CN107418551B - A kind of skeleton proppant and its uneven spread method for realizing macrovoid channel - Google Patents

Abstract

The invention relates to a skeleton-type proppant for realizing large-pore channels and its uneven paving method, including a proppant particle skeleton, and the shape of the proppant particle skeleton is spherical, centered on the center of the sphere in the sphere There are three cylindrical channels perpendicular to each other and running through the sphere, the proppant particle skeleton is filled with fracturing fibers, and a degradable polymer is arranged at the port of the cylindrical channel to seal the port of the cylindrical channel Blocking. After the degradable polymer of the present invention is degraded, it is discharged into the stratum along with the fracturing fluid, and the internal fibers are released to form a network structure, so that the proppant is unevenly laid, forming the effect of channel fracturing, and finally the unevenly laid support The flow conductivity of the channels between the proppant and the transparent pores inside the proppant framework will increase by 10 to 30 times compared with the flow conductivity of conventional fracturing.

Description

A skeleton type proppant and its uneven paving method for realizing large pore channels

technical field

The invention relates to a skeleton type proppant for realizing large pore channels and a non-uniform laying method thereof, belonging to the technical field of oil and gas field development.

Background technique

Low-permeability and ultra-low-permeability oil and gas reservoirs are widely distributed in my country. Most of the low-permeability oil and gas reservoirs are difficult to obtain industrial oil and gas without reservoir stimulation. At present, hydraulic fracturing technology is the main measure for oil and gas reservoir stimulation. The purpose of hydraulic fracturing is to create a flow path from the formation to the wellbore, increasing the productivity of oil and gas wells. Conventional fracturing technology usually uses proppant to fill fractures, keep the fractures open, and make the fractures have high conductivity, so as to establish effective production channels. Therefore, in hydraulic fracturing, the increased conductivity of the proppant laid in the fracture plays a crucial role.

At present, in domestic oil field fracturing, many construction processes use traditional proppants to directly fill fractures, so that compared with the original oil and gas reservoirs, its conductivity is indeed much improved. For example, Chinese patent document CN105315985A (application number: ) discloses a hollow ceramsite proppant and its preparation method, crushing and grinding anthracite coal powder to make spherical seeds; Mixing, using anthracite coal powder spherical seeds as seeds, forming balls in a ball rolling machine; after screening, drying and calcining, a hollow ceramsite proppant is obtained, and the center of the hollow ceramsite proppant is a hollow structure. Although this kind of proppant has a hollow structure, the oil and gas conduction channels still only exist in the gaps between the proppants, and after the fracturing fluid gel-breaking residue and proppant broken particles block the pores, the flow conductivity in the fracture is greatly improved. As a result, the fracture permeability measured by post-fracture well testing can often only reach one-tenth, or even one percent, of that in the laboratory.

In recent years, a high-speed channel fracturing technology has emerged at home and abroad. The difference between this technology and conventional fracturing is that it changes the laying form of proppant in the fracture, and changes the conventional uniform laying into non-uniform scattered laying. . Artificial fractures are supported by many "pillars" like bridge piers, and smooth "channels" are formed between the pillars, and many "channels" form a network, thus realizing the form of large fractures containing many small fractures, which greatly improves oil and gas seepage. ability, so it is vividly called "high-speed channel" fracturing technology. The disadvantage is that it mainly uses conventional proppant and fiber, and the fiber is easy to block the fracture channel during the carrying process, and cannot prevent the proppant from settling deep in the fracture.

Contents of the invention

In view of the deficiencies of the existing technology, especially the use of conventional proppants and fibers in the existing fracturing technology of non-uniform proppant laying, the defects that the fibers are easy to block the fracture channels and prevent the proppant from settling during the carrying process, this paper The invention provides a skeleton type proppant for realizing large pore channels and its uneven laying method. The present invention changes the shape of conventional proppant granular entities to form a skeleton-like proppant frame, and fills the frame with a mixture of polymers that can be automatically degraded and fracturing fibers. By changing the density of the filled polymer, the Change the density of the overall proppant to ensure the suspension of the proppant in fracturing fluids of different densities. After the proppant is injected into the fracture, under the condition of high temperature in the formation, the polymer will automatically degrade and release the fracturing fibers combined with it, and the fiber will form a network structure in the fracture, which is conducive to the formation of proppant clusters and realizes the unevenness of the proppant Laying, forming high-speed channel fracturing. After the degraded polymer flows back with the fracturing fluid, the remaining proppant framework can also be laid well in the formation, and the interior of the proppant framework also forms a high-permeability channel for oil and gas flow.

Technical scheme of the present invention is as follows:

A skeleton-type proppant for realizing large-pore channels, including a proppant particle skeleton, the shape of the proppant particle skeleton is spherical, and three mutually perpendicular and penetrating spheres are arranged in the sphere with the center of the sphere as the center. The cylindrical channel is filled with fracturing fibers in the proppant particle skeleton, and a degradable polymer is arranged at the port of the cylindrical channel to block the port of the cylindrical channel.

According to the present invention, preferably, the thickness for sealing the cylindrical channel port is one-twentieth to one-tenth of the diameter of the proppant. The inner cavity of the proppant particle skeleton is close to the hollow state.

According to the present invention, preferably, the radii of the three cylindrical channels are one-fifth to one-third of the radius of the sphere; preferably, the particle size of the proppant is 5-40 mesh, larger than the conventional proppant particle size.

According to the present invention, preferably, the total volume of the proppant (that is: the volume of the entire sphere) is taken as the sum of the volumes of the proppant particle framework, the degradable polymer and the fracturing fiber, and the volume of the proppant particle framework accounts for the total volume of the proppant. 50%-80% of the volume, the degradable polymer accounts for 5%-10% of the total volume of the proppant, and the internal cavity accounts for 15%-40% of the total volume.

According to the present invention, preferably, the apparent density of the proppant particle skeleton is 1.6-2.7 g/cm ³ ;

Preferably, the apparent density of the degradable polymer is 1.1-1.35g/cm ³ ;

Preferably, the apparent density of the skeleton proppant after the fracturing fibers are filled and the cylindrical channel port is blocked is 1.2-2.6 g/cm ³ .

According to the present invention, preferably, the material of the proppant particle skeleton is ceramic, metal or glass;

Preferably, the degradable polymer is polyethylene oxide, polypropylene oxide, water-reducible acrylic acid, water-reducible phenoxy resin, polyester, polyvinyl alcohol, polyvinyl acetate, poly Graft copolymers of vinyl alcohol and polyvinyl acetate, polylactide, polyglycolic acid or polyglycolic acid;

Preferably, the fracturing fibers are glass fibers or polyvinyl alcohol fibers.

The method for establishing the internal channel of the skeleton type proppant of the present invention is: with the center of the sphere as the origin, establish a mutually perpendicular X-Y-Z three-axis coordinate system, and cut out three cylinders inside the proppant along the direction of the coordinate axes Channels, i.e. the formation of three transparent holes, remove the radius of the cylinder from one-fifth to one-third of the radius of the sphere.

According to the present invention, the uneven laying method of the above-mentioned skeleton type proppant comprises steps as follows:

(1) At the beginning of fracturing, the pre-fluid is pumped into the formation to form cracks of a certain width and length in the formation;

(2) Pump the sand-carrying fluid mixed with the skeleton proppant of the present invention into the formation at a displacement of 3 to 10 m ³ /min to support the geometry of the fractures that have been formed, that is, to complete the uneven laying of the skeleton proppant .

According to the laying method of the present invention, preferably, in step (2), the ratio of the volume fraction of the skeleton proppant to the total sand-carrying liquid volume is the sand ratio, and the sand ratio is 40%-80%.

After the degradable polymer in the skeleton type proppant of the present invention is degraded and melted, it flows back along with the fracturing fluid. The fracturing fibers mixed with the polymer are released, come out from the inside of the proppant and enter the fracture, forming a network structure, which has the effect of inhibiting the settlement of the proppant to a certain extent, and makes the proppant aggregate into clusters. Channels for oil and gas diversion are also formed between them, that is, high-speed channel fracturing is realized. Before the degradable polymer in the skeleton proppant of the present invention is degraded, the entire spherical proppant particle enters the formation fracture along with the sand-carrying fluid, similar to conventional fracturing, after the polymer in the particle is degraded and melted, it flows back rapidly , leaving only the particle framework and fibers in the formation, forming a state of uneven laying in the formation. After the fracture is closed, the formed diversion channel consists of two parts: the channel between the proppant particles and the transparent channel inside the proppant.

Features and advantages of the present invention:

1. The three cylindrical channels of the skeleton type proppant of the present invention are distributed perpendicularly to each other, the distribution is even, the force is balanced, and it is not easy to deform and break when squeezed in the crack; there are 6 holes in the appearance of the spherical proppant skeleton , when the adjacent proppant is closely arranged in the formation, at least two pores are connected to the external space, so that oil and gas can pass through the inside of each proppant particle frame. If there are more than three cylindrical channels, the mechanical properties of the proppant cannot be maintained, and the structure is not strong.

2. The present invention utilizes the degradable and low-density properties of some polymers to fill the outer part of the skeleton channel of the skeleton proppant, and inject the whole proppant into formation fractures along with the sand-carrying fluid. After the polymer blocking the proppant is degraded, the fracturing fibers will overflow the particle skeleton and diffuse to the outside to form a network structure, which is conducive to the uneven laying of the proppant, thereby forming high-speed channel fracturing.

3. According to the combination with the fracturing fluid, the present invention selects a suitable degradable polymer to reduce the density of the overall proppant. When using a high-density fracturing fluid, use a high-density polymer and use a low-density fracturing If liquid is used, low-density polymer is used; the density of the selected degradable polymer is about 1.1-1.35g/cm ³ , which is much lower than the density of the proppant skeleton. The low-density properties of the polymer make it easier for the proppant to be suspended in the sand-carrying fluid during migration, and it is not easy to settle, and the proppant is easier to enter the deep part of the fracture. The integral proppant particles are spherical, and are easier to migrate with the sand-carrying fluid than pure particle skeletons.

4. After the degradable polymer of the present invention is degraded, it is discharged into the stratum with the fracturing fluid, and the internal fibers are released to form a network structure, so that the proppant is laid unevenly, forming the effect of channel fracturing, and finally laid unevenly The flow conductivity of the channels between the proppant and the transparent channels inside the proppant framework will increase by 10 to 30 times than that of conventional fracturing.

Description of drawings

Figure 1: Schematic diagram of the appearance of the framework of the framework proppant of the present invention.

Fig. 2 is a cross-sectional view of the framework of the framework proppant of the present invention after removing one-eighth of the volume of the sphere.

Fig. 3: After the degradable polymer of the skeleton type proppant of the present invention is degraded, the laying effect diagram of the proppant skeleton in the formation fracture. Among them, 1 is the proppant group connected together by fiber entanglement, 2 is the fiber, and 3 is the direction of oil and gas flow.

Detailed ways

The present invention will be described in detail below in conjunction with the embodiments and the accompanying drawings, but is not limited thereto.

Embodiment 1-8:

A skeleton-type proppant for realizing large-pore channels, including a proppant particle skeleton, the shape of the proppant particle skeleton is spherical, and three mutually perpendicular and penetrating spheres are arranged in the sphere with the center of the sphere as the center. A cylindrical channel, the proppant particle skeleton is filled with fracturing fibers, a degradable polymer is arranged at the port of the cylindrical channel to block the cylindrical channel port, and the inner cavity of the proppant particle is close to hollow state, the thickness of the plugging is between one-twentieth and one-tenth of the proppant diameter.

The establishment method of the cylindrical channel is: establish a three-axis coordinate system at the center of the sphere, and remove the inside of the proppant along the direction of the polar axis, that is, form three transparent holes, and the radius of the removed cylinder is five times the radius of the sphere. One-third to one-third. The schematic diagram of the appearance of the proppant framework is shown in Figure 1. It can be seen from Figure 1 that the proppant framework has three holes along three mutually perpendicular polar axes. The intersection of the polar axes is at the center of the sphere, and the structure is stable. And the force is even.

Taking the sum of the volumes of the proppant particle framework, the degradable polymer and the fracturing fiber as the total volume of the proppant (that is: the volume of the entire sphere), the volume of the proppant particle framework accounts for 50%-80% of the total volume of the proppant , the degradable polymer accounts for 5%-10% of the total volume of the proppant, and the internal cavity accounts for 15%-40% of the total volume.

The material of the proppant skeleton, the material of the degradable polymer, the material of the fracturing fiber, the particle size and the apparent density of the skeleton proppant in Examples 1-8 are shown in Table 1.

Table 1

Examples 9-11

As described in Example 1, the difference is:

The selected meshes of proppant are 20 mesh, 30 mesh, and 40 mesh respectively, and the basic materials are all composed of ceramsite. The inner diameter of the skeleton proppant channel is one-third of the inner diameter of the overall proppant; the fracturing fiber is polyvinyl alcohol, The density is 1.2g/cm ³ . After the skeleton proppant is filled with polyvinyl alcohol fracturing fibers, the channel ports are blocked with polyethylene oxide; the overall density of the skeleton proppant is 1.3g/cm ³ .

Example 12:

A method for unevenly laying a skeleton type proppant for realizing a large pore channel, comprising the following steps:

(1) At the beginning of fracturing, the pre-fluid is pumped into the formation to form cracks of a certain width and length in the formation;

(2) Pump the sand-carrying fluid mixed with the skeleton-type proppant described in Examples 1-8 into the formation at a displacement of 3-10m ³ /min to support the geometry of the fractures that have been formed, that is, to complete the skeleton-type proppant Uneven distribution of agents.

In this embodiment, the ratio of the volume fraction of the skeleton proppant to the total volume of the sand-carrying liquid is the sand ratio, and the sand ratio is 50%.

After the degradable polymer is degraded and melted, it will flow back and flow out with the fracturing fluid. The fracturing fibers mixed with the degradable polymer are released, come out from the inside of the proppant and enter the fracture, forming a network structure, which can inhibit the settlement of the proppant to a certain extent, and make the proppant aggregate into clusters. Channels for oil and gas diversion are also formed between the clusters. The rendering is shown in Figure 3. It can be seen from Figure 3 that oil and gas can pass through the pores inside the sphere from any direction, thereby greatly increasing the permeability.

Test case

Taking the conventional proppant as a comparison, test the flow conductivity of the proppant of Examples 9-11 and the conventional proppant, the specific experimental method is as follows:

(1) Experimental displacement

In the experiment, a small-displacement pump was used to fill the sand-carrying fluid and the intermediate displacement fluid. The pumping flow rate of both was set to 50 L/min. At the beginning, no closing pressure was applied to the visible plate fracture device, and the fracture width was set to 8 mm.

(2) Viscosity of fracturing fluid

The viscosity of fracturing fluid is mainly affected by temperature, and this experimental device is suitable for experiments at room temperature. The viscosity of the fracturing fluid base fluid prepared in the experiment was 1 mPa·s.

(3) sand ratio

The sand ratio is the volume fraction of proppant in the total sand-carrying liquid volume. The sand ratio for this experiment was chosen to be 80%. After a period of time after the polyvinyl alcohol polymer was degraded under high temperature conditions, the conductivity was tested, and the results are shown in Table 2.

Table 2

It can be seen from Table 1 that the proppant filled in the fractures in Examples 9, 10, and 11 is far more than the conventional proppant in the comparative example. This is because the unique hollow structure of the skeleton proppant makes the overall density lighter. It is easier to be carried, so the amount that can enter the fracture is more; and the flow conductivity of Examples 9, 10, and 11 is larger than that of the comparative example, this is because after the polymer that blocks the pores of the skeleton proppant is degraded, the fibers Discharge, entangled on the proppant, and further prevent the proppant from settling, so that there are certain channels between the proppant, and the hollow structure is formed inside the proppant, which also provides a huge internal channel. The higher the mesh number of the proppant, that is, the smaller the particle size, the more serious the Jamin effect is, which reduces the conductivity. From this point of view, the large particle size framework has a higher conductivity than conventional proppants.

Claims (10)

1. a kind of skeleton proppant for realizing macrovoid channel, including proppant particles skeleton, which is characterized in that the branch Support agent grain skeleton shape is spherical, and there are three orthogonal and pass through for setting in sphere centered on the centre of sphere of sphere The cylindrical channel for wearing sphere is filled with fracturing fibre, at the end of the cylindrical channel in the proppant particles skeleton Degradable polymer is provided at mouthful to block cylindrical channel port.

2. skeleton proppant according to claim 1, which is characterized in that the thickness blocked to cylindrical channel port Degree is 1st/10 to ten/20ths of proppant diameter.

3. skeleton proppant according to claim 1, which is characterized in that the radius of three cylindrical channels is equal 1/5th for radius of sphericity arrive one third.

4. skeleton proppant according to claim 1, which is characterized in that the proppant partial size is 5 ~ 40 mesh.

5. skeleton proppant according to claim 1, which is characterized in that with proppant particles frame, degradable polymerization The volume summation of object and fracturing fibre is proppant total volume, and the volume of the proppant particles skeleton accounts for proppant total volume 50%-80%, the degradable polymer accounts for the 5%-10% of proppant total volume, and internal cavities account for total volume 15% ~ 40%.

6. skeleton proppant according to claim 1, which is characterized in that the apparent density of the proppant particles skeleton For 1.6-2.7g/cm³；

The apparent density of the degradable polymer is 1.1-1.35g/cm³；

It fills fracturing fibre and the apparent density for carrying out blocking back skeleton formula proppant to cylindrical channel port is 1.2-2.6g/ cm³。

7. skeleton proppant according to claim 1, which is characterized in that the material of the proppant particles skeleton is Ceramics, metal or glass.

8. skeleton proppant according to claim 1, which is characterized in that the degradable polymer is polycyclic oxygen second The graft copolymer of alkane, polypropylene oxide, polyvinyl alcohol, polyvinyl acetate, polyvinyl alcohol and polyvinyl acetate, polyactide Or polyglycolic acid；

The fracturing fibre is glass fibre or vinal.

9. the uneven spread method of the described in any item skeleton proppants of claim 1-8, comprises the following steps that

(1) when pressure break starts, it is pumped into prepad fluid to stratum, stratum is made to form the crack of one fixed width and length；

(2) load fluid of the described in any item skeleton proppants of claim 1-8 is blended with 3 ~ 10m³The displacement pump of/min Enter stratum, to support the fracture geometry formed, that is, completes the uneven laying of skeleton proppant.

10. spread method according to claim 9, which is characterized in that always take sand in step (2) with skeleton proppant Zhan The ratio between the volume fraction of liquid product is sand ratio, and the sand ratio is 40%-80%.