RU2115726C1 - Method of forcing out residual oil from oil formation - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: invention, in particular, relates to microbiological methods of developing watered oil formations. Method includes activation of microflora by pumping in crude oil and aerated aqueous solution of nutrients into aerobic zone of injection well. Crude oil drawn out from production well is pumped in amount corresponding to 20-30% of pore volume of the production well aerobic zone. When concentration of hydrocarbon-oxidizing bacteria in this zone is less than 1000 clones per 1 ml or in complete absence of these bacteria, into aerobic zone, a culture of hydrocarbon-oxidizing bacteria is added. If crude oil contains less than 25% of 10³-n-paraffins, they are supplemented by light hydrocarbon fractions (e. g. distillate). EFFECT: enhanced efficiency of microbiological method. 3 cl

Description

 The invention relates to biotechnology and the oil industry, in particular to microbiological methods for developing flooded oil reservoirs, and can be used to extract residual oil.

Closest to the proposed is a method of displacing residual oil from a flooded oil reservoir using microorganisms, which involves alternating the introduction of a water-air mixture and a nutrient solution. Taking into account the fact that the oil located in the bottom-hole zone (PZ) of the injection well, as a result of prolonged pumping through the PZ of water and biodegradation, increases the content of heavy high molecular weight products - resins and asphaltenes unsuitable for consumption of DRR, “fresh” oil is preliminarily pumped into the PZ, moreover, oil taken from a well in which the outflowing formation water of which the BEP content is not less than 10 ³ cells / ml, and the volume of injected oil is set equal to the volume of the outflowing formation water with the indicated content of BEC.

Since the purpose of the prototype is to replace the old, "inedible" residual bottomhole oil with fresh, the injection of fresh oil in an amount equal to the volume of poured water, in which the DRR content is at least 10 ³ cells / ml, is unjustified, leading to unnecessary oil costs .

In addition, in the near-well zone of the injection well, where it is supposed to activate the DRR, their concentration may be insufficient (less than 10 ³ cells / ml), or they are absent. In this case, the known method will show low efficiency or cannot be applied at all.

 Replacing old residual oil with fresh oil alone is not a guarantee of the success of the process. It is known that n-paraffin hydrocarbons and the number of carbon atoms 4 - 16 are most easily amenable to bacteria. By introducing a portion of fresh oil, it is possible to increase the content of these hydrocarbons in the bottomhole zone of the injection well. However, oils from different fields vary significantly in composition. In some oils, the content of n-paraffin hydrocarbons with the number of carbon atoms 4-16 is low, so even replacing the residual oil with the same, but fresh, does not activate the DRR.

 All of the above significantly reduces the effectiveness of the known method.

 The aim of the invention is to increase the efficiency of the method of developing an irrigated reservoir using microorganisms while reducing the amount of oil used.

 This goal is achieved by the proposed method, including the activation of microflora by pumping oil and an aerated aqueous solution of nutrients.

New in the method is that the oil extracted from the producing well is pumped into the injection well in the amount of 20-30% of the pore volume of the aerobic zone, when the content of the DRR in the aerobic zone of the injection well is less than 10 ³ cells / ml or, if there is no aerobic the zone introduces DRR culture.

 Other differences of the proposed method are as follows: light hydrocarbon fractions are added to oil containing n-paraffin hydrocarbons with the number of carbon atoms 4-16 less than 25%, and, for example, distillate is used as light hydrocarbons.

 Oil injection in the volume of 20-30% of the pore volume of the aerobic zone of the injection well is determined by the volume of residual oil in it after a long washing. This volume is quite enough to replace the old residual oil with fresh. It is important that the unit of reference take the volume of the aerobic zone, because it is in the aerobic zone that DRR can exist.

DRR is not always detected in the aerobic zone of the injection well. But this can not serve as an obstacle to the implementation of the proposed method, since in this case it is proposed to introduce into the aerobic zone a culture of DRR in such a concentration that they contain at least 10 ³ cells / ml in 1 ml of bottomhole liquid.

 Since replacing residual oil with fresh oil does not yet guarantee the creation of optimal conditions for DRR, it is proposed to enrich it, if necessary, with light paraffin hydrocarbons, the most readily consumed by DRR.

 The lower limit of the content of light hydrocarbons in oil (with the number of carbon atoms 4–16) is the average content in the Devonian oils of the Romashkinskoye field - 25%. In this case, as a source of light hydrocarbons, for example, distillate from oil treatment plants containing mainly n-paraffin hydrocarbons with 9 carbon atoms can be used.

In commercial "conditions, the method is carried out" as follows
The development of an oil reservoir drilled by at least one injection and one production well is carried out by prolonged displacement of oil by pumping water through an injection well.

By self-discharge, portions of water, for example, 5 m ³ , are taken from the injection well, and the oxygen and DRR contents are determined in them. Thus, the volume of the aerobic zone of the bottom-hole part of the injection well is determined, as well as the presence (or absence) of DRR in it.

 The content of n-paraffin hydrocarbons with the number of C 4 - 16 atoms in the oil extracted from the producing well is determined by reference or by analytical method.

Further, on the basis of the studies they make the appropriate decisions:
1. If the DRR is absent in the aerobic zone or is in a concentration of less than 10 ³ cells / ml, then the DRR culture, for example, Devoroil biological product, is used to pump it into the aerobic zone of the injection well so as to create at least a DRR concentration there 10 ³ cells / ml.

 2. If the content of n-paraffin hydrocarbons in the produced oil is less than 25%, then light fractions of oil, for example distillate, are used to add to the oil.

 If the oil from the producing well is highly emulsified, for example, as a result of injection of surfactants into the formation, then oil can be taken from the oil treatment unit.

 Further, depending on the results obtained, the method is carried out in several ways.

If a DRR of at least 10 ³ cells / ml is detected in the aerobic zone of the injection well, and the oil extracted from the producing well contains at least 25% n-paraffin hydrocarbons, then it (oil) is pumped into the aerobic zone of the injection well in the amount of 20 - 30% of its volume.

If the DRR content is lower than 10 ³ cells / ml, then the DRR culture is pumped into the aerobic zone of the bottom-hole part of the injection well so that their content in the aerobic zone is at least 10 ³ cells / ml, after which oil is pumped.

 If preliminary tests showed that the content of n-paraffin hydrocarbons in oil is less than 25%, light hydrocarbons are added to the oil.

 After that, for all options, an aerated solution of salts containing nitrogen and phosphorus is pumped into the injection well. The injection time of the aerated solution is set depending on the change in the injectivity of the injection well and the quantitative characteristics of the microflora of water extracted after treatment.

Example. By self-spout, 5 m ^{3 of} water is taken from the injection well and the oxygen content and DRR are determined in it. It was found that the volume of the aerobic zone is 10 m ³ , the content of DRR in it is 10 ² cells / ml. As a DRR culture, the Devoroil biological product is used containing a complex of hydrocarbon-oxidizing microorganisms and yeast and obtained from natural reservoir microflora of injection wells.

An analysis of the oil recovered from a producing well operating the Bobrikovsky horizon showed a 21% n-paraffin hydrocarbon content. To enrich the oil with light hydrocarbons, the distillate from the Shugurovsky oil bitumen plant of the following composition was used, wt.%: C ₄ 0.01; C ₅ 0.02; C ₆ 0.18; C ₇ 0.35; C ₈ 0.31; C ₉ + higher. 99.13.

The volume of injected oil is 20-30% of the volume of the aerobic zone, i.e. 2 - 3 m ³ . 40 l of distillate must be added to 1 m ^{3 of} oil, i.e. 80 - 120 liters for the entire volume. Enriched with n-paraffin hydrocarbons, oil is pumped into the aerobic zone of the injection well, after which an aerated solution of diammonium phosphate is pumped.

 Due to the preliminary introduction of the DRR culture into the aerobic zone of the injection well and the enrichment of oil with light hydrocarbons, the implementation of the method and its effectiveness increase.

Claims (3)

1. The method of displacing residual oil from a flooded oil reservoir, drilled, at least one injection and one producing wells, including the activation of microflora injection into the aerobic zone of the injection wells of oil and an aerated aqueous solution of nutrients, characterized in that the oil extracted from the producing well , injected into the injection well in a volume of 20-30% of the pore volume of the aerobic zone of the injection well, when the hydrocarbon acid is in the aerobic zone of the injection well bacteria boiling less than 10 ³ cells / ml or complete absence of hydrocarbon bacterial culture is introduced into the aerobic zone.  2. The method according to p. 1, characterized in that light fractions of hydrocarbons are added to the oil containing less than 25% hydrocarbons with the number of carbon atoms from 4 to 16 inside the fraction of n-paraffin hydrocarbons.  3. The method according to claim 2, characterized in that, for example, distillate is used as light fractions of hydrocarbons.