阅读说明：本技术 一种用于断溶体储层的酸压方法 (Acid fracturing method for solution reservoir ) 是由 赵海洋 张�雄 赵兵 黄燕飞 李春月 房好青 罗攀登 耿宇迪 刘志远 纪成 宋志 于 2020-04-27 设计创作，主要内容包括：本发明提出了一种用于断溶体储层的酸压方法,包括形成射孔步骤,进行射孔操作,以在目标储层内形成射孔；形成人工裂缝步骤,在射孔的基础上,实施压裂操作,以在目标储层形成人工裂缝,从而沟通目标井眼区域内的油气储集体,其中,在形成人工裂缝步骤中,可以进行多次压裂操作,并且至少一次后次压裂操作相对于前次压裂操作能使得裂缝的下缝高向下延伸,该酸压方法可以控制缝高,尤其是避免上缝高扩展,并保证下缝高进行扩展,使得裂缝更好的连通储层,获得最优势的通道,进而提高生产能力。(The invention provides an acid fracturing method for a solution reservoir, which comprises a perforation forming step, a perforation treating step and a fracturing step, wherein the perforation forming step is used for performing perforation operation so as to form a perforation in a target reservoir; the method comprises the steps of forming artificial fractures, and performing fracturing operation on the basis of perforation to form the artificial fractures in a target reservoir so as to communicate oil and gas reservoirs in a target well bore region, wherein in the step of forming the artificial fractures, multiple times of fracturing operation can be performed, and at least one time of later fracturing operation can extend the lower fracture height of the fractures downwards relative to the former fracturing operation.)

1. An acid fracturing method for fracturing a solution reservoir, comprising:

a perforating step of performing a perforating operation to form perforations in the target reservoir,

a step of forming artificial fractures, which is to perform fracturing operation on the basis of perforation so as to form the artificial fractures in the target reservoir layer and further communicate oil and gas reservoir bodies in the target well bore area,

wherein, in the step of forming the artificial fracture, a plurality of fracturing operations can be carried out, and at least one subsequent fracturing operation can extend the lower fracture height of the fracture downwards relative to the previous fracturing operation.

2. The acid fracturing method according to claim 1, wherein, in the step of forming artificial fractures,

a first stage, performing a fracturing operation to form an initial fracture,

in the second stage, slick water carrying floating agent is injected into the stratum to form an upper partition plate on the upper wall surface of the initial crack,

and in the third stage, performing fracturing operation on the basis of the initial fracture, so that the lower fracture height of the initial fracture extends downwards until the fracture length of the fracture reaches a preset value.

3. The acid fracturing method of claim 2, further comprising, in the step of forming artificial fractures,

in the fourth stage, slick water carrying the temporary plugging agent is injected into the stratum to temporarily plug the front end of the crack,

and in the fifth stage, performing fracturing operation, and further extending the lower joint height of the crack downwards under the action of the upper partition plate and the temporary plugging agent positioned at the front end of the crack.

4. The acid fracturing method of claim 3 further comprising a sixth stage of pumping a cross-linked acid system into the formation to acid erode the walls of the fracture to increase the conductivity of the fracture.

5. The acid fracturing method according to any one of claims 2 to 4, wherein the pressure during the first stage of the fracturing operation is not less than 6.5m³The displacement of/min pumps the fracturing fluid.

6. The acid fracturing method according to any one of claims 2 to 5, wherein in the second stage, the floating agent is glass beads or a liquid temporary plugging agent which can float relative to the drilling fluid and bear the formation pressure, and preferably the pumping displacement during injection is not less than 3.0m³/min。

7. The acid fracturing method according to any one of claims 2 to 6, wherein in the third stage, the pressure is controlled to be not less than 6.5m³The displacement of/min pumps the fracturing fluid.

8. The acid fracturing method according to any one of claims 2 to 7, wherein in the fourth stage, the pressure is controlled to be not less than 6m³Pumping slickwater at the displacement of/min, wherein the mass concentration of the temporary plugging agent in the slickwater is 2.5-3.5%.

9. The method of any one of claims 2 to 8, wherein the fracturing fluid comprises, in weight percent, 0.5% guar gum, 0.02% pH modifier, 1.0% demulsifier, 0.5% temperature stabilizer, and 0.6% organic boron crosslinker during the fracturing operation.

10. The acid fracturing method of claim 4, wherein the crosslinked acid system comprises, in weight percent, 20% HCl, 0.7% thickener, 1.0% corrosion inhibitor, 1.0% iron stabilizer, 1.0% demulsifier, 2.0% crosslinker, and 0.03% breaker.

Technical Field

The invention relates to the technical field of oil and gas exploitation, in particular to an acid fracturing method for a solution reservoir.

Background

With the development of oil and gas development, great oil and gas breakthrough is obtained in the field of extra-deep carbonate rocks. The comprehensive analysis of the structural evolution, the reservoir, the oil and gas reservoir characteristics, the oil and gas enrichment rule and the like of some oil and gas fields considers that the oil and gas reservoirs are the dissolved hydrocarbon reservoirs and have the characteristics of integral oil content and nonuniform enrichment along a fracture zone. The dissolved gas is an oil-gas migration channel and an oil-gas enrichment place.

Generally, the carbonate reservoir has the characteristics of natural crack development and strong brittleness, the longitudinal stress difference of the reservoir is small, and the control difficulty of the vertical crack height is large. When the drill bit drills into the reservoir of the dissolution reservoir, the heterogeneity is strong, the drilling risk is high, and the bottom of a well is generally positioned at the upper part of the dissolution reservoir. If the acid fracturing is directly carried out on the reservoir stratum, the height of the upper seam is easy to extend to a non-productive layer, and the effective production increase cannot be obtained.

Therefore, the invention of a fracturing method for breaking the solution to effectively increase the yield is a technical problem to be solved urgently.

Disclosure of Invention

In view of some or all of the above technical problems in the prior art, the present invention provides an acid fracturing method for breaking a solution. The acid fracturing method can control the seam height, particularly avoid the expansion of the upper seam height, ensure the expansion of the lower seam height, enable the cracks to be better communicated with a reservoir stratum, obtain the most advantageous channel and further improve the production capacity.

In order to achieve the above object, the present invention provides an acid fracturing method for breaking a solution, comprising:

a perforating step of performing a perforating operation to form perforations in the target reservoir,

a step of forming artificial fractures, which is to perform fracturing operation on the basis of perforation so as to form the artificial fractures in the target reservoir layer and further communicate oil and gas reservoir bodies in the target well bore area,

wherein, in the step of forming the artificial fracture, a plurality of fracturing operations can be carried out, and at least one subsequent fracturing operation can extend the lower fracture height of the fracture downwards relative to the previous fracturing operation.

In one embodiment, in the step of forming the artificial crack,

a first stage, performing a fracturing operation to form an initial fracture,

in the second stage, slick water carrying floating agent is injected into the stratum to form an upper partition plate on the upper wall surface of the initial crack,

and in the third stage, performing fracturing operation on the basis of the initial fracture, so that the lower fracture height of the initial fracture extends downwards until the fracture length of the fracture reaches a preset value.

In one embodiment, the step of forming the artificial fracture further comprises,

in the fourth stage, slick water carrying the temporary plugging agent is injected into the stratum to temporarily plug the front end of the crack,

and in the fifth stage, performing fracturing operation, and further extending the lower joint height of the crack downwards under the action of the upper partition plate and the temporary plugging agent positioned at the front end of the crack.

In one embodiment, the step of forming the artificial fracture further comprises a sixth stage of pumping a cross-linked acid system into the formation to acid erode the walls of the fracture to increase the conductivity of the fracture.

In one embodiment, during the first stage of the fracturing operation, at no less than 6.5m³The displacement of/min pumps the fracturing fluid.

In one embodiment, in the second stage, the buoyant agent is a glass bead or liquid plugging agent that is buoyant relative to the drilling fluid and able to withstand formation pressures, preferably with a pumping capacity of no less than 3.0m during injection³/min。

In one embodiment, in the third stage, at least 6.5m³The displacement of/min pumps the fracturing fluid.

In one embodiment, in the fourth stage, at least 6m³Pumping slickwater at the displacement of/min, wherein the mass concentration of the temporary plugging agent in the slickwater is 2.5-3.5%.

In one embodiment, the fracturing operation is performed wherein the fracturing fluid comprises, in weight percent, 0.5% guar gum, 0.02% pH modifier, 1.0% breaker, 0.5% temperature stabilizer, and 0.6% organoboron crosslinker.

In one embodiment, the crosslinking acid system comprises, by weight, 20% HCl, 0.7% thickener, 1.0% corrosion inhibitor, 1.0% iron ion stabilizer, 1.0% demulsifier, 2.0% crosslinker, and 0.03% breaker.

Compared with the prior art, the invention has the advantages that: the acid fracturing method can extend the lower seam height of the fracture downwards through multiple fracturing operations, and avoid the upper seam height from expanding, so that the fracture is better communicated with a reservoir stratum, the most advantageous channel is obtained, and the production capacity is improved.

Drawings

Preferred embodiments of the present invention will be described in detail below with reference to the attached drawing figures, wherein:

fig. 1 shows an effect diagram of the acid fracturing method according to the present invention.

The figures are not drawn to scale.

Detailed Description

In order to make the technical solutions and advantages of the present invention more apparent, exemplary embodiments of the present invention are described in further detail below with reference to the accompanying drawings. It is clear that the described embodiments are only a part of the embodiments of the invention, and not an exhaustive list of all embodiments. And the embodiments and features of the embodiments may be combined with each other without conflict.

The invention provides a fracturing method capable of controlling the fracture height, which is established for a method for drilling a communication reservoir layer with a high drilling risk in an upper part of a solution reservoir layer at the bottom of a well. The method is suitable for the fracturing fluid, but is not limited to the fracturing fluid, and can be applied to any fracturing construction needing to control the height of the crack. An embodiment of the method proposes an acid fracturing method for breaking a solution. As shown in fig. 1, the acid fracturing method is performed on the basis of the completion of the well, and a perforation operation is performed (at the position 05 in fig. 1). That is, after drilling is completed, a perforating device is lowered into the wellbore and a perforating operation is performed as designed to create perforations in the target reservoir. Then, on the basis of the perforations, a fracturing operation is performed to create artificial fractures in the target reservoir to communicate hydrocarbon reservoirs within the target wellbore region. According to the acid fracturing method, fracturing is carried out in multiple times, wherein one or more subsequent fracturing operations can control the extension of the fracture downward from the lower fracture height of the fracture relative to the previous fracturing operation. That is, at least one fracturing operation can extend the lower leg of the fracture further downward relative to the previously performed fracturing operation. For example, in the second fracturing operation, the lower fracture height of the fracture extends relatively downwards on the basis of the first fracturing operation.

Specifically, in the step of forming the artificial fracture, a fracturing operation is first performed to form an initial fracture (indicated by the reference numeral 08 in fig. 1, wherein the lower fracture height bottom of the initial fracture is indicated by the reference numeral 09). While pumping the fracturing fluid into the formation, the fracturing fluid fractures the formation from the previous perforations to form initial fractures. The fracturing fluid adopted in the stage comprises, by mass, 0.5% of guanidine gum, 0.02% of pH value regulator, 1.0% of demulsifier, 0.5% of temperature stabilizer and 0.6% of organic boron crosslinking agent. In the fracturing process, the thickness of the slurry can be not less than 6.5m³Displacement pumping of/min. It should be noted that the pumping temperature needs to be above 0 ℃, and if the pumping temperature is lower than the pumping temperature, anti-freezing measures need to be adopted.

And injecting slickwater into the stratum, wherein the slickwater carries the floating agent into the stratum. After the pumping is stopped for a while, the floating agent floats up to the upper wall surface of the initial crack to form an upper partition (the floating agent is denoted by reference numeral 06 in fig. 1). The slickwater can be prepared on site, and comprises 0.3% of guanidine gum and 0.02% of pH value regulator by mass percentage, and the balance is clear water. And the floating agent is glass beads or a liquid plugging agent which has low density, can float and can bear formation pressure. The injection concentration of the buoyant agent in the slick water may be about 3-5%. In the injection process, the displacement of the pump for injecting the slickwater is more than or equal to 3m³Min, stop pump time 20 minutes.

The fracturing fluid is again pumped at high displacement to recompress the formation on the basis of the initial fracture. Since the upper partition plate is formed on the upper wall surface of the fracture in the previous construction, when the fracturing fluid is pumped, the length of the fracture is increased while the height of the lower fracture of the fracture extends downwards (in fig. 1, the number 10 of the expanded fracture is shown in the figure)). The fracturing fluid at the stage can be the same as the pumped fracturing fluid in the previous stage in material, so that the operations such as the proportion of the fracturing fluid are simplified. However, the pumping capacity of the fracturing fluid at this stage cannot be small relative to the pumping capacity of the fracturing fluid at the first stage, such as greater than 6.5m³Min, specifically 7m³Min to allow the fracturing fluid to better extend deep into the formation to allow the fracture length to reach a predetermined value (which is determined by simulation calculations after the geological exploration is completed). Preferably, at this stage, a buoyant agent may be incorporated into the fracturing fluid to increase the resistance of the upper barrier and form the upper barrier at the new fracture, thereby urging the fracturing fluid to extend downward. The injection concentration of the floating agent in the fracturing fluid is selected to be 2-3%, and the pump injection displacement is more than or equal to 6.5m³Min, at last 80-100m³The floating agent is not added into the fracturing fluid, the specific numerical value is determined according to 1.5 times of the volume of the pipe column, and the pump is stopped for 20 minutes.

And then injecting slick water carrying the temporary plugging agent into the stratum. The slickwater carries the temporary plugging agent into the stratum, so that the temporary plugging agent reaches the tail part of the crack, and the temporary plugging effect on the tail part of the crack is achieved. The temporary plugging agent can be carried to the far end of a crack, the plugging strength is greater than 10MPa, and the temporary plugging agent comprises 90% of polyester, 5% of surfactant and 5% of degradation agent in percentage by mass. And the same skimming water as the preamble can be used. The injection concentration of the temporary plugging agent in the slickwater is selected to be more than or equal to 3 percent, and the pump injection displacement is controlled to be not less than 6m³/min。。

Through the construction, the length of the crack reaches the ideal length, and an upper partition plate is formed on the upper wall surface of the crack. At this time. And pumping the fracturing fluid again to enable the lower seam height of the crack to extend downwards under the action of the upper partition plate and the temporary plugging agent, so as to open the reservoir stratum to a greater extent. Wherein the pressure of the fracturing fluid is controlled to be about 120MPa, and the discharge capacity is more than or equal to 8m³Min, e.g. 12m³/min。

After the whole crack meets the requirements, a crosslinking acid system with slow reaction, small filtration and strong penetration distance is injected into the stratum to carry out acid etching on the wall surface of the crack so as to eliminate or reduce the floating agent and the temporary crackThe influence of the plugging agent on the cracks is increased, so that the flow conductivity of the cracks is increased. Preferably, the formulation of the crosslinking acid system comprises: 20% of HCl, 0.7% of thickening agent, 1.0% of corrosion inhibitor, 1.0% of iron ion stabilizer, 1.0% of demulsifier, 2.0% of cross-linking agent and 0.03% of gel breaker, wherein the specific gravity is mass percent. The construction pressure of the cross-linking acid is less than or equal to 120MPa, and the discharge capacity reaches 10m³More than min.

And injecting slick water into the stratum to squeeze residual acid liquor in the shaft into the stratum, so that the acid liquor is fully utilized.

And finally, stopping the pump, closing the well for about 30min, measuring the pressure drop, ensuring that the acid liquor and the stratum completely react, and reflecting the communication condition between the fracturing and the deep part of the stratum through measuring the pressure drop.

In addition, for the sake of understanding, names of the remaining components in fig. 1 are introduced, specifically, in fig. 1, reference numeral 01 denotes a tubing, 02 denotes a casing, 03 denotes a packer, 04 denotes a liner, 05 denotes a perforation location, 07 denotes an open hole section, and 11 denotes a formation.

The method aims at the transformation problem of the dissolved gas reservoir which is wide in oil gas distribution in the longitudinal direction of the ultra-deep reservoir but poor in connectivity, the effect of expanding the large seam height of acid fracturing is achieved by adopting the acid fracturing method, the dissolved gas reservoir is effectively communicated, and effective yield increase is achieved.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to be construed to include preferred embodiments and all such changes and/or modifications as fall within the scope of the invention, and all such changes and/or modifications as are made to the embodiments of the present invention are intended to be covered by the scope of the invention.