Wireline HPHT Operations

High-Pressure High-Temperature (HPHT) wireline operations require careful planning and preparation. In this week’s Tool Tuesday we outline some of the key considerations for these types of operations with a focus on high temperature.

The intense conditions of HPHT wells can quickly degrade equipment resulting in premature failure. Detailed planning ensures that tools and materials used can withstand such stresses to mitigate such risks. Failures in HPHT operations can lead to high non-productive time (NPT) and increased costs. Proper planning minimises risks and potential downtime, enhancing overall operational efficiency.

Defining HPHT

High-Pressure High-Temperature (HPHT) conditions in relation to wireline tools are typically defined by specific temperature and pressure thresholds that affect the performance of the materials and electronics used. An often referenced classification system has been published by SLB in the Oilfield Review in 2008 (ref, ref, ref, ref). These guidelines, which have been established in the absence of any recognised industry standard, are based on “commonly encountered technology thresholds” – mainly electronic and elastomeric components.

HPHT: Wells are classified as HPHT when the conditions meet or exceed a bottomhole temperature (BHT) of 150°C (300°F) or a bottomhole pressure (BHP) of 69 MPa (10,000 psi).

Ultra-HPHT: This category refers to conditions that surpass the practical operating limits of existing downhole electronics, defined as greater than 205°C (400°F) BHT or 138 MPa (20,000 psi) BHP. Handling these conditions often requires special adaptations, such as vacuum flasks or heat sinks to protect sensitive electronic components.

HPHT-hc (high challenge): Represents the most extreme environments, with conditions exceeding 260°C (500°F) BHT or 241 MPa (35,000 psi) BHP. These conditions are so severe that they are typically beyond the common technological capabilities for drilling and production equipment.

Electronics Failures with Increased Temperature

Temperature has the potential to damage electronic components and the materials used in the construction and fixings of these materials housed within a downhole tool housing. Understanding potential mechanisms for failure is a good starting point before planning an HPHT wireline operations:

Operational Limits of Electronics: Electronics have a defined operational thresholds, or threshold ranges. If planning to operate tools above these thresholds the electronics needs to be protected in some way (flasks, coooling mechanism).

Material Vulnerability to Heat: This sensitivity primarily arises due to the instability of plastics and composite materials, which are crucial for maintaining the structural integrity and insulation of modern electronics.

Thermal Fatigue (Thermal Cycling): Continuous expansion and contraction of materials can cause fatigue. Components and their connections, like solder joints, may weaken, warp, crack, or break over time due to the stress from thermal cycling.

Solder Joint Failure: Solder, which acts like a glue to bond components, can degrade due to the different rates of thermal expansion among the materials it joins. This mismatch in expansion rates often results in solder fatigue where the joints deform, crack, or break, leading to disconnection and failure of the electronic components.

Stress Concentration: High-strain areas on a circuit board, especially around mounting holes, between stiff components, or near edges, are critical spots where failure is more likely.

Sharon & Creswal (ref) suggest that the majority of The majority of electronic failures occur due to thermally induced stresses and strains caused by excessive differences in Coefficients of Thermal Expansion (CTE) across materials. Additionally, that the rate of change of temperature can also increase failure rate due to issues including: Thermal Shock, Increased Stress in Solder Joints, Component Warpage, Condensation Issues, Microstructural Changes in Materials, Crack Propagation.

Planning HPHT Wireline Operations

At one&zero we would highly recommend an operations specific Service Quality Plan (SQP) is drafted well in advance of any equipment preparation phase. The purpose of any HPHT SQP should be to systematically manage the complex array of challenges posed by such environments, ensuring that operations are not only efficient, but effective at delivering the data acquistion objectives.

Examples of what one&zero’s SQP includes:

• Client Collaboration: Requirements for data exchange between parties and timelines to reach operational goals, and unique challenges associated with the project.
• Personnel Selection: Measures to ensure all personnel involved in equipment preparation and operation are specifically trained and experienced in HPHT operations. This includes technical knowledge, safety protocols, and emergency response procedures.
• Risk Management: Implement comprehensive risk assessment processes to identify potential hazards and develop mitigation strategies tailored to HPHT conditions. Consider an operational readiness audit to identify any potential gaps.
• Safety Protocols: Establish stringent safety guidelines that exceed standard requirements to handle the increased risks associated with HPHT environments.
• Equipment Selection: Provide detailed guidelines for selecting and modifying logging any downhole equipment, heads and cables to ensure they can withstand the maximum expected pressures and temperatures.
• Tool Modifications: Assess the need for further modifications to enhance tool reliability and performance under extreme conditions. This might include upgrading materials or redesigning components to better handle the thermal and mechanical stresses of HPHT environments.
• Equipment Testing and Qualification requirements: Define a rigorous qualification procedure for all HPHT tools, requiring them to undergo tests under simulated downhole conditions to verify their resilience and operational capabilities.
• Agree the role of the independent QA/QC consultant: All critical procedures, tests, and operational checks should be witnessed by an independent wireline specialist to ensure adherence to the highest quality standards and provides an unbiased verification of the vendors quality plan.
• Historical Performance Review: Agree data exchange to facilitate asset records inspection to identify any historical equipment concerns (failures) or proven performance at temperature. Agree how this data will be used to inform equipment selections on upcoming operation. Will assets be rotated to reuced thermal stress on components, how many of each asset type will be available for the campaign etc.
• O-Rings and Elastomers: Specify any requirement elastomer materials / o-rings suitable for HPHT conditions, and agree replacement frequency (every run).

Equipment Preparation

Heat checking, or heat qualification, ensures that downhole tools can withstand the extreme temperatures they will encounter. Natuarlly, it is preferable to identify potential failures in a controlled lab setting rather than at the wellsite which may result in NPT and therefore cost.

Heat checking equipment provides a means of early failure detection. A heat check in an oven not only confirms a tool’s ability to operate in high temperatures, but also reveals any of the potential causes of failure highlighted earlier.

How is a heat check performed:

• Place the electronics into a specialised oven: Firstly, only the electronic parts of the tool are placed in the oven, especially if they contain hydraulic oil, to avoid overheating and possible expansion issues.
• Gradual Temperature Increase: The tool should be heated gradually to prevent failures associated with thermal shock. Temperature is started at room temperature and increased in pre-defined increments (~25 degC) every half hour until the maximum expected bottomhole temperature (BHT) is reached / the pre-agreed temperature as defined in the SQP is reached).
• Monitoring and Calibration: The tool should remain powered up during the test to simulate operations, including internal heat generation. Tool sensors should be logged and monitored continuously, where possible internal tool tests and calibrations should be performed to assess any drifts. A soft tap with a rubber hammer can help locate any connections which may be on the verge of failure (speak with the vendor first about this practice as part of the agreed SQP).
• Controlled Cooling: After reaching the maximum temperature, the oven should be cooled down at the same rate it was heated to prevent thermal shock, which could damage the tool. The oven should not be opened prematurely during the cooling phase to prevent rapid temperature changes that could stress electronic components.

Operational Execution Hints

Efficient Logging Practices: Best practices can minimise exposure time of components to temperature. These include strategies such as:

• Maximise efficiency whilst coming out of hole with the drilling BHA to reduce the time since last circulation and hence borehole temperature at time of logging.
• Clearly define the logging plan and optimise logging speed as much as possible – do you really need very high resolution data, or will standard suffice?
• Prioritise pressures and sample depths and take the shallowest of those first.
• Not turning on the tool electronics until just prior to logging (downlog) to reduce the contribution to temperature from the tool electronics themselves.
• Perform a downlog to i) monitor tool function and internal/external tool temperature ii) acuqire insurance log data.
• Minimise the time the tool is exposed to high temperature through efficient winch and logging turnaround/ data acquisition software changes (wetware!)
• Consider Performing a repeat log just below the casing shoe before moving to the deeper and hotter parts of the well. (ref)
• Effective Communication channels and real-time data transmission to facilitate efficient decision making and “on-the-fly” programme modiciations (ref)
• Procedural Alignment – ensure operational procedures are thoroughly reviewed with onshore drilling superintendents to ensure they align with rig interfaces and overall procedures ref
• Pay close attention to conveyance strategy and hangup/sticking risk mitigation. This can include downhole tool accessories (rollers/Jars/standoffs) as well as strategic wiper trips to mitigate risks associated with high-solids muds and potential tool sticking.
• Cooling the wellbore – consider wiper trips in between runs to reduce wellbore temperature.
• Consider carefully the requirement to tag TD for each run. In wells with high-solids muds, there can often be barite sag, which can cause a tool string to become stuck (ref).
• In the event of a suspected temperature related failure, pull to a safe, cooler part of the wellbore and see if the tool regains functionality.
• Heat-sensitive indicators can be used inside each HPHT housing to monitor the maximum internal temperature experienced by each asset.
• Break every connection after each descent into the well, clean and re-grease collars. Inspect the insulation at the head, cable, and adapter’s insulation after every descent into the well.

Technical Advisory

All wireline operations rely on meticulous planning and preparation, HPHT well environments amplify this need. The following is a summary of what to consider if you are entering into a world of HPHT on your next well:

• Develop a comprehensive SQP tailored to HPHT conditions, incorporating detailed guidelines for equipment selection, personnel training, and risk management.
• Ensure all equipment undergoes rigorous testing under simulated downhole conditions to validate performance and operational capabilities.
• Work closely with clients to align on specific needs and operational goals. Ensure all personnel are trained and experienced in HPHT operations.
• Regularly review asset records and historical performance data to inform equipment selection and identify potential areas for improvement.
• Conduct heat checks in controlled settings to identify potential failures. Gradually increase temperature in predefined increments to simulate downhole conditions.
• Monitor tool performance and internal conditions continuously during heat checks to detect any signs of malfunction or degradation.
• Utilise real-time data transmission and effective comms systems to enable timely decision-making and adapt operations based on actual conditions.
• Ensure all procedures, tests, and checks are independently verified by QA/QC specialists to ensure heat testing is performed correctly (Trust, but verify).
• Implement strategies to minimize tool exposure to high temperatures, such as optimising logging speeds and prioritizing data acquisition processes.
• Align operational procedures with onshore planning to ensure smooth execution and adherence to safety protocols.
• Regularly inspect and maintain tools, replacing sensitive components such as O-rings and elastomers after each run.
• Consider modifications to improve tool reliability and performance under HPHT conditions, such as upgrading materials or redesigning components to better handle thermal and mechanical stresses.

By adhering to these guidelines and continuously improving based on operational feedback and technological advancements, ooperators can enhance the reliability, safety, and efficiency of HPHT operations. These practices not only protect valuable equipment but also ensure the successful delivery of critical well data.