RU2153533C1 - Method for physico-chemically assisted microbiological stimulation of oil stratum - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: treatment of bottom zone and cleaning of downhole equipment from paraffin deposits are accomplished with microorganism suspension in aqueous solution of nutrients under optimal for microorganism vitality conditions in combination with physico-chemical action on stratum. Microorganisms utilized is biomass from protein-vitamin concentrate production with cell concentration 10¹⁰-10¹⁸ in 1 l (weight percentage of crude protein not below 50% on conversion to absolutely dry materials). Prior to treating stratum, casing string is perforated within productive stratum region. After treatment, stratum is intensely drained to remove mudding products and clogging agents using implosion and swabbing means. Before performing perforation operation, composition of nonionic hydrocarbon-based surfactants is applied. EFFECT: enhanced microbiological action on oil- stratum bottomhole zone in desired direction with no increased expenses on reagents. 2 cl, 1 tbl

Description

 The invention relates to the field of the oil industry, in particular to methods for treating an oil reservoir using microorganisms and physico-chemical methods in order to increase oil recovery and restore productivity of the bottom-hole zone of the oil reservoir (PZP).

 Known methods of dealing with asphalt and resin-paraffin deposits (AFS) on the downhole equipment and in the bottomhole formation zone (BHP) by injecting various solvents into the well, for example, based on toluene, turpentine, ethoxylated alkyl phenol and gas gasoline / 1 /; gasoline, kerosene, naphtha, diesel fuel in combination with machining / 2 /.

 Methods / 1 / and / 2 / involve the use of expensive and flammable reagents.

 There are also known methods of increasing oil recovery by pumping chemicals into it, for example surface-active substances (surfactants) / 3 /. However, the use of these methods is constrained by the high cost of the reagents.

 Closest to the proposed is a method of processing an oil reservoir using microorganisms / 4 /. The method involves injecting into the formation a suspension of hydrocarbon-oxidizing microorganisms (UOM) in a nutrient solution.

 The disadvantage of this method is the insufficiently high efficiency associated with the relatively low oil laundering properties of the resulting oil displacing agents - products of microbiological degradation of part of the reservoir hydrocarbons, the lack of impact on the bottom-hole zone of production wells.

 The aim of the proposed method is to increase the efficiency of the formation treatment using microorganisms by actively stimulating the bottom-hole zone of producing wells.

 The goal is achieved by the described method of developing an oil reservoir by pumping a suspension of microorganisms in a solution of nutrients and a chemical under optimal conditions for the life of microorganisms.

A feature of the method is that to stimulate the oil reservoir, an aqueous suspension of biomass of microorganisms for the production of protein-vitamin concentrates with a cell concentration of 10 ¹⁰ - 10 ¹⁸ cells / l (mass fraction of crude protein in terms of ACB of at least 50%) is pumped into it in combination with mineral fertilizer (diammofes, urea).

 In addition, before the treatment of the formation, the casing is perforated in the interval of the productive formation, and after the treatment, intensive drainage of the formation is carried out to remove the clogging products and plugging agents using implosion and swab devices.

 Another difference of the method is that for the hydrophobization of the pore channels of the bottomhole zone of the reservoir before conducting perforation, compositions of nonionic carbon-based surfactants are used.

 The advantage of using microbial biomass produced by BVK is a wide species set of microflora, adaptability to oil-containing substrates. Due to the relatively high concentration of microorganisms (calculated on absolutely dry matter), the release of biogas during the fermentation of the substrate in the formation is more intense, which leads to increased oil recovery.

The microbial biomass of BOC is non-toxic, able to withstand temperatures up to 90 ^o C, auto-ignition temperature does not exceed 400 ^o C.

 As shown by laboratory and field studies, the addition of nonionic and composite surfactants (nonionic surfactants AF-6 and AF-12, ML-72, ML-80) at a concentration of 0.1 - 1.0% to the reservoir environment does not reduce the activity of microorganisms. In particular, for UOM used to increase oil recovery, the addition of surfactants of the above types helps to intensify their vital activity and leads to an increase in the overall effect, because contributes to better washing of oil from the reservoir and more effective cleaning of the bottomhole zone. Due to the activation of capillary forces both under the influence of surfactants and as a result of the shooting of the formation, microorganisms can penetrate into previously unreached areas of the formation.

 In field conditions, the method is as follows.

 At the producing well, preparatory and research work is carried out related to the determination of the parameters of the formation, its injectivity and pressure testing of the production string. If necessary, work is carried out to clean the production casing from ASPO by injecting an organic solvent in the well volume and holding the well at rest for the duration of the response, depending on the type of solvent used (at least 24 hours).

Then the underground equipment rises and the calculated amount of hydrocarbon solution is pumped through the tubing string (butyl benzene fr. / TU 38-102-97-78 /, kerosene fr. / TU 6-01-18-37-78 /, hexane fr. / TU 38.103-81-83 /, petroleum distillate) with a 0.1-1.0% surfactant concentration (Neonol AF ₉ -6 or ML-80) and is pressed into the reservoir.

 After this, the tubing rises, and the well is prepared for perforation according to the requirements of perforating and blasting operations. The formation is shot in the perforation interval with an intensity of up to 10 holes per 1 p / meter in order to increase the perfection of the degree of opening the formation.

Then, on the surface in special containers, the necessary volumes of microbiological solution are prepared in fresh water or industrial water with the addition of nutrients, for example diammophos, with a concentration of 0.05-0.1%, the calculated amount of surfactant is also added there (Neonol AF ₉ - 12 or ML - 80) with 0.1-1.0% concentration based on:
V = πR ² hm,
where V is the volume of the solution in m ³ ;
R is the radius of the formation covered by the bottom-hole zone in m, the value of which is taken based on the reservoir properties of the formation and the multiplicity of treatment (1.5 + 3.5) m,
h - perforated formation thickness in m,
m - porosity in dol.ed.

The treatment composition is brought to the receiving downhole pump and is forced into the PPP aqueous surfactant solution to 0.1-1.0% (AF Neonol -6 or ₉ ML - 80) in a volume of tubing.

 After that, the well is closed for microbiological processes for 1 ... 3 days. In this case, the previously injected hydrocarbon solution serves as an additional feed for the UOM, and the surfactant has a positive effect on the desorption and disaggregation of paraffin deposits.

Further, depending on the type of well and the type of equipment used to clean the formation of mud products and plugging agents, the method is carried out in two versions:
1. An implosion device is lowered into the well to the middle of the interval of the treated formation. By increasing the pressure at the mouth, the membrane is ruptured or the inlet valve of the implosion chamber opens from the control panel of the actuator (depending on the type of implosion device), resulting in a deep depression on the formation. The implosive effect is carried out pointwise, after 0.5 m of the thickness of the reservoir, but not less than 3 times, while an aqueous surfactant solution with 0.1% surfactant concentration (Neonol AF ₉ -6 or ML-80) is used as a fracturing fluid.

 2. A tubing with a non-return valve and a swab device is lowered into the well to a depth agreed with the geological service of the customer enterprise, and the well is swabbed. Structurally swab devices can be arranged in different ways. The main structural element of the swab is a plunger pair with a valve device at the bottom. As the swab rises, the liquid above it is transported upward, while simultaneously creating a depression effect on the perforated formations. Depending on the flow rate of the well, development is carried out until the formation fluid is obtained or the well flow rate can be determined.

 The treatment is completed by lowering the underground equipment and putting the well into operation.

 The technical and economic advantage of the proposed method lies in the fact that it allows you to enhance the microbiological effect on the bottomhole zone of the oil reservoir in the right direction without a significant increase in the cost of reagents.

 The effectiveness of the proposed and well-known methods of stimulation of wells is determined by the additional oil production in accordance with the approved industry regulatory documents and guidelines.

 Table 1 presents data on the technological efficiency of the known (basic) methods for processing bottom-hole zones of wells that have been tested in the oil fields of Tatarstan. These methods or their components and principles of stimulation are included in the proposed integrated method of stimulation of the oil reservoir using microorganisms and physico-mechanical methods of exposure, which due to the synergistic effect and new technological solutions should have higher technological efficiency compared to known methods of stimulation wells.

USED INFORMATION SOURCES
1. A.S. USSR N 15624433, E 21 B 37/06.

 2. RJ Mining, 1990, 5G 389.

 3. A.S. USSR N 1511375, E 21 B 43/22, 09/30/1989.

 4. Patent RU 2078916, E 21 B 43/22, 05/10/97

Claims (2)

1. A method of stimulating an oil formation by injecting a chemical agent and a suspension of microorganisms into a solution of nutrients in the formation, characterized in that prior to treatment of the formation, the casing is perforated in the interval of the producing formation, then an aqueous suspension of biomass of microorganisms producing protein-vitamin concentrates with cell concentration of 10 ¹⁰ - 10 ¹⁸ cells / l (mass fraction of crude protein in terms of ASV not less than 50%) in combination with mineral fertilizer, and then, after processing, p Intensive formation drainage is performed using implosion and swab devices.  2. The method according to p. 1, characterized in that the composition of nonionic hydrocarbon-based nonionic surfactants is used as a chemical agent before perforating.

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