Among the many challenges of managing a mature oil field is the need to obtain as accurate as possible an understanding of its remaining recovery potential. Greater accuracy in assessing characteristics that influence recovery—geologic changes, rate of saturation, water cut, microseismic events, aging infrastructure—enables reservoir teams to make better decisions regarding mature field production optimization. With the right software tools that take advantage of the wealth of reservoir data, reservoir engineers can more easily determine when, where, and how to improve well performance.
Integrating Data to Assess Remaining Recovery Potential
Mature fields have the inherent benefit of a long history of geologic and operational data, complemented by even larger volumes of recent surveillance data made available through increased oilfield instrumentation. When these data (seismic surveys, cores, geocellular analyses, reservoir simulations, completion plans, production data, tracers, and well stimulations) are integrated, visualized, and analyzed reservoir teams more accurately determine how much ultimate recovery potential has already been achieved and how much remains.
Further analysis can help determine the appropriate mature field optimization methods. Below, we highlight three of the many ways that integrating relevant subsurface data, and collaboratively evaluating it, facilitates mature field production optimization.
1. Efficiently Evaluate Opportunities for Production Optimization
Shared access to relevant data enables team members to more easily explore the interdependencies of their various datasets. Collaborative visualization and interpretation enable teams to more readily identify and diagnose factors that can extend the reservoir’s economic life. For example:
- Compare wells with similar geologic characteristics but different production metrics to isolate factors affecting performance.
- Visualize geologically complex reservoirs in 3D to determine the feasibility of drilling and recovering residual hydrocarbons (attic oil).
- Diagnose downhole pressure, determining why pressure doesn’t match production volumes in a specific well. Is the reason associated with problems in cement, safety valves, tubulars, or artificial lift equipment?
- Correlate permeability with oil viscosity and recommend alternative tertiary recovery strategy.
Once identified, the team can then evaluate the feasibility of various options, prioritize the recommendations, then develop detailed implementation plans.
2. Identify Bypassed Pay
The ability to identify and evaluate bypassed hydrocarbons and monitor fluid movement is vital in improving recovery in mature fields. Fortunately, the volume and details of reservoir data acquired in recent years can make it easier to identify bypassed pay. Time-lapse seismic surveys, reservoir fluid saturations, tracer data, and updated geocellular models can reveal previously undetected promising zones. Utilizing data that changes over time (4D) engineers can see the extent and effectiveness of previous steam injections, as well as uncover zones that have not been swept and drained by steam injection.
3. Optimal Infill Drilling Strategy
When reservoir analysis reveals opportunities for infill drilling, reservoir engineers need to determine the proper well density and determine the best location of infill wells to reach areas of high oil saturation. However, mature fields contain a jungle of existing wellbores and sidetracks that challenge well planners and drilling engineers to place wells in the context of existing offset wellpath data.
With a detailed 3D model of geologic structures, existing wellbores, including well logs and completions, well planners can evaluate various infill drilling strategies. Comparison with nearby well logs can advise drilling methods. Clear delineation of faults helps avoid problematic drill angle intersections. Proposed trajectories can be depicted relative to horizons to ensure the wellbore remains in the pay zone. To proactively prevent collisions, wellpath planning software should automatically maintain minimum allowable separation distance (MASD) from a reference wellpath.
By using the most up-to-date data to visualize and evaluate various infill well options, well planners can select those options that most cost-effectively reach the targets while minimizing risks that could negatively impact the recovery of remaining potential.
Case Study: Mature Field Production Optimization
An oil field established in 1932 characterized by highly-faulted asymmetrical anticlines was producing with water cuts exceeding 96% as the reservoir was reaching its economic limit.
By combining and analyzing a range of subsurface data, engineers were able to isolate inconsistencies and apply corrections to create a more accurate geologic model. Combining the geologic model with computerized mappings, simulations, and detailed petrophysical attributes to create highly-accurate 3D visualizations of reservoir models enabled the reservoir team to:
- Identify and capture bypassed oil with a tight-radius horizontal well.
- Determine the optimal wellpaths and drilling techniques using updated geologic models.
- Optimize the steamflood strategy by replacing vertical wells with carefully located horizontal wells.
Highly accurate 3D visualizations of evolving reservoir conditions (provided through the integration of all relevant subsurface data) give reservoir teams greater confidence in determining the most suitable strategies for mature field production optimization.
The ability to easily integrate relevant data and collaboratively analyze it gives reservoir engineers a better understanding of current reservoir characteristics and remaining reserves.
CoViz 4D: An Essential Tool for Mature Field Production Optimization
CoViz 4D is a powerful tool that supports rapid, integrated, quantitative analysis and statistical comparison of a wide range of oil field datasets. The ability to easily integrate relevant data and collaboratively analyze it gives reservoir engineers a better understanding of current reservoir characteristics and remaining reserves. Analysis of time-series data clearly depicts changing oil field conditions and their impact on production, allowing engineers to evaluate the efficacy of various production techniques and apply this insight in determining the optimum techniques to further enhance recovery.
