TY - JOUR
T1 - Role of proppant distribution on the evolution of hydraulic fracture conductivity
AU - Wang, Jiehao
AU - Elsworth, Derek
N1 - Funding Information:
This work is the result of support from DOE under the Small Business Innovation Research program (grant number: DE-SC0013217). This support is gratefully acknowledged.
Funding Information:
This work is the result of support from DOE under the Small Business Innovation Research program (grant number: DE-SC0013217 ). This support is gratefully acknowledged. Appendix For a proppant layer in contact with a fracture wall, the densest packing is a hexagonal lattice, as shown in . Fig. 20 (a) Fig. 20 (b) plots three adjacent proppant particles (solid-line circles) and contact zones between particles and the fracture wall (dashed-line circles), where R and a represent radii of the particle and the contact zone, respectively. The equilateral triangle shown in Fig. 20 (b) has an area of 3 R 2 and overlaps the contact zones with an area of π a 2 / 2 . Thus, the mean contact pressure, p m ( z ) , and the compacting stress, σ p ( z ) , are related as (32) p m ( z ) π a 2 = 2 3 σ p ( z ) R 2 . Therefore, the constant η in Eq. (14) is 2 3 for the densest packing type (hexagonal lattice), and η > 2 3 for other looser ones.
Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/7
Y1 - 2018/7
N2 - The residual opening of fluid-driven fractures is conditioned by proppant distribution and has a significant impact on fracture conductivity - a key parameter to determine fluid production rate and well performance. A 2D model follows the evolution of the residual aperture profile and conductivity of fractures partially/fully filled with proppant packs. The model accommodates the mechanical response of proppant packs in response to closure of arbitrarily rough fractures and the evolution of proppant embedment. The numerical model is validated against existing models and an analytic solution. Proppant may accumulate in a bank at the fracture base during slick water fracturing, and as hydraulic pressure is released, an arched zone forms at the top of the proppant bank as a result of partial closure of the overlaying unpropped fracture. The width and height of the arched zone decreases as the fluid pressure declines, and is further reduced where low concentrations of proppant fill the fracture or where the formation is highly compressible. This high-conductivity arch represents a preferential flow channel and significantly influences the distribution of fluid transport and overall fracture transmissivity. However, elevated compacting stresses and evolving proppant embedment at the top of the settled proppant bed reduce the aperture and diminish the effectiveness of this highly-conductive zone, with time. Two-dimensional analyses are performed on the fractures created by channel fracturing, showing that the open channels formed between proppant pillars dramatically improve fracture transmissivity if they are maintained throughout the lifetime of the fracture. However, for a fixed proppant pillar height, a large proppant pillar spacing results in the premature closure of the flow channels, while a small spacing narrows the existing channels. Such a model provides a rational means to design optimal distribution of the proppant pillars using deformation moduli of the host to control pillar deformation and flexural spans of the fracture wall.
AB - The residual opening of fluid-driven fractures is conditioned by proppant distribution and has a significant impact on fracture conductivity - a key parameter to determine fluid production rate and well performance. A 2D model follows the evolution of the residual aperture profile and conductivity of fractures partially/fully filled with proppant packs. The model accommodates the mechanical response of proppant packs in response to closure of arbitrarily rough fractures and the evolution of proppant embedment. The numerical model is validated against existing models and an analytic solution. Proppant may accumulate in a bank at the fracture base during slick water fracturing, and as hydraulic pressure is released, an arched zone forms at the top of the proppant bank as a result of partial closure of the overlaying unpropped fracture. The width and height of the arched zone decreases as the fluid pressure declines, and is further reduced where low concentrations of proppant fill the fracture or where the formation is highly compressible. This high-conductivity arch represents a preferential flow channel and significantly influences the distribution of fluid transport and overall fracture transmissivity. However, elevated compacting stresses and evolving proppant embedment at the top of the settled proppant bed reduce the aperture and diminish the effectiveness of this highly-conductive zone, with time. Two-dimensional analyses are performed on the fractures created by channel fracturing, showing that the open channels formed between proppant pillars dramatically improve fracture transmissivity if they are maintained throughout the lifetime of the fracture. However, for a fixed proppant pillar height, a large proppant pillar spacing results in the premature closure of the flow channels, while a small spacing narrows the existing channels. Such a model provides a rational means to design optimal distribution of the proppant pillars using deformation moduli of the host to control pillar deformation and flexural spans of the fracture wall.
UR - http://www.scopus.com/inward/record.url?scp=85043599220&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85043599220&partnerID=8YFLogxK
U2 - 10.1016/j.petrol.2018.03.040
DO - 10.1016/j.petrol.2018.03.040
M3 - Article
AN - SCOPUS:85043599220
SN - 0920-4105
VL - 166
SP - 249
EP - 262
JO - Journal of Petroleum Science and Engineering
JF - Journal of Petroleum Science and Engineering
ER -