Reservoir Modelling PDF (4th Year)

Reservoir Modelling 4th Year 8. Data in Reservoir Modelling: 8.1 Input Data: Oil and gas reservoir modelling involves two broad classes of data:  Static (for example, core, well logs, and seismic interpretation)  Dynamic (pr...

Reservoir Modelling 4th Year 8. Data in Reservoir Modelling: 8.1 Input Data: Oil and gas reservoir modelling involves two broad classes of data:  Static (for example, core, well logs, and seismic interpretation)  Dynamic (pressure and fluid production observed at wells). Integration of dynamic data together with static data enhances the quality of the reservoir models generated and provides the reservoir engineers with a better basis for reservoir simulation and management. The importance of data integration are: 1- Improved accuracy in predictions 2- Enhanced risk assessment 3- Better decision-making in resource management Notes: Data required to define the geometry of a reservoir model include a polygon that delineates the lateral extension of the model and the top and base surfaces of the reservoir, which define the vertical positions and thickness of the model. In addition, intermediate surfaces may be required to define the internal stratigraphic architecture of the model. The bounding and intermediate surfaces can be from seismic interpretations and/or mapped from the formation markers at wells, typically derived from stratigraphic correlations. 12 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4th Year When faults are present and influence the fluid flow, they are inputs for defining a faulted model framework. Faults are usually obtained from the interpretation of seismic data. For petrophysical properties model data, are generally obtained from petrophysical analysis of well logs and cores. Dynamic data that change with time can also be used for reservoir modeling. These include production data measured at wells, such as pressures and liquid and gas production rates. 8.2 Data Collection and Management: Data management is probably the most important part of any modelling project. The quality of input data is the essential element of a modelling project; if there are any inconsistencies in the input data, they will show up in the end results and at every intermediate modelling steps. The primary data types used for reservoir modelling are as follows: Well Data: direct sampling from cores, indirect measurements from well logs (with high-resolution indication of facies and fluids), and modern image logs (information on sedimentary structures and faults). Seismic Data: provide valuable information on large-scale reservoir geometry. Dynamic Data: from well tests, historical production 13 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4th Year 8.2.1 Well Data: The well data are generally represents a very small investigation volume for the reservoir that is to be modelled, but it is also the ‘hardest’ data available to the project team. A- Core Data: Available from a limited number of wells. Core may be sampled by relatively small core plugs, or entire sections of core may be measured for whole core data. Core derived data give us information detailed about Sedimentology, petrography, environment of deposition, Porosity, permeability, grain density, fluids shows and Petrophysical core-to-log calibration Fig-7: Core Sample B- Wellbore Path: Wellbore path data are computed from suitable corrected direction survey data and are stored in the database. Wellbore path is the trajectory of a directionally drilled well in three dimensions. Data is the emphasis on the following (Fig-8): 1- Calculate directional coordinates. 2- Calculate the true vertical depth (TVD) and Total depth (TD). 3- Identify Kick-off point (KOP) (is the depth at which the well is first deviated from the vertical) and End of Build-up point (EOB) (Landing point). 14 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4th Year Note: (Directional drilling is the methodology for directing a wellbore along a predetermined trajectory to a target. Vertical wells are usually defined as wells with an inclination within 5°. Wells with a section having an inclination greater than 85° for a significant distance are called Horizontal wells). Fig-8: Well Path C- Wireline Logs and MWD/LWD Logs: Provide a continuous high-resolution record of accurate information on stratigraphic surfaces, measurements of petrophysical properties such as facies types, φ, and, perhaps, k measurements The graphical logs containing all the primary measurements in a wellbore. As a minimum, it will contain well header data, primary well logs. The Composite log should integrate the geological columnar section with selected petrophysical logs 15 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4th Year i.e. a lithology indicating log, a porosity log and a resistivity log. Geological zones lithology core intervals. Logs should be pre-processed for modelling purposes and a set of curves assembled either in the project data store or in a separate petrophysical database (Fig- 9). These data will form the ‘basic input data’ for reservoir modelling. Fig-9: Well Logs D- Computer-Processed Interpretation (CPI) Logs: 16 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4th Year Well logs data processing and interpretation are complex processes and they involve mathematical, statistical, and numerical techniques. Well-log data evaluation and analysis can be carried out manually and/or by employing a computer. The primary source for reservoir property data is the petrophysical interpretation of porosity and water saturation (Fig-10). Fig-10: CPI Logs 17 Dr. Maha M. 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