Reservoir simulation grid colored by mobile oil for a future time step is used as a guide to plan a well. Data used with permission of the owner.
Geologic models have had many uses in the oil industry over the years. Creating surfaces from well picks, interpreted seismic horizons and faults is often done by geologists to understand the overall stratigraphy and structure of an oil field. Distributing rock properties throughout that structural framework adds another layer of understanding of possible depositional settings of the various rock types present and better define the best reservoir rock. These models can be used as the framework for many types of studies like regional stress/strain analysis, basin temperature and pressure analysis, and velocity modeling. Reservoir engineers also use geological models as the framework to simulate how fluids will migrate and flow through the reservoir. This reservoir simulation is an important aspect to an asset team as it can show how oil and gas have moved in a fields’ history as well as predict where the oil will be in the future. Planning future wells based on the geologic model information and reservoir simulation is an ideal way to lessen the risks of low producing or dry wells.
Benefits of a 3D Geological Model
All too often reservoir rock is thought of as being laterally-extensive and homogeneous. However, 3D geological models consistently show that is not the case. Changes in rock properties like porosity and permeability are extremely common over large and small areas, even in what are considered to be laterally-extensive and homogeneous rocks. These changes can come from common depositional changes but also many other reasons like differences in thickness, compaction, grain size, or even presence of former organic material. Given that even slight changes in porosity, as small as 1%, will affect a wells’ productivity, the economic viability of any well depends on the best understanding of the rock properties the well is landed (or planned) in.
Geologic models can also incorporate faulting if present in an area. Faults present a challenge in that they can range from small scale features similar to fractures with very little offset, to large scale faults that juxtapose different rock types against each other. Generally speaking, small scale faults and fractures create pathways for fluids to migrate along while faults with large offsets create impermeable barriers due to significant fault gouge. That means understanding faulting is very important to predicting where oil and gas are in a reservoir.
Benefits of a Reservoir Simulation
Reservoir simulation is a process where an asset team can make a best guess at where the oil, gas and water are in a reservoir. This usually entails taking an accurate 3D model and all its properties and usually upscaling it into a grid. Then pressures, fluid parameters, transmissibilities along faults and other inputs are carefully chosen to match the historical production and well tests known for the area. Computer simulation is then performed to come up with the best guess as to where the fluids migrate or get trapped. That means reservoir simulation provides an asset team a way to visually see where the highest concentrations of oil and gas are in a field. Furthermore, it shows what parts of the reservoir are depleted of fluids and pressure, which are areas to avoid in drilling future wells.
Once an asset team has built their 3D geologic model and done a reservoir simulation, the next logical step is to use that data to plan future wells. A good visualization tool will be the key to unlock the power of well planning with geologic models and simulation grids. Integrating the simulation grid with all other relevant data like precise offset well locations and trajectories, fracture locations or discrete fracture network models, and even microseismic events from previous wells in the area is one way to plan wells into desirable areas. Further visualization techniques, like filtering the simulation model to only show areas of high oil or gas saturation, gives even more confidence to placing well plans into the most productive areas of the reservoir left.
With the temporal component of reservoir simulations, a 4D viewer with well planning capabilities, like CoViz 4D by Dynamic Graphics, can be used to plan most if not all the wells in a drilling campaign. Creating well plans at each individual time step of a reservoir simulation allows for the identification of best fluid locations well into the future. These future plans can also be exported back to the simulator to get and even better picture of fluid flow as if the planned wells came online.
Integrating 3D geologic models with 4D reservoir simulation in order to plan wells that exploit the highest oil or gas saturated layers of a reservoir can be done in a 4D visualization package with well planning capabilities. One such package is CoViz 4D which has numerous temporal visualization features along with an Integrated Well Designer to plan wells quickly and accurately within an environment that allows for integration of numerous other data types. CoViz 4D in integrated software solution that helps operators save costs while gaining confidence in their well plans.
