Viscous Oil Dynamics Evaluation for Better Fluid Sampling

Canas, Jesus Alberto; Low, Steven; Adur, Nicolas; Teixeira, Vinicius Ligiero

doi:10.2118/97767-ms

Cited by 6 publications

(1 citation statement)

References 9 publications

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“…Often, high drawdown pressures required to mobilize heavy oils may enhance the potential for two-phase (oil and gas) flow in the near-wellbore regions -particularly when the oil is at or near saturated conditions; this is another serious challenge to surface or down-hole sampling. The low mobility and the resulting slow flow rates may tend to increase near-wellbore cleanup time 5 , thus increasing operational risks. However, the high viscosity of the oil may slow down invasion of external fluids introduced during drilling, completion, and acidization jobs, and thus requires removing relatively smaller volumes of nearwellbore fluids.…”

Section: Sample Challengesmentioning

confidence: 99%

Challenges of Heavy Oil Fluid Sampling and Characterization

Nagarajan

Dong

Mullins

et al. 2012

SPE Annual Technical Conference and Exhibition

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A significant portion of the world's hydrocarbon reserves is found in heavy oil reservoirs. Heavy oils are often found in shallow and highly unconsolidated reservoirs, or sometimes in deep, tight formations. Often the high asphaltic content of these oils results in relatively higher oil density and viscosity; hence, their lower reservoir mobility poses significant challenges to both sampling and PVT data measurements. Furthermore, modeling these fluids for reservoir evaluation requires special techniques to capture their unique phase behavior.The challenges of representative down-hole or surface fluid sample acquisition demand customized sampling methods to deal with:• low oil mobility • sand production from unconsolidated formations • high asphaltene content and resulting high gradients • formation of water-in-oil emulsion during co-production of water or gas lift operations or addition of diluents In addition, the prerequisite for laboratory measurement is special sample preparation to remove emulsified water. These high viscosity oils exhibit slower gas liberation below the bubble point and hence delayed gas-phase formation, thus making "true" oil property measurements a challenge. Difficulties associated with fluid modeling include characterizing apparent bubble point behavior, large viscosity changes with pressure and temperature, and asphaltene dropout.In this paper, we present a comprehensive methodology for heavy oil sampling and characterization in unconsolidated sands as well as in low permeability reservoirs. We present field examples to highlight the challenges and illustrate the methodology for fluid sampling, down-hole fluid analysis, laboratory PVT data acquisition, and modeling. Sampling methods for heavy and asphaltic oils were custom designed with special tools and sensors to obtain representative samples and precise down-hole fluid analysis data. New laboratory techniques were developed to prepare the samples for analysis and to distinguish between the "true" and "apparent" bubble point behavior exhibited by the heavy oil due to its non-equilibrium behavior. Fluid models based on a special equations of state (EoS) were employed for accurate description of heavy oil fluid phase behavior. In particular, we successfully applied the industry's first EoS for asphaltene gradients in heavy oil reservoirs that match down-hole fluid data.

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Section: Sample Challengesmentioning

confidence: 99%

Challenges of Heavy Oil Fluid Sampling and Characterization

Nagarajan

Dong

Mullins

et al. 2012

SPE Annual Technical Conference and Exhibition

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Effects of Harsh Weather on Delayed Wireline Formation Fluid Sampling

Wang¹,

Lei

Hardikar

et al. 2018

Springer Series in Geomechanics and Geoengineering

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Mini-DST Applications for Shell Deepwater Malaysia

Daungkaew

Harfoushian

Cheong

et al. 2007

Asia Pacific Oil and Gas Conference and Exhibition

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fax 01-972-952-9435. AbstractExploration and appraisal campaigns for deepwater environments are a continuous challenge in today's operations. Data acquisition in such environments requires reservoir information of the highest quality before expensive development plans can be put in place. New technology, real time monitoring and integrated reservoir data are essential to understand such reservoirs. Another challenge presented by thinly bedded reservoirs is the presence of vertical heterogeneity and varying layer flow properties.Wireline formation testers have been commonly used to acquire formation pressures pressure and reservoir fluid samples for a number of decades. Many hardware technologies and interpretation methods have been developed to acquire better quality reservoir information. Dual packer wireline formation testers offer an alternative an additional way to selectively straddle a section of a reservoir and provide the capability to conduct controlled local production and interference as well as to enable the capture of reservoir fluids. Formation permeability, anisotropy, skin factor, vertical connectivity and zonal productivity index are additional reservoir information that can be obtained from a mini-Drill Stem Test (mini-DST) and a Vertical Interference Test (VIT).Pressure transient analysis of a mini-DST data however in such reservoirs is challenging due to the associated uncertainties such as layer flow compartments and flowing fluid viscosity. This paper discusses the use of integrated reservoir information obtained from Downhole Fluid Analyzers (DFA), borehole images, and numerical simulation models to minimize these uncertainties. A systematic pressure transient analysis method for mini-DSTs is also introduced. * Currently with Santos Ltd.Reservoir parameters obtained from mini-DSTs in thinly laminated deepwater reservoirs are then compared with other available static and dynamic reservoir information such as petrophysical data, core analysis, well tests, production logs, and single probe wireline formation tests in order to obtain accurate interpretation results of highest consistency.Field examples will be discussed which show that smaller scale pressure transient tests often have an advantage over full scale well tests testing in terms of providing detailed layer flow behavior, vertical connectivity and flow potential in thinly bedded environments. It will also be noted that the radius of investigation of a mini-DST is limited, typically within tens of feet. This paper demonstrates using field examples that reservoir boundaries can be detected when sufficient radius of investigation is achieved. In addition, the understanding of limitations and advantages will allow the proper selection of test types in order to meet specific objectives and maximize the full potential use of acquired data for field development plans in thinly laminated deepwater environments.

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Viscous Oil Dynamics Evaluation for Better Fluid Sampling

Cited by 6 publications

References 9 publications

Challenges of Heavy Oil Fluid Sampling and Characterization

Challenges of Heavy Oil Fluid Sampling and Characterization

Effects of Harsh Weather on Delayed Wireline Formation Fluid Sampling

Mini-DST Applications for Shell Deepwater Malaysia

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