RU2096604C1 - Method for treatment of bottom-hole zone of bed - Google Patents

Abstract

FIELD: oil production technology. SUBSTANCE: this is aimed at increasing injectivity of injection wells of terrigenous bed by injecting solvent and acid. This is achieved by modifying surface of rock skeleton and reducing secondary hydrocarbon saturation of buttonhole zone by injecting mixture of acid solutions. According to method, used as surface modifying agent are liquid hydrocarbon wastes of isoprene production through double-stage dehydration, which contain pipeline - 20-25%, toluene - 63-70%, absorbent - 17-5%. Used as mixture is 15-% solution of muriatic acid and 10-% solution of hydrofluocilicic acid taken in proportion of 1:1. Liquid wastes of hydrocarbons are stable, low toxic, easily transportable, low corrosive, and possess high degree of interaction with skeleton surface. Method requires no special technological procedures, nor high material and economic spending. Method permits increasing injectivity of injection wells by 7-10 times with retaining this feature during long period of time. EFFECT: high efficiency. 1 cl, 1 tbl

Description

 The invention relates to oil production technology, in particular to methods for processing bottom-hole zones of injection wells in terrigenous formations.

 Known methods for treating the bottom-hole zone of injection wells by pumping it in various combinations of solvent and inorganic acids (Loginov B.G. et al. Guide to acid treatment of wells, M. Nedra, 1966; Sergeev B.Z. et al. Use of solvents before conducting acid treatments of wells. RNTS, Oilfield Business, 1978, N 8, p.12-13). The disadvantage of these methods is the low processing efficiency of the terrigenous formation.

 Closest to the proposed technical essence is the method of acid treatment of the bottom-hole formation zone according to a.s. N 1740642, cl. E 21 B 43/27, which consists in injecting solvent and acid into the formation, using oil pretreated with a magnetic field of a certain intensity as a solvent.

 However, the known method also has low efficiency when using terrigenous seams in injection wells, which is explained by the low content of magnetizable metal components in oil, the rapid adsorption of these components on the washed rock surface, the decrease in the magnetic properties of the solvent, the decrease in phase permeability to water, and also due to low dissolution rock skeleton and shielding the rock surface with a film of injected oil solvent.

 The purpose of the invention is to increase the efficiency of processing the bottom-hole zone of an injection well in a terrigenous formation.

This goal is achieved by the fact that solvent and an acid solution are successively pumped into the formation, moreover, the solvent used is a modified solvent, liquid hydrocarbon wastes from isopropene production by the two-stage dehydrogenation process, containing the following components,
Piperylene 20.0 25.0
Toluene 63.0 70.0
Flavored gasoline 5.0.0.0.0
and as an acid solution, a mixture of acid solutions. In this case, a 15% solution of hydrochloric acid and a 10% solution of hydrofluoric acid, taken in a 1: 1 ratio, are used as a mixture of an acid solution.

Flavored gasoline (adsorbent A-2) included in the composition of liquid hydrocarbon wastes according to TU-38-202-05-27-92 has the following composition:
Isoamylene (C ₅ H ₁₀ ) 31%
Isoprene (C ₅ H ₈ ) 5%
Normal piperylene (nC ₅ H ₈ ) 77.9%
C ₆ 7%
Cyclopentadiene 7%
The efficiency of processing the bottom-hole zone of the injection well of a terrigenous reservoir increases due to an increase in the phase permeability of the reservoir through water, which does not occur due to the dissolution of the skeleton, but due to a change in the state of the rock surface when treated with a modifier and subsequent reduction in hydrocarbon saturation, by the interaction of an acid solution while maintaining the surface modification.

 The proposed method is implemented as follows.

 Based on hydrodynamic studies of the well, a layer or perforation interval with a deteriorated water pick-up characteristic is determined. A direct circulation flushing of the perforation zone is carried out. The processed interval is separated from the annulus by the packer and the required volume of modifying solvent, determined by engineering calculations, is pumped. The injection pressure should not exceed the value of the steady-state pressure at the time before processing.

 The required volume of the modifying solvent should be at least 5 6 pore volumes of the part of the bottomhole zone to be treated. After injecting the modifying solvent without extracting, the mixture of acid solutions is injected in a volume exceeding the volume of the modifier by 15 20%. After the mixture of acid solutions is injected, the mixture is aged for 24 to 26 hours, and then a partial injection of water in a volume of 8 to 10 volumes of the modifier is performed. An indicator of the success of the treatment is the pressure drop during partial injection of water at a constant flow rate. After obtaining the results of this diagnosis, the well is connected to the injection line of the cluster pumping station.

Example (laboratory test)
As test samples, core samples from the Urshak (well 518) and Yangurchinsky (well 88) deposits were used.

The sequence of core operations simulating the bottom-hole zone of injection wells was as follows:
the test samples were saturated with water and the phase permeability in water was determined;
water was displaced from the core by oil and the phase permeability of the oil was determined;
oil was displaced by water and the phase permeability of water with residual oil saturation was determined;
through the 1st sample, a modifying solvent was filtered in a volume of 5 to 10-fold replacement of the pore volume, then a mixture of hydrochloric and silicon fluorosilicic acid solutions was taken in a 1: 1 ratio, the sample was kept for 24 hours and then water was filtered through it to determine permeability;
through the 2nd sample, a mixture of hydrochloric and hydrofluoric acids was first filtered, the sample was kept for 24 hours, then a modifying solvent was filtered, followed by water to determine permeability.

 In the filtration experiments, our own degassed oil of the fields was used as a model of oil. After the experiments, the core samples under study were extracted and their absolute permeability and weight loss were determined.

 The results of filtration studies, depending on the sequence of treatment with a modifying solvent and a mixture of acid solutions are shown in the table.

 The research results indicate that during the processing sequence of the modifier-acid solution, the phase permeability in water increased by 9.9 and 6.5 times, respectively, and in the reverse sequence by 1.48 and 2.84 times. The mass loss of core samples was 2.04 and 0.48%, respectively.

 To carry out processing by the proposed method does not require scarce materials, special technological techniques and new equipment. In this case, after the processing behavior, the phase permeability in water increases by 7 10 times, and the absolute permeability increases by only 1.2 1.3 times.

Claims (2)

1. A method of treating a bottom-hole formation zone, including sequentially injecting a solvent and an acid solution into the formation, characterized in that when processing the bottom-hole zone of a terrigenous formation in an injection well, a modified solvent uses liquid wastes of hydrocarbons from isopropene production by the two-stage dehydrogenation process, containing the following Components,
Piperylene 20 25
Toluene 63 70
Adsorbent A-2 flavored gasoline 5 17
and as an acid solution, a mixture of acid solutions.  2. The method according to claim 1, characterized in that as a mixture of acid solutions using a 15% solution of hydrochloric acid and a 10% solution of hydrofluoric acid, taken in a ratio of 1 to 1.

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