RU2083811C1 - Method for developing oil deposit with use of in-reservoir burning - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: according to method, operations are performed in following succession: injected into reservoir through injection well prior to initiation of burning is solution containing 25-26% mass of potassium carbonate. After injection of solution, initiation of burning is started and oxidizer is injected for example air, then other operations are performed needed in realization of in-reservoir burning method. EFFECT: increased oil output, reduced speed of corrosion, preventing formation of water-oil emulsion of high stability. 1 tbl

Description

 The invention relates to the oil industry, in particular to methods for developing oil deposits by heat treatment.

 A known method of developing an oil reservoir using in situ combustion. The method provides for the creation of a combustion zone and subsequent pushing of the hot rim with cold water. The combustion zone is created by initiating the ignition of oil in the bottom-hole zone of the injection well with special heat sources while simultaneously injecting the oxidizing agent - air. Further, the process is carried out by injecting air and water simultaneously or sequentially.

 The disadvantage of this method is the low oil recovery coefficient due to the uneven coverage of the formation by combustion. In addition, the acid gases generated during combustion, dissolving in the produced water, leach iron-containing components from the collector and cause increased corrosion of the oilfield equipment. Ferrous ions leached from the rock interact with hydrogen sulfide contained in the formation with the formation of iron sulfide, which in turn increases the stability of the water-oil emulsion.

 Closest to the proposed is a method of developing an oil field, when steam and water are pumped into the injection well prior to initiation of combustion. The method allows to slightly increase the intensity of the development process to increase the capture of the formation by the impact and oil recovery. During steam treatment, the viscosity of the oil decreases, and the injection of water evens out the combustion front, provides uniform coverage of the formation by heat.

 However, acidic combustion gases resulting from combustion are not neutralized by injected steam and water. The presence of combustion acid gases and rock leaching products (ferrous iron ions) in the produced products leads to the formation of a stable, hard-to-break emulsion and causes intense corrosion of oilfield equipment.

 The aim of the invention is to increase oil recovery, lowering the corrosiveness of the produced products, preventing increased stability of the water-oil emulsion.

 The goal is achieved by the described method of developing an oil reservoir using in-situ combustion (SH), including initiating combustion in the bottom-hole zone of the injection well and pumping oxidizer and cold water through it and taking products through the producing well, while steam and water are injected before the SH is initiated.

 What is new is that before the initiation of combustion, a 25-26% (wt.) Solution of potassium carbonate is pumped into the formation.

В результате реакции получается хорошо растворимая в воде соль и углекислый газ, растворимость которого значительно выше в нефти, чем в воде. Углекислый газ, растворяясь в нефти, понижает вязкость, увеличивает подвижность ее.Laboratory studies have shown that the liquid injected before the initiation of combustion, which is a solution of potassium carbonate, neutralizes the acidic combustion gases by reaction

The reaction results in a water-soluble salt and carbon dioxide, the solubility of which is much higher in oil than in water. Carbon dioxide, dissolving in oil, lowers viscosity, increases its mobility.

 The injected fluid has an alkaline environment. When acidic combustion gases are absorbed, the medium remains alkaline until the complete decomposition of the calculated potassium carbonate introduced into the liquid.

The volume of injected solution (V, m ³ ) is calculated by the formula:
V = π • R ² • h • K _f • K • K _{n draw,}
where π 3.14; R is the radius of the rim injection zone, m (it has been experimentally established that R (0.08-0.1) L, where L is the distance between the injection and production wells; h is the effective oil-saturated formation stratum, m; K _p porosity coefficient, fractions of unit K _n oil saturation coefficient, fractions of units

 When moving along the formation, such a liquid does not leach iron ions from the reservoir, thereby preventing the formation of iron sulfide, which increases the stability of the emulsion.

 When selecting well products together with a liquid having an alkaline reaction of the medium, the corrosion rate of the equipment is 5-6 times lower than when producing a water-oil emulsion containing dissolved acidic combustion gases.

 The effectiveness of the proposed method was tested in laboratory conditions by comparing the data obtained using the proposed and known methods, and conducting experiments in identical conditions.

 The experiments were carried out on a special installation consisting of a reservoir model and devices designed for cooling, separation, collection and measurement of oil, water and gas, as well as gas sampling for analysis and removal of gaseous products of combustion.

 The reservoir model is a double-walled pipe, 1.2 m long, consisting of an inner steel pipe with a diameter of 100 mm and a casing (outer steel pipe) with a diameter of 240 mm. The inner pipe is centered using centralizers. To eliminate heat loss, the annular space is filled with a heat insulator.

Non-cemented quartz sand with a fraction of less than 0.4 mm was used as a porous medium. The pore volume of 1050 cm ³ . The model was saturated with formation water with a density of 1.16 g / cm ³ and then with oil with a density of 0.92 g / cm ³ and a viscosity of 110 cPa.

When modeling the proposed method (examples 2, 3, 4), water solutions containing 24, 25, 26% (weight) potassium carbonate (K ₂ CO ₃ ) GOST 106960-93 were pumped prior to the initiation of combustion.

 Solutions were prepared in a standard manner. A white powder, well soluble in water, was taken at the top of the potassium carbonate, mixed with fresh water, mixed, and a true solution was obtained, ready for use. 3 experiments were conducted on the proposed and 1 on the known (prototype) methods. The results are shown in the table.

 With a decrease in the concentration of potassium carbonate below the lower limit (25%), the efficiency in the absorption of acidic combustion gases decreases, and the upper limit is limited by the practical solubility of potassium carbonate.

 Example 1 (prototype).

Prior to initiation of combustion, steam was pumped in an amount of 0.6 pore volume and 0.05 pore volume water (50 ml). The injection volume is determined based on the combustion conditions. The initiation of the process inside the reservoir combustion was carried out by heating the input end of the model with an electric heater to a temperature of 320-340 ^o C with a minimum air flow. The beginning of the combustion process was determined by the abrupt temperature motion at the inlet of the model and by the composition of the exhaust gases. After the combustion front came close to the output end of the model, the experiment was terminated.

 Example 2 (by the proposed method).

 Prior to initiating combustion, 50 ml of a 24% potassium carbonate solution were pumped into the model. Then combustion was initiated and further the experiment was continued, as in example 1.

 Example 3 (by the proposed method).

 Prior to initiation of combustion, 50 ml of a 25% potassium carbonate solution were pumped into the model. Then combustion was initiated and further the experiment was continued, as in example 1.

 Example 4

 Prior to the initiation of combustion, 50 ml of a 26% potassium carbonate solution were pumped into the model. Then combustion was initiated and further the experiment was continued, as in example 1.

 The table shows that when applying the proposed method, compared with the prototype method, the oil recovery coefficient increases by 4.9%, the reaction of the medium with strongly acidic decreases to neutral, the corrosion rate decreases by 7 times, the content of iron ions decreases by more than two orders of magnitude.

 The technical and economic effectiveness of the proposed method lies in the fact that when it is applied, the amount of extracted products increases, the corrosion rate of the equipment decreases, and the formation of a water-oil emulsion of increased stability is prevented.

Claims (1)

 A method for developing an oil reservoir using in-situ combustion, including injecting a rim, initiating combustion in the bottomhole zone of an injection well, injecting oxidizer and cold water through it, and selecting products through a producing well, characterized in that 25 26 are pumped into the reservoir before initiation of combustion wt. potassium carbonate solution.

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