CN-122014196-A - Nano tackifying fluid and supercritical CO2Fluid synergistic fracturing method

CN122014196ACN 122014196 ACN122014196 ACN 122014196ACN-122014196-A

Abstract

The application relates to a method for cooperatively fracturing a nano viscosity-increasing fluid and a supercritical CO 2 fluid. The method comprises the steps of adopting nano tackifying fluid and supercritical CO 2 fluid to cooperatively fracture in a target stratum development area, combining sand-carrying fluid and displacing fluid to form a fracture network, establishing a corresponding relation between a construction parameter combination and fracture conductivity and fracturing construction fluid quantity, constructing a multi-target optimization model which aims at maximizing the fracture conductivity and minimizing the fracturing construction fluid quantity based on the corresponding relation, and outputting construction parameter optimization results through population initialization, non-dominant sorting, crowding distance calculation, cross variation selection and iterative updating. The application can improve the fracture conductivity and the network-seaming complexity of the shale reservoir, reduce the construction liquid amount and improve the fracturing transformation effect and the economy.

Inventors

WANG DAOBING
LI YANTAO
WANG YUEKANG
WU YUE
LI SANBAI
DI SHIYING
LU CHAOHUI
ZHANG NA
CHEN GONG
LIU YAHUI
MIAO YANGYANG

Assignees

北京石油化工学院

Dates

Publication Date: 20260512
Application Date: 20260402

Claims (10)

1. A method for CO-fracturing a nano-viscosified fluid and a supercritical CO 2 fluid, comprising: S1, carrying out collaborative fracturing by adopting a nano tackifying fluid and a supercritical CO 2 fluid in a target stratum development area, forming a fracture network by combining sand-carrying fluid and displacement fluid, and establishing corresponding relations among different construction parameter combinations, fracture conductivity and fracturing construction fluid quantity; S2, constructing a multi-objective optimization model which takes the crack diversion capacity as a maximum and the fracturing construction liquid as an optimization target based on the crack diversion capacity and the fracturing construction liquid corresponding to different construction parameter combinations; S3, setting initial population numbers of the multi-objective optimization model by taking at least two of construction parameters as parameters to be optimized, and generating an initial population, wherein each individual in the initial population corresponds to a group of construction parameter combinations, and the construction parameters comprise the displacement, liquid quantity, viscosity and density of the nano viscosity-enhancing fluid, the displacement, liquid quantity, viscosity and density of the supercritical CO 2 fluid, and the concentration, density and particle size of the propping agent; S4, calculating crack flow conductivity and fracturing construction liquid quantity corresponding to each body in the population; S5, carrying out rapid non-dominant sequencing and crowding distance calculation on each body according to the crack flow conductivity and the fracturing construction liquid quantity corresponding to each body, and selecting a father individual according to a calculation result; s6, performing crossing and mutation operations on the parent individuals to generate offspring individuals; s7, merging the parent individuals and the offspring individuals to generate a new generation population; s8, repeatedly executing the steps S4-S7 until a preset iteration termination condition is reached; S9, outputting an optimal solution set of the multi-objective optimization model as a construction parameter optimization result, wherein the optimal solution set comprises optimization solutions corresponding to different construction parameter combinations.
2. The method of claim 1, wherein performing a CO-fracturing with the nano viscosified fluid and the supercritical CO 2 fluid in the target formation development zone in combination with the sand-carrying fluid and the displacement fluid to form a fracture network comprises: s11, injecting nano viscosity-increasing fluid into a target formation development area to form a main crack in the target formation development area; S12, injecting supercritical CO 2 fluid into a target stratum development area to activate branch cracks on the basis of the main cracks; S13, alternately repeating injection of the nano tackifying fluid and injection of the supercritical CO 2 fluid according to preset cycle times to form an initial fracture network; s14, injecting sand-carrying fluid into the target stratum development area to support the initial fracture network, so as to form a support fracture network; s15, acquiring the crack permeability and the crack width of a supporting crack network, and calculating the crack conductivity; s16, injecting displacement fluid into the target stratum development area to displace sand-carrying fluid in the shaft, so as to form a final fracture network.
3. The method according to claim 2, wherein the method further comprises: And (3) adjusting the construction parameter combination, and repeatedly executing the steps S11-S16 to establish the corresponding relation between different construction parameter combinations and the crack flow conductivity and the fracturing construction liquid amount.
4. The method of claim 2, wherein obtaining the fracture permeability of the propped fracture network comprises: And calculating the fracture permeability of the propping fracture network according to the rock porosity of the target stratum development area, the particle specific surface area of the propping agent and the preset constant.
5. The method of claim 2, wherein obtaining the fracture width comprises: And calculating the crack width of the supporting crack network according to the rock poisson ratio and the rock Young modulus of the target stratum development area, the net pressure in the crack and the crack height.
6. The method of claim 2, wherein calculating fracture conductivity comprises: The product of fracture permeability and fracture width of the propping fracture network was calculated as fracture conductivity.
7. The method of claim 1, wherein each individual in the population is represented encoded with a parameter combination comprising all parameters to be optimized, the input parameter dimension corresponding to the number of parameters to be optimized.
8. The method of claim 1, wherein the fast non-dominated ordering and crowding distance calculation is performed for each individual based on the fracture conductivity and the fracturing construction fluid volume corresponding to each individual, and the parent individual is selected based on the calculation results, comprising: determining the non-dominant grade of each body according to the crack flow conductivity and the fracturing construction liquid amount corresponding to each body; Calculating a crowding distance for individuals at the same non-dominant level; preferably, the parent is selected from individuals with low non-dominant ranking and large crowding distance.
9. The method according to claim 1, wherein the method further comprises: The optimization plate is output to characterize the distribution characteristics of the different optimization parameter values.
10. The method according to claim 1, wherein the method further comprises: And comparing and verifying the optimized construction parameter combination with the original construction parameter combination, and outputting a verification result.

Description

Synergistic fracturing method of nano tackifying fluid and supercritical CO 2 fluid Technical Field The application relates to the technical field of petroleum and natural gas exploitation, in particular to a method for collaborative fracturing of a nano tackifying fluid and a supercritical CO 2 fluid. Background The shale oil in China is rich in resources, and the formation of a complex artificial joint net through hydraulic fracturing transformation is one of key technologies for realizing efficient and economic development of shale oil. However, the shale oil is rich in clay minerals, so that the conventional water-based fracturing fluid fracturing has the defects of formation damage, low flowback rate and the like in the fracturing reformation of the shale oil reservoir. To overcome these problems, supercritical CO 2 fracturing techniques have been developed. Besides the advantages of low reservoir damage, high flowback rate, water resource saving and the like, the supercritical CO 2 fluid can more easily transfer flow pressure to the slit tip due to the characteristic of ultra-low viscosity (0.12-0.16 mPa.s) so as to invade and communicate a micro-crack system to form a complex slit net. However, supercritical CO 2 fracturing has some challenges. On the one hand, its low viscosity makes its ability to form main fractures relatively inadequate, which may affect the effectiveness of the fracturing. Second, the poor viscoelasticity of supercritical CO 2 fluid makes it difficult to efficiently deliver proppants deep into the micro-fracture while the conductivity of the branch fracture remains to be further enhanced. In recent years, nanometer tackifying fluids (nanometer viscosified slick water fracturing fluids) are emerging, which have superior viscoelasticity, sand carrying and main joint making capabilities. In comparison, the energy in the supercritical CO 2 fracturing crack extension is mainly consumed in rock fracture, the viscosity of the nano tackifying fluid is relatively high, so that the crack extension mechanism is mainly liquid viscosity, the defect of single supercritical CO 2 fracturing can be overcome by the combined use of the two, and the artificial shale fracture network complexity and the crack diversion capability are improved. In addition, the shale oil micro-nano pore canal develops, the stratum pressure coefficient is lower, the crude oil flow resistance is larger, and if the nano viscosity-increasing fluid and the supercritical CO 2 are subjected to the composite action, the surface tension can be reduced, the stratum pressure can be improved, and the nano imbibition oil displacement efficiency can be enhanced. Therefore, the nano tackifying fluid and supercritical CO 2 composite fracturing technology becomes one of the important means for realizing the increase and stable production of shale oil in the future. The construction flow of the collaborative fracturing of the nano tackifying fluid and the supercritical CO 2 is defined, and the construction parameter optimization method is provided, so that the method has great significance for the transformation of the shale oil reservoir. Disclosure of Invention The application provides a method for collaborative fracturing of a nano tackifying fluid and supercritical CO 2, which aims to solve the problem that construction parameters are difficult to determine when collaborative fracturing of the nano tackifying fluid and the supercritical CO 2 fluid is performed at least to a certain extent. The scheme of the application is as follows: A method of collaborative fracturing of a nano-viscosified fluid with supercritical CO 2 comprising: S1, carrying out collaborative fracturing by adopting a nano tackifying fluid and a supercritical CO 2 fluid in a target stratum development area, forming a fracture network by combining sand-carrying fluid and displacement fluid, and establishing corresponding relations among different construction parameter combinations, fracture conductivity and fracturing construction fluid quantity; S2, based on the fracture conductivity and the fracturing construction liquid amount which are corresponding to different construction parameter combinations, constructing a multi-objective optimization model which takes the fracture conductivity as a maximum and the fracturing construction liquid amount as an optimization objective, wherein the multi-objective optimization model takes the construction parameters as decision variables; S3, setting initial population numbers of the multi-objective optimization model by taking at least two of construction parameters as parameters to be optimized to generate initial population numbers, wherein each individual in the initial population numbers corresponds to a group of construction parameter combinations, and the construction parameters comprise the displacement, liquid quantity, viscosity and density of the nano tackifying fluid, the displacement, liquid quantity, viscosit