fax 01-972-952-9435. AbstractThis paper introduces a new technology in which a logging while drilling (LWD) tool is used to pressure test a formation during the drilling process. The Formation Testing While Drilling (FTWD) or GeoTAP * tool described in this paper uses a testing technique similar to wireline formation testers. A probe is extended to the formation and a small sample chamber is used to pressure test the formation. The drilling environment offers many new challenges to pressure testing, however.Wireline tools require a great deal of interaction with the engineer, which is very limited in the drilling environment. Therefore, the new tool has up-link and down-link capabilities and is highly automated for test control. New data compression routines are described that enable not only some of the raw data to be transmitted, but formation permeability (mobility) and test quality estimates to be obtained in realtime. An efficient algorithm is used down-hole to analyze the data where testing parameters and selected pressure data are transmitted to the surface in real-time for continuous monitoring of the test.The drilling environment is more dynamic than is the case for wireline testers. Pressures in the borehole are constantly changing due to several factors. Invasion and the resultant supercharge effect can affect FTWD measurements. Supercharging results from mud filtrate invasion increasing the sandface pressure just behind the mudcake. Additionally it is desirable to keep the mud pumps on while testing to avoid hole deterioration and pipe sticking. Slower hydrostatic pressure changes can also occur due to drill pipe movement causing a swabbing effect. These pressure transients can be transmitted through the mudcake and into the formation. Using a newly developed near wellbore model that considers mudcake properties and invasion, these effects are simulated. A sensitivity study demonstrates the conditions that affect the stability and accuracy of the FTWD measurements.Field data from the new GeoTAP tool are presented and compared with wireline formation test (WFT) data in test wells. The new tool requires the drill pipe to stop rotating/sliding for about 7 minutes per pressure test. During this time the pumps can be turned on or off. Most of the test results were taken with the pumps on. A "pumps on" GeoTAP tool field example is also presented, and the results compared very favorably with WFT data in terms of the absolute pressure measurement, repeatability and accuracy. The field example demonstrates the robustness of the measurement with three repeat pressure tests that were taken at three different depth points where, in each case, the pressures recorded were within 1 psi. Final conclusions are drawn regarding FTWD technology and its future direction.

A new generation crossed-dipole acoustic-logging tool acquires data that can be utilized to calculate shear anisotropy. This new tool, the WaveSonic™ tool, was designed using a systems approach so that tool functions such as transmitted pulse shape, center frequency, amplitude and duration are programmable from the surface. Additionally, the tool design is robust enough to allow drillpipe conveyance if well conditions warrant. It can also be combined with other logging tools and is "double-ended", allowing it to be located at any position in the logging tool-string. Shear data can be collected in orthogonal X-Y directions and oriented by a navigational package using data from a four or six-arm caliper device run with the WaveSonic tool. From these measurements, shear slowness anisotropy can be determined, as well as the direction of the fast shear slowness. These slowness values provide input to a model that calculates maximum and minimum principal stresses and their orientations. Information about principal stresses can be instrumental in optimizing completion and stimulation design. In cases where natural fracture information is desired, crossed dipole data can be used to help detect and orient such fracture systems. Introduction The WaveSonic crossed dipole sonic tool is an entirely new wireline sonic tool design.1 The design engineers and scientists were given the luxury of designing the tool "from the ground up", without being required to incorporate legacy features from other tool platforms. The key mechanical design requirement was physical strength, so that the crossed dipole sonic tool could be positioned anywhere in the tool string, allowing extremely "heavy" tools, such as new generation pump-through formation test tools and nuclear magnetic resonance tools, to run in combination below (or above) this tool. The WaveSonic tool is the first acoustic waveform wireline logging tool designed robustly enough to allow drillpipe-conveyed logging operations, where necessary. The WaveSonic tool is composed of the following components: transmitter with associated control electronics, isolator, receiver array and main electronics. All tool functionality is controlled by a surface computer, thus eliminating the necessity to pull out of the hole to change logging parameters. One of the key features of this tool is the ability to control the frequency of the crossed dipole source, allowing flexural shear wave transmission in reservoir rocks having a broad range of shear slowness values. Dipole transmitters are of the "Bender Bar" variety. The "X" and "Y" dipole sources are mounted orthogonally at the same position of the tool, ensuring maximum utilization of all received waveforms for post-processing analysis. The receiver array consists of 8 receiver "rings" spaced 0.5 feet apart. Each receiver ring is comprised of four independent receivers that are matched for frequency response and oriented in the directions of the "X" and "Y" transmitters. Detailed shear anisotropy analysis necessitates matching of frequency responses of receivers over a broad band of frequencies. The tool transmitters (monopole, and X- and Y-dipole) are fired sequentially, and all 32 waveforms associated with each transmitter firing are digitized and sent uphole - real-time - for every 0.5 feet of log. The logging speed for crossed dipole acquisition is 30 ft/min (1800 ft/hour).