A Collaborative Study on DFIT Interpretation: Integrating Modeling, Field Data, and Analytical Techniques

McClure, Mark; Bammidi, Vidya Sagar; Cipolla, Craig L.; Cramer, Dave; Martin, Lucas; Savitski, Alexei A.; Sobernheim, Dave; Voller, Kate

doi:10.15530/urtec-2019-123

Cited by 43 publications

(14 citation statements)

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“…It is debatable whether fracture closure can be picked for small-scale mini-frac tests in a crystalline rock mass. Several authors have argued that it is likely that small scale hydraulic fractures in vertical wells and low-permeability formations close immediately once pumping has stopped (Zoback and Kohli 2019;McClure et al 2019). This rapid closure of the hydraulic fracture after shut-in can explain that most of the stress estimation methods yield comparable values within a narrow range.…”

Section: Comparison Of Methods To Determine the Magnitude Of Smentioning

confidence: 99%

“…Such rapid closures can occur because of the low volume of injected fluid or the intersection of highly permeable natural fractures. Dutler et al (2020) and McClure et al (2019) stated that the intersection of highly permeable natural fractures leads to monotonically declining plots of dP/dG against the G-function. McClure et al (2019) interpreted this monotonically declining derivative as the instant contact of the fracture walls after shut-in and suggested that in this case the shut-in pressure can be taken as an estimate of S 3 .…”

Section: Comparison Of Methods To Determine the Magnitude Of Smentioning

confidence: 99%

“…Dutler et al (2020) and McClure et al (2019) stated that the intersection of highly permeable natural fractures leads to monotonically declining plots of dP/dG against the G-function. McClure et al (2019) interpreted this monotonically declining derivative as the instant contact of the fracture walls after shut-in and suggested that in this case the shut-in pressure can be taken as an estimate of S 3 . We observed a monotonically declining pressure derivative on G-function plots in most of our data (e.g., Fig.…”

Section: Comparison Of Methods To Determine the Magnitude Of Smentioning

confidence: 99%

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Estimating the Least Principal Stress in a Granitic Rock Mass: Systematic Mini-Frac Tests and Elaborated Pressure Transient Analysis

Bröker

2022

Rock Mech Rock Eng

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The hydraulic fracturing technique (also termed mini-frac test) is commonly used to estimate the in situ stress field. We recently conducted a mini-frac stress measurement campaign in the newly-established Bedretto Underground Laboratory (BedrettoLab) in the Swiss Alps. Four vertical boreholes, dedicated for stress characterization of the granitic rock mass, hosted a total of 19 mini-frac test intervals. Systematic pressure transient analysis was performed to carefully estimate the magnitude of the least principal stress ($$S_\mathrm {3}$$ S 3 ). We compared five different methods (inflection point, bilinear pressure decay rate, tangent, fracture compliance, and jacking pressure) to identify an adequate approach best suited for our test scale and the host rock mass. We found that the methods used to determine the fracture closure pressure underestimate the magnitude of $$S_\mathrm {3}$$ S 3 , presumably due to the rapid closure of the hydraulic fracture after shut-in. The most consistent results were found using the inflection point and bilinear pressure decay rate method, which both determine the (instantaneous) shut-in pressure as the proxy for the $$S_\mathrm {3}$$ S 3 magnitude. The determined shut-in pressure, or $$S_\mathrm {3}$$ S 3 magnitude, is $$14.6\pm 1.4$$ 14.6 ± 1.4 MPa from the inflection point method. This allowed us to further estimate the stress environment around the BedrettoLab, which is transitional between normal and strike-slip faulting. The measured local pore pressures from extended shut-in periods are between 2.0 and 5.6 MPa, significantly below hydrostatic. A combination of drainage, cooling, and the excavation damage zone of the tunnel may have significantly perturbed the in situ stress field in the vicinity of the BedrettoLab.

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Section: Comparison Of Methods To Determine the Magnitude Of Smentioning

confidence: 99%

Section: Comparison Of Methods To Determine the Magnitude Of Smentioning

confidence: 99%

Section: Comparison Of Methods To Determine the Magnitude Of Smentioning

confidence: 99%

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Estimating the Least Principal Stress in a Granitic Rock Mass: Systematic Mini-Frac Tests and Elaborated Pressure Transient Analysis

Bröker

2022

Rock Mech Rock Eng

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“…(2) and (3) gives where V b is the flowback volume. The system stiffness can be expressed as where C w is the wellbore storage coefficient, A f is the fracture area, and s f is the fracture stiffness (derivative of pressure with respect to the average fracture aperture according to, McClure et al 2019). That is to say that the system stiffness is composed of two components: wellbore storage and fracture stiffness (Shlyapobersky et al 1988;.…”

Section: Stiffness Analysis Of Flowbackmentioning

confidence: 99%

Flowback Test Analyses at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) Site

et al. 2021

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In 2017 and 2019, injection testing was carried out in three zones in a vertical well in granite at the Frontier Observatory for Research in Geothermal Energy site near Milford, Utah, USA. In several injection cycles, flowback was implemented rather than shut-in. The goal was to explore an alternative to prolonged shut-in periods for inferring closure stress, formation compressibility, and formation permeability (permeability thickness product). The flowback procedures involved a cyclic flowback/shut-in, while pressure decreased. The flowback data are presented, and analyses are shown. The inferred closure stress(es) from flowback analyses are lower than for equivalent injection cycles that were strictly shut-in. Relatively high formation compressibility obtained from the flowback analyses indicates an extensive, fractured system. This study also includes numerical simulation of the flowback events. The numerical model shows that the rebound pressure is not necessarily the lower bound of the minimum principal stress. The signature of stiffness change can be identified as the process when the depletion mainly transitions from hydraulic fracture to natural fractures from numerical analysis. Overall, flowback potentially has advantages over shut-in because of the reduced time to closure.

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“…During DFITs, a small hydraulic fracture is created, and then the well is shut-in for a period of days to months. The pressure decline curve is used to estimate stress, pore pressure, and formation permeability [15]. Six DFITs were collected in the 7SU pilot well, and DFITs were collected at the 'toe' of horizontal wells 4SU, 6SU, and 8SU in the UW and 6SM in the MW (Figure 2).…”

Section: Stress Measurementsmentioning

confidence: 99%

Stratigraphically Controlled Stress Variations at the Hydraulic Fracture Test Site-1 in the Midland Basin, TX

Kohli

Zoback

2021

Energies

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We investigated the relationship between stratigraphy, stress, and microseismicity at the Hydraulic Fracture Test Site-1. The site comprises two sets of horizontal wells in the Wolfcamp shale and a deviated well drilled after hydraulic fracturing. Regional stresses indicate normal/strike-slip faulting with E-W compression. Stress measurements in vertical and horizontal wells show that the minimum principal stress varies with depth. Strata with high clay and organic content show high values of the least compressive stress, consistent with the theory of viscous stress relaxation. By integrating data from core, logs, and the hydraulic fracturing stages, we constructed a stress profile for the Wolfcamp sequence, which predicts how much pressure is required for hydraulic fracture growth. We applied the results to fracture orientation data from image logs to determine the population of pre-existing faults that are expected to slip during stimulation. We also determined microseismic focal plane mechanisms and found slip on steeply dipping planes striking NW, consistent with the orientations of potentially active faults predicted by the stress model. This case study represents a general approach for integrating stress measurements and rock properties to predict hydraulic fracture growth and the characteristics of injection-induced microseismicity.

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A Collaborative Study on DFIT Interpretation: Integrating Modeling, Field Data, and Analytical Techniques

Cited by 43 publications

References 0 publications

Estimating the Least Principal Stress in a Granitic Rock Mass: Systematic Mini-Frac Tests and Elaborated Pressure Transient Analysis

Estimating the Least Principal Stress in a Granitic Rock Mass: Systematic Mini-Frac Tests and Elaborated Pressure Transient Analysis

Flowback Test Analyses at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) Site

Stratigraphically Controlled Stress Variations at the Hydraulic Fracture Test Site-1 in the Midland Basin, TX

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