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Third EAGE/SPE Workshop on Tar Mats
- Conference date: 20 May 2012 - 23 May 2012
- Location: Muscat, Oman
- ISBN: 978-94-6282-043-2
- Published: 20 May 2012
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Novel Technique for Tar mat identification and mapping
Authors N. Al-Jabari and R. ShokeirTar mat identification and mapping has been a challenge for the oil industry for years. Limited number of techniques and tools are available to identify tar presence in an oil field. These can be divided to three main categories: • Laboratory based on drilling cuts, core or side cores in suspected tar zone. • Log based, using mainly NMR and Formation Tester • Surface and borehole Seismic. Each of these three main techniques has its own advantages and disadvantages. The first two techniques suffer from limited availability across the field to allow mapping of tar. Furthermore, NMR logs also have difficulty distinguishing tar from heavy oil as both show similar NMR characteristics. Surface and borehole seismic on the other hand are excellent tools for mapping but lacks the ability to accurately identify tar mats. The Novel technique proposed in this paper combines cheomstratigraphy, NMR, formations tester, geochemical logging and borehole seismic to identify and map tar mats. The main concept behind the new technique is to link tar identification to three independent measurements chemical, NMR and acoustic to overcome limitation associated with each technique. Then use borehole seismic to map tar mats based on the tar attributes defined by laboratory and wireline acoustic measurement. The technique is implemented in three main stages first identifying tar and separating it from any heavy oil that might be associated with it. Second stage, is finding the tar cheomstratigraphic finger print that can be linked to a geochemical log. This stage will allows identification of tar map thickness in well by well bases. The third and final stage, is linking tar acoustic properties measured in both laboratory and wireline to borehole seismic attributes then surface seismic to map tar across the field.
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Estimating Reservoir Connectivity and Tar-Mat Occurrence Using Gravity-Induced Asphaltene Compositional Grading
Authors F.M. Vargas, S. R. Panuganti and W.G. ChapmanThis work proposes a combined solution to the individually ill-posed problems of reservoir compartmentalization and tar-mat occurrence. Reservoir compartmentalization is one of the major issues in both onshore and offshore reservoirs, making it essential to assess prior to production the extent of compartmentalization within a reservoir.
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New Insights into Tar Mat Formation in Oil Reservoirs
Authors J. ZuoNew insights to reservoir tar mats are made by integrating advances in asphaltene science and downhole fluid analysis (DFA). The Yen-Mullins model of asphaltenes has enabled development of the industry’s first predictive equation of state (EOS) for asphaltene concentration gradients, which has been referred to as the Flory-Huggins-Zuo (FHZ) EOS.
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Vertical and Lateral Delineation of Tar and Heavy Oil Reservoirs; Practical Considerations for a Challenging Task – Towards Optimum and Improved Recov
Authors K. IdrisTar and heavy oils have imposed several challenges to the oil industry professionals in many aspects. Starting from definition, characterization, identification, delineation and through to development and production. Proper vertical and lateral delineation of tar and heavy oil reservoirs in a quantitative and a qualitative manner is imperative for proper reserves assessment, well placement and optimal field development plans.
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Heavy Oil Exploitation: Pushing the envelope of Enhanced Oil Recovery
Authors G. VassilellisSteam or CO2 injection methods account for most of the oil recovered worldwide with Enhanced Oil Recovery (EOR) methods. Currently heavy oil production is less than 7% of the world's oil production; this percentage is not expected to increase dramatically without significant changes in reservoir management. Steam and CO2 have been used successfully since early 1960s -- steam in viscous heavy oils and CO2 mostly in pressurized light oil fields but also in some heavy oil fields. What limits a wider application is depth and high pressure for steam and CO2 availability for the relatively large inventory of light oil fields that exist worldwide. Although there is some overlap in fields that could benefit from either application, there are not many recorded attempts to implement both methods simultaneously. Air injection, although it was tried first as an EOR method, has not been widely implemented as in-situ combustion is difficult to control in shallow reservoirs and especially without water coinjection.
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Detecting and Avoiding Tar While Drilling, Technique Developed by Saudi Aramco
Authors S. AbdelbagiThe presentation will discuss Saudi Aramco’s proprietary pyrolytic technologies to quantitatively assess the volumes of oil, tar and pyrobitumen in oil reservoirs in real time to avoid drilling within unproductive/non-injective zones of tar mats and heavy oil. The technology uses temperature programmed pyrolysis with a flame ionization detection to measure the amount of hydrocarbons in powdered cuttings and core samples.
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Production of thick crude through concentric coiled tubing
Authors M. AbabouThe drilling of exploration wells in thick Oil reservoirs has proven to be a major challenge for Oman Operator when it came to establish the presence of Oil in these wells. Traditional method consisted of using Nitrogen lifting to recover the oil, but this has proven to be very uneconomical option due to the extremely low pressure reservoirs. The option to recover the fluids using Beam pumps out of these low pressure/ high viscosity wells is possible, but as these wells are under exploration program, the client needs to assess the presence of Oil first before committing to bring in Beam pump/ PCP.
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Assessment of the Variation of the Fluid Properties and the Tar Formation by Investigating the Asphalthene Fraction
Authors H. ZhouAsphaltene rich hydrocarbon fluids often present strong variation of their composition and characteristics within a same reservoir. Sometimes, tar mat can be present. Understanding the origin and the logic of the variation of fluid properties and of the tar formation is a challenging issue because fluid properties variation as well as the tar mat formation can be due to many factors: gravity segregation, fluid loading history, biodegradation, water washing, gas striping, liquid-liquid separation, asphaltene precipitation etc. The analysis of the driving forces leading compositional and properties variation is challenging. Many potential explanations are possible and often none can be easily proven or refuted.
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Integrating Subsurface Core and Log Data to Model Tar Mat in a Carbonate Upper Jurassic Reservoir in Offshore Abu Dhabi, UAE
Authors K. Ibrahim, M.I. Sayed and T.M. MataridThis paper presents an interpretation, evaluation and modeling a Tar Mat within an Upper Jurassic Reservoir, Offshore Abu Dhabi. The Tar Mat was observed in 6 cored wells out of 9 drilled wells in a Green Field.
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Innovative integration of seismic and well data to characterize Tar Mat in Carbonate Reservoirs
Authors T. Matarid, K. Al Hosani, C. Lehmann and A. SmithThis paper presents an integrated approach using the 3D seismic and well data to enhance our understanding of the lateral and/or vertical distribution of the Tar Mat. The study was carried out utilizing a recent state-of-the-art, high resolution and high quality 3D ocean-bottom seismic dataset (OBC) acquired offshore Abu Dhabi and several wells with an excellent suite of logs, thousands of feet’s of core data and geochemical studies.
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How to Identify Tar in heavy Oil Reservoirs
Authors N. Al-JabariTo calculate reserves in heavy oil reservoirs, the amount of possible tar needs to be accurately estimated. This presentation discusses how Halliburton’s tar mapping technique was developed based on combining experience from different product lines over the years. The mapping technique combines successful NMR based tar identification techniques, heavy oil sampling, stimulation and chemostratigraphy.
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Field Case: The Origin of the Fluid Properties Variation and the Tar Mat
Authors H. ZhouIn this work, a field case will be presented to induce discussion on the relevance of the data to be acquired and to be analyzed according to the objectives of the investigation. In the field case presented, a strong segregation was observed in a connected reservoir. The in situ viscosity of the oil varies from less than 1 cPo for samples taken close to the gas cap, to more than 100 cPo for oil sampled 400 meters deeper. “Tar mat deposits” were also observed in the bottom part, but also in some specific area of the reservoir.
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Impact of Tar Mat on Steam Development Options
Authors P.M. BoerrigterThis presentation is about the impact of a tar mat on steam development options for heavy oil fields with a strong bottom aquifer. In principle the standard steam development options, Cyclic Steam Stimulation (CSS), Steam Drive or Steam assisted Gravity Drainage (SAGD), can be used to develop heavy oil fields with strong aquifers. Efficient operation of such steam developments require that aquifer water influx is controlled and fields are operated at low pressure. A low reservoir pressure maximizes usage of the latent heat content of steam, which is the main source of heat transferred to the reservoir. Both effects, water control and low pressure, can be achieved by implementing an aquifer pump-off scheme. A potential additional benefit of an aquifer pump-of scheme is to use the produced water as source water for steam.
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