RU2112137C1 - Gel-forming composition to control flooding front of productive oil pool - Google Patents

Abstract

FIELD: oil production. SUBSTANCE: gel-forming composition is meant for increase of oil recovery from pools by pumping it both into injection holes to control flooding process in pools inhomogeneous in penetration and into production wells during performance of water insulation operations. Given composition includes oxyethylcellulose, iron chloride, bonding agent and water. Novelty of invention consists in usage of urotropine as bonding agent and water of chlorine- calcium type with mineralization from 0.001 to 180.0 g/l and density 1.000-1.125 g/cu.cm in the capacity of solvent with following proportion of components, per cent by mass: oxyethylcellulose 00.5-1.0; iron chloride 0.03-1.5; urotropine 0.05-0.5; water of chlorine-calcium type with mineralization from 0.001 to 180.0 g/l and density 1.000- 1.125 g/cu.cm being the balance. Usage of gel-forming composition based on oxyethylcellulose, urotropine and iron chloride to control flooding of productive pool and isolation of water influxes in production wells makes it possible to rise coefficient of embracing of pool by flooding which leads in its turn to increased oil recovery from pool. EFFECT: increased oil recovery.

Description

 The invention relates to the field of the oil industry, namely to gel-forming compositions for regulating the development of oil fields.

Known composition "Polymer drilling fluid" containing cellulose ether, inorganic salt of trivalent chromium and water [1]. After mixing these components, a gel is formed at pH = 10-11. The main disadvantage of this composition is that the obtained gel has low strength properties (shear strength of the gel at a shear rate of 1.5 s ^-1 less than 100 Pa). In addition, chromium salts are toxic.

 The closest technical solution to the proposed one is a gel-forming composition for regulating the waterflooding front of a reservoir [2], containing hydroxyethyl cellulose 0.5-1.0%, hydroquinone 0.05-0.1%, ferric chloride 0.05-0.1% , alkali in an amount providing a pH of the composition equal to 6-8. The disadvantage of the composition is the low efficiency of the composition due to the insufficiently high strength characteristics of the gel.

 In addition, known gel-forming compositions contain only fresh water as a solvent, and gel formation does not occur in calcium-chloride waters.

 The objective of the invention is to increase the strength of the gel.

The problem is achieved in that the gel-forming composition for regulating the waterflooding front of the reservoir contains hydroxyethyl cellulose, ferric chloride, a crosslinking agent and a solvent (water). What is new is that it contains urotropin as a crosslinking agent, and calcium chloride water with a mineralization of 0.001-180, g / l, with a density of 1.00-1.125 g / cm ³ , in the following ratio of components, wt. %:
Oxyethyl cellulose - 0.5-1.0
Ferric Chloride - 0.03-1.5
Urotropin - 0.05-0.5
Calcium chloride type water with a salinity of 0.001 to 180 g / l with a density of 1.00 - 1.125 g / cm ³ - Else
In the proposed composition, due to the presence of a crosslinking agent of urotropin, crosslinking of hydroxyethyl units of hydroxyethyl cellulose molecules occurs in both fresh and mineralized waters. In addition, a gel is formed in which the ions of salts included in the composition of calcium chloride water (which is a complex of salts based on CI ^- , SO ions $\genfrac{}{}{0ex}{}{\text{2-}}{\text{4}}$ HCO $\genfrac{}{}{0ex}{}{\text{-}}{\text{3}}$ , S ^2- , Ca ⁺² , Mg ⁺² , K ⁺ , Na ⁺ , Fe ⁺² , Fe ⁺³ ), has high strength characteristics. At the same time, the process of preparing the composition is greatly simplified, because mineralized wastewater used in waterflooding.

 As a result of the analysis, we can conclude that the claimed technical solution meets the criteria of the invention "significant differences", since the claimed technical solution has, in addition to the known essential features, new features (the compositions contain, as a crosslinking agent, urotropine and calcium chloride water with a mineralization of 0.001 -180 g / l), the ratio of the components in the composition that are associated with a new property achieved by use - the resulting gels have increased strength properties.

 The substantiation of the essential features of the claimed technical solution was carried out by studying the kinetics of gelation of the composition prepared in various waters. A gelling composition is prepared as follows.

 With stirring, hydroxyethyl cellulose is dissolved in water (fresh or mineralized) for 1.0-1.5 hours. Urotropin is added to the resulting solution and dissolved with stirring for 10-15 minutes, then ferric chloride is added and dissolved with stirring for 10- 15 minutes.

Domestic-produced hydroxyethyl cellulose (TU 6-55-221-1407-95) and Tyloze EHH brand hydroxyethyl cellulose (Germany) were used as hydroxyethyl cellulose, ferric chloride was used as ferric chloride (GOST III-59-76), and urotropin was used as a cross-linking agent. , as a solvent - fresh water or mineralized wastewater used for flooding productive formations in oil fields. Wastewater is potassium chloride water with a wide range of total salinity, as it is prepared by mixing fresh Devonian potassium chloride water. The studies took into account the total content of salts in the water (total salinity of the water). The kinetics of gelation was studied on a Reotest-2 rotational viscometer by measuring the effective viscosity at a shear rate of 0.5 s ^-1 at certain time intervals. The research results are presented in table. 1.

 From the table. 1 it follows that the gel-forming composition has the following optimal composition: wt.% Hydroxyethyl cellulose 0.5-1.0, urotropin 0.05-0.5, ferric chloride 0.03-1.5, calcium chloride water with a salinity of 0.001-180 g / l the rest (compositions 1, 2, 5-11, 18-21, 24, 25, 30-36, 46-49, 53-57).

 Such a composition has an optimal gelation period of 1 to 5 days.

 With the exclusion from the composition of one of the components - urotropine or ferric chloride (compositions 15, 16, 26, 27) the composition does not have the ability to gel. Therefore, the joint presence of urotropine and ferric chloride in the composition is necessary.

 When the content of urotropine in the composition is less than 0.05 wt.%, The composition does not have the ability to gel (composition 17). An increase in the content of urotropine in the composition of more than 0.5 wt.% Is impractical, since it does not lead to an improvement in the quality of the resulting gels (composition 59).

 A composition with a content of ferric chloride of less than 0.03 wt.% Does not have the ability to gel, and with a content of more than 1.5% does not lead to an improvement in the quality of the resulting gels (compositions 3, 4, 29, 43).

 A composition with a hydroxyethyl cellulose content of less than 0.5 wt.% Does not have the ability to gel (compositions 38, 50) or has low viscosity parameters (compositions 12, 37), and a composition with a hydroxyethyl cellulose content of more than 1.0 wt.% Is not practical point of view, as well as from a technological point of view, since it has a large initial viscosity (viscosity of a 1.1% hydroxyethyl cellulose solution is more than 0.5-Pa • s) (compositions 52, 58). The composition has an optimal salt content from 0.001 to 180 g / l (formulations 1, 2, 5-11, 18-21, 24, 25, 30-36, 46-49, 53-57).

 Compositions prepared on water with a salinity of more than 180 g / l form gels with high strength, however, they have a short induction period of gelation (formulations 64-67).

 To compare the gelation kinetics, the table shows the compositions of the gel-forming composition based on hydroxyethyl cellulose, ferric chloride, hydroquinone and water, described in the known composition (compositions 41, 42, 62, 63).

 Compositions prepared on calcium chloride water with a salinity of 0.001-180 g / l, with a content of hydroxyethyl cellulose less than 0.5%, ferric chloride less than 0.03%, urotropine less than 0.05%, do not have the ability to gel (compositions 28, 60 )

 Compositions prepared on calcium chloride water with a salinity of 0.001-180 g / l, with an oxyethyl cellulose content of more than 1.0%, ferric chloride more than 1.5%, urotropine more than 0.5%, form gels with high strength, but they have induction the gelation period is not more than 27 hours, which is clearly not enough for their successful application in the field to regulate the front to waterflooding of oil reservoirs (compositions 40, 61).

Studies of the strength properties of the gels were carried out on a Reotest-2 viscometer. Method for measuring shear strength: a gel-forming composition was poured into a cylinder measuring device of a viscometer, the composition was left to gel (for 3 days), then the shear strength of the gel was measured at a shear rate of 1.5 s ^-1 /
The research results are presented in table. 2.

 From the table. 2 it can be seen that compositions on the calcium chloride type water with a mineralization of 0.001-180 g / l form gels with high strength characteristics (gel strength 120-600 Pa). For comparison, experiments were carried out with a composition - analogue (A.S. 1587986). The measurement results show that the gel formed from the analogue composition has insignificant strength characteristics (80-100 Pa).

 The use of a gel-forming composition based on hydroxyethyl cellulose, urotropine and ferric chloride to regulate water flooding of the reservoir and isolate water inflows in production wells allows increasing the coverage factor of the reservoir by water flooding, which in turn will provide enhanced oil recovery.

Claims (1)

A gel-forming composition for regulating the waterflooding front of a reservoir containing hydroxyethyl cellulose, ferric chloride, a crosslinking agent and a solvent, characterized in that it contains urotropin as a crosslinking agent and calcium chloride water with a salinity of from 0.001 to 180 g / l s with a density of 1.00 - 1.125 g / cm ³ in the following ratio of components, wt.%:
Oxyethyl cellulose - 0.5 - 1.0
Ferric Chloride - 0.03 - 1.5
Urotropin - 0.05 - 0.5
Calcium chloride type water with a salinity of from 0.001 to 180 g / l with a density of 1.00 - 1.025 g / cm ³ - The rest

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