Does the Presence of Natural Fractures Have an Impact on Production? A Case Study From the Middle Bakken Dolomite, North Dakota

Mullen, Michael; Pitcher, Jason L.; Hinz, David; Everts, Michael Lynn; Dunbar, D.; Carlstrom, George M.; Brenize, Galen R.

doi:10.2118/135319-ms

Cited by 26 publications

(10 citation statements)

References 7 publications

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“…Gale, 2008;Mullen et al, 2010). Instead, we introduced here the bedding corridors as an addition to the natural fractures for optimizing hydrofracking design.…”

Section: Impact On Hydrofrackingmentioning

confidence: 99%

Detection of Bedding Corridors From Open-hole Logs in Vertical Wells and Their Impact on Geomechanical Assessment

Sirat

Noufal

2015

Day 2 Tue, September 15, 2015

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Bedding corridors are sub-horizontal tabular bodies of bedding plane weak zones formed as shear swarms, which vertically divide the entire reservoir thickness and extend laterally as their layers. Bedding corridors are genetically related to shearing along the bedding planes and they contribute to the conductive systems in few Abu Dhabi reservoirs. They can be best identified from horizontal borehole image logs, and as spikes in open-hole logs. Natural bedding corridors can be considered as indicators of the reservoir stress history, where they form extraordinary clusters of a huge number of quasi-parallel shear fractures in a transpressional regime.In many oil and gas reservoirs, natural bedding corridors networks help drain hydrocarbons and other fluids. The role of bedding corridors is particularly important in reservoirs having a tight matrix. In carbonate formations, for example, it is quite common to observe a permeability contrast of 1000mD or more between the rock matrix and surrounding bedding corridors. In this paper we differentiate between image-log porosity and density-neutron porosity, which is regarded as secondary porosity attributable to fractures. We also introduce here a working hypothesis about their effect on hydrofraccing being part of geomechanical assessment.Results indicate that the horizontal stress anisotropy (Shmin/SHmax ratio) is the key parameter to predict bedding corridors behavior under different stress regimes. Swapping stresses with depth is common in Abu Dhabi fields, where a strike-slip regime can open and dilate the shear along the bedding planes. It is recommended to opt for horizontal wells hydrofraccing to maximize the intersection of those bedding corridors compared to vertical wells.The significance of this approach is that once a diagnostic signature can be recognized in open-hole logs, in combination with lost circulation data, it can be used to locate bedding corridors in other vertical wells with no image logs. Geomechanically, these corridors can be used efficiently to increase production particularly in tight and unconventional reservoirs.

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“…Gale, 2008;Mullen et al, 2010). Instead, we introduced here the bedding corridors as an addition to the natural fractures for optimizing hydrofracking design.…”

Section: Impact On Hydrofrackingmentioning

confidence: 99%

Detection of Bedding Corridors From Open-hole Logs in Vertical Wells and Their Impact on Geomechanical Assessment

Sirat

Noufal

2015

Day 2 Tue, September 15, 2015

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“…6). Mullen et al (2010) showed another fracture study for Bakken based on LWD micro-resistivity images. He reported the highest fracture density zone for Bakken in the well is as high as 0.69 fracture/ft or 1.45ft spacing in the sweet spot zones.…”

Section: Bakken Shalementioning

confidence: 99%

Natural Fractures in Unconventional Shale Reservoirs in US and their Roles in Well Completion Design and Improving Hydraulic Fracturing Stimulation Efficiency and Production

2014

SPE Annual Technical Conference and Exhibition

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Most of the shale reservoirs in US land are naturally fractured. The fracture intensity and types vary from one shale to another. Even within the same shale in the same field, the heterogeneity of fracture intensity can be often expected to be high in a horizontal well. The current popular geometrical completion design can potentially ignore the existence of natural fractures. Hence, maximizing stimulation efficiency without understanding existing natural fractures can be a challenge. In this paper, study was made of the majority of the published case studies related to natural fractures in the US shales in the last 20 years. The evidence of natural fractures from either outcrops or subsurface data, i.e. core, borehole images, or other data is summarized for each studied shale. The latest studies show that the hydraulic fracture propagation can be strongly influenced by existing natural fractures regardless of whether they are open or closed. The roles of existing fractures in the shales include: 1) providing enhanced reservoir permeability for improved productivity if they are open and effectively connected by hydraulic fractures; 2) promoting much better fracturing network complexity regardless of whether they are open or closed prior to the stimulation; 3) giving possible negative impact sometimes, i.e. high water cut, if they are connected with wet zones below or above the reservoirs. It can be concluded that engineered completion designs that employ accurate knowledge of natural fracture data, in-situ stresses, and other reservoir and completion quality indicators as inputs can provide opportunities for enhancing stimulation efficiency and fracturing network complexity. This in turn can lead to better connectivity to a larger reservoir volume and access to more drainage area in the shales.

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“…Recently, LWD electrical borehole images are used to design the optimum placement of the packers for multi-stage fracturing in the horizontal braches, (Mullen et al 2010). Recently, LWD electrical borehole images are used to design the optimum placement of the packers for multi-stage fracturing in the horizontal braches, (Mullen et al 2010).…”

Section: Lwd Horizontal Borehole Image Logging For Multi-stage Hydraumentioning

confidence: 99%

“…Several shale gas operators are also characterizing their lateral and horizontal boreholes with LWD images not only for reservoir navigation but also for better placement of the hydraulic fracturing stages, (Mullen et al 2010). These analyses are utilized to quantify the intrinsic rock anisotropy which can be used to derive anisotropic stress profiles.…”

Section: Introductionmentioning

confidence: 99%

State-of-the-art Openhole Shale Gas Logging

2012

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFaced with increasing field maturity and production decline from conventional gas reservoirs, oil companies are shifting their focus and pursuing new alternatives; one of them being the development of shale and gas plays. To be economically viable, these low-permeability formations require fracture stimulation. Interval selection within shale reservoirs for hydraulic fracturing or horizontal laterals are based on several variables: sufficient organic matter or total organic carbon (TOC) and favorable hydraulic fracturing stimulation. The presence and extent of the natural fracture system can also influence the performance of a shale reservoir; therefore, natural fractures should be characterized within the shale formation not only from wireline or LWD borehole images logs but also from cross-dipole deep shear wave imaging which can illuminate fractures up to 60 ft away that do not intersect the well. To assess these aspects, a mineralogical, structural, and geomechanical characterization of the shale formation should be conducted. The mineralogical characterization and TOC quantifications mainly rely on a pulsed neutron spectroscopy and nuclear magnetic resonance (NMR) logs. The processing of capture and inelastic gamma ray spectra obtained from the pulsed neutron tool quantifies the formation's basic elemental composition, including silicon, calcium, aluminum, iron, sulfur, magnesium, and carbon. Geomechanical characterization is based on acoustic and density log responses. Variation in the reservoir mineralogy and TOC content affect the rock mechanics properties. Stress vs. strain curves can be derived from a micro-mechanical model of the rock which enable correlations between dynamic (obtained from acoustic logs) and static elastic properties (obtained from triaxial compression testing on core samples). Additionally, the azimuthal and transverse shear wave anisotropies are processed from cross-dipole acoustic logs to characterize the vertical and horizontal rock stiffness. This anisotropic characterization of the rock enables the evaluation of the fracture gradient and stress contrast between the target formation and the overlying and underlying formations. The paper focuses on the interaction between mineralogy, organic content and geomechanical analyses in shale gas reservoir evaluation.

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Does the Presence of Natural Fractures Have an Impact on Production? A Case Study From the Middle Bakken Dolomite, North Dakota

Cited by 26 publications

References 7 publications

Detection of Bedding Corridors From Open-hole Logs in Vertical Wells and Their Impact on Geomechanical Assessment

Detection of Bedding Corridors From Open-hole Logs in Vertical Wells and Their Impact on Geomechanical Assessment

Natural Fractures in Unconventional Shale Reservoirs in US and their Roles in Well Completion Design and Improving Hydraulic Fracturing Stimulation Efficiency and Production

State-of-the-art Openhole Shale Gas Logging

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