Production Forecasting of Hydraulically Fractured Conventional Low-Permeability and Unconventional Reservoirs Linking the More Detailed Fracture and Reservoir Parameters

Sierra, Leopoldo; Mayerhofer, Mike; Jin, Chaochao

doi:10.2118/163833-ms

Cited by 15 publications

(9 citation statements)

References 19 publications

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“…Figs. For this paper, as discussed by Sierra et al (2013) and Jin et al (2013), it is assumed that the associated reservoir area is effectively drained with planar fractures placed at each perforation cluster or entry point. 3 illustrates the relative permeability considered for the fracture system.…”

Section: Considerations For the Study And Reservoir Modelingmentioning

confidence: 99%

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Is Induced Fracture Complexity Always Required in Unconventional Reservoir Stimulation?

Sierra

2016

Day 2 Thu, June 02, 2016

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Induced fracture complexity maximization, in addition to the primary hydraulic fracture, to improve the recovery efficiency or productivity of gas or liquids in unconventional resource shale reservoirs has been accepted and fully implemented by the industry. As a result, stimulation fluids and/or completion strategies have been engineered to maximize induced fracture complexity in many unconventional reservoirs. In typical unconventional horizontal completions, induced fracture complexity is beneficial for the productivity of nanodarcy (nd) shales if conductivity is sustained in time, although induced fracture complexity may not be a requirement for all unconventional reservoirs, especially tight sands.In some unconventional reservoirs, operators have observed similar productivity in wells with predominantly planar fractures compared to wells that appear to have more complex fractures. This paper, supported by extensive reservoir simulations, aims to develop criteria for situations in which induced fracture complexity and sustained conductivity are required and when they are not. The simulations include a reservoir permeability range of 10 nd to 0.001 md and a fracture complexity conductivity of 1 to 5 md-ft with and without stress dependence. The simulation results show that the fracture complexity with a constant and sustained conductivity (no stress dependent) are generally important for reservoir permeabilities lower than 100 nd for gas and 500 nd for liquid-producing reservoirs, but this benefit is minimized when the induced or existing stresses negatively affect the fracture complexity conductivity.Based on these results, an optimized completion strategy is suggested to maximize the productivity or recovery factor (RF) in unconventional gas-and liquid-producing reservoirs.

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Section: Considerations For the Study And Reservoir Modelingmentioning

confidence: 99%

“…The ideal fracture spacing to maximize the 30-year RF for each fluid type and permeability level was calculated using the correlations published by Sierra et al (2013) and Jin et al (2013). Fig.…”

Section: Considerations For the Study And Reservoir Modelingmentioning

confidence: 99%

Is Induced Fracture Complexity Always Required in Unconventional Reservoir Stimulation?

Sierra

2016

Day 2 Thu, June 02, 2016

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“…3 provides the relative permeability considered for each fracture system. As Sierra et al (2013), Sierra and Mayerhofer (2014), and Jin et al (2013) discussed in previous publications, this paper also considers the generation of planar fractures at each perforation cluster or entry point to drain the associated reservoir area. Fig.…”

Section: Considerations For the Study And Reservoir Modelingmentioning

confidence: 99%

“…The simulator considers changes of fracture conductivity as a function of drawdown. The ideal perforation cluster or fracture spacing required to maximize the RF for each fluid type and permeability level was calculated using the simplified correlations published by Sierra et al (2013) and Jin et al (2013), respectively. Fig.…”

Section: Considerations For the Study And Reservoir Modelingmentioning

confidence: 99%

Evaluating the Benefits of Zipper Fracs in Unconventional Reservoirs

Sierra

Mayerhofer

2014

SPE Unconventional Resources Conference

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In cemented and cased wells, perforation cluster spacing is optimized based on the type of reservoir fluid, permeability, fracture conductivity, proppant distribution, and associated stresses to place multiple fractures along horizontal wellbores. Specifically, in very low-permeability reservoirs, the requirement for smaller perforation or fracture spacing might not be possible because of the geomechanical interference between fractures. In this case, the commonly used zipper-frac technique can provide a means to create fractures in projects with closer spacing.The benefits of zipper fracs can be maximized by generating proper fracture geometry and properly staggering the perforation/fracture system. This paper reviews and discusses numerical reservoir-modeling results of zipper fracturing that demonstrate the individual or combined effects of the perforation/fracture staggering, comparing these to the fracture length, fracture overlap, fracture conductivity, and/or proppant distribution effects of a conventional completion that does not use the staggered zipper-frac approach. The simulation results are assessed over a wide range of unconventional reservoir permeabilities for both gas and light oil. IntroductionExploitation strategies in unconventional reservoirs that produce wells at commercial rates and maximize the reservoir fluids' recovery factor (RF) are required in nanodarcy (nd) permeability reservoirs. To align with these strategies, operators have implemented various drilling strategies, horizontal well placement, fluid-type testing, single well or well group completions/stimulations (e.g., the zipper-frac methodology), and others. As documented by Rafiee et al. (2012), Warpinski et al. (2009), and Water et al. (2009), zipper-frac methodology has the potential to increase a stimulated fracture area and induce more fracture complexity in unconventional reservoirs.Once the drilling, mechanical completion, and lateral well spacing have been optimized, completion efficiency must be addressed. For the cases of unoptimized fracture spacing, industry-reported completion efficiencies within the range of 30 to 75% resulted in lower well productivity and lower RF.Where multiple wells are drilled or completed from the same pad by staggering the induced fractures or zipper fracturing, lower completion efficiency is still an issue, which affects the productivity and RF, particularly when the staggered, induced fracture spacing had not been properly optimized. For staggered, overlapping fractures, Sahai et al. (2013) reports that, because of the stimulated reservoir volume's (SRV's) competency, a maximum of 50% overlapping can help ensure a positive net-present value (NPV). For staggered and overlapping fractures, another issue to consider is well interference, as reported by Mayerhofer et al. (2005).In this paper, various parameters, including reservoir properties, such as fracture conductivity, fluid composition, optimized staggered fracture spacing, completion efficiencies, and overlapping fracture lengths, are co...

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“…Work has been performed, which supports the notion that one third of the perforations produce two-thirds of the production (Meyer 2010). Sierra et al (2013) have derived a correlation that allows for the calculation of the optimum fracture spacing for a gas reservoir to maximize recovery. The correlation calculation is is based on the formation permeability, pressure drawdown, and gas viscosity.…”

Section: Fracture Initiation Designmentioning

confidence: 99%

Optimizing Lateral Lengths in Horizontal Wells for a Heterogeneous Shale Play

Chorn

Stegent

Yarus

2014

Day 2 Wed, February 26, 2014

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A successful evaluation and development program in oil-and gas-bearing shales requires considerable analysis and investment, not to mention optimization to help ensure a profitable outcome. Accelerating optimization, reducing capital expenditures, and improving lifecycle net present value (NPV) for the asset are reasonable goals. Seven shale properties are key drivers to help achieve successful play economics. However, the heterogeneity of shales makes well location selection difficult without appraisal well logs and geostatistical mapping of shale property quality. The analysis method allows operators to quickly high-grade areas within a large, heterogeneous shale play using logging suites from a limited number of wellbores in the play. Further, the methodology has been extended to quantify the play's potential reward versus risk distribution for in-fill drilling investments. This study extends the method to optimizing lateral lengths of horizontal wells. Geostatistics provides a means to determine correlation lengths of aggregate shale properties known to be critical to successful economics. The correlation length is used to determine the appropriate length of the horizontal well lateral, restricting it within the highest rock quality for stimulation effectiveness and production rates. Because optimal lateral lengths can be predicted using this approach, it is now possible to pinpoint the best wellhead location, the best landing point for the horizontal portion of the well, and set the optimal length of the lateral. This reduces the drilling of unproductive lateral lengths and targets stimulations. By shortening the "trial-and-error" evaluation lifecycle stage using this methodology, an operator can develop an asset more quickly and at less cost than with previous approaches.

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Production Forecasting of Hydraulically Fractured Conventional Low-Permeability and Unconventional Reservoirs Linking the More Detailed Fracture and Reservoir Parameters

Cited by 15 publications

References 19 publications

Is Induced Fracture Complexity Always Required in Unconventional Reservoir Stimulation?

Is Induced Fracture Complexity Always Required in Unconventional Reservoir Stimulation?

Evaluating the Benefits of Zipper Fracs in Unconventional Reservoirs

Optimizing Lateral Lengths in Horizontal Wells for a Heterogeneous Shale Play

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