Well test analysis of low permeability medium-rich to rich gas condensate homogeneous and layered reservoirs

This study investigates near-wellbore effects during well testing in low permeability, single- and multi-layered, medium-rich to rich, gas condensate reservoirs. Theoretical results obtained from compositional simulations are validated with actual well test data. We first study well test behaviours...

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Main Author: Kgogo, Thabo C.
Other Authors: Gringarten, Alain
Published: Imperial College London 2011
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622
Online Access:http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533563
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spelling ndltd-bl.uk-oai-ethos.bl.uk-5335632017-08-30T03:18:55ZWell test analysis of low permeability medium-rich to rich gas condensate homogeneous and layered reservoirsKgogo, Thabo C.Gringarten, Alain2011This study investigates near-wellbore effects during well testing in low permeability, single- and multi-layered, medium-rich to rich, gas condensate reservoirs. Theoretical results obtained from compositional simulations are validated with actual well test data. We first study well test behaviours for a range of gas condensate fluids with increasing condensate to gas ratios (CGR), from lean to medium-rich to rich. We verify that, during a drawdown below the dew point pressure, a condensate bank forms around the wellbore for all fluids studied. We show that, in the case of a medium-rich gas, as pressure increases above the dew point pressure in a subsequent build up, part of the condensate bank closer to the well dissolves into the gas, with the fluid returning to being a single-phase gas. This is different from what happens with rich gas, where the bank disappears completely; and with lean gas, where condensate saturation at the end of a drawdown and in the subsequent build up are very similar. Lean and medium-rich gas condensate fluids yield three-region radial composite derivative behaviours corresponding to dry gas away from the well, condensate bank, and capillary number effects in the immediate vicinity of the well. Only two-region radial composite behaviours are created in the case of rich gas fluids, as rates required to see capillary number effects are not reached in practice. We then study layered systems and show that composite behaviour due to condensate bank and a multi-layer behaviour are superimposed, with the condensate bank appearing on top of multi-layer effects. In addition, the production rate ratio of the most permeable layer rate to the total rate tends to one as the least permeable layer is choked by its condensate bank. We also investigated gravity effects and conclude that gravity has little impact on pressure response once the condensate bank develops near the wellbore and in particular does not create a partial penetration behaviour. Lastly, we show that drilling horizontal wells and hydraulically-fracturing vertical wells improve well productivity when pressure is below the dew point pressure. Condensate drop-out effects are minimized when wells are fractured prior to being produced.622Imperial College Londonhttp://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533563http://hdl.handle.net/10044/1/6856Electronic Thesis or Dissertation
collection NDLTD
sources NDLTD
topic 622
spellingShingle 622
Kgogo, Thabo C.
Well test analysis of low permeability medium-rich to rich gas condensate homogeneous and layered reservoirs
description This study investigates near-wellbore effects during well testing in low permeability, single- and multi-layered, medium-rich to rich, gas condensate reservoirs. Theoretical results obtained from compositional simulations are validated with actual well test data. We first study well test behaviours for a range of gas condensate fluids with increasing condensate to gas ratios (CGR), from lean to medium-rich to rich. We verify that, during a drawdown below the dew point pressure, a condensate bank forms around the wellbore for all fluids studied. We show that, in the case of a medium-rich gas, as pressure increases above the dew point pressure in a subsequent build up, part of the condensate bank closer to the well dissolves into the gas, with the fluid returning to being a single-phase gas. This is different from what happens with rich gas, where the bank disappears completely; and with lean gas, where condensate saturation at the end of a drawdown and in the subsequent build up are very similar. Lean and medium-rich gas condensate fluids yield three-region radial composite derivative behaviours corresponding to dry gas away from the well, condensate bank, and capillary number effects in the immediate vicinity of the well. Only two-region radial composite behaviours are created in the case of rich gas fluids, as rates required to see capillary number effects are not reached in practice. We then study layered systems and show that composite behaviour due to condensate bank and a multi-layer behaviour are superimposed, with the condensate bank appearing on top of multi-layer effects. In addition, the production rate ratio of the most permeable layer rate to the total rate tends to one as the least permeable layer is choked by its condensate bank. We also investigated gravity effects and conclude that gravity has little impact on pressure response once the condensate bank develops near the wellbore and in particular does not create a partial penetration behaviour. Lastly, we show that drilling horizontal wells and hydraulically-fracturing vertical wells improve well productivity when pressure is below the dew point pressure. Condensate drop-out effects are minimized when wells are fractured prior to being produced.
author2 Gringarten, Alain
author_facet Gringarten, Alain
Kgogo, Thabo C.
author Kgogo, Thabo C.
author_sort Kgogo, Thabo C.
title Well test analysis of low permeability medium-rich to rich gas condensate homogeneous and layered reservoirs
title_short Well test analysis of low permeability medium-rich to rich gas condensate homogeneous and layered reservoirs
title_full Well test analysis of low permeability medium-rich to rich gas condensate homogeneous and layered reservoirs
title_fullStr Well test analysis of low permeability medium-rich to rich gas condensate homogeneous and layered reservoirs
title_full_unstemmed Well test analysis of low permeability medium-rich to rich gas condensate homogeneous and layered reservoirs
title_sort well test analysis of low permeability medium-rich to rich gas condensate homogeneous and layered reservoirs
publisher Imperial College London
publishDate 2011
url http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533563
work_keys_str_mv AT kgogothaboc welltestanalysisoflowpermeabilitymediumrichtorichgascondensatehomogeneousandlayeredreservoirs
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