The tool suite that is introduced in this paper provides Logging-While-Drilling (LWD) formation evaluation with tools rated up to 350°F (175°C) and 25,000 psi (172.4 MPa). These ratings qualify as High Pressure High Temperature (HPHT) environments for LWD services, where the standard ratings are much lower. The HPHT LWD suite consists of measurement-while-drilling (MWD), annular pressure, resistivity and nuclear porosity services. The MWD service provides surveys, optional gamma ray measurements and the mud-pulse telemetry connectivity to the surface. Changes to the real-time pulsed telemetry data streams can be requested from the MWD surface system to accommodate customer requirements for any sections logged within the wellbore. A retrievable MWD system is also available for high-risk drilling environments and conditions. The quartz pressure tool measures annular pressure, drill pipe pressure and mud temperature. The resistivity service comprises of a dual frequency (2MHz and 500 kHz) borehole compensated wave propagation tool with three transmitter-to-receiver coil spacings. The combination of dual frequency, triple transmitter coils and phase/attenuation measurements provides twelve resistivity curves with different diameters of investigation. Advanced resistivity analysis compute six dielectric assumption independent resistivities, and the related dielectric constants. In anisotropic formations in high angle wells, the horizontal and vertical resistivities are calculated. The porosity service is a density-neutron-stand-off-caliper tool. The spectral bulk density (Rhob) measurement is compensated for stand-off. Three neutron porosities are computed from the three neutron detectors. The more environmentally friendly Californium252 source emits a neutron output comparable with a conventional LWD Americium-Beryllium source but at a much lower radioactivity. The source is recyclable, thus removing the need for quasi-eternal storage for depleted sources. The tools in this suite are modular and can be configured in any order. A selection of Bottom Hole Assemblies (BHA) will be shown. Examples will show the range of measurements and the advanced applications. Introduction There is a wide variety of pressure and temperature ratings for the different M/LWD tools on the market1. It appears that ratings above 302°F (150°C) and above 20,000 psi (137.9 MPa) are considered high temperature and high pressure ratings. 350°F and 25,000 psi may not be considered HPHT in some drilling environments, nor would they be considered HPHT in wireline logging tools. In the LWD industry however, where the tools must withstand the temperature and pressure for extended periods of several hundred hours, these ratings indicate HPHT qualification. The M/LWD tool suite that is introduced here is rated up to 350°F and 25,000 psi. Temperature/Pressure Rating The rating is achieved by pre-screening all the electronic components and testing to 350°F. The tools are tested to 25,000 psi. One of the main challenges to meeting the 350°F requirement is the design of electronics. Components have to be carefully selected and individually tested to ensure that they are reliable and capable of operating at these high temperatures. In addition to component testing, rigorous testing of electronics at the system level is necessary to ensure the performance and reliability of the tools at high temperatures. In order to achieve a higher pressure rating, high tensile strength materials are used. Finite element stress analysis of the geometry of the components is also performed and suitable changes are made to accommodate the higher stresses associated with high pressure. The HPHT LWD suite consists of MWD survey, gamma ray and resistivity services for nominal collar sizes ranging from 4 ¾-in - 9 ½-in and in 4 ¾-in nominal collar size for MWD survey, gamma ray, annular pressure, resistivity and nuclear porosity services. The annular pressure service is also available for HP/HT environments in a 6 ¾-in nominal collar size.

In the deepwater Gulf of Mexico (GOM), an operating company planned to drill and log a challenging wellbore in a mature field within the Upper Tertiary set of target sands. High levels of depletion as well as extremely tight pore pressure margins were anticipated. The operator and the service company's drilling and evaluation (D&E) integrated teams developed a highly collaborative environment from the early planning stage of the project, aligning people and processes and enabling applications. Regional knowledge from an archived geomechanical model was updated during collaborative planning sessions, enabling both parties to have a consistent understanding of the subsurface challenges to correctly drill and log each interval. Potential wellbore instability issues were mitigated using a proactive geomechanics analysis and hydraulics management from an integrated real-time operations center (iROC). Formation compressional slowness from a logging-while-drilling (LWD) sonic system was used, updating the geomechanical model for accurate real-time pore pressure and wellbore stability analysis. Additionally, the sonic system was used for top-of-cement (TOC) evaluation behind the intermediate casing to satisfy the Bureau of Safety and Environmental Enforcement (BSEE) requirements to differentiate fully bonded pipe from free pipe. Geosteering services from real-time log response correlations and at-bit geological predictions were used to correctly geostop for an intermediate casing point before pressure regression. An LWD formation pressure system provided pressure tests over various depth intervals, providing excellent fluid gradient determination for the primary target sand package. An LWD azimuthal density system delivered high-quality borehole images within the 16 ½-in. borehole section, providing dip information for geological correlation to seismic. Further, the azimuthal density image system resolved the interbedded shale/sand sequences, allowing dip analysis for geological model correlation within the reservoir. Challenges for this wellbore included shallow water hazards, wellbore instability, setting intermediate casing above the sand targets, and the depleted reservoir section. The deployment of specific technologies with associated unique applications discussed in detail within this paper led to superior well construction execution under time (8 days) and under budget (USD 4 million).

In the current market, operational geology and geoscience asset teams have clear and aggressive financial reduction targets that need to be met without compromising the formation evaluation (FE) requirements of a well construction project. Advances in drilling and completion technologies and practices for deep-water wells commonly require operators to drill larger borehole sizes throughout the well construction process. For deep-water subsalt wellbores, this often implies exiting a thick salt layer with borehole deviation in borehole sizes ranging from 14.5 to 17.5 in. This paper introduces a unique 9.5-in. nominal collar size logging-while-drilling (LWD) density tool that makes it possible to address the FE challenges encountered in large borehole sizes. Any LWD method that can provide crucial cost-effective and accurate FE data can add value to well drilling and logging programs. The new tool provides density and photoelectric measurements in large-diameter boreholes. It also contains an ultrasonic sensor that can provide accurate borehole geometry information, which is useful for identifying stress-related breakout and providing accurate estimates of borehole volume for later placement of cement for zonal isolation. In such settings, formation density measurements are crucial for determining key evaluation parameters, such as porosity and rock mechanical properties, but acquisition of these measurements can be challenging using existing LWD technologies. In addition, real-time structural dip information for subsalt environments provides insight for the interpretation of the geological structure of the field but is often difficult to obtain in large-diameter boreholes. Several case studies demonstrate the value added by the new tool and its breadth of application, as well as the implications for pre-job analysis, bottom-hole assembly (BHA) modeling, data-acquisition procedures, sensor response analysis, and economic benefits to the operator. The capability of acquiring logging data for interpretation purposes and to fulfill specific regulatory requirements without negatively affecting the drilling program provides a desirable cost-management opportunity. The results presented here provide a reference for appropriate business cases to help justify the use of this unique LWD technology in drilling and logging projects involving large-diameter boreholes.