector treated with a hydrophobizing substance remains practically unchanged. The use of organosilicon water-repellent agents for stimulating the formation is more effective, since they have higher stability in the reservoir conditions and do not lose their properties and ability to penetrate deep into the reservoir volume. For injection into the formation, it is possible to use organosilicon water-repellents with different chemical activity, capable of both reversibly and irreversibly adsorbing on the surface of the rock, which allows you to adjust the intensity of the impact on the formation and the depth of penetration of the reagent.

The following substances can be used as organosilicon hydrophobizing agents: GKZh-11, product 119-204, organosilicon emulsions of the SE type (manufactured by Dow Coming Gmbh, Belgium), other emulsions based on polymethylsiloxanes, etc. It is preferable to use domestic organosilicon emulsions based on polysiloxanes, as well as water-soluble silicone block copolymers.

When sodium bisulfate is dissolved in water, hydrolytic sulfuric acid and sodium sulfate are formed. During the interaction of dignosulfonate with reagents obtained by hydrolysis of sodium bisulfate in water, a coagulation process occurs leading to the enlargement of lignosulfonate molecules with the formation of globules. Globules precipitate in the form of microdispersion, the formation of which contributes to the achievement of the goal. The dissolved medium contains calcium ions Ca ^{+ 2} , which are present in mineralized water, which interact with sulfate ions SO ₄ ^2– to form a poorly soluble precipitate Ca SO ₄ (gypsum).

When the composition is filtered through the rock, in addition to mechanical adsorption, chemisorption adsorption of the high molecular weight fraction of lignosulfonates on the rock occurs.

The formation of dispersion occurs instantly, the precipitate formed is in solution in the form of a suspension in a finely dispersed state and does not cause technological difficulties in use. As microdispersion advances in the formation, the water-washed zones are completely isolated, while the pressure gradient increases in the isolated area, and zones of the low-permeability formation become accessible to the displacing agent. To increase the efficiency of the process, a gel-forming composition is injected, eliminating the erosion of the sediment-forming composition. To prevent a decrease in the strength of the gel-forming composition, it is strengthened by pumping a cement solution modified with a plasticizer rim.

The total volume of injected formulations is selected at the rate of 0.8-1.4 m ³ per 1 meter of reservoir capacity.

Thus, the proposed sequence of injection of reagents of a certain composition allows you to achieve the most effective isolation of permeable water-saturated sections of the reservoir.

In the proposed method for research, the following industrial multi-tonnage chemical products are used:

1. Hydrolytic sulfuric acid.

2. Water-repellent substances:

GKZH-11 TU 6-02-696-76

product 119-204 TU 6-02-1294-84

product 136-41 and emulsion compositions on it

based on GOST 10834-76

siloxane polymethyl fluid GOST 13032-77

3. Lignosulfonate technical KPB, KSSB TU 13-0281036-05-89

4. Water soluble polymers: DKS-ORP; PDA; FP 107, 207, 307.

5. Sodium dichromate GOST 2651-78

6. Cements GOST 1581-85

7. Plasticizer TU 18 RSFSR 780-78

mortars, surfactants

KBP ₅ lignosulfonates, KSSB - large-tonnage waste from the pulp and paper industry are non-toxic water-soluble powders that are anionic surfactants. KSSB - condensed sulphite-alcohol stillage, calcium salt of lignosulfonate; molecular weight 2000-100000 cu

Sodium bisulfate is a free-flowing crystalline substance; hygroscopic, soluble in water with the formation of sodium sulfate and hydrolysis of sulfuric acid.

The following are examples of laboratory studies of the proposed compounds.

Example 1. Investigated the process of sedimentation by the amount in grams of sediment from solutions of saline water containing 3-20% lignosulfonate and 3-20 wt.% Sodium bisulfate. Mineralization was 18 g / l, including salt content, g / l: calcium chloride 2.5; sodium chloride 15.5; magnesium chloride 0.07, this composition corresponds to the average salinity of the formation water of most deposits in Western Siberia. The results of the study of the process of sedimentation in mineralized water are summarized in table 1.

From the table it follows that the presence of Ca ²⁺ , Mg ²⁺ , Na ^{+ ions} in water positively affects the precipitation process. Weakly mineralized waters (produced water from Western Siberian deposits) increase the total mass of sediment in the solution, which during filtration leads to an increase in filtration resistance in highly permeable layers.

Table 1 The dependence of the sediment-forming properties of lignosulfonate on the concentration of sodium bisulfate in water with mineralization 1; 5 and 10 g / l at 20 ° C Experience The amount (BN) of sodium bisulfate,% The amount of sediment, g, released from 50 ml of the composition at various concentrations of the PBC,% 3 5 Mineralization of water, 1 g / l one 3 0.009 0.011 2 5 0.017 0.024 3 10 0,041 0,043 four twenty 0,088 0,092 5 23 0,089 0,092 Mineralization of water, 5 g / l 6 3 0.015 7 5 0,027 8 10 one 0.046 9 twenty 0,090 0.105 10 23 0,090 0.109 Mineralization of water, 10 g / l eleven 3 0.014 0.017 12 5 0,020 0,030 13 10 0,045 0,054 fourteen twenty 0,092 0,112 fifteen 23 0,094 0.116

continuation of table 1 Experience The amount (BN) of sodium bisulfate,% The amount of sediment, g, released from 50 ml of the composition at various concentrations of the PBC,% 10 twenty 25 Mineralization of water, 1 g / l one 3 0,025 0,050 0,061 2 5 0,042 0,062 0,074 3 10 0,047 0,088 0,099 four twenty 0.103 0.158 0.164 5 23 0.102 0.163 0.166 Mineralization of water, 5 g / l 6 3 0,028 0,054 0,065 7 5 0.051 0,079 0,101 8 10 0,070 0,132 0.144 9 twenty 0.0141 0.243 0.265 10 23 0.0152 0.274 0.282 Mineralization of water, 15 g / l eleven 3 0,033 0.056 0,069 12 5 0,057 0,089 0,101 13 10 0,095 0.151 0.162 fourteen twenty 0.183 0.294 0.316 fifteen 23 0.195 0,309 0.320

table 2 Dependence of the sediment-forming properties of lingosulfonate on the concentration of sodium bisulfate in water with a salinity of 1.5 and 18 g / l Experience The amount of sodium bisulfate,% The amount of precipitate, g, released from 10 ml of the composition at various concentrations of lignosulfonate in water with a salinity of 18 g / l 3 5 10 one one 0.004 0.004 0.012 0.012 0.015 0.018 2 3 0.013 0.016 0,020 0.024 0.024 0,025 3 5 0.018 0,022 0,038 0,042 0,044 0,048 four 7 0,036 0,039 0,043 0,054 0,062 0,067 5 10 0,045 0.056 0,067 0,069 0,083 0,089 6 13 0,070 0,080 0,089 0,098 0,096 0,101 7 fifteen 0,079 0,088 0.102 0,110 0.107 0,112 8 eighteen 0,085 0.105 0.115 0,120 0.125 0.130 9 twenty 0,095 0.125 0.117 0.138 0.170 0.185 10 21 0,092 0.115 0.109 0.115 0.143 0.165

Continuation of table 2 The amount of precipitate, g, released from 10 ml of the composition at various concentrations of lignosulfonate in water with a salinity of 18 g / l fifteen twenty 25 20 ° C 60 ° C 20 ° C 60 ° C 20 ° C 60 ° C 0,032 0,045 0,048 0,054 0.056 0,067 0.049 0,069 0,063 0,075 0,071 0,080 0,097 0,112 0.105 0.115 0.114 0.130 0.109 0,120 0.141 0.160 0.157 0.168 0.127 0.165 0.167 0.185 0.177 0.225 0.144 0.189 0.175 0.229 0.190 0.257 0.159 0.205 0.189 0.239 0.201 0.268 0.241 0.251 0.248 0.364 0.282 0.275 0.275 0.421 0.364 0.435 0.415 0.495 0.335 0.388 0.353 0.390 0.402 0.465

Example 2. Laboratory tests were carried out according to the proposed method on linear models of a layered heterogeneous formation in accordance with the methodology for determining the coefficients of oil displacement by water under laboratory conditions (OST 38-195-86). The reservoir model consists of two parallel-connected columns with thermal shirts, 30 cm long, 1.4 cm in diameter. The columns are filled with a disintegrated core of the Samotlor field with a grain size in the first column of 0.2-0.3 mm, in the second - 0.07-0 , 14 mm. The columns are evacuated for 2 hours, then saturated with mineralized water with a total salt content of 14 g / l. At the entrance to the model, the pressure of fluid injection was maintained, which ensured a filtration rate in the most permeable layer that corresponded to the real reservoir (no more than 1 m / day). The air permeability of one layer is 8.5 μm ² , the second - 30.4 μm ² .

The water in the columns was replaced by three pore volumes of Samotlor oil with a viscosity at 20 ° C of 1.9 MPa · s. To create residual oil saturation, the oil was displaced by formation water to the maximum water cut of the outgoing liquid samples in the least permeable interlayer. Then, through the model, various volumes of the rims of the reagents needed to equalize the filtration rates in both columns were successively filtered, after which at least two pore volumes of formation water were filtered.

Table 3 shows the volumes of reagent pumping through reservoir models of various permeabilities. Each row in table 3 shows what the total volume of liquid is pumped through the interlayer of low permeability for a fixed volume of pumping reagents through the interlayer of high permeability. For example, when water, reagents according to the prototype and the proposed reagents are injected into the model at the moment when 2 pore volumes of liquid are pumped through the interlayer of high permeability, respectively, through the interlayer of low permeability: 0.18; 0.55; 0.72 pore volumes of fluid. The presented results clearly show that the change and redistribution of filtration flows in the model of the proposed method allows to increase the coverage of the reservoir and increase oil recovery by 25-35%.

Table 3 Change in filtration flows for pumping reagents through a model of a layered heterogeneous formation Example Pumping liquids through interbeds of high permeability, vol. since Pumping liquids through interbeds of high permeability, vol. since Water According to the prototype According to MFR one 1.00 0.10 0.38 0,07 2 1.25 0.12 0.39 0.20 3 1,50 0.14 0.43 0.36 four 1.75 0.16 0.45 0.63 5 2.00 0.18 0.55 0.72 6 2.25 0.20 0.67 0.88 7 2,50 0.22 0.71 1.09

The proposed method is implemented as follows. After applying the development method by injecting water, solutions of sodium bisulfate mixed with water repellent and lignosulfonate with a total volume of 0.2-0.5 pore volumes of the formation are sequentially irrigated with a reservoir composition that is heterogeneous in reservoir composition. The exact size of the rim is calculated based on the specific geological and physical conditions of the deposits.

During the movement of solutions throughout the formation as a result of coagulation and complexation processes, microdispersed sedimentation occurs, and the permeability of the formation decreases. The decrease in permeability occurs primarily where filtration is stronger, more mass transfer. This leads to equalization of the filtration rates of water-washed, highly permeable and low-permeability zones. After injection of the proposed solutions, a gel-forming composition is injected into the formation, and then the rim of the cement mortar.

The method is economical, environmentally friendly, the components used are powdery, convenient for transportation, and are not subject to the negative influence of sharp temperature fluctuations characteristic of Western Siberia. The increase in additional oil production due to the application of this method will be 4-7 thousand tons for each experimental plot.

Claims (2)

1. The method of selective isolation of water inflow, including sequential injection of an acid solution and sediment-forming composition into the formation, characterized in that after injection of the sediment-forming composition, the gel-forming composition and the cement mortar rim are successively pumped, while hydrolysis sulfuric acid is used as the acid solution, sediment-forming composition using a composition based on sodium bisulfate containing, wt.%:
sodium bisulfate 3-20 5-20% solution of technical lignosulfonate in water with salinity up to 18 g / l 3-20 organosilicon water-repellent rest,
as a gelling composition contains polyacrylamide, sodium dichromate and technical lignosulfonate in the following ratio of components, vol.%:
polyacrylamide 0.5-1.0 sodium bichromate 0.1-0.2 technical lignosulfonate 0.2-0.4 water rest 2. The method according to claim 1, characterized in that the cement mortar is modified by the addition of plasticizer APAV in the amount of 10-20%.