New-technology MWD and LWD systems designed for ultra-deepwater drilling

This paper discusses the development of two completely new measurement-while-drilling systems. The first system is the Hostile Environment Logging (HEL ) MWD system that comprises directional and gamma ray tools, with options for downhole pressure, vibration, and temperature sensors. The second system is the Precisi - onLWD system that uses all components of the HEL MWD system, but adds resistivity, neutron, and density tools to the tool string. Combining the two systems provides a triple combo logging suite of gamma ray, resistivity, and neutron/density sensors. The primary focus of this paper is the PrecisionLWD triple combo. The systems use technology specifically designed to meet the challenging needs of ultra-deepwater drilling operations. The main design objective for the LWD system was to develop the industry's most reliable and most accurate service for the global deepwater drilling market. The capabilities of the new LWD system provide the following improvements over competitive LWD systems: - Fastest logging speed with wireline accuracy for LWD triple combo. Newly designed gamma ray, resistivity, density, and neutron porosity tools achieve accuracy equivalent to wireline tools, even at high drilling rates up to 122 m/h. This is a significant improvement over the industry average for LWD tools of 61 m/h maximum ROP (or logging speed) for similar accuracy specifications. - Greater reliability. The environmental qualifications for both systems are believed to be the most demanding in the industry. The environmental specifications were defined to meet the needs of today's aggressive drilling practices. Testing includes combinations of thermal cycling, vibration, flow-loop and pressure testing. This is expected to result in higher reliability compared to competitive MWD and LWD systems. - Highest flow rate capability. Superior erosion resistance, high-strength materials, and larger bore diameter permit using continuous flow rates that meet or exceed the maximum capability for competitive systems. - Highest bottomhole pressure rating of 207 MPa is 20% higher than the highest rated competitive system [1]. This pressure rating allows drilling 9754 m MD wells with mud weights as high as 2.16 cm 3 /kg. - High temperature capability. The HEL MWD system is rated to a maximum operating temperature of 180 °C and survival to 200 °C. Laboratory tests, theoretical calculations, and field data are presented to demonstrate these capabilities.