CN111827949A - A method for accurate production of remaining oil in ultra-low permeability sandstone reservoir - Google Patents

Abstract

The present invention provides a method for accurately producing remaining oil in an ultra-low permeability sandstone reservoir, comprising the following steps: S1, selecting a low permeability weak water washing section enriched with remaining oil; S2, opening a window side to the low permeability weak water washing section in an old wellbore Drilling an ultra-short radius horizontal well; S3, running a tubing string in the vertical well section of the old wellbore; S4, unplugging the open-hole section of an ultra-short-radius sidetracking horizontal well; S5, running a string to consolidate the open-hole section with resin Sand; S6, well flushing, shut-in reaction; S7, lower production string and put into production. The invention can accurately produce the remaining oil enriched in the longitudinal weak water washing section of the oil layer and the lateral waterline under the condition of oilfield water flooding, so as to achieve the purpose of controlling water and increasing oil.

Description

A method for accurate production of remaining oil in ultra-low permeability sandstone reservoir

technical field

The invention relates to the field of oil production engineering, in particular to a method for accurately producing remaining oil in an ultra-low permeability sandstone reservoir.

Background technique

After the water flooding development of the ultra-low permeability reservoir, the wells are drained to form a waterline, and the remaining oil lateral to the waterline cannot be effectively produced. The method of filling holes + temporary plugging and turning to fracturing is mainly used to tap the potential, but there are the following problems: First, the reservoir is an ultra-low permeability reservoir, and fracturing is required to obtain productivity after hole filling, but because the interlayer is only about 1m, It is easy to communicate with the upper and lower strong water wash sections after fracturing in the weak water wash section, and the proportion of wells with high water cut after fracturing is high. Second, due to the large horizontal in-situ stress difference of the reservoir, the controllability of boost pressure after temporary plugging in the layer is poor. The microseismic monitoring results show that The success rate of fracture turning is low, and the remaining oil in the lateral direction cannot be effectively tapped.

SUMMARY OF THE INVENTION

In order to overcome the problem that the existing remaining oil cannot be effectively tapped, the present invention provides a method for accurately producing the remaining oil in an ultra-low permeability sandstone reservoir. The invention can accurately produce the remaining oil enriched in the longitudinal weak water washing section of the oil layer and the lateral waterline under the condition of oilfield water flooding, so as to achieve the purpose of controlling water and increasing oil.

The technical scheme adopted in the present invention is:

A method for accurately producing remaining oil in an ultra-low permeability sandstone reservoir, comprising the following steps:

S1, select the low-permeability weak water washing section enriched by the remaining oil;

S2, in the old wellbore, open the window and sidetrack ultra-short radius horizontal well in the low-permeability and weakly washed section;

S3, run the tubing string in the vertical well section in the old wellbore;

S4, perform plug removal treatment on the open hole section of the ultra-short radius sidetracking horizontal well;

S5, the lower pipe string fills the open-hole section with resin-consolidated sand;

S6, well flushing, well shut-in reaction;

S7, the lower production string is put into production.

In step S1, the low-permeability weakly washed section enriched with remaining oil refers to the screening permeability ≤0.8mD, remaining oil saturation ≥40% and the thickness of the weakly washed section ≥2.0 according to the neutron lifetime logging interpretation result. The producing interval of m is the potential interval.

In step S2, the ultra-short-radius horizontal well with windowed sidetracking refers to the horizontal well with windowed sidetracking in the potential section, the radius of curvature of the sidetracking hole is less than 3m, and the extension direction of the wellbore is perpendicular to the direction of the maximum main force of the reservoir, The length of the sidetrack drilling hole is greater than 50m and less than 80m.

In step S3, the running of the tubing string in the vertical well section in the old wellbore refers to the running of the tubing string above the sidetrack drilling section, and the lowermost part of the tubing string is the inclined tip.

In step S4, the open hole treatment of the ultra-short radius sidetracking horizontal well is performed to remove the blockage, and the mud pollution zone in the sidetracking hole section is removed. ) of a mixture of earth acid and barite plugging solution.

The soil acid is prepared from industrial hydrochloric acid with a volume ratio of 10-15%, hydrofluoric acid with a volume ratio of 2-3%, and the rest is water.

The barite blocking solution is composed of: 0.25-0.35% of heavy gold blocking-releasing agent, 0.025-0.05% cellulose degrading agent, 0.5% drainage aid, 0.5% clay stabilizer, and the rest is water composition.

In the step S5, the pipe string fills the open-hole section with resin-consolidated sand, which is filled with linear glue mixed with resin sand and pumped into the side-tracking open-hole section by a fracturing truck.

The linear glue is a guar gum base liquid with a mass concentration of 0.2-0.3%, wherein the viscosity of the guar gum base liquid is greater than or equal to 18mpa·s, the pumping displacement is less than or equal to 0.8m ³ /min, the construction pressure is less than the formation fracture pressure, and the average sand ratio>25%.

In step S6, the well flushing and well shut-in reaction refers to the well shut-in reaction for more than 72 hours after reverse circulation well flushing, so that the resin-consolidated sand is completely consolidated under formation temperature conditions to form a channel with long-term conductivity.

The beneficial effects of the present invention are:

In the present invention, the ultra-short radius sidetracking horizontally replaces the traditional hole-filling and fracturing diverted fractures in the potential interval, and the wellbore size and wellbore length can be considered to be controlled, which is equivalent to ensuring the “fracture height” and The precise control of "seam length" effectively avoids the strong water washing section and the lateral water line, and realizes the precise use of the remaining oil in the longitudinal and lateral directions.

The invention uses acid liquid and barite plugging removal liquid to treat the formation, effectively removes additives such as cellulose and barite in the drilling fluid, and restores the fracture conductivity near the open-hole wellbore.

The invention fills the open-hole wellbore with consolidated sand to satisfy the long-term wellbore conductivity and achieve the purpose of long-term stable production.

In the present invention, the ultra-low permeability sandstone is flooded to develop oil reservoirs, and the ultra-short radius horizontal wellbore is drilled through the window through the preferred weak water wash section. Then, the plugging removal fluid is injected to remove the mud pollution zone, and the consolidated sand is filled in the wellbore, so that the wellbore has long-term fracture conductivity, and finally achieves the purpose of water control and oil increase.

Detailed ways

Example 1:

In order to overcome the problem that the existing remaining oil cannot be effectively tapped, the present invention provides a method for accurately producing the remaining oil in an ultra-low permeability sandstone reservoir. The invention can accurately produce the remaining oil enriched in the longitudinal weak water washing section of the oil layer and the lateral waterline under the condition of oilfield water flooding, so as to achieve the purpose of controlling water and increasing oil.

A method for accurately producing remaining oil in an ultra-low permeability sandstone reservoir, comprising the following steps:

S1, select the low-permeability weak water washing section enriched by the remaining oil;

S2, in the old wellbore, open the window and sidetrack ultra-short radius horizontal well in the low-permeability and weakly washed section;

S3, run the tubing string in the vertical well section in the old wellbore;

S4, perform plug removal treatment on the open hole section of the ultra-short radius sidetracking horizontal well;

S5, the lower pipe string fills the open-hole section with resin-consolidated sand;

S6, well flushing, well shut-in reaction;

S7, the lower production string is put into production.

In the present invention, the ultra-short radius sidetracking horizontally replaces the traditional hole-filling and fracturing diverted fractures in the potential interval, and the wellbore size and wellbore length can be considered to be controlled, which is equivalent to ensuring the “fracture height” and The precise control of "seam length" effectively avoids the strong water washing section and the lateral water line, and realizes the precise use of the remaining oil in the longitudinal and lateral directions. The invention uses acid liquid and barite plugging removal liquid to treat the formation, effectively removes additives such as cellulose and barite in the drilling fluid, and restores the fracture conductivity near the open-hole wellbore. The resin-consolidated sand is filled in the open-hole wellbore to meet the long-term wellbore conductivity and achieve the purpose of long-term stable production.

The invention can accurately produce the remaining oil enriched in the longitudinal weak water washing section of the oil layer and the lateral waterline under the condition of oilfield water flooding, so as to achieve the purpose of controlling water and increasing oil.

Example 2:

On the basis of Embodiment 1, in this embodiment, preferably, in step S1, the low-permeability weak-water washing section enriched with remaining oil refers to the screening permeability ≤ 0.8 according to the neutron lifetime logging interpretation result The production interval with mD, remaining oil saturation ≥40% and the thickness of weakly washed section ≥2.0m is the potential section.

In the present invention, due to the strong heterogeneity of the oil well production layer, strong and weak water washes alternate in the vertical direction, and the low-permeability and weak water wash section is the main section for the remaining oil to tap potential. An old well with good casing condition was selected. According to the neutron lifetime log interpretation results, the permeability of the screening potential section was ≤0.8mD, the remaining oil saturation was ≥40%, and the thickness of the weakly washed section was ≥2.0m. This ensures a certain material basis for increased production and a certain remaining geological reserves.

Preferably, in step S2, the ultra-short radius horizontal well with windowed sidetracking refers to the horizontal well with windowed sidetracking in the potential section, the radius of curvature of the sidetracking hole is less than 3m, and the extension direction of the wellbore is related to the maximum main force of the reservoir. The direction is vertical, and the length of the side drilling hole is greater than 50m and less than 80m.

The invention performs window sidetracking and ultra-short radius horizontal well in the target potential section of the old wellbore, so that the sidetracking hole trajectory is in the weak water wash section, and at the same time, it ensures that the extension direction of the wellbore is kept perpendicular to the original old fracture, that is, perpendicular to the maximum principal stress Orientation, the sidetracked wellbore is equivalent to turning to the "fracture", accurately reaching the remaining oil-rich area. The curvature radius of the sidetracking hole is less than 3m, the extension direction of the wellbore is perpendicular to the direction of the maximum main force of the reservoir, and the length of the sidetracking hole is greater than 50m and less than 80m. The purpose of this step is to extend the sidetrack drilling hole along the remaining oil-rich zone both longitudinally and laterally, and accurately reach the remaining oil-rich position. The length of the wellbore for sidetracking is equivalent to the length of the fractures formed by traditional steering fracturing, so as to accurately reach the remaining oil-rich area, while avoiding the strong water wash section and the lateral waterline vertically.

Preferably, in step S3, the running of the tubing string in the vertical well section of the old wellbore refers to the running of the tubing string above the sidetrack drilling section, and the lowermost part of the tubing string is an inclined tip. The pipe string can be used as a channel for subsequent injection of plugging removal fluid and consolidated sand.

After the open hole of the ultra-short radius sidetracking horizontal well in the present invention is completed, the vertical well section above the window opening point of the old wellbore is run from top to bottom with the combination of N80 thickened tubing and inclined tip into the window opening point position.

Preferably, in step S4, the open hole treatment of the ultra-short radius sidetracking horizontal well is performed to remove the plugging, and the mud pollution zone in the sidetracking hole section is removed, and the plugging removal liquid used in the plugging removal treatment is 3:( 1-3) A mixture of earth acid and barite plugging solution.

Preferably, the soil acid is prepared by volume ratio of 10-15% industrial hydrochloric acid, 2-3% hydrofluoric acid, and the rest is water.

Preferably, the barite plugging solution is composed of: 0.25-0.35% of the heavy gold stone plugging-removing agent, 0.025-0.05% of the cellulose degrading agent, 0.5% of the drainage aid, and 0.5% of the clay stabilizer. The rest consists of water. The heavy gold stone blocking remover, cellulose degrading agent, drainage aid and clay stabilizer involved in the present invention can be directly purchased in the market or are in the prior art, and will not be further described in the present invention.

During the drilling process in the middle and old areas of the present invention, in order to stabilize the well wall and control the well control, so as to ensure safe drilling, barite and other additives are generally added to the drilling mud. However, the invasion of mud and filter cake after drilling will cause the formation of an invasion zone near the wellbore and pollute the strata, which will deteriorate the permeability of the polluted zone and affect the single-well production. Sequentially inject soil acid and barite plug-removing fluid into the tubing to remove the mud-contaminated zone in the side drilling section. Among them, the soil acid removes the cellulose additives in the pollution zone, and the barite blocking solution removes the blocking ^of the barite additives. The injection displacement of plug-removing fluid is 0.3-0.5m ³ /min, and the construction pressure is lower than the formation fracture pressure. The purpose of this step is to restore the permeability of the formation near the sidetrack drilling hole, reduce the skin coefficient, and improve the single well production. At the same time, the acidic environment can accelerate the consolidation speed of the later filled consolidated sand and shorten the shut-in reaction time.

Preferably, in the step S5, the pipe string fills the open-hole section with resin-consolidated sand, which is filled with linear glue mixed with resin sand and pumped into the side-drilling open-hole section by a fracturing truck.

Preferably, the linear glue is a guar gum base liquid with a mass concentration of 0.2-0.3%, wherein the viscosity of the guar gum base liquid is greater than or equal to 18 mpa·s, the pumping displacement is less than or equal to 0.8 m ³ /min, and the construction pressure is less than the formation fracture pressure. , the average sand ratio> 25%.

Due to the small curvature radius of the ultra-short-radius sidetracking horizontal wellbore in the present invention, casing cementing completion cannot be used like conventional low-permeability oil reservoirs, and open-hole completion is usually the main method. However, due to the influence of the horizontal two-way stress difference and the production pressure difference during the mining process, the long-term mining sandstone reservoir will have wellbore collapse and oil layer sand production, which will lose the wellbore conductivity. Mixed resin sand with linear glue is pumped from the oil pipe to the open-hole section of the sidetrack for filling, where the viscosity of the linear glue base fluid is greater than or equal to 18mpa s, the pumping displacement is less than or equal to 0.8m ³ /min, and the construction pressure is less than the formation fracture pressure, and the average Sand ratio>25%. This step of filling the wellbore with consolidated sand is equivalent to the effect of placing proppant in artificial fractures in the traditional fracturing process, ensuring long-term conductivity in the later production process of the sidetrack drilling hole, and avoiding the loss of conductivity in the collapse of the open-hole formation. flow capability. At the same time, the construction pressure does not exceed the rupture pressure to avoid the formation of cracks to communicate with the strong water washing section.

The purpose of this step is to use the wellbore that has been sidetracked to replace the fractures created during the fracturing process, so that the wellbore is filled with consolidated sand, so that the consolidated sand can function as a proppant, so as to prevent the wellbore from collapsing and closing in the later stage. loss of flow capacity. At the same time, during the construction process, the stratum is not pressed open, avoiding the communication between the upper and lower strong water washing sections, so as to achieve the purpose of controlling water and increasing oil.

Preferably, in step S6, the well cleaning and well shut-in reaction refers to the well shut-in reaction for more than 72 hours after reverse circulation well cleaning, so that the resin-consolidated sand is completely consolidated under formation temperature conditions to form a long-term flow conductivity. channel. Among them, the reverse circulation flushing can ensure that no sand surface is left in the vertical well section above the window sidetracking point, so that the filling material is completely retained in the open hole section. The shut-in reaction enables the consolidated sand to be completely consolidated under the formation temperature to form a channel with a certain conductivity, while preventing sand production from the formation.

In the present invention, after filling the consolidated sand technology, after backwashing the well to ensure that there is no sand in the vertical well section, the well shut-in reaction is performed for at least 72 hours, so that the consolidated sand is naturally consolidated under the formation temperature condition, forming a certain conductivity channel, and at the same time consolidating After the sand is consolidated, it can prevent the formation of sand.

In step S7 of the present invention, lowering the production pipe string and putting it into production means pulling out the oil pipe string drilling tool for plug removal and sand filling, running the production pipe string for oil production, and putting the oil well into production.

Example 3:

On the basis of Example 2, in this example, a sidetracking lateral well exploration test of a high water cut well was carried out at the ultra-low permeability sandstone reservoir site, and the sidetracking lateral wells were subjected to plug-removing fluid and packing support. In the early stage of production, the daily oil production of a single well was 3.05 tons, and the comprehensive water content was 30.5%, with a remarkable effect.

The above examples are only examples of the present invention, and do not constitute a limitation on the protection scope of the present invention, and all designs that are identical or similar to the present invention belong to the protection scope of the present invention. The reagents and method steps not described in detail in this embodiment are all known techniques and common methods in the industry, and will not be described one by one here.

Claims (10)

1. An accurate residual oil utilization method for an ultra-low permeability sandstone reservoir is characterized by comprising the following steps: the method comprises the following steps:

s1, selecting a hypotonic weak water washing section enriched with residual oil;

s2, windowing a hypotonic weak water washing section in an old well barrel and sidetracking an ultra-short radius horizontal well;

s3, tubing strings are put into the straight well section in the old well bore;

s4, performing deblocking treatment on the open hole section of the ultra-short radius sidetracking horizontal well;

s5, filling resin consolidated sand into the open hole section by the lower pipe column;

s6, washing and closing the well;

and S7, putting the production string into production.

2. The accurate residual oil utilization method for the ultra-low permeability sandstone reservoir according to claim 1, wherein the method comprises the following steps: in step S1: the low-permeability weak washing section enriched with the residual oil is a potential section which is produced by screening a production layer section with the permeability of less than or equal to 0.8mD, the saturation of the residual oil of more than or equal to 40 percent and the thickness of the weak washing section of more than or equal to 2.0m according to the neutron life logging interpretation result.

3. The method for precisely using the residual oil of the ultra-low permeability sandstone reservoir according to claim 1 or 2, wherein the method comprises the following steps: in the step S2, the windowing sidetrack drilling of the ultra-short radius horizontal well means that the windowing sidetrack drilling of the horizontal well is performed in the potential section, the curvature radius of the sidetrack drilling is less than 3m, the extension direction of the well bore is perpendicular to the direction of the maximum principal force of the reservoir, and the length of the sidetrack drilling is greater than 50m and less than 80 m.

4. The accurate residual oil utilization method for the ultra-low permeability sandstone reservoir according to claim 1, wherein the method comprises the following steps: in step S3, the step of placing the tubing string in the straight section of the old well casing means that the tubing string is placed above the lateral wellbore section, and the lowest part of the tubing string is a slant tip.

5. The accurate residual oil utilization method for the ultra-low permeability sandstone reservoir according to claim 1, wherein the method comprises the following steps: in step S4, the deblocking treatment is performed on the open hole of the ultra-short radius sidetracking horizontal well to remove a mud pollution zone of the sidetracking well bore section, and the deblocking liquid used in the deblocking treatment is 3: (1-3) a mixture of the earth acid and the barite plugging removal liquid.

6. The method for precisely using the residual oil of the ultra-low permeability sandstone reservoir according to claim 5, wherein the method comprises the following steps: the soil acid is prepared from 10-15% of industrial hydrochloric acid, 2-3% of hydrofluoric acid and the balance of water by volume ratio.

7. The method for precisely using the residual oil of the ultra-low permeability sandstone reservoir according to claim 5, wherein the method comprises the following steps: the barite blockage removing liquid comprises the following components in percentage by volume: 0.25-0.35% of heavy-weight gold blocking remover, 0.025-0.05% of cellulose degradation agent, 0.5% of cleanup additive, 0.5% of clay stabilizer and the balance of water.

8. The accurate residual oil utilization method for the ultra-low permeability sandstone reservoir according to claim 1, wherein the method comprises the following steps: in the step S5, the tubular column is used to fill the open hole with resin consolidated sand, and the linear glue mixed resin sand is pumped into the open hole section of the sidetrack by a fracturing truck for filling.

9. The method for accurately using the residual oil of the ultra-low permeability sandstone reservoir according to claim 8, wherein the method comprises the following steps: the linear gum is a guar gum base solution with the mass concentration of 0.2-0.3%, wherein the viscosity of the guar gum base solution is more than or equal to 18mpa · s, and the pump displacement is less than or equal to 0.8m³Min, construction pressure is less than stratum fracture pressure, and the average sand ratio is more than 25%.

10. The accurate residual oil utilization method for the ultra-low permeability sandstone reservoir according to claim 1, wherein the method comprises the following steps: in step S6, the well flushing and closing reaction refers to well closing reaction for more than 72 hours after reverse circulation well flushing, so that the resin consolidated sand is completely consolidated at the formation temperature to form a passage with long-term conductivity.