CN112112617B - Method for developing thick-layer sand conglomerate oil reservoir by ectopic energy storage fracturing - Google Patents

Abstract

The invention provides a method for developing a thick-layer sand reservoir by ectopic energy storage fracturing, which comprises the following steps: step 1, preferably a frac well; step 2, directional perforation is carried out; step 3, carrying out low sand ratio and large liquid amount layering fracturing; step 4, performing energy storage replacement; and 5, carrying out alternate injection and production development. The method for developing the thick-layer sand conglomerate oil reservoir by ectopic energy storage fracturing can perform energy storage replacement and alternate exploitation, and solves the problems of weak natural energy and low natural productivity; the problem of mutual displacement between adjacent energy layers due to extremely low permeability is solved; stratum energy is effectively supplemented, and yield decrease is delayed; adjacent layers are mutually displaced, energy is mutually supplemented, and recovery ratio is improved.

Description

Method for developing thick-layer sand conglomerate oil reservoir by ectopic energy storage fracturing

Technical Field

The invention relates to the technical field of oil and gas reservoir development engineering, in particular to a method for developing a thick-layer sand conglomerate oil reservoir by ectopic energy storage fracturing.

Background

The sand reservoir is a composite fan reservoir with a steep slope and a debris flow carrying and messy accumulation cause, and has large longitudinal span and rapid transverse change; the reservoir physical property is poor, the low permeability and the extremely low permeability are mainly, the porosity of the middle and deep layers is generally 9.4-10.2%, the permeability is generally less than or equal to 5.0md, and the level difference is 30-100 times; the reservoir has large thickness, more layers and complex communication condition, and the longitudinal oil-containing well section is long and is between 50 and 500 meters.

The mining characteristics mainly include:

1. natural energy is weak, elastic development yield decreases rapidly, as shown in fig. 1, yield characteristics of thick layer sandstone: the yield drops very rapidly.

2. The natural productivity is greatly different and is generally required to be transformed by fracturing

Table 1 table xx block fracturing effect comparison table

3. The permeability is low, the connectivity is poor, the energy is difficult to effectively supplement, and the yield is fast to decrease.

FIG. 2 is a schematic diagram of post-fracturing production, wherein the X66 well is developed for post-fracturing water injection, but the stratum permeability is low, the connectivity is poor, the energy is difficult to effectively supplement, and the production/energy is fast to decrease. The initial yield after fracturing is high but drops very rapidly. The energy is supplemented by the water injection corresponding to the water injection well, and the energy of the well cannot be supplemented by the water injection due to extremely low permeability of the sandstone, so that no response of water injection takes effect.

Therefore, the invention provides a novel method for developing a thick layer of sandstone oil reservoir by ectopic energy storage fracturing, and solves the technical problems.

Disclosure of Invention

The invention aims to provide a method for developing a thick-layer sand reservoir by adopting an off-site energy-storage fracturing development method aiming at the defects of rapid energy reduction and difficult supplementation of the existing thick-layer sand reservoir development, so that the energy of a stratum after fracturing is effectively supplemented, and the recovery ratio is improved.

The aim of the invention can be achieved by the following technical measures: the method for developing the thick-layer sand reservoir by using the ectopic energy storage fracturing comprises the following steps of: step 1, preferably a frac well; step 2, directional perforation is carried out; step 3, carrying out low sand ratio and large liquid amount layering fracturing; step 4, performing energy storage replacement; and 5, carrying out alternate injection and production development.

The aim of the invention can be achieved by the following technical measures:

in step 1, the preferred fracture well reservoir thickness is above 50 meters.

In the step 2, deep penetration perforation is carried out on a second section with a phase angle of 0 degrees according to the main ground stress direction; the first section is perforated by deep penetration at a 90 DEG phase angle, and the two sections are separated by a distance of 20-40 meters.

In the step 3, large-scale fracturing is carried out on the first section, the sand is added for 70 sides, and a large liquid amount of more than 500 sides is adopted; and carrying out large-scale fracturing on the second section, wherein the sand adding amount is 80, and the liquid amount is more than 500.

In the step 4, after the fracturing is finished, the well is braised for 15-20 days, and a large amount of injected liquid is utilized to supplement stratum energy, increase the volume of a far-end fracture network and restore fracture conductivity; thereafter, the well is opened to produce, and the displaced oil and gas is produced along with part of the injected water.

The step 5 comprises the following steps:

1) After the well is closed, the second section is mined by self energy, and after the self energy is reduced, the energy of the first section acts to drive the second section, so that the mining time is longer than that of single well throughput;

2) After the second section is exploited, water is injected into the second section, the water injection amount is not lower than the extracted liquid amount, then bridge plugs are drilled, and the first section is exploited singly;

3) After the energy of the first section is reduced, the energy of the second section acts to drive the first section;

4) After the first section is mined, water is injected into the section, and the water injection amount is not lower than the produced liquid amount. And then singly picking the second section.

In step 5, a plurality of cycles are alternately mined, with each segment of energy supplementing energy from the horizon.

The method for developing the thick-layer sand conglomerate oil reservoir by ectopic energy storage fracturing solves the problems of weak natural energy and low natural productivity; the mutual displacement between the energy adjacent layers due to extremely low permeability is solved. Stratum energy is effectively supplemented, and yield decrease is delayed; adjacent layers are mutually displaced, energy is mutually supplemented, and recovery ratio is improved. Compared with the prior art, the method for developing the thick-layer sand conglomerate oil reservoir by using the ectopic energy storage fracturing has the following advantages:

1) And (5) energy storage replacement. The injected large amount of liquid is utilized to supplement stratum energy, increase the volume of a far-end fracture net, restore fracture conductivity and replace oil gas.

2) Alternate production, supplementing energy to other intervals that are simultaneously fractured. Because the two layers are adjacent, the interval distance is relatively short, and the problem that the energy of the conglomerate oil reservoir is difficult to supplement is solved.

Drawings

FIG. 1 is a schematic diagram of natural yield;

FIG. 2 is a schematic diagram of post-fracturing production;

FIG. 3 is a side view of a single wing slit in an embodiment of the present invention;

FIG. 4 is a top view of a double wing crack according to an embodiment of the present invention;

FIG. 5 is a schematic view of a fracturing string according to an embodiment of the present invention;

FIG. 6 is a schematic diagram of the daily oil production of an ex situ energy storing fractured well in accordance with an embodiment of the present invention;

FIG. 7 is a schematic diagram of a comparison of 4 years cumulative oil production from an ex situ energy storing fracturing well x560 and two other wells in the same interval of a zone according to an embodiment of the present invention;

FIG. 8 is a flow chart of one embodiment of a method of developing a thick layer of a conglomerate reservoir using ex-situ energy-storing fracturing in accordance with the present invention.

Detailed Description

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments, as illustrated in the accompanying drawings.

As shown in fig. 8, fig. 8 is a flow chart of a method of developing a thick layer of conglomerate reservoir using ex-situ energy-storing fracturing in accordance with the present invention.

Step 101, preferably fracturing the well, the reservoir thickness being above 50 meters.

Step 102, directional perforation.

According to the main ground stress direction, deep penetration perforation is carried out on the second section with a phase angle of 0 degrees; the first segment is perforated by deep penetration at a 90 deg. phase angle. The distance between two sections is 20-40 m, so that the fracturing is easy to channeling, and the energy conduction is slow.

And 103, low sand ratio and large liquid amount are used for fracturing in a layered manner.

The first stage was subjected to large-scale fracturing, and a large liquid amount (the liquid amount was 500 or more) was used for the sand addition 70.

And carrying out large-scale fracturing on the second section, wherein the sand adding process is 80 times, and a large liquid amount (the liquid amount is more than 500 times) is adopted.

Step 104, energy storage replacement.

After the fracturing is finished, the well is braised for about 15-20 days. The injected large amount of liquid is utilized to supplement stratum energy, increase the volume of a far-end fracture net, restore fracture conductivity and the like. The microcosmic mechanism is as follows: after water is injected into the oil producing layer, the injected water is filled with the parts such as high porosity, high permeability zone, large pore throat or crack. After well shut-in, under the action of capillary force, oil gas in water replacement, small pore throat or matrix is injected to redistribute oil water in the producing layer. Thereafter, the well is opened to produce, and the displaced oil and gas is produced along with part of the injected water. The large liquid injection can not only effectively supplement stratum energy and maintain original reservoir physical characteristics, but also overcome capillary force, a Jack effect and blockage of solid particles, so that petroleum trapped in a large pore canal by the capillary force during original water injection flows more easily.

And 105, alternate injection and production development.

1) After the well is closed, the second section is mined by self energy, and after the self energy is reduced, the energy of the first section acts to drive the second section. Longer than single well throughput production time.

2) After the second section is exploited, water is injected into the second section, and the water injection amount is not lower than the extracted liquid amount. The bridge plug is then drilled off and the first section is mined singly.

3) After the energy of the first section is reduced, the energy of the second section acts to displace the first section.

4) After the first section is mined, water is injected into the section, and the water injection amount is not lower than the produced liquid amount. And then singly picking the second section.

The energy supplement of each section of the alternating mining system mainly comes from the energy of the different layers, and the energy supplement is short in distance and quick in conduction, so that effective displacement can be realized, and the recovery ratio is improved.

In one embodiment of the invention, the method comprises the following steps:

1. preferably, the fracturing well is used, and the thickness of an oil layer is more than 50 meters.

Table 2 x560 well geophysical log interpretation outcome table

Explaining an oil layer of 86.6m/10 layer with an effective thickness of 69.8 m; 26.2 m/1 layers of oil-water layers; a difference oil layer of 15.3m/4 layers; the dry layer was 66.5 m/10 layer. The fracturing is divided into two layers: 7-10# layers and 12-24# layers.

2. Directional perforation

According to the main ground stress direction, deep penetration perforation is carried out on the second section with a phase angle of 0 degrees; the first segment is perforated by deep penetration at a 90 deg. phase angle. The distance between two sections is 20-40 m, so that the fracturing is easy to channeling, and the energy conduction is slow.

Table 3 x560 well perforation data table

3. Low sand ratio, large liquid volume stratified fracturing

The first stage was subjected to large-scale fracturing, and a large liquid amount (the liquid amount was 500 or more) was used for the sand addition 70.

Table 4 first stage pumping schedule

And carrying out large-scale fracturing on the second section, wherein the sand adding process is 80 times, and a large liquid amount (the liquid amount is more than 500 times) is adopted.

Table 5 second stage pumping schedule

After fracturing, a fracture shown in fig. 3 is formed, fig. 3 is a schematic diagram of initial extension of two single-wing fractures formed by two stages of fracturing, the initial extension direction of the fracture is determined through directional perforation, and the two fractures are deflected by an angle of 90 degrees. FIG. 4 is a top view of a dual-wing fracture, where the first fracture has an included angle with the second fracture and returns to the main stress direction after being separated from the wellbore, and is parallel to the second fracture.

4. Energy storage displacement

After the fracturing is finished, the well is braised for about 15-20 days. The injected large amount of liquid is utilized to supplement stratum energy, increase the volume of a far-end fracture net, restore fracture conductivity and the like. The microcosmic mechanism is as follows: after water is injected into the oil producing layer, the injected water is filled with the parts such as high porosity, high permeability zone, large pore throat or crack. After well shut-in, under the action of capillary force, oil gas in water replacement, small pore throat or matrix is injected to redistribute oil water in the producing layer. Thereafter, the well is opened to produce, and the displaced oil and gas is produced along with part of the injected water. The large liquid injection can not only effectively supplement stratum energy and maintain original reservoir physical characteristics, but also overcome capillary force, a Jack effect and blockage of solid particles, so that petroleum trapped in a large pore canal by the capillary force during original water injection flows more easily.

5. Alternate injection and production development

1) After the well is closed, the second section is mined by self energy, and after the self energy is reduced, the energy of the first section acts to drive the second section. Longer than single well throughput production time.

2) After the second section is exploited, water is injected into the second section, and the water injection amount is not lower than the extracted liquid amount. The bridge plug is then drilled off and the first section is mined singly.

3) After the energy of the first section is reduced, the energy of the second section acts to displace the first section.

4) After the first section is mined, water is injected into the section, and the water injection amount is not lower than the produced liquid amount. And then singly picking the second section.

The energy supplement of each section of the alternating mining system mainly comes from the energy of the different layers, and the energy supplement is short in distance and quick in conduction, so that effective displacement can be realized, and the recovery ratio is improved.

6. Effect of the invention

1) Production curve

2) Effect comparison

The 2 normal fracturing recovery wells at the same level of the same block are compared, and the oil production amounts are obviously different.

FIG. 5 is a schematic illustration of a two-layer fracturing of a pipe in which the bridge plug intermediate passage is open and fluid can pass through. When fracturing, the first stage is firstly fractured, and after the first stage fracturing is finished, the bridge plug middle channel is closed by means of ball throwing/rod throwing and the like. Continuing to fracture the second stage, after the second stage fracturing is finished, performing well stewing for a period of time, and putting into production.

In fig. 6 (1) is the upper layer after fracturing and soaking, namely the daily oil production of the second section. (2) Is the operation construction for opening the bridge plug. (3) The lower layer, i.e. the first stage, is the daily oil production. (4) The first section and the second section are injected with water and the well is closed after the well is closed. (5) Is the upper layer, i.e. the daily oil production of the second stage. (6) Is the operation construction for opening the bridge plug. (7) Is the daily oil production of the second section.

X560 in fig. 7 is a thick layer conglomerate well developed via ex situ energy storage fracturing. 222-1 and 22-x5 are sand wells with similar physical properties to the horizon of x560 well and are transformed by ordinary fracturing. Comparison shows that the accumulated oil yield in 4 years far exceeds that of a common fracturing reformation well.

Claims (1)

1. The method for developing the thick-layer sand reservoir by ectopic energy storage fracturing is characterized by comprising the following steps of:

step 1, preferably a frac well;

step 2, directional perforation is carried out;

step 3, carrying out low sand ratio and large liquid amount layering fracturing;

step 4, performing energy storage replacement;

step 5, alternate injection and production development is carried out;

in step 1, the preferred fracturing well reservoir thickness is above 50 meters;

in the step 2, deep penetration perforation is carried out on a second section with a phase angle of 0 degrees according to the main ground stress direction; deep penetration perforation is carried out on the first section with a phase angle of 90 degrees, and the distance between the two sections is 20-40 meters;

in the step 3, large-scale fracturing is carried out on the first section, the sand is added for 70 sides, and a large liquid amount of more than 500 sides is adopted; carrying out large-scale fracturing on the second section, adding sand 80, and adopting a large liquid amount of more than 500;

in the step 4, after the fracturing is finished, the well is braised for 15-20 days, and a large amount of injected liquid is utilized to supplement stratum energy, increase the volume of a far-end fracture network and restore fracture conductivity; thereafter, producing the well, and extracting the replaced oil gas along with part of injected water;

the step 5 comprises the following steps:

1) After the well is closed, the second section is mined by self energy, and after the self energy is reduced, the energy of the first section acts to drive the second section, so that the mining time is longer than that of single well throughput;

2) After the second section is exploited, water is injected into the second section, the water injection amount is not lower than the extracted liquid amount, then bridge plugs are drilled, and the first section is exploited singly;

3) After the energy of the first section is reduced, the energy of the second section acts to drive the first section;

4) After the first section is mined, water is injected into the first section, the water injection amount is not lower than the extracted liquid amount, and then the second section is mined singly;

in step 5, a plurality of cycles are alternately mined, with each segment of energy supplementing energy from the horizon.