Citation: Iferobia, C.C.; Ahmad, M.;
Ali, I. Experimental Investigation of
Shale Tensile Failure under
Thermally Conditioned Linear
Fracturing Fluid (LFF) System and
Reservoir Temperature Controlled
Conditions. Polymers 2022, 14, 2417.
https://doi.org/10.3390/
polym14122417
Academic Editors: Alberto
Campagnolo and Alberto Sapora
Received: 1 March 2022
Accepted: 12 May 2022
Published: 14 June 2022
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Article
Experimental Investigation of Shale Tensile Failure under
Thermally Conditioned Linear Fracturing Fluid (LFF) System
and Reservoir Temperature Controlled Conditions
Cajetan Chimezie Iferobia
1
, Maqsood Ahmad
1,
* and Imtiaz Ali
1,2
1
Department of Petroleum Engineering, Universiti Teknologi PETRONAS, Seri Iskandar 32610,
Perak Darul Ridzuan, Malaysia; cajetan_17007975@utp.edu.my (C.C.I.); imtiaz_17003333@utp.edu.my (I.A.)
2
Department of Petroleum and Gas Engineering, BUITEMS, Quetta 87300, Balochistan, Pakistan
* Correspondence: maqsood.ahmad@utp.edu.my
Abstract:
Linear fracturing fluid (LFF) provides viscosity driven benefits of proppant suspensibility
and fluid loss control, and with the use of a breaker agent, flowback recovery can be greatly enhanced.
Shale tensile strength is critical in the prediction of fracture initiation and propagation, but its behavior
under the interaction with LFF at reservoir temperature conditions remains poorly understood. This
necessitated an in-depth investigation into the tensile strengths of Eagle Ford and Wolfcamp shales
under thermally conditioned LFF and reservoir temperature controlled conditions. Brazilian Indirect
Tensile Strength (BITS) testing was carried out for the quantitative evaluation of shale tensile strength,
followed by extensive failure pattern classifications and surface crack length analysis. The thermally
conditioned LFF saturation of shale samples led to average tensile strength (ATS) increases ranging
from 26.33–51.33% for Wolfcamp. Then, for the Eagle Ford samples, ATS increases of 3.94 and 6.79%
and decreases of 3.13 and 15.35% were recorded. The exposure of the samples to the temperature
condition of 90
◦
C resulted in ATS increases of 24.46 and 33.78% for Eagle Ford and Wolfcamp
shales, respectively. Then, for samples exposed to 220
◦
C, ATS decreases of 6.11 and 5.32% were
respectively recorded for Eagle Ford and Wolfcamp shales. The experimental results of this research
will facilitate models’ development towards tensile strength predictions and failure pattern analysis
and quantifications in the LFF driven hydraulic fracturing of shale gas reservoirs.
Keywords:
linear fracturing fluid; shale gas reservoir; surface crack length; failure pattern;
tensile strength
1. Introduction
Water-based fracturing fluids have been the main drivers of shale gas reservoirs’
hydraulic fracturing, with slickwater being more widely used in comparison to linear
fracturing fluid of remarkable viscosity. Slickwater utilization leads to the generation of
highly conductive fractures [
1
], easy flowback, highly stimulated reservoir volume [
2
],
and effective cost savings [
3
]. However, it requires large water volumes and is equally
associated with poor proppant carrying capacity, the creation of narrow fracture widths,
and high leak-off due to minimal wall building [
4
]. Linear fracturing fluid with the benefit
of higher viscosity ensures proppant suspensibility, better fluid loss control, and maximized
flowback recovery achieved by breaker agent utilization.
Linear fracturing fluid (LFF) is formulated by the addition of a polymeric agent into an
aqueous solution for viscous gel formation. Other chemical additives could be introduced
for the enhancement of fluid properties. Guar gum and its derivatives are widely used
polymers in the industry [5] for hydraulic fracturing fluid preparations. However, certain
draw backs are encountered, such as the high cost and significant amounts of polymeric
residues being left after fluid breakdown [
6
]. These polymeric residues have tendencies to
Polymers 2022, 14, 2417. https://doi.org/10.3390/polym14122417 https://www.mdpi.com/journal/polymers
