RU2057916C1 - Method of exploitation of oil pool - Google Patents

Abstract

FIELD: oil industry. SUBSTANCE: this method of exploitation of oil pool involves pumping of heat transfer agent and polymer solution through injection holes in sequence and cyclically and lifting of oil through production wells. Pumping of heat transfer agent and polymer solution is conducted by alternating endings. Heat transfer agent ending is pumped before polymer solution ending. Volumes of endings of heat transfer agent and polymer solution as well as their temperatures are found from analytical relations. Cycles of pumping of endings of heat transfer agent and polymer solution are continued till major mass of oil stock is exhausted. After this unheated water is pumped. EFFECT: method is meant for exploitation of oil pools having high viscosity. 1 dwg

Description

 The invention relates to the oil industry and can be used in the development of oil deposits of high and high viscosity.

 A known method of developing an oil reservoir with a permeable reservoir, including the injection of polymer solution and cold water through injection wells and the selection of oil through production wells [1] The disadvantage of this method is the low return of highly viscous oil from a diffuse reservoir.

 Closest to the invention in technical essence is a method of developing an oil reservoir, including heating the reservoir by pumping coolant through injection wells, then pumping a solution of polymer and water and extracting oil through production wells [2] The disadvantages of this method are the high consumption of thermal energy and its low effectiveness due to the rapid cooling of the polymer solution in the reservoir and as a result of this, the implementation of conventional polymer flooding a great distance from production wells.

 The aim of the invention is to increase oil recovery while reducing the consumption of a chemical per ton of produced oil.

-1 (1) где V_т объем оторочки теплоносителя, м³;
V_п объем оторочки раствора полимера, м³;
m пористость пласта;
С_ск удельная теплоемкость минерального скелета пласта, кДж/кг^оС;

остаточная нефтенасыщенность;
С_н удельная теплоемкость нефти, кДж/кг^оС;
C_ж удельная теплоемкость теплоносителя, кДж/кг^оС;
ρ_ск плотность минерального скелета пласта, кг/м³;
ρ_н плотность нефти, кг/м³;
ρ_ж плотность теплоносителя, кг/м³;
α отношение радиуса фронта концентрации раствора полимера к радиусу фронта возмущенной температуры в пласте α1,1-1,9;
Г коэффициент Генри адсорбции полимера, м³/м³; а температуры теплоносителя и раствора полимера в пластовых условиях определяют из соотношения:

(2)
где η_п коэффициент теплопотерь через кровлю и подошву пласта;
Т_т температура теплоносителя на забое скважины, ^оС;
Т_о начальная невозмущенная температура пласта, ^оС;
Т $\genfrac{}{}{0ex}{}{\text{о}}{\text{п}}$ температура закачиваемого раствора полимера на забое нагнетательной скважины, ^оС;
Т_п температура раствора полимера в пластовых условиях, ^оС;
С $\genfrac{}{}{0ex}{}{\text{о}}{\text{п}}$ удельная теплоемкость раствора полимера, кДж/кг^оС;
ρ $\genfrac{}{}{0ex}{}{\text{о}}{\text{п}}$ плотность раствора полимера, кг/м³;
β коэффициент, учитывающий цикличность закачки теплоносителя и раствора полимера (выбирается в зависимости от продолжительности закачки оторочек теплоносителя и раствора полимера в пределах β 1-2).This is achieved by the fact that in the method of developing an oil deposit, which includes pumping a coolant and a polymer solution through injection wells and extracting oil through a producing well, according to the invention, the coolant and the polymer solution are injected in cyclically alternating rims, and the coolant rim is pumped in front of the polymer solution rim, volumes the rim of the coolant and the polymer solution is determined from the ratio:

-1 (1) where V _{t is the} volume of the rim of the coolant, m ³ ;
V _{p the} volume of the rims of the polymer solution, m ³ ;
m formation porosity;
C _cc, specific heat of the mineral skeleton of the formation, kJ / kg ^° C;

residual oil saturation;
C _n specific heat of oil, kJ / kg ^o C;
C _{w the} specific heat of the coolant, kJ / kg ^about ;
ρ _{ck the} density of the mineral skeleton of the reservoir, kg / m ³ ;
ρ _{n the} density of oil, kg / m ³ ;
ρ _{W the} density of the coolant, kg / m ³ ;
α is the ratio of the radius of the front of the concentration of the polymer solution to the radius of the front of the perturbed temperature in the formation α1.1-1.9;
G Henry coefficient of polymer adsorption, m ³ / m ³ ; and the temperature of the coolant and the polymer solution in reservoir conditions is determined from the ratio:

(2)
where η _{p the} coefficient of heat loss through the roof and bottom of the reservoir;
T _{t the} temperature of the coolant at the bottom of the well, ^about With;
T _{about the} initial undisturbed temperature of the reservoir, ^about With;
T $\genfrac{}{}{0ex}{}{\text{about}}{\text{P}}$ the temperature of the injected polymer solution downhole injection well ^C;
T _{p the} temperature of the polymer solution in reservoir conditions, ^about With;
FROM $\genfrac{}{}{0ex}{}{\text{about}}{\text{P}}$ specific heat of the polymer solution, kJ / kg ^° C;
ρ $\genfrac{}{}{0ex}{}{\text{about}}{\text{P}}$ the density of the polymer solution, kg / m ³ ;
β coefficient taking into account the cyclicality of the injection of the coolant and the polymer solution (selected depending on the duration of the injection of the coolant rims and the polymer solution within β 1-2).

 In the method of developing an oil deposit, the injection cycles of the coolant rims and the polymer solution are continued until the bulk of the oil reserves are developed, after which they switch to the injection of unheated water.

The essential features of the invention are:
1. Injection through the injection wells of the coolant.

 2. The polymer solution.

 3. Unheated water.

 4. Oil extraction through production wells.

 5. Injection of the coolant and the polymer solution with alternating rims.

 6. The priority of downloading the coolant rim.

 7. The formula for the ratio of the volumes of the edges of the coolant and the polymer solution.

 8. The formula for the ratio of the temperature of the coolant and the polymer solution in reservoir conditions.

9. Cyclicity of injection of heat carrier rims and polymer solution, expressed by coefficient β
10. The ratio of the radius of the front of the polymer concentration to the radius of the temperature front in the reservoir, expressed by the coefficient α.

 Signs 1-4 are common with the prototype, signs 5-10 are the salient features of the invention.

 During the usual polymer impact, the polymer solution injected through injection wells penetrates the most permeable zones of the formation, leads to their partial blockage and increased filtration resistance. Subsequently, water injected flows around clogged areas and displaces oil from less permeable zones of the formation. Due to this, the coverage of the formation by the process of displacement increases, the oil recovery of the reservoir increases. Such a mechanism of oil displacement is realized at a relatively small (10-15 m) distance from the injection well, since clogging of highly permeable zones prevents the penetration of a viscous polymer solution deep into the formation.

 When the coolant is pumped through the injection wells, a heated zone is formed in the formation. During the subsequent injection of the polymer solution, it, passing through the heated zone, heats up, its viscosity decreases, and the heated polymer solution acquires the ability to penetrate not only into highly permeable zones of the formation, but also into less permeable ones. As a result, the coverage of the reservoir with a working agent increases and oil recovery increases.

 The technical solution of the prototype provides for the curing of the polymer in the reservoir, its translation into the form of a solid, insoluble and non-melting substance. Moreover, further transfer of the polymer to the mobile current state is impossible.

 The proposed technical solution involves the use of a thermoplastic soluble polymer that is not able to cure in reservoir conditions. The technology provides for the creation of conditions in the reservoir under which thermal degradation of the polymer is impossible. The alternation of the edges of the coolant and the polymer solution provides for the alternate heating of the formation and polymer in the formation due to the heat accumulated in the latter. At the same time, as in the known method, when the polymer is heated, the viscosity of its solution decreases, the polymer solution penetrates into the highly permeable zones to the greatest depth. The proposed method provides for advancing the front of the polymer concentration, i.e., exceeding the radius of the polymer concentration in the formation relative to the radius of the temperature front. This ensures the implementation of the described mechanism of oil displacement by a polymer solution not only in the heated zone of the reservoir, but also outside this zone.

 Along the route, the polymer solution is cooled by heat removal by the mineral skeleton of the formation, due to natural heat transfer to the roof and the bottom of the formation, etc. The heated polymer that has penetrated deep into the formation is gradually cooled. However, it cools, having already penetrated not only into highly permeable regions, but also into less permeable ones, into which it can penetrate only in a heated state, i.e., in a state of reduced viscosity. After cooling, the polymer temporarily loses mobility.

 The coolant injected into the formation in the second rim performs two functions at once: a displacing agent and a coolant. Since the formation heating takes place over time, the coolant, having a lower viscosity than even a heated polymer solution, initially encounters the barrier of the polymer solution that has “gained” viscosity in the zones filled with it, bypasses these zones through low-permeability areas, heating and displacing oil from there. However, as the coolant is injected, the polymer solution gradually warms up, its viscosity decreases, the polymer acquires mobility and starts to move again, releasing highly permeable zones for the movement of oil flowing from low-permeability zones under the influence of the coolant. After washing the highly permeable and low permeability zones, the need again arises for the colmatation of these washed zones. To do this, again inject the rim of the polymer solution, etc.

 The increased efficiency of the process is achieved by the fact that the polymer solution passes not only through the heated zone, but also reaches the unheated zones of the formation. In the unheated zone, the polymer solution cools, penetrates only into the most permeable zones and blocks them. In this case, oil is displaced from these zones, and due to the “gain” of viscosity by the polymer solution as it cools, in this area there is a kind of “blocking” of the flow of the working agent, and in the heated region it penetrates into less permeable regions.

 The cyclicality of the injection of the rims provides for the cyclicality of heating and cooling the polymer solution in the formation and, therefore, the cyclicality of the change in its viscosity, i.e., penetrating and plugging properties in the formation. Thus, there is a favorable self-regulation of the impact of working agents throughout the entire volume of the reservoir, which ensures an increase in oil recovery and a decrease in the consumption of a chemical agent per tonne of oil produced.

0,40. Удельная теплоемкость нефти С_н 2,2 кДж/кг^оС; плотность нефти ρ_н 913 кг/м³. Удельная теплоемкость теплоносителя (горячей воды) С_ж 4,2 кДж/кг, плотность теплоносителя ρ_ж 1000 кг/м³. Отношение радиуса фронта концентрации полимера к радиусу фронта возмущенной температуры в пласте составляет α 1,37. Коэффициент Генри адсорбции полимера Г 0,03 м³/м³. Коэффициент теплопотерь через кровлю и подошву пласта η_п 0,313. Начальная невозмущенная температура пласта Т_о 32^оС. Температуру нагрева раствора полимера в пласте с учетом конкретных геолого-физических условий объекта принимаем Т_п 58^оС. Коэффициент, учитывающий цикличность закачки теплоносителя и раствора полимера, β 1,29.PRI me R. An oil field of 125 m ^{2 is} developed by 50 injection and 50 producing wells. The thickness of the reservoir is h 16.8 m. The depth of the reservoir is 1000 m. The viscosity of oil under reservoir conditions is 75 MPa · s. The porosity of the reservoir is m 0.137. Specific heat capacity of the mineral skeleton of the formation C _ck 0.85 kJ / kg ^o C. The density of the mineral skeleton of the formation ρ _cc 2700 kg / m ³ . Specific heat of polymer C solution $\genfrac{}{}{0ex}{}{\text{about}}{\text{P}}$ 4.2 kJ / kg ^° C; polymer density ρ $\genfrac{}{}{0ex}{}{\text{about}}{\text{P}}$ 1000 kg / m ³ ; average residual oil saturation

0.40. Specific heat capacity of oil C _n 2.2 kJ / kg ^o C; oil density ρ _n 913 kg / m ³ . The specific heat capacity of the coolant (hot water) C _w 4.2 kJ / kg, the density of the coolant ρ _w 1000 kg / m ³ . The ratio of the radius of the front of the polymer concentration to the radius of the front of the perturbed temperature in the formation is α 1.37. The coefficient of Henry adsorption of the polymer G of 0.03 m ³ / m ³ . The coefficient of heat loss through the roof and the bottom of the reservoir η _p 0,313. Starting undisturbed formation temperature T _of 32 ° ^C. The temperature of heating the polymer solution in the reservoir to the specific physical conditions of geological object accept T _n 58 ^o C. The coefficient that takes into account the cyclical injection of the polymer solution and coolant, β 1,29.

The temperature of the coolant and the polymer solution in reservoir conditions is in accordance with formulas (1) and (2) in the ratio:
(T _p -T _o ) / (T _t -T _o ) 0.433.

Hence we obtain the temperature of the coolant at the injection well bottom T _m 92 ° ^C is pumped through an injection well a hot water having a bottomhole temperature of 92 ^{° C,} for 76 days. with a flow rate of 150 m ³ / day. Then after 3 days pumped 0.05% aqueous solution of polyacrylamide with a temperature of 15 ^{° C} for 46 days at a rate of 150 m ³ / day. This corresponds, according to formulas (1) and (2), the volume ratio V _t / V _p 1.65. Again, water is pumped, wherein the downhole temperature T _m of 92 ^{° C,} for 76 days at a rate of 150 m ³ / day. After 3 days pumped 0.05% aqueous solution of polyacrylamide with a temperature of 15 ^{° C} for 46 days at a rate of 150 m ³ / day.

 The injection cycles of the coolant rims and the polymer solution are continued by analogy with the first two cycles until the bulk of the reservoir reserves are developed, after which untreated water is pumped into the injection well and the remaining oil reserves are recovered. The total number of cycles is 5.

 Similar actions are carried out at other injection wells of the field.

 The application of the proposed method in the conditions of the given example allows to increase oil recovery by 7-9% compared with the prototype and other similar technical solutions.

Claims (2)

1. A METHOD FOR DEVELOPING AN OIL DEPOSIT, which includes pumping a coolant and a polymer solution through injection wells and taking oil through production wells, characterized in that the coolant and the polymer solution are injected in cyclically alternating rims, the coolant rim being pumped in front of the polymer rim and the rim of the polymer polymer solution is determined from the ratio

where V _{t the} volume of the rim of the coolant, m ³ ;
V _{p the} volume of the rims of the polymer solution, m ³ ;
m formation porosity, unit C _SK - specific heat of the mineral skeleton of the reservoir, kJ / kg ^o C;
S _n residual oil saturation, d.ed. C _n specific heat of oil, kJ / kg • ^o C;
C _{w the} specific heat of the coolant, kJ / kg • ^o C;
ρ _{ck the} density of the mineral skeleton of the reservoir, kg / m ³ ;
ρ _{n the} density of oil, kg / m ³ ;
ρ _W - the density of the coolant, kg / m ³ ;
α is the ratio of the radius of the front of the concentration of the polymer solution to the radius of the front of the perturbed temperature in the reservoir, a = 1.1-1.9;
G Henry coefficient of polymer adsorption, m ³ / m ³ ;
and the temperature of the coolant and polymer solution in reservoir conditions is determined from the ratio

where η _{p the} coefficient of heat loss through the roof and bottom of the reservoir, d.ed. T _{t the} temperature of the coolant at the bottom of the well, ^o C;
T ₀ initial undisturbed temperature of the reservoir, ^o C;
T $\genfrac{}{}{0ex}{}{\text{o}}{\text{P}}$ the temperature of the polymer solution at the bottom of the injection well, ^o C;
T _{p the} temperature of the polymer solution in reservoir conditions, ^o C;
β coefficient taking into account the cyclicality of injection (coolant and polymer solution), depends on the duration of the injection cycles of both agents, is selected in the range b = 1-2;
C $\genfrac{}{}{0ex}{}{\text{o}}{\text{P}}$ specific heat of polymer solution, kJ / kg • ^o С;
ρ $\genfrac{}{}{0ex}{}{\text{o}}{\text{P}}$ the density of the polymer solution, kg / m ³ .  2. The method according to p. 1, characterized in that the injection cycles of the rims of the coolant and the polymer solution continue until the bulk of the oil reserves are developed, after which they switch to the injection of unheated water.