CN110529089B

CN110529089B - Repeated fracturing method for open hole horizontal well

Info

Publication number: CN110529089B
Application number: CN201910891487.XA
Authority: CN
Inventors: 赵仁凤
Original assignee: Sichuan Jieneng Ruisi Petroleum Technology Co ltd
Current assignee: Sichuan Jieneng Ruisi Petroleum Technology Co ltd
Priority date: 2019-09-20
Filing date: 2019-09-20
Publication date: 2020-04-28
Anticipated expiration: 2039-09-20
Also published as: CN110529089A

Abstract

The invention provides a repeated fracturing method for a barefoot horizontal well, and belongs to the field of oil and gas exploitation. The repeated fracturing method of the open hole horizontal well provided by the invention can realize fixed-point reconstruction, has high construction efficiency, excavates the productivity from an effective reservoir which is not developed by one-time fracturing, has residence property of the plugging agent, can form an interpenetrating network structure, and has micro-expansion performance of a plugging slurry solidified body; the plugging strength of the plugging agent is high; the plugging agent completely reaches or exceeds the index of 5500 under the elastic modulus of high-quality cement slurry in the medium petroleum well cementation cement standard; the construction safety of the plugging agent is high.

Description

Repeated fracturing method for open hole horizontal well

Technical Field

The invention relates to the technical field of oil and gas exploitation, in particular to a repeated fracturing method for an open hole horizontal well.

Background

Staged fracturing of horizontal wells is an effective way to improve the single well yield of oil and gas reservoirs. However, as the development is gradually deepened, due to the influence of factors such as low transformation degree of primary fracturing, reduction of flow conductivity of a fracture system and the like, part of low-production horizontal wells appear, the yield of a single well needs to be recovered by adopting repeated fracturing, and the development effect is improved. The horizontal well repeated fracturing technology is difficult due to factors such as primary fracturing multi-section perforation, uneven extraction degree between sections, large difference of horizontal section cementing quality and the like, and the targeted process technology is still in an exploration test stage. At present, the horizontal well repeated fracturing process at home and abroad mainly comprises two types: the first is a mechanical packing repeated fracturing process, which has the advantages that a pipe column and a packer are adopted to clamp and seal a target well section, fixed-point reconstruction is realized through oil pipe injection, and the defects are that a running pipe string drags operation, the requirement on shaft conditions is high, the operation is influenced by the inner diameter of the pipe column, and the large-scale fracturing construction efficiency is low (only 1 section is constructed by a single pipe column). The second type is a dynamic multistage temporary plugging repeated fracturing process, which has the advantages of optical casing operation, lower requirement on a shaft, realization of intersegmental steering fracturing by pumping and injecting temporary plugging agents through a wellhead, high construction efficiency, and the defects of incapability of fixed-point reconstruction and poor multistage temporary plugging boosting controllability (the boosting amplitude of the 1 st stage is more than 5MPa, and the boosting amplitude is smaller later), so that the reservoir reconstruction has uncertainty.

Disclosure of Invention

In view of the above, the present invention provides a method for repeatedly fracturing an open hole horizontal well. The repeated fracturing method for the open hole horizontal well provided by the invention can realize fixed-point reconstruction and has high construction efficiency.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a repeated fracturing method of a bare hole horizontal well, which comprises the following steps:

performing repeated fracturing potential analysis by using the geological characteristics of the regional structure, the reservoir characteristics, the single-well control reserve and the previous extraction degree as analysis parameters, and selecting an open hole horizontal well;

putting a coiled tubing string with an electric motor and a drill bit into the existing base pipe of the selected open hole horizontal well, drilling and grinding all ball seats, and circulating base fluid of water-based fracturing fluid to remove fragments;

a coiled tubing string with a drift gauge and a scraper is put into the existing base pipe of the selected open hole horizontal well, and the coiled tubing string passes through the original ball seat repeatedly for three times, so that the drift diameter in the base pipe is ensured to be not deformed;

a coiled tubing string with upper and lower cup packers and a nozzle is put into the existing base pipe of the selected open hole horizontal well, and the nozzle is placed between the two cup packers;

aligning the position of a nozzle to the position of an original first sliding sleeve, forcibly extruding and injecting plugging slurry to the corresponding open hole horizontal well section, excessively displacing the plugging slurry to the position 1 meter inside an original artificial crack, stopping the pump for 10 minutes, utilizing the specific residence characteristic of the plugging slurry, starting the pump again to forcibly extrude and inject the rest part of the designed plugging slurry amount, filling the annular space of an oil sleeve of the horizontal well section, excessively displacing the plugging slurry, and taking the principle that no plugging slurry remains in a base pipe as a principle;

repeating the steps, completing the squeezing of the original artificial cracks and the oil sleeve annulus in all the sections of the open hole horizontal well section, and then closing the well to wait for the complete solidification of the plugging slurry, wherein the plugging slurry comprises a plugging agent and water, and the plugging agent comprises calcium sulphoaluminate hydrate, gypsum, calcium oxide and magnesium oxide;

using a water-based fracturing fluid base fluid, and carrying out integral pressure test on the whole well section base pipe of the selected open hole horizontal well by using a fracturing truck group, wherein the pressure is stabilized for 30 minutes under 80MPa, and the pressure drop is qualified when the pressure drop is not more than 0.5 MPa;

obtaining a complete horizontal well shaft to be fractured;

carrying out conventional multi-cluster perforation volume fracturing, high-density perforation seam volume control fracturing and multi-stage fracturing operation of dragging fracturing by a continuous oil pipe with a spray gun bottom seal on the complete horizontal shaft to be fractured;

for the obtained fractured horizontal shaft, a coiled tubing with an electric motor and a drill bit is used, a well is drilled and ground to reach the bottom of the well, and meanwhile, base fluid of a water-based fracturing fluid is circulated to discharge bridge plug fragments;

and pumping and injecting a special degrading agent to ensure that the solidified plugging slurry in the fractured horizontal well is completely hydrated, so that the joint production of new and old fractured fractures is realized.

Preferably, the reservoir characteristics include log and tectonic depositional characteristics, reservoir longitudinal and transverse distribution, three-dimensional stress state, natural fracture development, and dessert interbed distribution.

Preferably, the dessert interlayer distribution includes reservoir dessert distribution characteristics and barrier distribution characteristics.

Preferably, the single well control reserves include hydrocarbon bearing area, hydrocarbon layer thickness, effective porosity, crude oil natural gas density, hydrocarbon saturation, and volume factor.

Preferably, the recoverable reserves of the horizontal wells are calculated according to the Arps yield decreasing method during the repeated fracturing potential analysis.

Preferably, the residual oil-gas distribution rule of the horizontal well is analyzed by adopting a reservoir engineering yield splitting method during the repeated fracturing potential analysis.

Preferably, the particle size distribution of the plugging agent is 8-2500 meshes, and the density is 3.15-3.20g/cm³。

Preferably, the apparent viscosity of the plugging slurry is 25-85mPa · s, and the fluidity is 17-27 cm.

Preferably, when the conventional multi-cluster perforation volume fracturing, the high-density perforation seam volume control fracturing and the multi-stage fracturing operation of the coiled tubing bottom seal dragging fracturing are carried out, the ground pressure of a well mouth is not higher than 90 MPa.

Preferably, the degradation agent comprises potassium permanganate or sodium persulfate.

obtaining a complete horizontal well shaft to be fractured;

The repeated fracturing method of the open hole horizontal well provided by the invention can realize fixed-point reconstruction, has high construction efficiency, and excavates productivity from an effective reservoir which is not developed by one-time fracturing; the plugging agent has particle grading and can be used for plugging in stratums with different physical properties; the plugging agent has residence property, the plugging slurry prepared by the plugging agent contains various chemical components of different particles, can realize synergistic interaction, is in a flat-plate flow pattern in the formation pore, has good residence property, can reside in the formation pore and is not easy to be eroded by formation fluid; the plugging agent can form an interpenetrating network structure, and the interpenetrating network structure can be quickly formed (within 68 s) as long as the acting force is 0.7 MPa; the plugging slurry solidified body has micro-expansion performance, and the interaction of chemical components in the plugging agent, especially some inorganic particle components, can form a crystal lattice with larger volume, so the plugging slurry solidified body has good micro-expansion function, can form a very compact solidified body with a stratum or a steel body medium, and can bear higher pressure; the plugging agent has high plugging strength and can bear the pressure difference operation of 90 MPa; the plugging agent has high triaxial stress resistance, a triaxial stress experiment shows very good deformation after the plugging agent is solidified, the Poisson ratio (0.203) of the plugging agent is far higher than that of well cementation cement (0.105), and the elastic modulus (4993.4) of the plugging agent is far smaller than that of the well cementation cement (6180.2); the plugging agent completely reaches or exceeds the index of 5500 under the elastic modulus of high-quality cement slurry in the medium petroleum well cementation cement standard; the construction safety of the plugging agent is high.

Drawings

FIG. 1 is a schematic diagram of a completion string configuration;

FIG. 2 is a plan view of the porosity of the central reservoir in the dessert;

FIG. 3 is a plan view of the oil saturation level of the oil layer in the center of the dessert;

FIG. 4 is a pictorial view of running a liner string into an existing casing of a selected open hole horizontal well;

FIG. 5 is a physical diagram of a plugging slurry pump injected into an open hole horizontal well;

FIG. 6 is a schematic diagram of an interpenetrating network structure formed by plugging slurry;

FIG. 7 is a photograph of a partially amorphous hydration product that has eroded;

FIG. 8 is a photograph of a fibrous CSH gel;

FIG. 9 is a schematic diagram of self-healing action;

FIG. 10 shows the results of the temperature resistance test of the plugging slurry;

FIG. 11 is the dilatancy results for plugging slurries;

FIG. 12 shows the results of the salt resistance test of plugging slurries;

FIG. 13 is a graph of the strength of the plugging agent under certain oilfield conditions;

FIG. 14 is a pictorial view of a fracturing operation;

FIG. 15 is a diagram of a substance pumped with a degradation agent or waiting for a sufficient period of time;

FIG. 16 is a diagram of a material object for plugging slurry and liquefying, and extracting the run-in string to carry out co-production of new and old fracturing horizons;

figure 17 is a pictorial representation of a plug of slurry evenly applied to the fractures created by each perforation cluster.

Detailed Description

obtaining a complete horizontal well shaft to be fractured;

Carrying out conventional multi-cluster perforation volume fracturing (fast drilling or soluble bridge plug), high-density perforation seam control volume fracturing (fast drilling or soluble bridge plug), continuous oil pipe bottom seal dragging fracturing (annulus sand filling) and other multi-stage fracturing operations on the complete horizontal shaft to be fractured;

for the fractured horizontal shaft, using a coiled tubing with an electric motor and a drill bit, drilling and grinding the shaft to the bottom of the well, and simultaneously circulating base fluid of a water-based fracturing fluid out of bridge plug scraps (except for fracturing dragged by a bottom seal of a spray gun of the coiled tubing (annular sand filling));

according to the method, the geological characteristics of the regional structure, the reservoir characteristics, the single-well control reserve and the previous extraction degree are used as analysis parameters, the repeated fracturing potential analysis is carried out, and the open hole horizontal well is selected. In the present invention, the existing basepipe hanger of the open hole horizontal well preferably has a basepipe inner diameter below 41/2 "or more, i.e., a four inch half casing. In the present invention, the reservoir characteristics preferably include log and tectonic sedimentary characteristics, reservoir longitudinal and transverse distributions, three-dimensional stress states, natural fracture development, and dessert interbed distributions.

In the present invention, the dessert core profile preferably includes a reservoir dessert profile characteristic and a barrier profile characteristic.

In the present invention, the single well control reserve evaluation preferably includes hydrocarbon bearing area, hydrocarbon layer thickness, effective porosity, crude oil natural gas density, hydrocarbon saturation, and volume factor.

In the invention, the recoverable reserves of the horizontal wells are preferably calculated according to the Arps yield decreasing method during the repeated fracturing potential analysis.

In the invention, the residual oil distribution rule of the horizontal well is preferably analyzed by adopting an oil deposit engineering yield splitting method during the repeated fracturing potential analysis.

After a horizontal well is selected, a coiled tubing string with an electric motor and a drill bit is put into the existing base pipe of the selected open hole horizontal well, all ball seats are drilled and ground, and meanwhile, debris is circulated by using a water-based fracturing fluid base fluid. The specific manner of running the coiled tubing string with the electric motor and the drill bit is not particularly limited by the present invention, and can be any manner known to those skilled in the art.

After a horizontal well is selected, a coiled tubing string with a drift gauge and a scraper is put into the existing base pipe of the selected open hole horizontal well, and the coiled tubing string passes through the original ball seat repeatedly for three times, so that the drift diameter in the base pipe is ensured to be not deformed.

After a horizontal well is selected, a coiled tubing string with upper and lower cup packers and a nozzle is put into an existing base pipe of the selected open hole horizontal well, and the nozzle is placed between the two cup packers; aligning the position of a nozzle to the position of an original first sliding sleeve, forcibly extruding and injecting plugging slurry to the corresponding open hole horizontal well section, excessively displacing the plugging slurry to the position 1 meter inside an original artificial crack, stopping the pump for 10 minutes, utilizing the specific residence characteristic of the plugging slurry, starting the pump again to forcibly extrude and inject the rest part of the designed plugging slurry amount, filling the annular space of an oil sleeve of the horizontal well section, excessively displacing the plugging slurry, and taking the principle that no plugging slurry remains in a base pipe as a principle;

and repeating the steps to finish the squeezing of the original artificial cracks and the oil sleeve annulus in all the sections of the open hole horizontal well section, and then closing the well to wait for the complete solidification of the plugging slurry, wherein the plugging slurry comprises a plugging agent and water, and the plugging agent comprises calcium sulphoaluminate hydrate, gypsum, calcium oxide and magnesium oxide. In the invention, the particle size distribution of the plugging agent is preferably 8-2500 meshes, and the density is preferably 3.15-3.20g/cm³。

In the invention, the apparent viscosity of the plugging slurry is preferably 25-85 mPas, and the fluidity is preferably 17-27 cm.

After the plugging slurry is completely cured, the whole base pipe of the whole well section of the selected open hole horizontal well is subjected to overall pressure test by using a fracturing truck group, and the pressure is stabilized for 30 minutes under 80MPa, and the pressure drop is qualified when the pressure drop is not more than 0.5 MPa; and obtaining the complete horizontal well shaft to be fractured.

The method comprises the steps of obtaining a complete horizontal well shaft to be fractured, and carrying out conventional multi-cluster perforation volume fracturing, high-density perforation seam volume control fracturing and multi-stage fracturing operation of dragging fracturing by a continuous oil pipe with a spray gun bottom seal on the complete horizontal well shaft to be fractured. In the present invention, the conventional multiple cluster shot pore volume fracturing is preferably a fast drilling or dissolvable bridge plug; the high-density perforation seam control volume fracturing is preferably fast drilling or soluble bridge plugs; the coiled tubing drag fracturing with a spray gun bottom seal is preferably annular sanding.

After the multi-stage fracturing operation is finished, the invention uses a coiled tubing with an electric motor and a drill bit to drill and mill the horizontal shaft to the bottom of the well, and simultaneously uses water-based fracturing fluid base fluid to circulate bridge plug fragments out. In the invention, the coiled tubing with the spray gun bottom seal drags fracturing (annular sand filling) without using the coiled tubing with an electric motor and a drill bit, and the well is drilled and ground to reach the bottom of the well.

After the bridge plug is drilled and ground, the special degrading agent is pumped and injected, so that the solidified plugging slurry in the fractured horizontal well is completely hydrated, and the joint production of new and old fractured fractures is realized. In the invention, the complete hydration is preferably the hydration of 1m solidified plugging slurry in the oil casing annulus and the primary fractured fracture in the fractured horizontal well.

In the present invention, the degrading agent preferably includes potassium permanganate or sodium persulfate. 0.2 ton of degradation agent is injected per 100 square of plugging pump.

For further illustration of the present invention, the method of repeated fracturing of open hole horizontal well provided by the present invention is described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.

Example 1

The well number is as follows: JHW019 well type: evaluation well

Maximum well inclination angle: 90.63 degree

The well completion method comprises the following steps: open hole completion

The length of the horizontal section is 1228.03m, and the vertical depth is 3233-3292.7m

6' horizontal section, adopting open hole packer and ball-throwing sliding sleeve to complete well, totally dividing into 15 grades

Dessert on LCG group, crack under development

Actually drilling the track of the borehole:

JHW019 well 2014 finished drilling in 4 months and 21 days, nuclear magnetic interpretation: the length of the horizontal section is 1228m, the oil layer drilling contact rate is 61.8% (759m), the oil layer drilling contact rate of the first type is 19.5% (239m), the oil layer drilling contact rate of the second type is 15.8% (194m), and the oil layer drilling contact rate of the third type is 26.6% (326 m). The average value of the effective porosity is 9.2 percent, and the average value of the oil saturation is 63.5 percent.

The completion string configuration is shown in FIG. 1 and the casing procedures are shown in Table 1.

TABLE 1 casing procedure

Conventional well logging:

the logging depth was 3459-4815m, accounting for the interval 1356m, liberating the oil layer 301.2m, the poor oil layer 469.3m and the oil layer 488.4m, the others being dry layers.

Nuclear magnetic interpretation:

and classifying the reservoirs according to the nuclear magnetic logging porosity. The well is explained together: the thickness of the reservoir is 302.3m, and the total well is 3459 and 4815m, which account for 22.3 percent; two types of reservoirs: the thickness is 470m, and the proportion is 34.7%; three types of reservoirs: the thickness is 488.5m, accounting for 36%. Wherein the drilling rate of the I and II reservoir reservoirs is 56.95%; I. the drilling rate of II and III reservoir layers is 92.98%. Similar to the conventional logging result.

Crack characteristics:

the well develops relatively at 4050-.

The crack type is mainly effective cracks such as straight cleft cracks, oblique intersection cracks and the like, and the partial layer sections can see the ablation holes.

Reservoir characteristics:

1) logging conditions

According to logging information, reservoir lithology is mainly siltstone and cloud debris sandstone, wherein the siltstone has good physical property and oil content.

Interpretation of well logs

LCG group: a rock debris fluorescent 46 layer with thickness of 1395.00 m; gas test abnormal 7 layers, 1342.00m thick, maximum 1.9001% of total hydrocarbon gas test, component out to nC 5. The log explains 1 layer, 1395.00m thick, with 4 layers of oil, 1060.00m thick, 3 layers of oil, 282.00m thick.

Lithology and oil-containing: light gray, dark gray fluorescent mudstone, dolomitic mudstone and polio mudstone, argillaceous siltstone, dolomitic siltstone, and argillaceous dolomitic. 1-3% of wet illumination fluorescence, 1-2% of dark yellow, weak luminescence, 3-5% of spray illumination fluorescence, yellow, medium luminescence, 8-9 grades of contrast, and milky-milky yellow.

Drilling fluid conditions: the density of the drilling fluid is 1.42-1.52g/cm when the section is drilled and uncovered³The viscosity is not obviously changed for 60-74s, and the outlet conductivity is 53.77-84.39mS/cm (the change of the conductivity is large because of the adjustment of the drilling fluid).

Gas measurement: all-hydrocarbon: 0.0316% ↓ 1.9001%, C1: 0.0107% × 1.1090%, fraction going to C5, interpreted as oil, oil-containing layer.

Physical properties: drilling time (43-1) min/m (influenced by directional drilling).

And (3) well logging interpretation: logging is interpreted as a reservoir.

2) Deposition characteristics

The dessert body is deposited by the mud plateau phase of shallow lake, coastal lake and coastal lake.

Dessert oil interbedded distribution

1) Reservoir distribution characteristics

The oil reservoir span of the dessert body in one region is 35m, the dessert body is divided into 3 small layers, and lithology mainly comprises sand-crumbed dolomite, rock-crumbed feldspar powder fine sandstone and cloud-crumbed sandstone.

The oil layer is concentrated, the transverse continuity is good, the superposition thickness is more than 10m, and the thickness of the main force layer is more than 4 m.

The JHW019 well target layer is a dessert middle part (rock debris feldspar powder fine sandstone) oil layer, the thickness of a main area is more than 4m, the type I is taken as the main part, and the transverse continuity is good.

Fig. 2 is a plan view of the porosity of the oil layer in the center of the dessert, and fig. 3 is a plan view of the oil saturation of the oil layer in the center of the dessert.

The porosity of an oil layer in the center of the dessert is 11.7 percent on average, the oil saturation is 67 percent on average, and the physical property and the oil property are good.

2) Dessert barrier distribution characteristics

The dessert is mainly developed into 3 interlayers, and the thickness of the two interlayers above the oil layer in the middle of the dessert is 0-1.6 m, so that the separating capacity is limited. The lower interlayer is 4.8-6.2 m.

The three tensile strength of the interlayer is 13.9MPa, the horizontal minimum principal stress is 50.1MPa, and the rupture pressure is 64 MPa;

the tensile strength of the interlayer II is 12.5MPa, the horizontal minimum principal stress is 49.8MPa, and the rupture pressure is 62.3 MPa;

the rupture pressure difference between the interlayer and the target layer is 1.1-2.8 MPa, the thickness of the lower interlayer is about 5m, and the crack is easy to expand upwards.

Table 2 shows the comparison of the target block layer fracture strength and the ground stress.

TABLE 2 target Block horizon Break Strength and ground stress comparison

JHW019 well individual well control reserve estimation:

1) oil bearing area

According to the following:the length of the horizontal section is 1228m, the width is 300m (the well spacing is 300m), and the oil-bearing area is 0.3684km²。

2) Thickness of oil layer

And taking 4.5m according to the oil layer thickness map completed in the earlier stage.

3) Effective porosity

Taking the thickness weighted average value of the oil layer encountered by the JHW019 well drilling and the oil difference layer as 0.11, and the porosity value of the JHW019 well drilling and the original reserve parameter I type + II type is 0.11.

4) Density of crude oil

And taking a value of 0.879 according to the analysis data of the crude oil after 12 months of delivery in 2014.

5) Degree of saturation of oil

The reserve volume parameter of the original reservoir is 0.673.

6) Volume factor

The reserve parameter of the original reservoir is 1.06.

And table 3 is a JHW019 well single well control reserve estimation table.

TABLE 3JHW019 single well control reserve estimation table

Area of

Thickness of

Porosity of

Degree of saturation

Density of

Volume factor

Amount of resources

km2

m

f

g/cm³

f

104t

0.3684

5.5

0.11

0.673

0.879

1.06

12.4

And (3) repeated fracturing potential analysis:

the recoverable reserves 18905t of the well are calculated according to the Arps yield subtraction method, the current accumulated oil recovery is 8633 tons, the recovery degree is 45.66%, and the residual recoverable reserves 10272t have the potential of repeated fracturing excavation.

Potential analysis: and analyzing the distribution rule of the residual oil in the well by adopting an oil reservoir engineering yield splitting method. Through analysis, although the first and second oil layers have large extraction amount, the residual oil is relatively enriched due to the high original storage amount, and the residual oil is still the potential key point of re-pressing excavation. And (4) conclusion: the first and second reservoir layers are the key points for repeated fracturing reconstruction.

And selecting the bottom temperature range of the open hole horizontal well from 51 ℃ to 120 ℃.

The model of the existing horizontal section base pipe of the old well is 41/2 ".

And (3) putting a coiled tubing into the existing base pipe of the selected open hole horizontal well, wherein the physical diagram is shown in figure 4.

Pumping plugging slurry into the open hole horizontal well, replacing and filling 1m of the primary fracturing crack of the run-in section and an oil sleeve annulus, and then solidifying the plugging slurry, wherein the plugging slurry comprises plugging slurry and water, the plugging agent comprises calcium sulphoaluminate hydrate, gypsum, calcium oxide and magnesium oxide, so that a horizontal well to be fractured is obtained, and a real object diagram is shown in FIG. 5;

the plugging agent is a product compounded by finely processing and grain composition of various multifunctional materials.

Appearance: grayish brown powder

Particle size distribution: 8-2500 meshes

Density: 3.15-3.20g/cm³

Preparing a fluid: similar to cement paste;

preparing density: 1.45-2.60g/cm³

Apparent viscosity: 25-85 mPa.s;

fluidity: 17-27cm

Thickening time: is arbitrarily adjustable

Drillability: the drillability of the concretion is good

Plugging agent plugging mechanism

1. Form an interpenetrating network structure

The plugging agent and water are prepared into plugging slurry with a certain concentration, when the plugging slurry enters a leakage layer (leakage point), under the action of pressure difference (greater than 0.7MPa), components in the plugging slurry are synergistically enhanced to generate chemical reaction, at the moment, the plugging slurry can quickly form an interpenetrating network structure to form a special flow state, other components in the plugging slurry can fill gaps in a compact network structure, and the plugging slurry has scouring resistance and has residence performance.

The interpenetrating network structure is mainly formed by winding and coupling various flexible fibers, rigid fibers, CSH gel which is a hydration product in the plugging slurry, crystals produced by a plurality of chemical reactions and the like in the plugging slurry into an integral structure. The plugging slurry does not return and flow in the plugging section (layer), and the slurry plugging does not generate a slurry mixing zone.

FIG. 6 is a schematic diagram of an interpenetrating network structure formed by plugging slurry.

2. Expansion effect

Calcium sulfoaluminate hydrate reacts with gypsum to produce ettringite, and the crystal lattice of the product occupies larger space than that of the original compound, so that obvious expansion effect is produced, and the volume can be increased.

The swelling effect of calcium oxide and magnesium oxide is: calcium hydroxide and magnesium hydroxide are generated from calcium oxide and magnesium oxide, the crystal form is changed, the volume is increased, and micro-expansion is generated.

The open expansion rate of the plugging agent is 1.8-4.5%.

The expansion rate of the API cured body is 0.3-0.8%.

3. Self-healing action

Under the condition of dynamic curing, the crystal on the surface of the plugging agent is perfect rod-shaped ettringite crystal, and under the ettringite crystal, part of amorphous hydration products are seen to be corroded (figure 7) to expose a fresh surface, and a large amount of fibrous CSH gel is generated on the fresh surface, belongs to CSH (II) type (figure 8) defined by Diamond and is a product in the early stage of hydration. Fig. 9 is a schematic diagram of the self-healing effect, and these cementing interfaces of the solidified bodies of the plugging agent can continuously generate a plurality of erosion-resistant hydration products, eliminate the harmful transition zone of the interfaces, so that the interfaces have strong high-pressure fluid erosion resistance, which is the self-healing effect of the plugging agent interfaces, and this effect fundamentally improves the plugging quality, improves the cementing strength of the interfaces, and prolongs the continuity of the interface strength.

Staying property

After entering the plugging layer, the plugging agent can quickly form an interpenetrating network structure through a special mechanism, and is effectively retained in the plugging layer without returning. When the plugging agent is applied on site, the thickening time of the plugging agent can be adjusted according to the specific situation on site so as to meet the requirement of site safety construction.

Triaxial stress analysis (toughness)

The results of the three-axis stress test of the basic set cement and the plugging agent solidified body at the circulating temperature of 140 ℃ are shown in Table 4.

TABLE 4 results of triaxial stress analysis

The plugging slurry has higher Poisson's ratio and lower elastic modulus value, namely, the plugging slurry solidified body has good effect of resisting three-dimensional stress, namely, the plugging slurry solidified body can meet the requirements of modern well cementation technology. The medium petroleum well cementation cement slurry standard requires that the elastic modulus is less than 5500, and the cement slurry system is qualified.

The results of the temperature resistance test are shown in fig. 10, fig. 11 is the results of the swelling property, fig. 12 is the results of the salt resistance test, and table 5 is the results of the rheological property test.

TABLE 5 rheology test results

The strength of the plugging agent under XX oil field working conditions is shown in FIG. 13, and can be obtained from the graph: the hydration reaction in the plugging agent is continuously carried out within 120 days at 95 ℃; at 150 ℃, the hydration reaction in the plugging agent is continuously carried out within 60 days, and the strength of the cured body of the plugging agent cured at 150 ℃ is higher than that of the plugging agent cured at 95 ℃. While the ordinary cement paste reaches a stable state within about 100 hours.

Carrying out multistage fracturing operation on the horizontal well to be fractured, wherein a physical diagram is shown in fig. 14;

and pumping a degrading agent, wherein a physical diagram is shown in fig. 15, so that the solidified plugging slurry in the horizontal well to be fractured is completely hydrated, the joint production of new and old fractured fractures is realized, and a physical diagram is shown in fig. 16.

The key points of the process

Production seeking process adopting plugging and hole repairing fracturing

1. An oil pipe is lowered by 1000m, and then a coiled oil pipe is lowered to the bottom of the artificial well;

2. plugging slurry to the bottom of the well, and dragging the coiled tubing; replacing the dragging and controlling the annular pressure to be 10-15 MPa;

3. dragging the coiled tubing to a safe position, and positively jacking and pressing well fluid;

4. closing the well, positively extruding well liquid, and extruding plugging slurry into a primary fracturing fracture section;

5. after waiting for the pressure to diffuse, pulling out the coiled tubing;

6. stopping pressure and closing the well for waiting coagulation;

7. drilling and grinding a drift well, and testing the pressure of 80 MPa;

8. and (3) fracturing a new layer section by multistage hole-filling, drilling a plug after fracturing, injecting a degrading agent to hydrate and solidify plugging slurry, and obtaining the yield of the new and old cracks together.

55t oil with water content of 12.5% is obtained in daily period.

1. The plugging agent has particle composition

The plugging agent has various chemical particle grading of 8-2500 meshes, so that the plugging agent can be used for plugging in stratums with different physical properties; the set cement only has one silicate granularity and no particle grading; the plugging agent used in the invention has wider application range.

2. The plugging agent has residence property

The plugging slurry prepared by the plugging agent contains various chemical components of different particles, can realize synergistic interaction, is in a flat plate type flow pattern in the formation pore, has good residence property, can reside in the formation pore, and is not easy to be eroded by formation fluid; the cement slurry is in a peak-type flow pattern (fingering phenomenon) in the formation pores, has no residence property and is easy to be eroded by formation fluid; the blocking agent does not return to be discharged after entering the stratum, and cement paste has a phenomenon of return to be discharged.

3. The plugging agent can form an interpenetrating network structure

The plugging slurry can quickly form an interpenetrating network structure (within 68 s) in a stratum as long as 0.7MPa of acting force is applied, and at the moment, a certain pressure bearing capacity (6-8MPa) is achieved, so that the plugging effect of the plugging agent is improved; the cement paste can form an interpenetrating network structure only when thickened (generally after 240 min), and is easily diluted and eroded by formation fluid before the structure is formed, so that the plugging effect is poor; the plugging success of the plugging agent is much higher than that of cement paste.

4. The plugging slurry solidified body has micro-expansion performance

The mutual action of chemical components in the plugging agent, particularly some inorganic particle components, can form a crystal lattice with larger volume, so that the plugging slurry solidified body has a good micro-expansion function, and can form a very compact solidified body with a stratum or a steel body medium to bear the action of higher pressure; the solidified body of the cement paste is micro-contracted, micro cracks are formed between surrounding media, the solidified body is easily damaged by stratum pressure, micro leakage occurs, and even if expansive components are added into the cement paste, the integral strength of the cement paste solidified body can be reduced; the effective period of the plugging agent is longer after plugging.

5. The plugging agent has high plugging strength

The plugging agent solidified body has very high plugging strength, and can bear 75MPa of fracturing effect in the field application at present; the API compressive strength of the cement paste solidified body is qualified as long as the API compressive strength is more than 14MPa, and the plugging strength is relatively less than that of the plugging agent; the plugging agent can meet the requirement of fracturing the hollow casing after plugging.

6. The plugging agent has high triaxial stress resistance

After the plugging agent is solidified, a triaxial stress experiment shows very good performance, the Poisson ratio (0.203) of the plugging agent is far higher than that of well cementation cement (0.105), and the elastic modulus (4993.4) is far smaller than that of the well cementation cement (6180.2); the plugging agent completely reaches or exceeds the index of 5500 under the elastic modulus of high-quality cement slurry in the medium petroleum well cementation cement standard; the plugging agent can be completely used for the requirement of producing zone cementing.

7. The construction safety of the plugging agent is high

The mutual action of the temperature-resistant and salt-resistant components in the plugging agent is very mild when the plugging agent is used on site, the thickening time is controlled at will, the plugging agent has good compatibility with formation water with the mineralization degree in the formation, has good salt-resistant and temperature-resistant capabilities, does not have the phenomena of 'flash coagulation' and 'coagulation', and has no downhole accident in more than 1400 constructed wells; when the cement paste is used on site, the cement paste is easily polluted by formation water with formation mineralization degree, and the phenomena of 'flash coagulation' and 'coagulation' are easily caused, so that complex underground accidents of 'flag inserting rod' and 'sausage filling' are caused; the construction safety of the plugging agent is very high.

The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be construed as the protection scope of the present invention.

Claims

1. The open hole horizontal well repeated fracturing method is characterized by comprising the following steps of:

aligning the position of a nozzle to the position of an original first sliding sleeve, forcibly extruding and injecting plugging slurry to a corresponding open hole horizontal well section, excessively displacing the plugging slurry to the position 1m inside an original artificial crack, stopping a pump for 10 minutes, utilizing the specific residence characteristic of the plugging slurry, starting the pump again to forcibly extrude and inject the rest part of the designed plugging slurry amount, filling the annular space between the existing base pipe and the well wall of the horizontal well section, excessively displacing the plugging slurry, and taking the principle that no plugging slurry is left in the base pipe as the principle;

repeating the steps, completing the squeezing of original artificial cracks of all sections of the open hole horizontal well section and the annular space between the existing base pipe and the well wall, then closing the well and waiting for the complete solidification of the plugging slurry, wherein the plugging slurry comprises a plugging agent and water, and the plugging agent comprises calcium sulphoaluminate hydrate, gypsum, calcium oxide and magnesium oxide;

obtaining a complete horizontal well shaft to be fractured;

and pumping a special degrading agent to ensure that the solidified plugging slurry in the fractured horizontal well is completely hydrated, so that the joint production of new and old fractured fractures is realized, wherein the special degrading agent comprises potassium permanganate or sodium persulfate.

2. The open-hole horizontal well re-fracturing method of claim 1, wherein the reservoir characteristics comprise log well characteristics and tectonic depositional characteristics, reservoir longitudinal and transverse distributions, three-dimensional stress states, natural fracture development, and dessert bedding distributions.

3. The open-hole horizontal well re-fracturing method of claim 2, wherein the sweet spot interbed profile comprises a reservoir sweet spot profile and an interbed profile.

4. The open-hole horizontal well re-fracturing method of claim 1, wherein the single well control reserves comprise hydrocarbon bearing area, hydrocarbon layer thickness, effective porosity, crude oil natural gas density, hydrocarbon bearing saturation and volume factor.

5. The open-hole horizontal well repeated fracturing method of claim 1, wherein the recoverable horizontal well reserves are calculated according to an Arps yield decreasing method during repeated fracturing potential analysis.

6. The open-hole horizontal well repeated fracturing method of claim 1 or 5, wherein the residual oil-gas distribution rule of the horizontal well is analyzed by adopting a reservoir engineering yield splitting method during repeated fracturing potential analysis.

7. The open hole horizontal well repeated fracturing method of claim 1, wherein the particle size distribution of the plugging agent is 8-2500 meshes, and the density is 3.15-3.20g/cm³。

8. The open hole horizontal well repeated fracturing method of claim 1 or 7, wherein the apparent viscosity of the plugging slurry is 25-85mPa ∙ s, and the fluidity is 17-27 cm.

9. The open hole horizontal well repeated fracturing method of claim 1, wherein the wellhead ground pressure is not higher than 90MPa during the multi-stage fracturing operation of conventional multi-cluster perforation volume fracturing, high-density perforation seam volume control fracturing and coiled tubing bottom seal dragging fracturing.