RU2644365C1 - Development method of non-homogeneous oil formation - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method for developing the non-homogeneous oil formation includes injecting hydrocarbon-oxidizing bacteria in nutrient solution into the injection well, forcing with water into the formation, stopping the well for process exposure, diammonium phosphate is used as a nutrient substance, a mixture of water-soluble natural polymer and fermentation bacteria is injected as nutrient substance before injecting said hydrocarbon-oxidizing bacteria, where the hydroxyethylcellulose or sodium carboxymethyl cellulose or xanthan or guar is used as water-soluble natural polymer, and natural source comprising community microorganisms represented by the families: Enterobacteriaceae, Clostridiaceae, Enterococcaceae are used as a fermentation bacteria, and injection of said mixture is conducted up to reduction of well specific infectivity by 10-30% at the following ratio of mixture components, wt %: water-soluble natural polymer 0.05-2.0, fermenting bacteria 0.005-2.0, the rest is water.

EFFECT: increased formation coverage due to blocking of high permeability formation zones and involvement of low permeability, earlier uncovered interlayers in the development, increased oil recovery of formation and reduced water content of production wells, expanded process capabilities of the method.

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Description

The proposal relates to the oil industry, in particular to methods for developing a heterogeneous oil reservoir by microbiological exposure.

A known method of developing an oil field (US Pat. RU No. 2060373, IPC EV 43/22, publ. 05/20/1996, Bull. No. 14), including the injection into the formation of an aqueous solution of polyacrylamide and a surfactant, which use biological surfactant KSHAS (KSHAS bio-surfactant) is a waste product of bacteria of the genus Pseuodomonas acruginosa S-7 with a mass ratio of polyacrylamide and KSAS bio-surfactant 1: 2.5, respectively.

This method is not effective enough in heterogeneous permeability formations, since the composition used does not sufficiently facilitate the washing of oil during its subsequent displacement.

A known method of developing an oil reservoir (US Pat. RU No. 2078916, IPC EV 43/22, publ. 05/10/1997, Bull. No. 13), including the injection into the reservoir of a composition containing hydrocarbon-oxidizing bacteria, nutrient medium, mineral supplement and water. It contains organic fertilizer as a nutrient medium, and diammonium phosphate as a mineral additive.

The disadvantage of this method is its low efficiency in washed highly permeable zones of the formation due to insufficient increase in filtering resistance, which ultimately leads to low coverage of the formation by exposure. As a result, oil recovery remains low.

The closest in technical essence is a method of developing an oil reservoir (US Pat. RU No. 1774691, IPC ЕВВ 43/22, publ. 09/20/1995, Bull. No. 26), which includes the injection of hydrocarbon-oxidizing bacteria - microorganisms in a nutrient solution.

The disadvantages of this method are the high loss of hydrocarbon-oxidizing bacteria in the nutrient solution in the washed high-permeability zones of the formation, insufficient connection to the development of previously unreached low-permeable oil-saturated interlayers and, as a result, low formation coverage. The use of this method in heterogeneous oil reservoirs slightly increases oil recovery.

The objectives of the invention are to increase the coverage of the reservoir by blocking the highly permeable zones of the reservoir and involvement in the development of low-permeability previously unreached layers, increase oil recovery and reduce water cut in production wells, as well as expanding the technological capabilities of the method.

The solution of these problems is ensured by the fact that in the method for developing a heterogeneous oil reservoir, which involves injecting hydrocarbon-oxidizing bacteria into the injection well - DRR in a nutrient solution, pumping water into the reservoir, shutting the well for technological exposure, diammonium phosphate is used as a nutrient before the DRR is injected into In a nutrient solution, a mixture of a water-soluble natural polymer - WFP and fermentation bacteria is injected, where hydroxyethyl is used as a runway cellulose or sodium carboxymethyl cellulose, or xanthan, or guar, as fermentative bacteria, is a natural source containing a community of microorganisms represented by the families: Enterobacteriaceae, Clostridiaceae, Enterococcaceae, and the mixture is injected to reduce the specific injectivity of the well by 10-30% in the following the ratio of the components of the mixture, wt. %:

Runway 0.05-2.0 fermentation bacteria 0.005-2.0 water rest

Biological products are used as a DRR, which is a community of hydrocarbon-oxidizing microorganisms of the genera Rhodococcus, Pseudomonas and Yarrovia, capable of effectively oxidizing a wide range of oil hydrocarbons, including aromatic hydrocarbons, in a wide range of pH 5–9.5, and temperatures from 5 up to 45 ° С and water mineralization 0.15-150 g / l.

As a nutrient, food diammonium phosphate (DAF) is used, manufactured according to GOST 8515-75, which is an inorganic compound - an acidic ammonium salt of phosphoric acid.

The following reagents are used to prepare a mixture of runway and fermentation bacteria:

- hydroxyethyl cellulose (OEC) of domestic or foreign production, which is a non-ionic derivative of cellulose, in appearance a white or slightly creamy loose powder, without taste and odor;

- sodium carboxymethyl cellulose (CMC) with a degree of substitution by carboxymethyl groups of at least 70 and a degree of polymerization of more than 800;

- domestic or imported xanthan, which is an exopolysaccharide obtained by fermentation using the bacteria Xanthomonas campestris;

- domestic or imported guar, which is a neutral water-soluble polysaccharide that contains galactose residues and has the general structure of galactomannans and obtained by extraction from seeds of the plant Cyanaposis tetragonolobus - leguminous crop;

- as a fermentation bacterium use a natural source containing a community of microorganisms represented by the families: Enterobacteriaceae, Clostridiaceae, Enterococcaceae, capable of producing solvents (ketones, alcohols), gases (carbon dioxide, molecular hydrogen), volatile fatty acids when using carbohydrate substrates - sugar , starch, in a wide range of medium acidity pH 4.5-9.5, temperatures from 5 to 45 ° C and water mineralization 0.15-150 g / l). As a natural source, sapropel is used, which is a sediment of freshwater bodies of water, consisting of organic matter and mineral impurities, formed as a result of biochemical, microbiological and physico-mechanical processes from the remains of plant and animal organisms inhabiting the body of water;

- fresh or technical water with a salinity of 0.15-150 g / l.

In the process of injecting a mixture of runway and fermentative bacteria into the formation, the permeability of the highly permeable zones of the formation decreases due to their blocking by a viscous solution containing the runway and, as a result, the formation coverage increases.

Then, the DRR is injected in a DAP solution, which, due to its low viscosity, enters less permeable oil-saturated interlayers.

After injecting the DRR in a DAF solution and forcing the water into the formation, the well is stopped for technological exposure.

During technological aging in more permeable interlayers, a gradual microbiological breakdown of polysaccharides by fermentation bacteria occurs, which leads to the formation of a complex of oil-displacing agents, including solvents and alcohols, which improve the recovery of residual oil, characterized by increased viscosity, and in the less permeable interlayers the conversion of DRR of oil hydrocarbons to oil displacing agents (bio-surfactants, volatile fatty acids) that improve the wettability of the rock, reduce interfacial tension in the water-oil-rock system and increasing the permeability of the interlayer, which leads to an increase in oil recovery.

The method in the field is as follows.

Preliminarily carry out preparatory work. A section of the injection well and production wells hydrodynamically associated with it are selected. The current condition of the wells, the profile of the injectivity of the well, the degree of formation depletion, the injection volumes of the mixture of runway and fermentation bacteria and DRR in the DAF solution are determined. The indicated mixture and DRR are injected into the DAF solution using standard equipment designed for the preparation, dosing and injection of technological solutions into the well.

A mixture consisting of runway and fermentation bacteria, prepared in water, is pumped into a flooded oil reservoir using a pumping unit to reduce the specific injectivity of the well by 10-30%.

The volume of injected specified mixture for each well is individual and depends on the injectivity of the injection well at injection pressure and the working thickness of the formation.

A mixture of runway and fermentative bacteria is prepared as follows.

The volumetric capacity of the pump unit volume of 5 m ³ filled with water with a salinity of from 0.15 to 150 g / L, made by fermenting the bacteria at a concentration of 0.005-2.0 wt. % in a pre-prepared runway solution with a concentration of from 0.05 to 2.0 wt. % and stirred for 30 minutes

From the mixing tank, the prepared mixture is pumped into the reservoir through the injection well by the pumping unit. Then injected into the reservoir of DRR in a solution of DAP.

The DRR injection volume in the DAF solution is calculated taking into account the thickness and porosity of the reservoir. The calculation of the volume of injection of DRR in a solution of DAF is carried out according to the formula (1):

where V ₃ - injection volume, m ³ ;

R is the radius of the formation (4-8 m), m;

h is the thickness of the reservoir, m;

m is the coefficient of porosity, d.

Water with a salinity of 0.15 to 150 g / l is used to prepare DRR in a DAP solution.

Preparation of DRR in a solution of DAP is carried out in the following sequence.

In the measured capacity of the pumping unit with a volume of 5 m ³ , filled with water, add the DRR with a concentration of 0.01-0.3 wt. % in pre-prepared solution of DAP with a concentration of 0.05-0.2 wt. % and stirred for 10 minutes

The prepared solution is pumped into the reservoir.

At the end of the injection process of the indicated mixtures of runway and fermentation bacteria and DRR in a DAF solution, they are pressed into the formation with water with a salinity of 0.15 to 150 g / l from the water supply in a volume of 15-20 m ³ and the well is stopped for technological exposure for 7- 15 days Then resume the operation of the well.

A set of geological, physical, hydrodynamic and geophysical studies is carried out before and after the injection of the indicated mixture and the DRR in the DAF solution.

The proposed method provides a decrease in the permeability of high-permeability zones of the formation by increasing the filtration resistance, involving low-permeability, previously unreached oil-saturated layers in the development, which leads to an increase in the effectiveness of the coverage of the formation by impact, an increase in oil recovery, and a decrease in the water cut of production wells.

The effectiveness of the proposed method and prototype was evaluated by two indicators: the residual resistance factor (OFS) and the growth rate of oil displacement. The experiments were carried out on reservoir models, which are two identical tubes 0.5 m long with a cross-sectional area of 6.4 cm ² filled with quartz sand. By selecting the size of the quartz sand grains, the necessary channel permeability of the formation model was created. Water with a mineralization of 0.15 to 150 g / l was passed through the model, which was then replaced with oil with a density of 0.810-0.890 g / cm ³ . Next, the primary displacement of oil by water was carried out with the measurement of the output of oil and water volumes and the coefficient of oil displacement was determined. Then, a mixture consisting of runway and fermentation bacteria in water with a salinity of 0.15 to 150 g / l and DRR in a solution of DAP was pumped. The reservoir model was stopped for technological exposure for 7-15 days. Next, oil was replaced by water with a measurement of the output of oil and water. OFS was determined. The displaced oil was determined by the increase in the coefficient of oil displacement.

In the table. Figure 1 shows the results on the determination of the general physical condition and the increase in the coefficient of oil displacement during the injection of a mixture of runway and fermentative bacteria and DRR in a solution of DAF.

Example 1. In a reservoir model, a mixture of runway and fermentative bacteria is pumped, for example, an OEC with a concentration of 2.0 wt. %, sapropel with a concentration of 2.0 wt. % and water with a salinity of 60 g / l (96.0 wt.%). Then injected DRR with a concentration of 0.15 wt. % in a solution of DAP with a concentration of 0.2 wt. % Stop the reservoir model for technological exposure for 7 days. Oil is replaced by water with a mineralization of 60 g / l by injection of water with measurement at the output of oil and water volumes. The increase in the oil displacement coefficient is 5.0%, and the OFS - 50.5 (see table. 1, experiment 1).

As can be seen from the table. 1, OFS for the proposed method for the development of an oil reservoir increases by 2.4-28.1 times compared with the prototype. The increase in oil displacement coefficient increases by 2.2-8.1 times.

An example of a specific implementation. When developing an oil reservoir represented by a terrigenous reservoir, geophysical and hydrodynamic studies are performed, a section of the injection well and production wells hydrodynamically associated with it are identified. The injectivity of the injection well is determined in three operating modes of the pumping unit by pumping water into the tubing. The injection volume of the mixture of runway and fermentation bacteria is determined depending on the injectivity of the injection well and the injection volume of the DRR in the DAF solution by calculation, taking into account the porosity and thickness of the reservoir according to (1). The injectivity of the injection well is 260 m ³ / day at a pressure of 10.0 MPa on the water conduit (specific injectivity of the well is 26 m ³ / day / MPa). The injection volume of the mixture of runway and fermentation bacteria is 200 m ³ . The porosity of the formation is 0.21 units, the thickness of the reservoir is 6.0 m, the radius of the formation is 4.5 m

The DRR injection volume in the DAF solution is calculated according to (1):

V ₃ = 3,14⋅R ² ⋅h⋅m = 3,14⋅4,5 ² ⋅6,0⋅0,21 = 80 m ³ .

A mixture of runway and fermentation bacteria, prepared in water with a salinity of 150 g / l in a volume of 200 m ^{3, is} pumped into a flooded oil reservoir using a pumping unit to reduce the specific injectivity of the well by 27%.

A mixture of runways, for example, OEC and sapropel is prepared as follows.

In the measured capacity of the pump unit with a volume of 5 m ³ filled with water with a salinity of 150 g / l, sapropel with a concentration of 0.05 wt. % in a pre-prepared solution of OEC with a concentration of 1.0 wt. % and stirred for 30 minutes

From the mixing tank, the prepared mixture is pumped into the reservoir through the injection well by the pumping unit.

Then injected into the reservoir UOB in a solution of DAP in a volume of 80 m ³ .

Preparation of DRR in a solution of DAP is carried out in the following sequence.

In the measured capacity of the pumping unit with a volume of 5 m ³ , filled with water with a salinity of 150 g / l, add the DRR with a concentration in the solution of 0.15 wt. % in pre-prepared solution of DAP (with a concentration in the solution of 0.3 wt.%) and stirred for 10 minutes

The prepared solution is pumped into the reservoir.

At the end of the injection process of the indicated mixtures of OEC and UOB sapropel in the DAF solution, they are pressed into the formation with water with a salinity of 150 g / l from the water supply in a volume of 15 m ³ and the well is shut down for technological exposure for 7 days. Then resume the operation of the well.

Before and after the injection of the indicated mixtures of the OEC and the BAP sapropel in the DAF solution, a complex of geological, physical, hydrodynamic and geophysical studies is performed.

The results are shown in table. 2 and 3 (example 1). The average additional oil production amounted to 1960 tons per well-treatment while continuing the technological effect, the water cut of producing wells decreased by an average of 3.3%.

Other examples of the implementation of the method of developing an oil reservoir are performed similarly, their results are shown in table. 2, 3. Additional oil production averaged over 1700 tons, water cut decreased on average by 5.3%.

Thus, the proposed method for developing a heterogeneous oil reservoir allows to increase oil recovery and reduce water cut of producing wells by changing the filtration flows in heterogeneous reservoirs by reducing the permeability of highly permeable zones of the reservoir, involving oil-saturated, previously unreached low-permeability layers in the development, and increasing the reservoir coverage by exposure. The proposal also allows to expand the technological capabilities of the method.

Continuation of table 1

Continuation of table 2

Claims (2)

A method of developing a heterogeneous oil reservoir, including injecting hydrocarbon-oxidizing bacteria into the injection well - DRR in a nutrient solution, pumping water into the reservoir, shutting the well for technological shutter speed, characterized in that diammonium phosphate is used as a nutrient, until the DRR is injected in the nutrient solution injection of a mixture of a water-soluble natural polymer - runway and fermentative bacteria, where hydroxyethyl cellulose or sodium carboxyme is used as runway ethyl cellulose, or xanthan, or guar, as fermentative bacteria, is a natural source containing a community of microorganisms represented by the families: Enterobacteriaceae, Clostridiaceae, Enterococcaceae, and the mixture is injected to reduce the specific injectivity of the well by 10-30% in the following ratio of mixture components, wt. %: Runway 0.05-2.0 fermentation bacteria 0.005-2.0 water rest