Reservoir Modelling PDF

Reservoir Modelling 4 th Year Reservoir Modelling 1- Introduction A reservoir model is a digital representation of a subsurface reservoir using geological, geophysical, and engineering data. Simulation r...

Reservoir Modelling 4 th Year Reservoir Modelling 1- Introduction A reservoir model is a digital representation of a subsurface reservoir using geological, geophysical, and engineering data. Simulation refers to the process of running numerical models on these representations to predict fluid flow behavior within the reservoir. Reservoir simulation is performed to infer fluid flow behavior from a mathematical model. The integration of these two processes allows engineers to optimize production strategies, estimate reserves accurately, and make informed decisions regarding field development plans. The goal of reservoir modeling and fluid simulation is increased hydrocarbon production with an increased rate of return. The 3D quantification is performed in a geo-cellular model that consists of reservoir geometry, lithology, porosity, permeability and initial fluid saturation (Fig.1). Integration of information from seismic data, cores, wireline logs and outcrops provide the quantification of the static reservoir model of the reservoir. Fig-1: 3D reservoir model (cellular model) 1 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4 th Year Static reservoir model provides a representation of the structure, thickness, lithology, porosity, initial fluids in the reservoir. A dynamic reservoir model is a representation of the changes in fluid flow in the reservoir model that needs to be validated with reservoir performance data-pressure changes, production and injection rates (Fig.2). Fig-2 Static and Dynamic Model Building a reservoir model includes the construction of a structural and stratigraphic model and determining the spatial distributions of facies and various petrophysical properties in the model. Therefore, when we build models of oil and gas resources in the subsurface we should never ignore the fact that the fluid resources are contained within rock formations. 2 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4 th Year Constructing a good reservoir model requires multi- specialties analyses and integration of geological, geophysical, petrophysical, and reservoir engineering data using scientific and statistical inferences. So building a model of an oil and gas reservoir is complex because of the variety of data types involved as the many different steps required. Reservoir modelling is also a challenge. The challenge is to integrate measurements that are of different Scale, Uncertainty, Resolution, and Environment or the SURE Challenge (Fig.3). In addition to the complex fluids present in the reservoir. Fig-3 SURE Challenge: Having to deal with the wide ranges of Scale, Uncertainty, Resolution and Environment of different data types when integrating them. 2- Evolution of Reservoir Modeling Techniques Over the Years: Reservoir modeling techniques have evolved significantly over the years, with the introduction of new technologies and advancements in data processing and analysis. The following is a general overview of the evolution of reservoir modeling techniques. 3 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4 th Year 1- Early Reservoir Models: The earliest reservoir models were basic and relied on simple geological data to estimate reservoir properties and fluid flow. They were limited in their accuracy and did not take into account complex geological features and heterogeneities. These models were mainly used for exploration purposes and to estimate the size of the reservoir. 2- 2D Reservoir Models: In the 1980s, 2D reservoir models were introduced, which allowed for a more accurate representation of geological features and heterogeneities. These models were able to simulate fluid flow in more complex reservoirs, such as those with faults and fractures. However, they still had limitations in their ability to capture the full complexity of the reservoir. 3- 3D Reservoir Models: In the 1990s, 3D reservoir models became more widely used, allowing for a more accurate representation of the reservoir and its properties. These models were able to simulate fluid flow in complex reservoirs and were used to optimize production strategies. They provided a more detailed understanding of the reservoir's structure and properties, enabling operators to make better decisions about drilling and production. 4- Integrated Reservoir Models: In the 2000s, integrated reservoir models were introduced, which combined geological, geophysical, and engineering data to create a more comprehensive model of the reservoir. These models allowed operators to simulate fluid flow and production in real-time, enabling them to adjust production strategies based on changing conditions. They also allowed for better prediction of future reservoir behavior and provided a more complete understanding of the reservoir. 4 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4 th Year 5- Advanced Reservoir Models: In recent years, advanced reservoir modeling techniques have been developed, including machine learning and artificial intelligence-based models. These models are able to analyze large amounts of data and make predictions about future reservoir behavior. They can identify patterns and trends that may not be immediately apparent to human operators, allowing for more informed decisions about production strategies. These models are particularly useful in unconventional reservoirs, where traditional modeling techniques may not be sufficient. The evolution of reservoir modeling techniques 5 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4 th Year 3- The Uses of Reservoir Modelling: 1- Evaluation of rock volumes and the original hydrocarbons in place. 2- Representation of geological and petrophysical descriptions of the reservoir for input to reservoir simulation. 3- Increase profitability through better reservoir management, including development plans for new fields and depletion strategies for mature fields. 4- Prediction of the fluid volume (oil, gas, and water), decline analysis, secondary or tertiary recovery option injection strategies, and well and completion designs. 5- Observation of fluid movement contacts and pressures. 6- Analysis of fault seal and transmissibility in addition to calculating the displacement of the fault vertically and laterally. 7- Assessment of wells number and types that required to produce the reservoir economically (e.g. vertical, slant, horizontal, multilateral, etc.) and locations. 4- Reservoir Modeling According to the Stages the Reservoir Life Cycle: 4-1 Exploration Stage: The exploration stage requires delineation of the reservoir limits and assessment of its economic feasibility.  Enhance depositional environment and conceptual model understanding.  Refine stratigraphic model.  Assess fault partition.  Identify new prospects.  Use the model as a data/information store. 6 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering  Reservoir Modelling 4 th Year 4-2 Development Stage: The development stage requires a somewhat more accurate assessment of the reservoir extent and better appraisal of the economic viability of the reservoir.  Build more-detailed structural and stratigraphic model.  Plan and design wells, including well path.  Computing the production profiles (oil, gas, and water).  Estimating the oil and gas technical reserves.  Assess intermediate-scale reservoir heterogeneities and connectivity. 4-3 Production Stage:  Assess small-scale heterogeneities, including flow units modeling.  Use for reservoir management.  Matching of the past production history (fluid rates, GOR, pressures, etc).  Optimize production in the field.  Perform enhanced oil recovery (EOR) 7 Dr. Maha M. Al-Dabagh Petroleum and Mining Engineering