Fluid Analysis and Sampling: The Next Big Step for Logging While Drilling Tools

Abstract

Abstract The first formation testing tools were introduced as wireline tools in the 1950s. Since then, many technological steps were achieved, starting with simple sampling devices adding different measurement technologies in the 1980s up to formation pressure while drilling (FPWD) tools introduced to the field in 2000. Over the last 20 years wireline technology evolved towards high-quality single-phase sampling that also led to the development of the first formation sampling while drilling (FSWD) tools being introduced just over a year ago. In this paper we present a new fluid analysis and sampling tool designed for logging while drilling (LWD) applications. As it is built on the widely proven FPWD technology, it includes all its functionality of optimized testing and seal control. This service operates using a closed-loop control system, integrates real-time downhole analysis of the pressure data, and provides a repeat pressure test with an optimized rate control based on the in-situ derived mobility. This is made possible by the highly accurate pump control system employed. In addition to pressure and mobility capabilities the fluid analysis and sampling tool can analyze and obtain formation fluid samples. The new tool is equipped with high-power pump-out capabilities and highly sophisticated sensors to measure the optical refractive index, the sound speed, the density and the viscosity of the fluid. The innovative pump control prevents alteration of the fluid sample by avoiding pumping below the bubble point. The tool employs the same sample tanks that are used in our wireline tools. The tanks are approved by the Department of Transportation (DOT) for direct transportation of a sample to a certified pressure-volume-temperature (PVT) lab without transferring the sample into another sample bottle. The tool can collect and preserve up to 16 single-phase samples at surface pressures up to 20,000 psi in a single run. It uses a nitrogen buffer system to ensure the suffienct pressure is applied to the sample to prevent alteration. In this paper the capabilities of this new LWD fluid analysis and sampling tool and its first field application on a land rig in Oklahoma are be shown. The field results are compared with a wireline results run to prove the concept of shorter clean-up times while sampling soon after the formation is penetrated by the drill bit. An outlook will be given how to apply this new technology in future applications.