Rock matrix and fracture analysis of flow in western tight gas sands

Morrow, Norman R.; Brower, K. R.; Kilmer, N.H.; Ward, J.S.

doi:10.2172/5053363

Cited by 5 publications

(6 citation statements)

References 7 publications

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“…7 ,10 Results of such treatments appear to depend mainly on the nature of the pore throats, such as quartz or carbonate overgrowths, that control permeability. [7][8][9][10] Three approaches to permeability enhancement by acid treatment of VMF(V*) samples were tested.…”

Section: Resultsmentioning

confidence: 99%

“…8,10 However, only a small number of the available MWX cores had been protected from evaporation after recovery, and in many instances, it was found that the adopted sealing procedure did not prevent drying. This, coupled with the problems of having enough preserved core samples containing fractures and then readily identifying them in their sealed state, made the use of preserved core infeasible.…”

Section: Experimental Methodsmentioning

confidence: 99%

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Fluid Flow in Healed Tectonic Fractures

Morrow

Brower

et al. 1990

Journal of Petroleum Technology

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Core samples recovered during the course of the Multiwell Experiment (MWX) contained numerous mineralized vertical tectonic fractures a few millimeters wide. Permeabilities of these calcite-filled fractures were higher but of the same order as the surrounding matrix. Increases in permeability of up to several-thousand-fold were obtained by treatment with acetic acid. Acid fracturing provides a possible approach to formation stimulation.

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Section: Resultsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Fluid Flow in Healed Tectonic Fractures

Morrow

Brower

et al. 1990

Journal of Petroleum Technology

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“…When both tests give the same prediction, then the key issues n b as gallons/1000 gal (gpt) or lb/1000 gal (ppt) or pe Unpropped Fracture Conductivity Testing All evidence points to the fact that there must be enhanced flow pathways in Unconventional Gas Shales to explain production rates. The literature is replete with the suggestion that fractured core experiments are needed to understand the flow characteristics of natural or induced fractures (Morrow 1987). Gall et al (1988) and Luffel et al (1991) report on the results of the examination of completion and stimulation fluids in low permeability sandstones containing artificial fractures.…”

Section: Ro Testingmentioning

confidence: 99%

“…The current discussion of stimulated reservoir volume indicates that the industry believes that we are activating enhanced flow pathways during the stimulation treatments. As we began to study the flow properties in Gas Shale samples, we reexamined the literature to find the results of such studies (Morrow et al 1987). They were woefully absent in the literature.…”

Section: Ro Testingmentioning

confidence: 99%

An Examination of Clay Stabilization and Flow Stability in Various North American Gas Shales

Conway¹,

Venditto²,

Reilly

et al. 2011

All Days

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There is a general uncertainty regarding the issues affecting shale stability in gas shale reservoirs. True swellable smectite is not present in most of the reservoirs currently being exploited. Illite and illite/smectite are the principal clay components, and they do have a distinct fixed water of hydration which is salinity and cation dependent. Historically, two factors had a major impact on the choices made for clay stability in clay rich reservoirs. Today, many hydraulic fracturing treatments are conducted with virtually fresh water, so this comprehensive study was undertaken to identify the role of salinity on the stability of various gas productive shales. Evaluated were various inorganic salts, temporary clay stabilizers and permanent clay/shale stabilizers, and the results of the comparisons will be presented.The petrophysical properties of the samples studied have been extensively characterized and the swelling and erosional characteristics have been examined with capillary suction time (CST), roller oven (RO) and unpropped fracture flow capacity tests. Some shale samples are inherently unstable, regardless of the fluid used in the measurement, while the majority responds positively to more compatible fluids. A few samples are extremely stable in all fluids. The native state of the clay in the shales has been characterized by a variety of tests, including specialized cation exchange and wettability studies, to help understand the fluid/rock interactions.The results of this study have identified the relationship between clay stabilizer type and concentration on the stability of the shale and the impact on flow capacity in the "stimulated reservoir volume". This is a compelling story of rock/fluid interaction studies on actual cores, fit for purpose product development, and supporting field production results.

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“…While conventional core analyses of these types of rocks generally yield permeabilities on the order of tens of microDarcies, detailed special core analyses funded by DOE and GRI in the 1980s showed that the in-situ permeabilities for gas flow were much lower (3) . The combined effects of confining stress and water saturation typically caused approximately a two-order-of-magnitude reduction in gas permeability from the conventionally measured value, resulting in effective gas-flow permeabilities of 0.1 -1.0 microDarcies in most of these reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Stimulating Unconventional Reservoirs: Maximizing Network Growth While Optimizing Fracture Conductivity

Warpinski

Mayerhofer

Vincent

et al. 2009

Journal of Canadian Petroleum Technology

318

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Unconventional reservoirs such as gas shales and tight gas sands require technology-based solutions for optimum development. The successful exploitation of these reservoirs has relied on some combination of horizontal drilling, multi-stage completions, innovative fracturing and fracture mapping to engineer economic completions. However, the requirements for economic production all hinge on the matrix permeability of these reservoirs, supplemented by the conductivity that can be generated in hydraulic fractures and network fracture systems. Simulations demonstrate that ultra-low shale permeabilities require an interconnected fracture network of moderate conductivity with a relatively small spacing between fractures to obtain reasonable recovery factors. Microseismic mapping demonstrates that such networks are achievable and the subsequent production from these reservoirs supports both the modelling and the mapping. Tight gas sands, having orders of magnitude greater permeability than the gas shales, may be successfully depleted without inducing complex fracture networks, but other issues of damage and zonal coverage complicate recovery in these reservoirs. As with the shales, mapping has proved itself to be valuable in assessing the fracturing results. Introduction Unconventional reservoirs provide a significant fraction of gas production in North America and increasing amounts in some other regions of the world. Such reservoirs include tight gas sands, coalbed methane (CBM), and gas shales; in 2006 these reservoirs provided 43% of the US production of natural gas [Kuuskraa(1)]. Because of their limited permeability, which is foremost among many other complexities, some type of stimulation process (and/or dewatering in the case of CBM) is required to engender economic recovery from wells drilled into these formations. The focus of this paper is on gas shales, with particular emphasis on how these reservoirs perform relative to tight gas sands. The important role of natural fractures in both the stimulation and production processes, the importance of conductivity in the developed fracture or fracture system, and the critical influence of the matrix permeability are investigated using both mapping and modeling results.

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Rock matrix and fracture analysis of flow in western tight gas sands

Cited by 5 publications

References 7 publications

Fluid Flow in Healed Tectonic Fractures

Fluid Flow in Healed Tectonic Fractures

An Examination of Clay Stabilization and Flow Stability in Various North American Gas Shales

Stimulating Unconventional Reservoirs: Maximizing Network Growth While Optimizing Fracture Conductivity

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