Fixed Depth of Investigation Log for LWD Resistivity Tool (2003)

Fixed Depth of Investigation Log for LWD Resistivity Tool M.S. Bittar; M.S. Bittar Halliburton Energy Services, Inc. Search for other works by this author on: This Site Google Scholar G. Hu; G. Hu Halliburton Energy Services, Inc. Search for other works by this author on: This Site Google Scholar J. Xiao J. Xiao Halliburton Energy Services, Inc. Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Annual Technical Conference and Exhibition, Denver, Colorado, October 2003. Paper Number: SPE-84098-MS https://doi.org/10.2118/84098-MS Published: October 05 2003 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Bittar, M.S., Hu, G., and J. Xiao. "Fixed Depth of Investigation Log for LWD Resistivity Tool." Paper presented at the SPE Annual Technical Conference and Exhibition, Denver, Colorado, October 2003. doi: https://doi.org/10.2118/84098-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Annual Technical Conference and Exhibition Search Advanced Search AbstractFor years, wireline array-induction resistivity data have been processed and displayed at fixed multiple depths of investigation on logs. Modern multi-frequency, multi-spacing logging-while-drilling (LWD) resistivity tools are capable of measuring resistivities at multiple radial depths of investigation. However, since wireline and LWD tools are governed by different tool physics, it is sometimes difficult to compare data obtained by these two devices. Therefore, it is desirable to deliver LWD resistivity data in a manner that is comparable to the presentation of wireline array-induction data.This paper presents a new approach to process and display LWD data at fixed depths of investigation. This approach starts with a non-linear, iterative deconvolution to simultaneously correct for both relative dip and shoulder-bed effects. Using these corrected logs, the formation resistivity and invaded zone resistivity are determined by an inversion technique that assumes a step-invasion profile. This enables the method to better address the non-linearity of the LWD tool's response. After that, a least-squares curve-fitting technique is used to derive a function that models the relationship between the physical spacing of the transmitter-to-receiver pair and the depth of investigation. Using the same technique, a second function, which models the relationship between the transmitter-to-receiver spacing and the resistivity reading is derived. The first function is utilized to determine a set of fictional spacings that, if used, would result in the desired fixed depths of investigation. These fictional spacings are then used with the second function to calculate resistivity values at the desired depths of investigation, which are chosen to match some of those typically used for wireline array induction tools. The processed data thus obtained provide a meaningful way of comparing array induction and LWD resistivity data.IntroductionSince their inception in 1983,1 LWD propagation resistivity tools have seen steady advancement in tool design and capability. The first LWD electromagnetic wave resistivity tool operated at a single frequency, had one T-R spacing, and provided one measurement. Two depths of investigation capability derived from a single spacing, single frequency tool, via measurement of both phase shift and attenuation was introduced in 1988.2 In 1991, a multiple depth of investigation tool that utilizes two frequencies and multiple T-R-spacings was introduced.3 A dual-spacing, dual-frequency, compensated LWD resistivity tool was introduced in 1995,4 as well as a multi-spacing, pseudo-compensated LWD resistivity tool.5 Today, with increasing demand for more accurate information from around the borehole, multi-frequency, multi-spacing (sometimes referred to as "array") tools that are capable of making many more measurements are becoming available. A multi-frequency, multi-spacing tool provides better delineation of the invasion profile in the radial direction. The advent of these array LWD tools poses a data presentation challenge, due to the large amount of raw data acquired. We have made an attempt to present array LWD data in a way that is similar to the way array- induction tool data are displayed. We will base our discussion in this paper on the multi-frequency, multi-spacing EWR-M5* resistivity tool. However, the proposed method can be easily adapted to any other array-type tools.The EWR-M5 tool (See Figure 1) is a multi-frequency, multi-spacing LWD wave propagation resistivity tool. This tool operates at three different frequencies, 2 MHz, 500 kHz, and 250 kHz, and produces five fully compensated phase shift-derived resistivity and five fully compensated attenuation-derived resistivity measurements at each frequency. The compensated T-R spacings are 16, 24, 32, 40, and 48 inches. A total of 30 compensated resistivity measurements, each having a different depth of investigation into the formation, are obtained per measurement cycle. The objective of the fixed depth-of-investigation processing method is to combine all these measurements into five curves having fixed depths of investigation of 10, 20, 30, 40, and 60 inches in radius, respectively. Keywords: lwd tool, background resistivity, radial geometric factor, bittar, resistivity tool, spe 84098, halliburton energy service, frequency, well logging, resistivity Subjects: Formation Evaluation & Management, Open hole/cased hole log analysis This content is only available via PDF. 2003. Society of Petroleum Engineers You can access this article if you purchase or spend a download.