CN-122014200-A - Atomization acid fracturing sand fracturing composite transformation method for tight limestone reservoir

Abstract

The invention belongs to the technical field of oil and gas field development and oil and gas reservoir transformation, and particularly relates to a compact limestone reservoir atomization acid fracturing and sand fracturing composite transformation method. The method mainly comprises the following steps of (1) a supercritical atomization acid pressing and net forming stage, (2) a slug temporary plugging pre-liquid seam making stage, (3) a multi-particle-size propping agent sand adding stage and (4) a low-viscosity displacing liquid displacing stage. The invention is based on the fracturing thought of 'first net forming and then seam forming, temporary blocking by slugs and multi-scale fracture support', has the advantages of strong fluidity, strong penetrability and strong lithology breaking of supercritical carbon dioxide, acid solubility of pre-acid, lasting and effective diversion capability of sand fracturing and the like, can be widely applied to the reformation of compact limestone reservoirs, forms a complex acid etching-supporting composite fracture system, and effectively improves the diversion capability of the fracture.

Inventors

• Yang Shangru
• LIU XIAORUI
• LU HONGJUN
• LIU HANBIN
• XIE YONGGANG
• CHEN BAOCHUN
• ZHOU CHANGJING
• MA ZHANGUO
• GU YONGHONG
• XIAO YUANXIANG

Assignees

• 中国石油天然气股份有限公司

Dates

Publication Date

20260512

Application Date

20241112

Claims (9)

1. 1. The method for compositely reforming the compact limestone reservoir by atomization acid fracturing and sand fracturing is characterized by comprising the following steps of: s1, forming an acid etching crack network in a tight limestone reservoir by supercritical atomization acid fracturing; S2, temporarily plugging an acid etching crack network by adopting a medium-viscosity fracturing fluid slug, and forming a main crack and a branch crack network in a tight limestone reservoir; S3, filling main cracks and branch cracks by using a medium-viscosity fracturing fluid carrying propping agent to form an acid etching-propping crack network; S4, displacing the medium-viscosity fracturing fluid by using a displacement fluid to finish the construction of the fracturing fluid; The medium-viscosity fracturing fluid is a polymer fracturing fluid with the viscosity of more than or equal to 60 mPas.
2. 2. The method for compositely reforming the tight limestone reservoir by atomized acid fracturing and sand fracturing according to claim 1, wherein the supercritical atomized acid in the step S1 is formed by combining a pre-acid and supercritical carbon dioxide.
3. 3. The method for compositely reforming the compact limestone reservoir by atomization acid fracturing and sand fracturing according to claim 2, wherein the injection amount of the pre-acid is 50-100 m 3 , the injection amount of carbon dioxide is 50-150 m 3 , and the injection displacement is 2-5 m 3 /min.
4. 4. The method for compositely reforming the compact limestone reservoir by atomized acid fracturing and sand fracturing according to claim 2, wherein the pre-acid is low-viscosity retarded acid.
5. 5. The method for compositely reforming the dense limestone reservoir by atomized acid fracturing and sand fracturing is characterized in that the specific implementation mode of the S2 is that firstly, a medium-viscosity fracturing fluid carries small-particle-size propping agent slugs to temporarily block an acid etching fracture network formed by supercritical atomized acid fracturing, and secondly, a medium-viscosity fracturing fluid is adopted to form main fractures and branch fracture networks in the dense limestone reservoir; the small-particle-size propping agent is 70-140 meshes of ceramsite or quartz sand, and the sand amount for the slug is 5-10 m 3 ; The discharge capacity of the medium-viscosity fracturing fluid is 8-12 m 3 /min.
6. 6. The method for compositely reforming the dense limestone reservoir by atomization acid fracturing and sand fracturing is characterized in that propping agents carried by the medium-viscosity fracturing fluid in S3 are medium-particle-diameter propping agents and large-particle-diameter propping agents; The medium-particle-diameter propping agent is 40-70 mesh ceramsite or quartz sand; the large-particle-size propping agent is 20-40-mesh ceramsite or quartz sand; The discharge capacity of the medium-viscosity fracturing fluid is 8-12 m 3 /min.
7. 7. The method for compositely reforming the dense limestone reservoir by atomization acid fracturing and sand fracturing according to claim 5 or 6, wherein the small-particle-size propping agent is pressed into the branch fracture network by the medium-particle-size propping agent, and the large-particle-size propping agent is pressed into the deep part of the fracture by the medium-particle-size propping agent to form a dense acid etching-supporting fracture network.
8. 8. The method for compositely reforming the tight limestone reservoir by atomization acid fracturing and sand fracturing is characterized in that a displacement fluid is adopted in the step S4 to displace a medium-viscosity fracturing fluid, and the medium-viscosity fracturing fluid is ejected into the tight limestone reservoir.
9. 9. The method for compositely reforming the compact limestone reservoir by atomization acid fracturing and sand fracturing is characterized in that the displacement fluid is low-viscosity slickwater of 5-10 mPa.s, and the displacement of the displacement fluid is 8-12 m 3 /min.

Description

Atomization acid fracturing sand fracturing composite transformation method for tight limestone reservoir Technical Field The invention belongs to the technical field of oil and gas field development and oil and gas reservoir transformation, and particularly relates to a compact limestone reservoir atomization acid fracturing and sand fracturing composite transformation method. Background Reservoir reformation is an indispensable technological measure for increasing production of various large oil and gas fields at home and abroad, and is widely applied to reservoirs such as carbonate, sandstone, shale gas and the like. The reservoir reformation mainly comprises three major categories, namely hydraulic fracturing, acid fracturing and acidification, wherein the hydraulic fracturing is mainly applied to sandstone and shale gas, the acid fracturing is mainly applied to carbonate rock, and the acidification is mainly applied to sandstone and carbonate rock. With the continuous development of exploration and development, oil and gas reservoirs are more and more complex, the price of oil and gas is greatly reduced, and higher requirements are put forward on reservoir reconstruction effects. The acid fracturing transformation is an important means for increasing the yield of the fractured and fracture-cavity carbonate rock hydrocarbon reservoirs, and an acid etching fracture system is mainly formed by corroding a carbonate reservoir matrix by using acid liquor to communicate hydrocarbon resources in a fracture space, a karst cave space and other reservoirs of the original carbonate reservoir, and a fracture channel for underground hydrocarbon flow is established. Compared with the conventional carbonate reservoir, the compact carbonate has the advantages of poor reservoir physical properties, high limestone component content, relatively developed microcracks and relatively high clay content, so that acid liquor and rock reaction rate is relatively high, acid liquor filtration loss is relatively high, acid corrosion crack distance is relatively short, acid insoluble substances block crack channels, acid corrosion crack flow conductivity is relatively low, and acid pressure modification and yield increase effects are relatively poor. Currently, tight limestone reservoirs are becoming increasingly important for natural gas exploration. The method for reforming the compact limestone reservoir at home and abroad mainly comprises ① matrix acidification, ② acid fracturing/deep acid fracturing, such as a pre-hydraulic acid fracturing technology, a multi-stage injection acid fracturing technology, a solid acid fracturing technology, a closed acidification technology, a volume acid fracturing technology and the like, and ③ cross-linked acid sand carrying acid fracturing, ④ sand fracturing and the like. The improvement of single well yield faces greater challenges due to the denser limestone reservoirs, uniform etching of the rock surface, lower acid etching crack conductivity, fast acid rock reaction rate, short effective acid etching action distance and the like. The support cracks formed by sand fracturing have more durable and effective diversion capability compared with acid fracturing transformation, but have the defects of high reservoir fracture pressure, high construction difficulty, difficult communication and non-communication of pores, natural cracks and the like. Disclosure of Invention The invention aims to solve the problems of low crack diversion capability, high acid rock reaction rate and short effective action distance of acid etching in the existing dense limestone reservoir reconstruction method, integrates various advantages of strong fluidity, strong penetrability and strong rock breaking property of supercritical carbon dioxide, acid solubility of pre-acid, lasting effective diversion capability of sand fracturing and the like, and provides a dense limestone reservoir atomization acid fracturing and sand fracturing composite reconstruction method based on the fracturing thought of 'first net forming, second net forming, temporary blocking by slug and multi-scale fracture support'. In order to achieve the above purpose, the invention adopts the following technical scheme: A compact limestone reservoir atomization acid fracturing sand fracturing composite transformation method comprises the following steps: s1, forming an acid etching crack network in a tight limestone reservoir by supercritical atomization acid fracturing; S2, temporarily plugging an acid etching crack network formed by supercritical atomization acid fracturing by adopting a medium-viscosity fracturing fluid slug, and forming a main crack and a branch crack network in a tight limestone reservoir; s3, filling main cracks and branch crack networks by using medium-viscosity fracturing fluid carrying propping agents to form an acid etching-propping crack network; S4, displacing the medium-viscosity fracturing fluid by using a displacement