Method for adjusting steam injection mode in steam huff-puff process

Abstract

The invention provides a method for adjusting a steam injection mode in a steam huff-puff process. The method is characterized in that in a stratum with obvious permeability difference in the horizontal direction, the phenomenon of uneven steam absorption of a horizontal well section is obvious along with the prolonging of a production period, so that less oil is used in a low-permeability area and more oil is used in a high-permeability area; after multiple periods of huff and puff, remaining oil in the high-permeability area is reduced, and uniform steam injection is adjusted to cold oil area steam injection; wherein the optimal adjustment time for adjusting the uniform steam injection into the steam injection of the cold oil area is as follows: when the temperature variation coefficientis continuously reduced by two cycles or more and reaches a minimum value after the Nth cycle is ended, the steam injection mode is adjusted before the (N-1) th cycle, the (N, N + 1) th cycle or the(N + 2) th cycle is started. By means of the method, the situation of uneven steam absorption of the horizontal section caused by stratum heterogeneity or other adverse factors can be improved, the utilization degree of oil in the low-permeability area is greatly improved, and the oil-steam ratio is increased.

Description

technical field

[0001] The invention relates to a method for adjusting a steam injection mode in the process of steam stimulation, and belongs to the technical field of oil and gas field development engineering. Background technique

[0002] Steam huff and puff means that a large amount of steam is periodically injected into the oil layer to bring heat into the formation, and the steam diffuses out a certain radius along the wellbore to heat the formation through a combination of heat convection and heat conduction.

[0003] However, due to the influence of steam flow pressure drop and heat loss in the horizontal section, formation heterogeneity, steam injection process, and pipe string structure, the “heel-toe effect” of the steam injection main pipe in the conventional general steam injection is obvious, making the water The uneven absorption of steam in formations around flat wells seriously restricts the uniform heating of formations and the producing effect of oil reser...

Examples

Embodiment 1

[0053] A method for adjusting the steam injection mode in the process of steam stimulation,

[0054] 1) The heterogeneous reservoir has serious uneven steam absorption, and the horizontal well section has high oil saturation. (Extreme difference in oil saturation R=So max -So min , where, So max is the maximum oil saturation in the region, So min is the minimum oil saturation in the region. ) If the coefficient of variation of formation permeability is 0.27, the horizontal well injects steam at 290m 3 / d, under the conditions of temperature 250°C and steam dryness 0.7, such as figure 1 As shown, after the end of the third period, the temperature in the low-permeability zone at the front end of the horizontal well is relatively low, and the temperature in the rear-end high-permeability zone is relatively high. The phenomenon of uneven steam absorption in periodic horizontal well sections is more obvious, and the steam absorption profile becomes more and more irregular; te...

Embodiment 2

[0067] When the stratum heterogeneity increases, V k =0.74, horizontal well steam injection 290m 3 / d, under the conditions of temperature 250°C and steam dryness 0.7, the coefficient of variation of temperature is higher than that of the previous situation, but the overall change has the same trend. The oil in the reservoir is produced in large quantities, the water saturation gradually increases, and the effect of the back-end steam heating the formation becomes smaller. As the front-end temperature rises, the temperature variation coefficient gradually decreases. Such as Figure 11 , the steam huff and puff began to decline in the second period, and after two consecutive periods of decline, the temperature coefficient of variation reached a minimum value in the fourth period. The coefficient of variation of temperature in the fourth cycle is 11.96, and that in the fifth cycle is 12.

[0068] The best adjustment time should be when the temperature variation coefficient ...

example

[0072] Oilfield 1 reservoir has a burial depth of 950m, oil layer thickness of 8m, average porosity of 40%, average permeability of 5000mD, initial oil saturation of 0.6, formation heterogeneity, crude oil viscosity of 2×10 under oil layer conditions 4 mPa.s, the original reservoir pressure is 9.5MPa.

[0073] A horizontal well in the oil layer has 14 cycles of steam huff and puff, and the daily oil production reaches its peak and then continues to decline (the daily oil production peak is in the first cycle), from the analysis of the temperature profile test curve ( Figure 13 ) found that the second half of the well at 1180-1260m had good steam absorption and high recovery, while the first half of the well had poor steam absorption and low recovery, and the horizontal well had serious uneven steam absorption. The coefficient of temperature variation dropped continuously after reaching the maximum value at the end of the sixth cycle, dropped to 6.72 at the end of the 13th cyc...

technical field

[0001] The invention relates to a method for adjusting a steam injection mode in the process of steam stimulation, and belongs to the technical field of oil and gas field development engineering. Background technique

[0002] Steam huff and puff means that a large amount of steam is periodically injected into the oil layer to bring heat into the formation, and the steam diffuses out a certain radius along the wellbore to heat the formation through a combination of heat convection and heat conduction.

[0003] However, due to the influence of steam flow pressure drop and heat loss in the horizontal section, formation heterogeneity, steam injection process, and pipe string structure, the “heel-toe effect” of the steam injection main pipe in the conventional general steam injection is obvious, making the water The uneven absorption of steam in formations around flat wells seriously restricts the uniform heating of formations and the producing effect of oil reser...

Examples

Embodiment 1

[0053] A method for adjusting the steam injection mode in the process of steam stimulation,

[0054] 1) The heterogeneous reservoir has serious uneven steam absorption, and the horizontal well section has high oil saturation. (Extreme difference in oil saturation R=So max -So min , where, So max is the maximum oil saturation in the region, So min is the minimum oil saturation in the region. ) If the coefficient of variation of formation permeability is 0.27, the horizontal well injects steam at 290m 3 / d, under the conditions of temperature 250°C and steam dryness 0.7, such as figure 1 As shown, after the end of the third period, the temperature in the low-permeability zone at the front end of the horizontal well is relatively low, and the temperature in the rear-end high-permeability zone is relatively high. The phenomenon of uneven steam absorption in periodic horizontal well sections is more obvious, and the steam absorption profile becomes more and more irregular; te...

Embodiment 2

[0067] When the stratum heterogeneity increases, V k =0.74, horizontal well steam injection 290m 3 / d, under the conditions of temperature 250°C and steam dryness 0.7, the coefficient of variation of temperature is higher than that of the previous situation, but the overall change has the same trend. The oil in the reservoir is produced in large quantities, the water saturation gradually increases, and the effect of the back-end steam heating the formation becomes smaller. As the front-end temperature rises, the temperature variation coefficient gradually decreases. Such as Figure 11 , the steam huff and puff began to decline in the second period, and after two consecutive periods of decline, the temperature coefficient of variation reached a minimum value in the fourth period. The coefficient of variation of temperature in the fourth cycle is 11.96, and that in the fifth cycle is 12.

[0068] The best adjustment time should be when the temperature variation coefficient ...

example

[0072] Oilfield 1 reservoir has a burial depth of 950m, oil layer thickness of 8m, average porosity of 40%, average permeability of 5000mD, initial oil saturation of 0.6, formation heterogeneity, crude oil viscosity of 2×10 under oil layer conditions 4 mPa.s, the original reservoir pressure is 9.5MPa.

[0073] A horizontal well in the oil layer has 14 cycles of steam huff and puff, and the daily oil production reaches its peak and then continues to decline (the daily oil production peak is in the first cycle), from the analysis of the temperature profile test curve ( Figure 13 ) found that the second half of the well at 1180-1260m had good steam absorption and high recovery, while the first half of the well had poor steam absorption and low recovery, and the horizontal well had serious uneven steam absorption. The coefficient of temperature variation dropped continuously after reaching the maximum value at the end of the sixth cycle, dropped to 6.72 at the end of the 13th cyc...

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