As the consumption of oil and gas
resources is increasing, secondary
exploitation in old wells and unconventional oil and gas exploitation
methods are becoming increasingly important. As a result of complex
reservoir environments and the reservoir properties, such as ultralow
porosity and permeability, hydraulic fracturing is an important means
to achieve effective recovery. Temporary plugging fracturing is currently
an efficient fracturing technology and is suitable for refracturing
of old wells and multi-stage fracturing in unconventional reservoirs,
which is conducive to constructing complex fracture networks and increasing
production. Recently, in the field of temporary plugging fracturing,
how to design the operation parameters of temporary plugging fracturing
still remains ambiguous and empirical. In this paper, a numerical
simulation study of the liquid–solid two-phase flow of the
temporary plugging agents and the fracturing fluid was conducted using
two physical models: a wellbore flow model and a wellbore–fracture
temporary plugging model. The transport processes of the temporary
plugging agents along with fracturing fluid in a vertical wellbore,
in a horizontal wellbore, and at a fracture position were simulated.
Simulations that coupled computational fluid dynamics and the discrete
element method were used in the simulation process. The effects of
the temporary plugging agent concentration, particle size, particle
size ratio, fracturing fluid rate, and fracturing fluid viscosity
on the migration process of the temporary plugging agent were investigated.
The simulation results show that a higher concentration and viscosity
of a temporary plugging agent help to sustain the flow stability in
the vertical wellbore, while the viscosity and flow rate of the fracturing
fluid have an impact on whether sedimentation of the temporary plugging
agent occurred in the horizontal wellbore. In addition, the particle
size ratio and concentration of the temporary plugging agent are the
key factors for a successful bridging and plugging. For a specific
field application in Longmaxi Formation, Sichuan Province, the operation
parameters of temporary plugging fracturing have been designed and
achieved a successful refracturing treatment.