RU1572092C - Compound for ejecting oil from oil bed - Google Patents

Abstract

FIELD: oil-producing industry. SUBSTANCE: compound contains the following proportions of components, wt.-%: ammonium saltpeter, 10-45; water, 55-90. The compound is prepared by mixing its components. Carbonate rock is decomposed in contact with saltpeter. The decomposition speed depends on the time of contact. The compound is transparent and stable in time. The use of this compound increases oil output 3.4 - 4.6 times. EFFECT: higher efficiency of compound when ejecting oil from a bed composed of low-permeable carbonate collectors. 1 tbl

Description

 The invention relates to the oil industry, in particular to compositions used to increase the amount of oil produced from productive deposits represented by low-permeability carbonate reservoirs.

 The purpose of the invention is to increase the efficiency of the composition during the displacement of oil from the reservoir, composed of low permeability carbonate reservoirs.

Ammonium nitrate when contacted with carbonate rock it decomposes, the rate of decomposition at the same temperature (at 20 ° ^C experiments) depends on contact time and pressure.

The decomposition of calcium carbonate under the influence of ammonium nitrate can be represented by the following reaction equation:
CaCO ₃ + 2NH ₄ NO ₃ = Ca (NO ₃ ) ₂ + (NH ₄ ) ₂ CO ₃ .

With increasing pressure (which always takes place in reservoir conditions, and in experiments the pressure varies from 0.3 to 1.8 MPa), ammonium carbonate (NH ₄ ) ₂ CO ₃ decomposes with the release of gaseous ammonia and carbon dioxide. At the same time, due to rock decomposition, an increase in the permeability of low-permeability layers occurs. In addition, calcium ions in the composition of Ca (NO ₃ ) ₂ react with the sulfate ions of formation water to form gypsum, which precipitates in pores, cracks, channels filled with formation water, and thus the oil displacement front is aligned. And, finally, carbon dioxide released during the decomposition of ammonium carbonate helps to reduce the viscosity of reservoir oil. All this ultimately contributes to enhanced oil recovery of low permeability carbonate reservoirs.

 In the preparation of the composition used ammonium nitrate and fresh water. The resulting composition is transparent and stable over time.

The experiments on oil displacement were carried out on the installation UIPK-1m. Cores representing carbonate rock samples 4 cm long and 2.6-3 cm in diameter were used as the porous medium. The pore volume of the samples was 2.76-3.93 cm ³ , water permeability 1.0-2.8 ˙ 10 ^-2 μm ² . The skeleton of the breed is represented by 98.5-98.9% calcium and magnesium carbonates.

 The cores were saturated with produced water with a salinity of 113 g / l and ion content, g / l: chlorine 101.33, bicarbonate 0.03, calcium 7.88, magnesium 2.54, potassium and sodium 52.31, and then these cores were saturated degassed oil. The oil saturation of the samples was 64.3-89.8% of the pore volume, and the water saturation was 10.1-35.7%.

,, (1) где V_н - объем вытесненной из керна нефти, мл;
V_н.н - начальный нефтенасыщенный объем того же керна, мл.To determine the coefficient of oil displacement by water, formation water was passed through each core in the amount of 10 pore volumes at a speed of 1 m / day. This fluid velocity was maintained due to a change in pressure in the system in the range of 0.3-1.8 MPa. The volume of oil displaced was determined. Then calculated the coefficient of oil displacement by water (K _el.n )
K _el.n =

,, (1) where V _n is the volume of oil displaced from the core, ml;
V _NN - initial oil-saturated volume of the same core, ml.

 As a result, it was found that the coefficient of oil displacement by reservoir water in the studied cores is 0.245-0.35.

Then, given and known (prototype) compounds were passed through the core. For this, compositions were prepared containing water and 5, 10, 30, 45, 60 g of ammonium nitrate in 100 ml of solution and a solution (prototype) containing, g: OP-10 1.1, ammonium nitrate 2.2, ammonia 1 , 3, ethylene glycol 0.5, saline water - the rest. The filtration conditions were the same as when passing formation water through the core. The solution passing through the core was examined for the presence of chlorine ions (c _{. ICS} ) and calcium (c. _ICS ) in it and the volume of oil recovered by this composition was measured.

, , (2) где с_х.пл - концентрация хлор-ионов в пластовой воде, г/л;
с_х.исс - концентрация хлор-ионов в исследуемом растворе, г/л.According to the content of chlorine ions, the fraction of produced water (K _sc ) in the solution that left the core was determined
K _sc =

_,, (2) where with _ch.pl - the concentration of chlorine ions in produced water, g / l;
with _x.iss - the concentration of chlorine ions in the test solution, g / l.

=

, (3) где с″_к.пл.- содержание ионов кальция в пластовой воде.Then, the content of calcium ions in the same solution was determined and, by calculation, it was determined how many calcium ions (with `` _{K. pl.} ) Should be contained as a result of mixing the solution with formation water
c

=

, (3) where with ″ _K.pl. - the content of calcium ions in produced water.

The difference between _c.s.iss and _s.k.pl. represents the number of calcium ions entering the solution as a result of the destruction of the carbonate rock. Then, calcium ions were converted to calcium carbonate. Thus, the amount of calcium carbonate decomposed in each core was determined.

The volume of oil displaced by the data and known compositions, calculated the increase in the coefficient of oil displacement (Δ K _el.n ).

100% ,, (4) где V_д.н - объем нефти, вытесненной данным или известным составами.ΔK _out.n =

100% ,, (4) where V _da is the volume of oil displaced by this or known formulations.

 The test results of the described and known (prototype) compositions are shown in the table.

 The decomposition of calcium carbonate and the removal of calcium is noted only in solutions of the proposed composition. With an increase in the concentration of ammonium nitrate in the solution, an increase in the amount of decomposed calcium carbonate is noted. In this regard, an increase in core permeability is noted. The greatest increase in permeability (from 2.7 to 19 times) is observed when exposed to formulations containing ammonium nitrate in an amount of 10-45%. With a decrease in the concentration of ammonium nitrate less than 10% and an increase of more than 45%, an increase in permeability is noted only by 1.1-1.7 times.

 The same slight increase in permeability by 1.3 times is observed when passing a known composition (prototype) through a core.

 The largest increase in oil displacement coefficient (by 12-16%) is observed with the use of solutions of this composition, in which the concentration of ammonium nitrate is 10-45%. With a lower and higher content of ammonium nitrate in the solution, the oil displacement coefficient increases by only 1.5-2.7%.

 Thus, when using this composition in comparison with the prototype, an increase in additionally extracted oil by 3.4-4.6 times is achieved.

Claims (1)

COMPOSITION FOR EXTRACTION OF OIL FROM THE FORMATION, including ammonium nitrate and water, characterized in that, in order to increase the efficiency of the composition when displacing oil from the formation, composed of low-permeability carbonate reservoirs, it contains these components in the following amounts, wt.%:
Ammonium nitrate 10 - 40
Water 55 - 90

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