Reservoir Simulation

Weatherford has a wide range of experience in reservoir simulation studies, related to the development of the company's software development, consulting, and training services.

Weatherford engineers have many years of practical experience in reservoir simulation modeling of fields around the world. In-house expertise in crucial areas of data interpretation such as well test analysis, production log interpretation, PVT studies, core analysis, petrophysics, and geomechanics allows Weatherford engineers a deeper understanding of the quality and relevance of the data on which reservoir simulation studies are based. The acknowledged expertise of Weatherford's staff in production optimization adds a further dimension to a simulation study, providing clients with practical solutions.

Weatherford software that can be employed in simulation studies include:

• PanSystem™ - well test design and analysis
• ReO™ - field and network optimization
• WellFlo™ - production simulation and optimization
• MatBal™ - analytical reservoir simulation

In addition, Weatherford has licenses for the following industry-standard software:

• Eclipse - reservoir simulator
• Grid - mapping and griding package

Weatherford has substantial experience in the construction and use of reservoir simulation models for field development planning, and Weatherford engineers have considerable experience in compositional simulation studies. In addition, Weatherford, in alliance with another service company, were the first UK consultancy to win a reservoir management contract with a major oil company and currently carry out all reservoir management tasks, including reservoir simulation, for eight of the client's geologically complex fields. Integrated studies form a major component of the reservoir management process of the client's assets.

Areas in which Weatherford's staff have skills vital to the successful completion of a simulation study are:

Well Test Analysis

Weatherford's staff include industry experts in the field of well test analysis, with many years of interpretation experience tempered by an understanding of the data quality acquired from working for the data acquisition companies.

Core Analysis

Weatherford has particular expertise in the area of core analysis, including core analysis laboratory auditing, and the critical interpretation of laboratory relative permeability data. The integration of validated laboratory data into the geological model of the reservoir allows Weatherford engineers to establish suitable reservoir descriptions for simulation.

Gas Condensates

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 engineers. 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.

Compartmentalized Reservoirs

Reservoirs which are composed of a number of blocks separated by partially communicating barriers are a very important feature of reservoir descriptions, especially in faulted traps. Weatherford pioneered the identification of compartmentalized reservoirs using well tests and material balance calculations, and have a proven track record in this area accumulated while successfully completing a number of volumetric studies.

Compositional Simulation

Building on the experience of Weatherford engineers with reservoir simulation and in-house expertise in the area of PVT studies and simulation, Weatherford provide a compositional simulation service to the industry. Recent in-house development regarding gas condensate deliverability based on Equations of State allow better understanding of the near-well processes important in the prediction of well deliverability from such fields. Experience gained through the development of the PVT models incorporated into Weatherford's PanSystem and WellFlo software packages is brought to bear on the reservoir processes being modeled for the client. Excellent understanding of the measurements made on the reservoir samples gained through practical laboratory experience enable representative simulation models to be constructed.

Complex Geological Environments

The interaction between core analysis and well test analysis allows Weatherford to effectively describe complex reservoirs. Vertical (fault planes) and horizontal (shales) barriers often combine to produce a geologically intricate body which cannot be satisfactorily analyzed using conventional well test techniques. The integration of validated laboratory core data permits Weatherford engineers to confirm possible interpretations and establish suitable reservoir models and optimum production profiles.

Extended Well Tests

The evaluation of variable rate production well test data is a much neglected area of analysis. Weatherford has developed new methods which allow real extended drawdown tests to be adequately interpreted.

Typical Reservoir Simulation Activities

• Several simulation studies, including history matching and prediction runs, over a wide range of field sizes and complexities, from giant oil fields to small fractured reservoirs.
• Model maintenance - upgrading of existing reservoir simulation models to incorporate new well data.
• Two major field studies have been carried out to identify interblock communication as a precursor to reservoir simulation.
• Studies carried out on South American fluvial reservoirs resulted in a clearer understanding of the connectivity of channel sand bodies.
• An EoS model was tuned to a gas condensate well and successfully used to accurately predict top hole conditions from measured bottom hole data.
• Petrophysical studies to reconcile initial reservoir and production data from material balance.
• Studies investigating the effects of wettability and test technique on end-point and relative permeability data used for simulator input.