Characterizing and Simulating the Non-Stationariness and Non-Linearity in Unconventional Oil Reservoirs: Bakken Application

Chu, Lifu; Ye, P..; Harmawan, Iwan; Du, Liangui; Shepard, Louis Robert

doi:10.2118/161137-ms

Cited by 27 publications

(28 citation statements)

References 19 publications

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“…RTA can provide information into the various flow regimes of the well and can be an indicator of total fracture face area given an estimation of the matrix permeability (Chu et al 2012). The parameter derived from RTA, often noted as , provides a numeric value for the product of the sum of surface area of the fractures and the square root of the matrix permeability.…”

Section: Completion Evaluation and Representative Reservoir Modelmentioning

confidence: 99%

“…With pore pressure depletion in the reservoir, net confining stress is increased causing a reduction in storage porosity and pore throat size. The impact on storage porosity is minor; however, the impact on pore-throat size can be significant and translate to a reduction in permeability (Chu et al 2012). This compaction can not only be observed in the matrix pore throats, but in the fractures as well.…”

Section: Skin and Nwb Damagementioning

confidence: 99%

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An Evaluation of Completion Effectiveness in Hydraulically Fractured Wells and the Assessment of Refracturing Scenarios

Dahl

Dhuldhoya

Vaidya

et al. 2016

Day 2 Wed, February 10, 2016

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For refracturing candidate selection, good reservoir understanding and a thorough evaluation of completion effectiveness is necessary to help minimize risk. However, this task can be difficult because of various uncertainties in terms of reservoir characterization and completion evaluation procedures.Failure to identify damage mechanisms when evaluating potential refracturing candidates can cause varying success rates and often minimal incremental recovery or marginal economics. Stimulation effectiveness is often modeled, but current fracture models often do not accurately describe realistic fracture flow capacity and complex geometry. Detailed reservoir characterization, simulation, and production history matching in conjunction with pressure tests and diagnostics can be a much better indicator of completion effectiveness to assess the impact of refracturing design. This paper presents a case study of a well in the Eagle Ford Shale in which a holistic reservoir evaluation was performed using reservoir analysis and simulation.The case study helped determine key reservoir and fracture attributes and allowed subsequent investigation into the effectiveness of various refracturing scenarios. Various information sources and tools were used, including a regional earth model, diagnostic fracture injection test (DFIT), and rate transient analysis (RTA) for the analyses. The study evaluated multiple models for the reservoir and fractures (fracture geometry length, height, and width) and cluster efficiency (number of fractures) and calibrated them to production history through the adjustment of various parameters (e.g., matrix permeability, relative permeability, gamma factor in both matrix and fractures, etc.). Comparison between the data derived from the DFIT and RTA to the calibrated reservoir models was performed to determine the most representative model. The refracturing study involved advanced reservoir analysis for these wells that identified the contribution of the various damage mechanisms and suggested the presence of significant near-wellbore (NWB) damage/skin. A comparison of the effectiveness of damage removal was performed for various refracturing scenarios (i.e., addressing only the NWB damage, new rock stimulation, and the combination of both). Simulation results indicated that, by addressing only the NWB damage, incremental recovery over a 10-year forecast yielded nearly identical or higher cumulative production than stimulating new rock (i.e., creating new fractures). These results suggest further inves-tigation of the associated damage mechanisms and the refracturing methods to remediate them is necessary.Refracturing economics have great potential for optimization; the need for optimization is especially prevalent during times of reduced drilling activity. Removal of NWB damage could likely be achieved at a lower cost in comparison to large scale refracturing treatments. Similar or greater simulated production provides strong support for the economic benefits of applying the methodologies presented. If...

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Section: Completion Evaluation and Representative Reservoir Modelmentioning

confidence: 99%

Section: Skin and Nwb Damagementioning

confidence: 99%

An Evaluation of Completion Effectiveness in Hydraulically Fractured Wells and the Assessment of Refracturing Scenarios

Dahl

Dhuldhoya

Vaidya

et al. 2016

Day 2 Wed, February 10, 2016

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“…One of the major effects on rock properties is the degradation of absolute permeability. Chu et al (2012) construct the compaction tables relating permeability reduction factor to the change of effective stress for Bakken tight oil reservoir based on laboratory measurements and history matches. Orangi et al (2011) performe a simulation study for Eagle Ford tight oil reservoirs including the rock compaction effect and conclude that the transmissibility could decrease by an order of magnitude due to degradation of the fracture permeability.…”

Section: Figure 1-characteristics Of Tight Oil Reservoirs and Associamentioning

confidence: 99%

Effect of Large Capillary Pressure on Fluid Flow and Transport in Stress-sensitive Tight Oil Reservoirs

Xiong

Winterfeld

Huang

et al. 2015

SPE Annual Technical Conference and Exhibition

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The pore sizes of unconventional reservoir rock, such as shale and tight rock, are on the order of nanometers. The thermodynamic properties of in-situ hydrocarbon mixtures in such small pores are significantly different from those of fluids in bulk size, primarily due to effect of large capillary pressure. For example, it has been recognized that the phase envelop shifts and bubble-point pressure is suppressed in tight and shale oil reservoirs. On the other hand, the stress-dependency is pronounced in low permeability rocks. It has been observed that pore sizes, especially the sizes of pore-throats, are subject to decrease due to rock deformation induced by the fluid depletion from over-pressurized tight and shale reservoirs. This reduction on pore spaces again affects the capillary pressure and therefore thermodynamic properties of reservoir fluids. Thus it is necessary to model the effect of stress-dependent capillary pressure and rock deformation on tight and shale reservoirs.In this paper, we propose and develop a multiphase, multidimensional compositional reservoir model to capture the effect of large capillary pressure on flow and transport in stress-sensitive unconventional reservoirs. The vapor-liquid equilibrium (VLE) calculation is performed with Peng-Robinson Equation of State (EOS), including the impact of capillary pressure on phase behavior and thermodynamic properties. The fluid flow is fully coupled with geomechanical model, which is derived from the thermo-poroelasticity theory; mean normal stress as the stress variable is solved simultaneously with mass conservation equations. The finite-volume based numerical method, integrated finite difference method, is used for space discretization for both mass conservation and stress equations. The formulations are solved fully implicitly to assure the stability.We use Eagle Ford tight oil formations as an example to demonstrate the effect of capillary pressure on VLE. It shows that the bubble-point pressure is suppressed within nano-pores, and fluid properties, such as oil density and viscosity, are influenced by the suppression due to more light components remained in liquid phase. In order to illustrate the effect of stress-dependent capillary pressure on tight oil flow and production, we perform numerical studies on Bakken tight oil reservoirs. The simulation results show that bubble-point suppression is exaggerated by effects of rock deformation, and capillary pressure on VLE also affects the reservoir pressure and effective stress. Therefore the interactive effects between capillary pressure and rock deformation are observed in numerical results. Finally, the production performance in the simulation examples demonstrates the large effect of large capillary pressure on estimated ultimate recovery (EUR) in stress-sensitive tight reservoirs.

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“…Это связано с тем, что нагружение породы приводит как к уменьшению раз-мера самих пор, так и выстраиваемых ими поровых каналов. К примеру, в [Chu et al, 2012] утверждается, что уменьшение поровых каналов от 20 до 60 % при-водит к снижению проницаемости матрицы от трех до десяти раз соответственно, так что формация может перейти из разряда низкопроницаемых в разряд ультра-низкопроницаемых, характеризуемых низкими гради-ентами давления, при которых имеет место существен-ное отклонение от закона Дарси [Baikov et al, 2014]. Уменьшение же в размерах самих пор столь малого размера ставит под вопрос применимость приближения классической равновесной термодинамики, использу-ющей концепцию фиксированного объема при реше-нии задачи о фазовом равновесии, которую, таким образом, следует изменить и решать, например, ите-рационно и самосогласованно с моделируемыми гео-механическими эффектами [Xiong et al, 2014].…”

Section: особенности моделирования гидрогеомеханических процессов воunclassified

Оn a hydro-geomechanical modeling of shale formations

2015

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В настоящей работе реализован первый этап построения самосогласованной сейсмогидрогео-механической модели разработки нетрадиционных сланцевых формаций. Сформулированы основные принципы гидрогеомеханического моделирования. Выявлены основные физико-механические фак-торы, определяющие особенности моделирования нетрадиционных коллекторов. Проведена класси-фикация трещиновато-пористых сред по отношению к представительному элементарному объему. Поставлены задачи моделирования недеформируемых и деформируемых формаций. В последнем случае предложен новый подход к определению эффективных упруго-прочностных свойств.4D Gory, 1, Moscow, 119991, Russia, e-mail: versh1984@mail.ru 3 National Research Nuclear University " MEPhI", Kashira Highway, 31, Moscow, 115409, Russia, e-mail: zingerman@rambler.ru In the paper the first stage of the self-consistent seismic and hydro-geomechanical model of unconventional shale formations production is considered. Main principles of hydro-geomechanical modeling are formulated. Basic physical and mechanical factors that determine details of unconventional reservoirs modeling are presented. Classification of fractured porous media with respect to the representative elementary volume is performed. Problem statements of non-deformable and deformable formations modeling are discussed. Finally, a new approach for an estimation of effective elastic-strength properties is suggested. 4D seismic, reservoir modeling, geomechanics, unconventional reservoir, fractured porous medium, nonlinear multiphase flow, diffusion, stress-strain state, hydraulic fracturing, alternative technologies to develop shale formations ВВЕДЕНИЕЦелью данной работы является выявление и ана-лиз особенностей построения гидрогеомеханических моделей, способных служить адекватной основой тех-нологий разведки и разработки баженовской свиты Фроловской мегавпадины Западно-Сибирского нефте-газоносного бассейна. Построение таких моделей в настоящее время вызывает серьезные затруднения, что связано в первую очередь с недостатком исходных данных о строении и свойствах пород залежи. В ре-зультате сравнительного анализа геологических, лито-логических, геохимических, петрофизических и про-мысловых данных, накопленных при изучении нетра-диционных нефтенасыщенных горных пород, удалось выявить некоторые физико-механические особенно-сти, присущие в той или иной степени всем сланцевым формациям и определяющие особенности их гидро-геомеханического моделирования по сравнению с тра диционными коллекторами. В связи с этим в настоящей работе реализована парадигма а posse ad esse -гидрогеомеханическая мо-дель предоставляет возможность реализации всех вы-явленных физико-механических особенностей в наи-более общем виде, с непременным выделением линеек определяющих параметров различной природы (фи-зических, вычислительных, геометрических), последо-вательное отключение (или подключение) которых поз во ляет упростить (или усложнить) модель для оп-тимально адекватного необходимого уровня [Мельни-кова, 2010].Данная работа является первым шагом на пути по...

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Characterizing and Simulating the Non-Stationariness and Non-Linearity in Unconventional Oil Reservoirs: Bakken Application

Cited by 27 publications

References 19 publications

An Evaluation of Completion Effectiveness in Hydraulically Fractured Wells and the Assessment of Refracturing Scenarios

An Evaluation of Completion Effectiveness in Hydraulically Fractured Wells and the Assessment of Refracturing Scenarios

Effect of Large Capillary Pressure on Fluid Flow and Transport in Stress-sensitive Tight Oil Reservoirs

Оn a hydro-geomechanical modeling of shale formations

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