Gas Condensate Systems

Well Test Analysis

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Weatherford has a deserved reputation in the industry as a world leader in well test analysis, especially of complex and difficult problems. Many years experience of original and detailed analyses of tests from all areas of the oil producing world back our consultants' work in this area. Tests on gas condensate systems have proved difficult to analyze for many years.

The methodology for prediction of gas condensate deliverability using steady state, two-phase pseudo-pressures and PVT is based on Equations of State (EoS) recently developed by Weatherford. These analyses allow gas condensate well tests to be interpreted taking into account liquid dropout over a wide range of pressures and temperatures, therefore better predicting fluid behavior and production modeling. Application of these techniques allows Weatherford's staff engineers, including some of the foremost experts in well test analysis in the industry, to use the in-house developed world leading PanSystem^® software well test analysis package to provide the client with an unparalleled depth of insight into well performance.

PVT Modeling

Weatherford engineers have been involved in the development of stand alone PVT modeling packages as well as modeling the behavior of fluids within packages, such as the well test analysis software PanSystem software and the Weatherford production modeling package, WellFlo^® software. The theoretical understanding of the behavior of gas condensate systems is bolstered by in house practical experience of running a large PVT laboratory for a major service company. This knowledge of the limitations and accuracy of the available data allows clients to receive sound advice from Weatherford engineers when involved in the study of gas condensate (and any other fluid) systems.

Reservoir Simulation

Weatherford engineers are experienced in reservoir simulation studies of all types of reservoir fluids, including gas condensate fields. Engineers have performed compositional simulation studies, acquiring expertise which can be utilized in the modeling of gas condensate reservoirs for clients. The unique blend of talents present in the Weatherford organization ensures that representative models are constructed with all data sources critically examined and the data quality understood.

Core Experiments

Weatherford has access to one of the UK's major laboratories for the measurement of relative permeability in gas condensate systems. This unique facility has been used for the study of critical condensate saturation and the dependence on water presence as well as other investigations of retrograde condensation in porous media.

Typical Gas Condensate Activities

• Well test design for a high temperature/pressure gas condensate reservoir.
• An EoS model was tuned to a gas condensate well and successfully used to accurately predict top hole conditions from measured bottom hole data.
• Extensive software and engineering support through maintenance contracts with PanSystem software.
• Industry training in well test analysis encompassing both basic and advanced interpretation techniques, well test analysis in horizontal wells, and PanSystem user courses. Over 1000 engineers have passed through schools run by Weatherford in Edinburgh and in-house throughout the world since 1985.

Recent Gas Condensate Projects

• Zielona Gora - Polish Oil & Gas
  Well test design and analysis for 5 gas fields. Reservoir engineering assessment of 5 gas fields delivery for a GTCC project.
• OMV Aktiengesellschaft, Austria
  Gas condensate fluid analysis, well completion, and gathering system modeling and analysis for improved system deliverability. Options and alternatives were considered. Recommendations made and implemented by client saving c. $1 million on completion equipment.
• YPF Gas Well Modeling
  Analysis of well performance from well head to separator and integration with transient reservoir responses. Gave client better tool and method to determine future field deliverability to meet gas contracts.
• Clyde Petroleum - Netherlands
  Various studies involving prospect evaluation and development/completion option comparisons. Production profiles were simulated and passed to economics department. Satellite development viability was assessed. Development plans for several fields produced.
• Conoco's "V" Fields - Southern North Sea
  Simulation studies focusing on long term deliverability and GIIP. Used for operational needs and contract evaluation, as well as partner/operator strategy meetings.
• Kazakh Government, Karashaganak, Kazakhstan
  Evaluation of development plans produced by BP/Statoil and Agip/BG consortia for the future development of this field, one of the largest in the world. Weatherford made recommendations on the best technical and economic plan put forward. Weatherford's recommended consortium was awarded the tender.
• Confidential Client
  Disputed gas purchase agreement adjudication; evaluation of well, field, and infrastructure performance.
• Confidential Client
  Re-evaluation of gas reserves for SNS reservoir based on reinterpretation of SCAL data. Original data interpretation was found to be invalid due to drilling mud damage effects not being considered.
• Confidential Client
  Integrated core and log evaluation of residual gas saturation to assess loss of reserves due to aquifer influx.
• Confidential Client
  Development of saturation height model for gas/condensate chalk reservoir involving development of model based on cop cap pressure data and its validation via log data.
• Confidential Client
  Gas reserves evaluation from integrated core and log study involving the development of saturation height models in a sandstone reservoir. Core and logs showed original Swi interpretation to be invalid and led to 10% increase in GIIP.
• Confidential Client
  Study of effects of well sand production on deliverability and system hardware life in G/C reservoir.
• Vulcan Field
  Analysis of gas/water contacts, pressure, and compartmentalization analyses. Used in equity and development negotiations.