| CPC E21B 43/24 (2013.01) [E21B 43/166 (2013.01)] | 8 Claims |
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1. A method for integral profile control and plugging of water encroachment and steam channeling of a heavy oil reservoir with edge and bottom water, comprising the following steps:
(i) selecting an oil reservoir: roughly screening an appropriate oil reservoir according to the following conditions: the oil reservoir is a heavy oil reservoir with edge and bottom water, the viscosity of stock tank oil at 50° C. is less than 100000 mPa·s, a buried depth of the oil reservoir is less than 1000 m, an effective thickness is greater than 5 m, an initial oil bearing saturation is greater than 0.5, a penetration rate is greater than 200 mD, and a volume ratio of a water body to an oil layer is less than 500;
(ii) arranging huff-puff wells: drilling the huff-puff wells in the oil layer according to a row-well pattern, wherein the huff-puff wells are vertical or horizontal wells; determining the number of well rows according to an area of the oil reservoir, wherein at least 3 columns of huff-puff well rows are arranged in the oil layer, a distance between two adjacent columns of well rows is 100-150 m, and a distance between two adjacent huff-puff wells in each column of well rows is 100-150 m; one column of well rows close to water body is a first line of well rows, followed by a second line of well rows and a third line of well rows, and so on, and a distance between the first line of well rows and the water body is greater than 150 m;
(iii) developing through cyclic steam stimulation: firstly beginning a first cycle of cyclic steam stimulation, wherein a steam injection volume for the first line of well rows is 1000-1200 t, a steam injection volume for the second line of well rows is 1500-1800 t, and a steam injection volume for the third line of well rows is 2000-2200 t; after the steam injection, soaking the wells for 3-5 days, and after the soaking, opening the wells for production, wherein a ratio of a fluid output of the first line of well rows to a cold water equivalent volume of the injected steam is less than 5; a ratio of a fluid output of the second line of well rows to a cold water equivalent volume of the injected steam is less than 10; a ratio of a fluid output of the third line of well rows to a cold water equivalent volume of the injected steam is less than 20; and huff-puff parameters of a next cycle are consistent with those of the first cycle;
(iv) carrying out the integral profile control and plugging: with the increase of huff-puff cycles, the formation pressure drops gradually, water encroachment and steam channeling occur, an integral profile control and plugging technology is adopted, and specific operations are as follows:
(a) after a moisture content of the first line of well rows is greater than 90%, injecting a high-intensity nitrogen foam system at the same time of a steam injection phase of the first line of well rows, reducing a cyclic steam injection volume of the first line of well rows to 800-1000 t, injecting nitrogen with the steam in a whole process, wherein an injection volume is calculated according to a gas-to-liquid ratio of foam formed downhole of 2:1; and after soaking the wells for 3-5 days, carrying out oil recovery;
(b) injecting a nitrogen foam system at the same time of steam injection of the second line of well rows, wherein a concentration of a foaming agent is 0.5%; a steam injection volume of the second line of well rows is 1500-1800 t; injecting the nitrogen with the steam in the whole process, wherein a nitrogen injection volume is calculated according to a gas-to-liquid ratio of the foam formed downhole of 3:1; and after the steam injection is finished, increasing well soaking time to 5-6 days, and then opening the wells for production; and
(c) injecting the nitrogen foam system at the same time of the steam injection of the third line of well rows, wherein the concentration of the foaming agent is 0.5%; a steam injection volume of the third line of well rows is 1500-2500 t; injecting the nitrogen with the steam in the whole process, wherein the nitrogen injection volume is calculated according to a gas-to-liquid ratio of the foam formed downhole of 4:1; and after the steam injection is finished, increasing the well soaking time to 6-8 days, and then opening the wells for production.
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