This paper presents the capabilities and operation of a logging-while-drilling (LWD) fluid analysis and sampling tool in a deep-water application in the Gulf of Mexico. The operation was performed during a drilling run in a high-pressure/high-temperature (HPHT) well with an expected downhole pressure of up to 22,000 psi and 300°F downhole temperature. This paper will show how a robust fluid analysis and sampling campaign was planned and executed, matching the various objectives and technical requirements with the appropriate technology. The challenges and opportunities of LWD sampling will be discussed, especially under tough environmental conditions.
The advantages of LWD sampling systems are well known, such as shorter pump-out time due to less invasion and the ability to capture reservoir fluid samples in extended reach drilling or highly deviated wells, which provides a new application range compared to current wireline systems. As the harsh drilling environment generates severe shocks and vibration, it requires precaution in the tool design and the selection of suitable components. The influence of the downhole dynamics on the reliability and durability of the system needs to be considered.
In response to these challenges, the new LWD tool incorporates an electro-mechanical driven drawdown pump that further improves the LWD fluid analysis and sampling service. This enables a nearly autonomous operation with the assurance that fluid phase integrity is being maintained. Automation allows optimal use of the available bandwidth to deliver the most complete set of fluid property data in real time for efficient decision making, including density, viscosity, sound speed and refractive index. It enables the operator to monitor the fluid identification (fluid ID) trend carefully and in real time, even from remote locations.
The sampling process is performed shortly after the hole is drilled and is therefore subjected to different levels of invasion and contamination arising from the effects of the drilling fluid and the reservoir properties. It will be discussed how this effects the clean-up and the ultimately achievable contamination level. The newly introduced compressibility value derived from the electro-mechanical pump offers a bulk measurement, where localized sensors observe scattered data. Examples from the application in the Gulf of Mexico (GOM) will be shown and discussed.
An outlook will be given how this technology evolves in future developments and how the operator and oil company can benefit from the new technologies in the drilling environment.