High-pressure, high-temperature (HPHT) wells—characterized by temperatures over 150°C and 10,000 psi at their deepest point—present challenges throughout all phases of the reservoir development cycle. The number of HPHT well completions have grown significantly in the past decade as improvements in data analysis and equipment designs allow operators to overcome the unique challenges of HPHT well development. Even though HPHT well completions are more expensive, their costs are justified by the significant hydrocarbon potential in light of the fact that an HPHT well will contain more gas per cubic foot than a conventional well.
To help realize the full potential of HPHT wells, reservoir teams are employing software that integrates and visualizes reservoir data sources that characterize HPHT conditions. With the ability to collaboratively analyze relevant data, reservoir teams obtain a clearer understanding of the unique challenges that HPHT wells present, then apply that insight to help determine the best HPHT well completion strategies.
Key HPHT Well Completion Challenges
The extreme environment of HPHT wells pose some significant challenges in comparison to the development of standard reservoirs. The more accurately reservoir teams understand subsurface conditions, the better prepared they are to address HPHT well completions challenges such as:
- High-temperature, corrosive environments (CO2 and H2S) require specialized (corrosion-resistant alloys, high-temperature elastomers) drilling, downhole, and casing equipment
- Limits on horizontal wellbore length due to damaging high-temperature effects on directional drilling tools
- Need for specially-developed drilling fluids—synthetic or oil-based mud (OBM)—that avoid risks of water-based fluid reactions and maintain the required rheological properties at high temperatures
- Cost of specialized drilling and logging tools to fit small diameter wellbores typical of ultradeep wells
- Wellhead design and BOP for HPHT well completions (up to 25,000 psi) to ensure safety of personnel and protect expensive surface facilities
In comparison to completions in non-conventional reservoirs, planning and developing HPHT well completions require a greater degree of accuracy in assessing subsurface conditions. The inherent risk of HPHT subsurface environments demands a higher margin of safety throughout all phases of the development cycle. Data integration, visualization, and analytics play a crucial role in helping development teams meet those requirements.
Data Visualization and Analytics Guide HPHT Well Completions
Software tools that easily integrate relevant data which characterize the subsurface environment and facilitate visual analysis enable reservoir teams to collaboratively evaluate conditions and develop the strategies to deal with the unique HPHT constraints. A 3D visualization environment can guide well path design, drilling methods, and HPHT well completion options.
Well Path Design
Seismic surveys transformed into 3D models depict the strata, faults, horizons, discontinuities, targets, and structures that must be navigated to reach the pay zone. A detailed 3D visualization of reservoir geology and geophysical characteristics provides a foundation for well planners to more accurately assess conditions and apply well planning tools to determine suitable well trajectories. Well path design in context of a detailed, 3D model of subsurface conditions allows geoscientists and well planners to:
- Analyze geological and petrophysical attributes to avoid risks and maintain wellbore integrity
- Evaluate the pros and cons of alternative well paths to minimize drilling costs for HPHT conditions
- Estimate the maximum feasible extent of laterals in the pay zones
HPHT wells make special demands on drilling engineers, specifically with respect to temperature and pressure factors that influence drilling methods. Combining 3D geological models with well log data enables engineers to visualize and analyze changing conditions from the wellhead to the bottom hole location with the goal of determining the drilling equipment and methods needed to successfully drill a well. Well log data assists geophysicists and drilling engineers in
- Calculating pore pressure gradients, which are critical metrics in determining drilling strategy and can rapidly increase with depth as geologic features change. Accurate calculations guide the selection of drilling fluids and their weights to prevent formation fluids from infiltrating the wellbore and maintain safe pressure balances
- Calculating temperature gradients and bottom hole temperature. High temperatures require special drilling equipment—bottom hole assemblies, logging-while-drilling (LWD) tools, and electronics—that tolerate the extreme environment for the duration of each drilling stage.
Additional downhole data obtained from the drilling process (by way of a WITSML server) give completion engineers an even better understanding of wellbore and bottomhole conditions. The added information can be used to confirm planning assumptions or refine completion plans to more effectively address bottomhole conditions.
Every well completion requires well-informed decisions. HPHT well completion decisions require special consideration in light of the extreme pressure or temperature conditions. With as accurate as possible information regarding a wellbore and surrounding geology, completion engineers are better prepared to:
- Choose casing dimensions and cementing techniques to accommodate high-pressure flows
- Select bottomhole completion hardware that can tolerate HPHT environments
- Determine if a multistage frac completion is possible or further development needs to be taken to successfully complete the well
- Select the proppant which is most effective in keeping fracture open after hydraulic pressure is released
Completion engineers can also benefit from detailed information regarding nearby HPHT well completions. By reviewing the geology, petrophysical data, completion design, stimulation methods, competition sequence, microseismic data, and production records, engineers can apply the methods that helped optimize recovery and avoid those that were problematic.
CoViz 4D: Essential Software for Understanding HPHT Well Conditions
Geologic and petrophysical conditions dictate a well’s drilling method and completion design. Conditions in HPHT wells require all the more accurate understanding of the subsurface environment to safely and cost-effectively plan and execute drilling and completions.
CoViz 4D easily integrates seismic, petrophysical, well logs, microseismic, and production data into a common visualization environment.
Operators worldwide have chosen CoViz 4D to give reservoir development teams the ability to integrate, visualize, and analyze a wide range of reservoir data to more accurately understand subsurface conditions. CoViz 4D easily integrates seismic, petrophysical, well logs, microseismic, and production data into a common visualization environment. An integrated view of subsurface conditions allows members of the reservoir team to carefully evaluate factors that influence HPHT well design, drilling, and completions and plan and execute development strategies to maximize hydrocarbon recovery in a safe and cost-effective manner.