Experimental investigation of fracturing-fluid migration caused by spontaneous imbibition in fractured low-permeability sands

R. Dutta, C. H. Lee, S. Odumabo, P. Ye, S. C. Walker, Zuleima Karpyn, Luis Ayala H.

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

During hydraulic-fracturing operations in low-permeability formations, spontaneous imbibition of fracturing fluid into the rock matrix is believed to have a significant impact on the retention of water-based fracturing fluids in the neighborhood of the induced fracture. This may affect the post-fracturing productivity of the well. However, there is lack of direct experimental and visual evidence of the extent of fluid retention, evolution of the resulting imbibing-fluid front, and how they relate to potential productivity hindrance. In this paper, laboratory experiments have been carefully designed to represent the vicinity of a hydraulic fracture. The evolution of fracturing fluid leakoff is monitored as a function of space and time by use of X-ray computed tomography (CT). The X-ray CT imaging technique allows us to map saturations at controlled time intervals to monitor the migration of fracturing fluid into the reservoir formation. It is generally expected for low-permeability formations (5 to 10 md) to show strong capillary forces because of their small characteristic pore radii, but this driving mechanism is in competition with the low permeability and spatial heterogeneities found in low-permeability sands. The relevance of capillarity as a driver of fluid migration and retention in a low-permeability sand sample is interpreted visually and quantified and compared with high-permeability Berea sandstone in our experiments. It is seen that although low-permeability sands are subject to strong capillary forces, the effect can be suppressed by the low permeability of the formation and the heterogeneous nature of the sample. Nevertheless, saturation values attained as a result of spontaneous imbibition are comparable with those obtained for high-permeability samples. Leakoff of fracturing fluids during the shut-in period of a well can result in delayed gas flowback and can hinder gas production. Results from this investigation are expected to provide fundamental insight regarding critical variables affecting the retention and migration of water-based fracturing fluids in the neighborhood of hydraulic fractures, and consequently affecting the post-fracturing productivity of the well.

Original languageEnglish (US)
Pages (from-to)74-81
Number of pages8
JournalSPE Reservoir Evaluation and Engineering
Volume17
Issue number1
DOIs
StatePublished - Jan 1 2014

Fingerprint

Fracturing fluids
imbibition
Sand
permeability
sand
fluid
Productivity
Tomography
Fluids
Hydraulics
X rays
productivity
tomography
Hydraulic fracturing
Capillarity
Sandstone
Gases
saturation
capillarity
Water

All Science Journal Classification (ASJC) codes

  • Fuel Technology
  • Energy Engineering and Power Technology
  • Geology

Cite this

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title = "Experimental investigation of fracturing-fluid migration caused by spontaneous imbibition in fractured low-permeability sands",
abstract = "During hydraulic-fracturing operations in low-permeability formations, spontaneous imbibition of fracturing fluid into the rock matrix is believed to have a significant impact on the retention of water-based fracturing fluids in the neighborhood of the induced fracture. This may affect the post-fracturing productivity of the well. However, there is lack of direct experimental and visual evidence of the extent of fluid retention, evolution of the resulting imbibing-fluid front, and how they relate to potential productivity hindrance. In this paper, laboratory experiments have been carefully designed to represent the vicinity of a hydraulic fracture. The evolution of fracturing fluid leakoff is monitored as a function of space and time by use of X-ray computed tomography (CT). The X-ray CT imaging technique allows us to map saturations at controlled time intervals to monitor the migration of fracturing fluid into the reservoir formation. It is generally expected for low-permeability formations (5 to 10 md) to show strong capillary forces because of their small characteristic pore radii, but this driving mechanism is in competition with the low permeability and spatial heterogeneities found in low-permeability sands. The relevance of capillarity as a driver of fluid migration and retention in a low-permeability sand sample is interpreted visually and quantified and compared with high-permeability Berea sandstone in our experiments. It is seen that although low-permeability sands are subject to strong capillary forces, the effect can be suppressed by the low permeability of the formation and the heterogeneous nature of the sample. Nevertheless, saturation values attained as a result of spontaneous imbibition are comparable with those obtained for high-permeability samples. Leakoff of fracturing fluids during the shut-in period of a well can result in delayed gas flowback and can hinder gas production. Results from this investigation are expected to provide fundamental insight regarding critical variables affecting the retention and migration of water-based fracturing fluids in the neighborhood of hydraulic fractures, and consequently affecting the post-fracturing productivity of the well.",
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Experimental investigation of fracturing-fluid migration caused by spontaneous imbibition in fractured low-permeability sands. / Dutta, R.; Lee, C. H.; Odumabo, S.; Ye, P.; Walker, S. C.; Karpyn, Zuleima; Ayala H., Luis.

In: SPE Reservoir Evaluation and Engineering, Vol. 17, No. 1, 01.01.2014, p. 74-81.

Research output: Contribution to journalArticle

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