Closing the Gap: Fracture Half Length from Design, Buildup, and Production Analysis

Barree, R.D.; Cox, Stuart Alan; Gilbert, John Victor; Dobson, Martin L.

doi:10.2118/84491-pa

Cited by 46 publications

(20 citation statements)

References 13 publications

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“…The current study differs from that of Barree et al (2005) in that (1) a multifractured horizontal well is studied, whereas Barree et al (2005) focus on vertical wells; (2) hydraulic-fracture property estimates from RTA of single-and multiphase flowback are included in the analysis, whereas Barree et al (2005) do not discuss flowback analysis; (3) a tight-oil reservoir producing below bubble point at late stages of flowback and during on-line production is studied and hence corrections for multiphase flow are required for rigorous production analysis, whereas Barree et al (2005) use single-phase PTA and RTA methods.…”

Section: Description Of Flow Periods and Flow Regimes Observed In Fiecontrasting

confidence: 59%

“…Barree et al (2005) perform an analogous study to compare hydraulic-fracture property estimates from hydraulic-fracture modeling, postfracture flow and buildup (pressuretransient) analysis, and RTA for a tight-gas reservoir. Barree et al (2005) discuss the causes of the differences in hydraulic-fracture property estimates from each method.…”

Section: Description Of Flow Periods and Flow Regimes Observed In Fiementioning

confidence: 99%

“…Common to both Barree et al (2005) and current studies is the use of hydraulic-fracture modeling to obtain propped hydraulic-fracture estimates prior to production. Figure 1 illustrates the full suite of data sources used in this study.…”

Section: Description Of Flow Periods and Flow Regimes Observed In Fiementioning

confidence: 99%

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Innovative use of rate-transient analysis methods to obtain hydraulic-fracture properties for low-permeability reservoirs exhibiting multiphase flow

2014

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Multifractured horizontal wells, while enabling commercial production from unconventional gas and light-oil reservoirs, are challenging to analyze quantitatively to obtain reservoir and hydraulic-fracture properties. Production rates and flowing pressures gathered immediately after hydraulic-fracture stimulation (flowback) and over a longer time period (on-line production) can be interpreted for hydraulic-fracture properties such as fracture surface area or half-length and fracture conductivity, but dynamic fracture properties and multiphase flow during both stages of production can complicate the analysis. Recent studies have suggested that flowback data can provide early insight into these fracture properties if high-resolution fluid rates/pressures are gathered, but the physics of the process are complex, and analytic methods for interpretation are at an early stage of development. Analytic methods for longer-term production data analysis, although better established, are still limited primarily to single-phase flow and simple fracture and reservoir behavior. Rate-transient methods can be applied to both flowback and long-term production data to quantify hydraulic-fracture properties and changes in effective hydraulic-fracture length during production. For the flowback period, simplified analytic methods have been developed for before-breakthrough production of hydraulic-fracturing fluids and after-breakthrough production of hydraulic-fracture and reservoir fluids. These methods are still under development, and early applications can be illustrated. For long-term production analysis, classic rate-transient analysis techniques, such as the square-root-of-time plot, have been modified to account for multiphase flow and stress-sensitive permeability exhibited by low-permeability gas condensate and black-oil reservoirs producing below saturation pressure. A field example consisting of a multifractured horizontal well completed in a tight-oil reservoir isused to to compare hydraulicfracture properties derived from flowback and long-term production data. Although flowback analysis yields hydraulic-fracture half-lengths consistent with hydraulic-fracture modeling results, long-term production analysis yields much smaller fracture half-lengths, possibly because of breakthrough of gas once bubble-point pressure is reached. Additional mechanisms for effective producing fracture half-length reduction can be proposed. Another important observation is that estimation of fracture properties from long-term production analysis of a reservoir producing below saturation pressure can be in significant error if the estimates are derived from techniques assuming singlephase flow. Corrections to the analytic methods for multiphase flow yield fracture half-lengths consistent with those obtained from history matching using rigorous numerical simulation. In a preliminary analysis, the techniques under development are intended to aid hydraulic-fracture evaluation and design in tight reservoirs that exhibit complex flow characteristics....

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Section: Description Of Flow Periods and Flow Regimes Observed In Fiecontrasting

confidence: 59%

Section: Description Of Flow Periods and Flow Regimes Observed In Fiementioning

confidence: 99%

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Innovative use of rate-transient analysis methods to obtain hydraulic-fracture properties for low-permeability reservoirs exhibiting multiphase flow

2014

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“…The objective was to place the optimum amount of proppant and obtain the optimum effective half-length and conductivity without growing into the S8 coals. Because Baree et al 8 have shown the importance of regained permeability, it was decided to increase the breaker concentration in the water pad aggressively. Since this will be the fluid that will flow back at the end, the assumption is that it would clean up the fracture and improve the regained permeability.…”

Section: Pictured Cliffs Sandstone Stimulation and Resultsmentioning

confidence: 99%

Hybrid Fracture Stimulation in Underpressured Coals

2006

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSome of the significant strides made in coal stimulation during the last 25 years can be attributed to the development of newgeneration fluid systems (i.e., low gel loading fluids with efficient low-temperature breaker systems that cause less polymer damage in coals). All these new developments were implemented to (a) minimize damage in coals, and (b) maximize production. Water fracture treatments in coals completely eliminated polymer damage but did not always maximize production. The use of new-generation crosslinked fluids did provide better half-lengths and conductivities but still left residual damage in coals. Based on production, it was confirmed that the benefits obtained with this fluid system outweighed the damage created. To further reduce the damage in coals and obtain better regained fracture permeability, implementing hybrid fracture treatments in coals was considered in this San Juan basin project. The term "hybrid" in this case refers to a water pad followed by crosslinked fluid sand stages. Potential benefits of this technique in coals include: (a) minimizing damage caused by gel, (b) maximizing regained permeability, (c) containing height growth, and d) lowering cost.There are two parts to this work. The first part presented in this paper contains the design, implementation, and encouraging initial results obtained from the seven wells in this project, which is in an underpressured area. This is the first project in which hybrid-type treatments have been applied in a low-pressured formation. This paper will discuss the lessons learned from such an application in coals. When sufficient production data becomes available, the second part of this work will quantify the results via reservoir simulation. The second part will also include quantified results from another current hybrid fracture-stimulation project where the coals are slightly overpressured.

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“…Barree et al (2003) mentions that phase segregation negatively impacts effective fracture length, yet he does not explain any possible causes for this. He also lists other causes for low effective fracture length, such as multiphase non-Darcy flow, inefficient cleanup, and capillary phase trapping.…”

Section: Literature Reviewmentioning

confidence: 99%

The Impact of Gravity Segregation on Multiphase Non-Darcy Flow in Hydraulically Fractured Gas Wells

Dickins

McVay

Schubarth³

2008

All Days

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Multiphase and non-Darcy flow effects in hydraulically fractured gas wells reduce effective fracture conductivity. Typical proppant pack laboratory experiments are oriented in such a way such that phase segregation is not possible, which results in mixed flow. Tidwell and Parker (1996), however, showed that in proppant packs, gravity segregation occurs for simultaneous gas and liquid injection at laboratory scale (1500 cm 2 ). Although the impact of gravity on flow in natural fractures has been described, previous work has not fully described the effect of gravity on multiphase non-Darcy flow in hydraulic fractures. In this work, reservoir simulation modeling was used to determine the extent and impact of gravity segregation in a hydraulic fracture at field scale. I found that by ignoring segregation, effective fracture conductivity can be underestimated by up to a factor of two.An analytical solution was developed for uniform flux of water and gas into the fracture.The solution for pressures and saturations in the fracture agrees well with reservoir simulation. Gravity segregation occurs in moderate-to-high conductivity fractures.iv Gravity segregation impacts effective fracture conductivity when gas and liquid are being produced at all water-gas ratios modeled above 2 Bbls per MMscf. More realistic, non-uniform-flux models were also run with the hydraulic fracture connected to a gas reservoir producing water. For constant-gas-rate production, differences in pressure drop between segregated cases and mixed flow cases range up to a factor of two. As the pressure gradient in the fracture increases above 1 to 2 psi/ft, the amount of segregation decreases. Segregation is also less for fracture half-length-to-height ratios less than or close to two. When there is less segregation, the difference in effective conductivity between the segregated and mixed flow cases is reduced. I also modeled the water injection and cleanup phases for a typical slickwater fracture treatment both with and without gravity effects and found that for cases with segregation, effective fracture conductivity is significantly higher than the conductivity when mixed flow occurs.Gravity segregation is commonly ignored in design and analysis of hydraulically fractured gas wells. This work shows that segregation is an important physical process and it affects effective fracture conductivity significantly. Hydraulic fracture treatments can be designed more effectively if effective fracture conductivity is known more accurately.v ACKNOWLEDGEMENTS

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Closing the Gap: Fracture Half Length from Design, Buildup, and Production Analysis

Cited by 46 publications

References 13 publications

Innovative use of rate-transient analysis methods to obtain hydraulic-fracture properties for low-permeability reservoirs exhibiting multiphase flow

Innovative use of rate-transient analysis methods to obtain hydraulic-fracture properties for low-permeability reservoirs exhibiting multiphase flow

Hybrid Fracture Stimulation in Underpressured Coals

The Impact of Gravity Segregation on Multiphase Non-Darcy Flow in Hydraulically Fractured Gas Wells

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